exfoliation microcracks in building granite implications for anisotropy abstract granite is found in many world heritage monuments and cities it continues to be one of the most widely used stones in today s construction given its abundance uniformity and durability quarrymen traditionally cut this rock along its orthogonal slip planes where splitting is easier ranked by ease of splitting these planes are rift grain and hardway granite is traditionally quarried along the rift plane where coplanar exfoliation microcracks coalesce developing a flat surface this splitting surface minimizes the cost and effort of subsequent hewing rift plane was predominantly used on the fair face of ashlars in heritage buildings worldwide determining the petrographic and petrophysical behaviour of these three orthogonal splitting planes in granite is instrumental to understanding decay in ashlars and sculptures the decay of building granite is different in each splitting plane alpedrete granite was the stone selected for this study based on the orientation and distribution of exfoliation microcracks and the characterisation of their implications for the anisotropy of petrophysical properties such as ultrasonic wave propagation capillarity air permeability micro roughness and surface hardness inter and intracrystalline microcrack length and spacing were also measured and quantified the findings show that the splitting planes in alpedrete granite are determined by the orientation of exfoliation microcracks which as a rule are generally straight and intracrystalline and determine the anisotropy of the petrophysical properties analysed splitting planes are the orientation that should be applied when performing laboratory tests for the petrographic and petrophysical properties of building granite

weathering and morphogenesis in a mediterranean climate calabria italy abstract deeply weathered plutonic rocks occur widely in the sila massif calabria southern italy three representative weathering profiles developed on the hilltops indicate that sand represents more than 50 by weight throughout most of the weathering profile and silt and clay size fractions are also well represented filling the interstices among corestones both sand and finer fractions of grus and soil horizons are thought to be derived from a combination of granular disintegration and chemical decomposition developed on relatively flat terrains of the sila massif these slopes are now experiencing transport limited morphodynamics under a montane modified mediterranean climate the depth of the weathered layers that have suffered little erosional truncation typically exceed 15 m and may reach 50 60 m or more major isolated or grouped exfoliation boulders are the most common minor landform feature developed on the sila massif granite boulders have developed as a result of spheroidal weathering and by removal of the sandy textured granite the schmidt hammer sh test on boulders and corestones suggests three distinctive degree of weathering from moderately to completely weathered rock and that biotite content is the major controlling factor of the granite mechanical behaviour understanding of the dynamics of this weathering system is crucial to the interpretation of the complex suite of variables that control landscape evolution of granitoid terrains

mechanism of exfoliation joint formation in granitic rocks yosemite national park abstract fractographic techniques reveal mechanical aspects of exfoliation in granitic rocks at yosemite national park and electronic surveying provides information on their attitudes and dimensions in the middle elevations of the cliff of el capitan exfoliation consists of early fractures a few meters to tens of meters in size which are fan shaped fans at upper elevations point upwards whereas fans at lower elevations point downwards parallel to the cliff the fans interact with each other and merge into composite joints hundreds of meters in size normal to the minimum compressive principal stress this polarity indicates exfoliation by longitudinal splitting and buckling the palaeostress causing the exfoliation on the southwestern side of half dome is estimated to range between 0 01 mpa and 0 94 mpa differences in fracture paleostresses of joints may be used in comparing their relative propagation velocities it is suggested that the large exfoliation on the southwestern side of half dome had undergone a prolonged sub critical growth before attaining rapid fracture velocities under post critical conditions

rossby waves mediate impacts of tropical oceans on west antarctic atmospheric circulation in austral winter recent studies link climate changearound antarctica to the sea surface temperature of tropical oceans with teleconnections from the pacific atlantic and indian oceans making different contributions to antarctic climate in this study the impacts of each ocean basin on the wintertime southern hemisphere circulation are identified by comparing simulation results using a comprehensive atmospheric model an idealized dynamical core model and a theoretical rossby wave model the results herein show that tropical atlantic ocean warming indian ocean warming and eastern pacific cooling are all able to deepen the amundsen sea low located adjacent to west antarctica while western pacific warming increases the pressure to the west of the international date line encompassing the ross sea and regions south of the tasman sea in austral winter these tropical ocean basins work together linearly to modulate the atmospheric circulation around west antarctica further analyses indicate that these teleconnections critically depend on stationary rossby wave dynamics and are thus sensitive to the background flow particularly the subtropical midlatitude jet nearthesejets wind shearis amplified which strengthens the generation of rossby waves on the other hand near the edges of the jets the meridional gradient of the absolute vorticity is also enhanced as a consequence of the rossby wave dispersion relationship the jet edge may reflect stationary rossby wave trains serving as a waveguide the simulation results not only identify the relative roles of each of the tropical ocean basins in the tropical antarctica teleconnection but also suggest that a deeper understanding of teleconnections requires a better estimation of the atmospheric jet structures

effects of thermal heating cycle treatment on thermal expansion behavior of different building stones abstract several types of natural stone show dimensional instability causing damage if used outdoors the extent of damage basically depends on the orientation of the crystal texture in the stone slabs the so called preferred orientation in order to examine the characteristics of natural stone the measurement was done with a quadruple dilatometer the dilatometer is a testing device for measuring the linear thermal expansion of materials as a function of temperature enabling the analysis a quadruple dilatometer was built which allows testing of four samples simultaneously under same conditions several types of marble wachauer marble limestone mannersdorfer limestone mocca creme schwarzenseer limestone and veselje unito calcareous arenite st margarethener calcareous arenite quartz arenite sun imperial and granite neuhauser granite and chinese granite g603 have been analyzed to create an assemblage of the thermal expansion properties of several stone types

mid latitude mesoscale variability neither homogeneous quasi geostrophic turbulence nor the effect of eddies on the interior ocean circulation remains the major focus of mesoscale research as was the case for much of the preceding 20 years following identification of the phenomena concentration on basin wide geographical exploration of eddy properties was rather well established by 1978 over the last few years a promising zero order description and rationalization of the mesoscale field has become available that is eddy energy is largest near strong flows intensification not only in western boundary currents but along their mid latitude open ocean extension roughly as indicated by gyre scale numerical models where eddies develop as a result of instability processes in the mid latitude jet and recirculation regimes and then propagate into the ocean interior our point of view is that mesoscale eddies drive recirculations but do not play a crucial role in the dynamics of the mean flow in the ocean interior in the north atlantic for example the idea is that the downstream increase in transport of the gulf stream is eddy driven but not the flow through the florida straits in addition the fluctuating response to forcing by variable winds may now be widely perceived as forming the horizontally homogeneous background signal in subtropical gyres the time dependent field associated with thermohaline flows at abyssal depths also has a special character

eddies in the northeastern north atlantic statistics from observations from a moving ship statistics of currents and hydrographic data collected from a moving ship in the northeastern north atlantic have been used to investigate the role of eddies in the circulation of the ocean the mean currents show besides a north atlantic current of about 12 cm s 1 a significant westward flow perhaps 4 cm s 1 just north of the azores eddy kinetic energies in the western basin reach about 1000 cm2 s 2 while there is indication of a weak secondary maximum of about 300 cm2 s 2 in the eastern basin both the eddy kinetic energy and the thermohaline variability show a strong asymmetry with greater variability on the south side of the main branch of the north atlantic current at about 51 n the momentum budget of the north atlantic current shows a dominant geostrophic balance with terms of order 10 cm s 1 the gradients of the reynolds stresses contribute about 0 1 cm s 1 and the nonlinear terms less than 0 01 cm s 1 the residual meridional velocity implied by the meridional heat transport is of order 3 cm s 1 the eddy scale was estimated by means of the average zero crossing length scale of the transverse velocity correlation function to be 46 km there is significant interannual variability of both mean conditions and mesoscale variability in the region of the north atlantic current the northward eddy heat transport appears to be zero in the mixed layer but may be a significant proportion of the total oceanic heat transport at the intergyre boundary in the thermocline estimates of the magnitudes of eddy diffusivities for both momentum and heat give values of about 104 m2 s 1

weathering of the oporto granite geotechnical and physical properties abstract this paper characterizes the weathering products of the two mica oporto granite in terms of its mineralogical chemical geotechnical and physical properties this information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties in outcrop the oporto granite is always weathered and weathering profiles frequently exceed 20 m within these profiles granitic saprolites are composed of quartz feldspars and some mica with kaolinite and gibbsite as final weathering products the average percentage of secondary minerals determined by bulk x ray diffraction xrd is low in both weathered rock 2 4 and saprolite 8 7 geotechnically the saprolites exhibit no or low plasticity plasticity index pi 12 the skeleton character of the saprolites is reflected in the significant proportion of fines 29 5

microcracks in new england granitoids a record of thermoelastic relaxation during exhumation of intracontinental crust the upper intracontinental crust carries an excess horizontal compression a remnant stress that arises because exhumation related thermoelastic relaxation of deeper horizontal stress lags behind the reduction in overburden stress this remnant stress appears in earth stress data as an interchange in orientation of vertical 2 and horizontal 3 so that the ratio of least compressive horizontal stress s hmin to vertical compressive stress s v is 1 in much of the top 2 km of intracontinental crust in theory rocks exhumed from beneath 2 km should carry some record of this stress interchange and this record is found in the orientation and density of healed filled and open micro cracks in exhumed new england granitoids fluid inclusion planes fip of older healed microcracks are the best developed in a vertical orientation and younger filled and open microcracks are best developed in the horizontal plane lateral unloading during initial isobaric cooling from the solidus of laterally constrained granite allows early microcrack growth once horizontal tension on the microscopic scale develops in response to vertical compression from the overburden load during exhumation further relaxation of lateral compressive stress takes place by a combination of decompression and cooling so that s hmin s v

observational evidence of salt lens formation in the iberian basin the quasi synoptic picture of the mesoscale eddy field off portugal is presented on the basis of recent hydrographic measurements the dynamic topography and the salinity field at middepths 900 1300 m is shown to be dominated by several isolated meddy structures superimposed on a general east west gradient deduced from the actual dynamical situation there is evidence for meddy generation in this region numerical process studies demonstrate the possibility of vortex formation by baroclinic instability of a northward middepth jet of mediterranean water and by fragmentation of larger scale mediterranean water blobs

the near surface flow in the subtropical gyre south of the azores this study presents evidence that the azores current azc is a permanent feature of the north atlantic subtropical gyre and that it feeds the north equatorial current nec the azc path is located south of the azores its velocity is mostly geostrophic and the energy level in the mesoscale range is higher than in the nec the nec velocity appears to be mostly ageostrophic and the wind driven surface velocity is at about 15 to the right of the mean wind field

distribution and inferred age of exfoliation joints in the aar granite of the central swiss alps and relationship to quaternary landscape evolution abstract exfoliation joints are well known natural fractures limited to near the ground surface relatively few details however are known about their distribution and age in the swiss alps exfoliation joints follow the landscape surface at the time of their formation the age of the associated landscape feature then provides a maximum age of exfoliation joints while landscape forms can change through time exfoliation joints preserve elements of former landscape morphologies by their undisturbed orientations the grimsel region of the central alps is well suited for analyzing the impact of erosional episodes and accompanying stress changes on exfoliation joint formation in granitic rocks mapping above and below ground revealed that exfoliation joints are widespread and occur between valley bottoms and mountain crests within glacial inner and hanging u shaped trough valleys glacial cirques and steep mountain crests and predominantly fluvial landforms gently inclined linear slopes above the inner trough valleys narrow inner valley gorges and steep v shaped side gullies based primarily on their geometric properties at the ground surface three exfoliation joint types were distinguished in our study area 1 closely spaced

linking microcracks and mineral zoning of detachment exhumed granites to their tectonomagmatic history evidence from the salihli and turgutlu plutons in western turkey menderes massif abstract the menderes massif western turkey is a metamorphic core complex that displays linked syntectonic plutonism and detachment faulting fabrics in s type peraluminous granites salihli and turgutlu in the detachment alasehir footwall change from isotropic to protomylonitic to mylonitic towards the structure samples from the isotropic and protomylonitic zones were imaged in transmitted light cathodoluminescence cl backscattered bse and secondary electrons se and show that these rocks contain abundant microcracks and that plagioclase grains have zoning consistent with magma mixing the granites contain fluid inclusion planes fips myrmekite replacing plagioclase and the removal of blue luminescence in k feldspar along microcracks and grain boundaries calcite and hydrous minerals commonly fill microcracks the samples record features that formed due to 1 magma crystallization and ductile deformation fips mineral zoning 2 changes in p and or t impingement and stress induced microcracks in protomylonitic rocks and 3 differences in intrinsic mineral properties radial cleavage blunted and deflected microcracks overprinted microcracks indicate exhumation during pulses the middle miocene ages of these granites reported elsewhere are similar to those from large scale extensional structures in greece s cycladic massif the menderes and cycladic core complexes may have developed simultaneously due to the widespread intrusion of subduction related granitoids

origin of sheet structure 1 morphology and boundary conditions abstract sheet structure or large scale exfoliation is the division of a rock mass into lenses plates or sheets approximately parallel to the earth s surface sheet fractures which separate the plates are characterized by surface markings resembling those formed during the brittle fracture of metals glass and ceramics and those on joints in rock lineations or hackle marks parallel to the direction of fracture propagation are common branching occurs during propagation so that the fractures appear as many echelon segments in profile the opposing surfaces of sheet fractures observed in quarry walls and natural exposures are typically in contact damage if any to rock adjacent to sheet fractures is generally limited to a zone less than one centimeter wide sheets tend to parallel preferred orientations of microcracks in many rock masses most sheets that are exposed today are of prehistoric origin but in some rock masses such as chelmsford granite in massachusetts new sheets continue to form sheet structure forms in environments of high differential stress dominated by large scale compression parallel to an exposed rock surface in parts of the chelmsford granite the magnitude of this compression is greater than 30 mpa in the zone of sheeting high differential stresses near the ground surface can result from several natural agents including contemporary tectonic forces vertical unloading of a rock mass that formed at depth under high triaxial compression and suppression of expansion that would otherwise result from temperature increases or chemical alteration of the rock exfoliation of boulders during forest fires and spheroidal weathering of boulders appears to occur under similar states of stress although the agents responsible for the stresses differ

influence of mineralogy on granite decay induced by temperature increase experimental observations and stress simulation abstract rocks can be subjected to high temperatures in several instances as for example in geothermal processes or if affected by fires temperature variations lead to a complex stress distribution in crystalline rocks due to mineral thermal expansion in polymineralic such as granites these stresses depend on fabric parameters such as mineral proportion grain size and their related thermal properties eight granitic rocks were heated to less than 400 c and their decay patterns were observed and quantified by means of scanning electron microscopy heating was also modeled by finite element simulations oof software with polymineralic microstructures quartz feldspar and biotite contents were used as a variable in the model in order to elucidate the influence of mineralogy on the thermal elastic response of granites real and modeled heating showed similar trends of microcracking in microstructures and of thermal expansion coefficients microscopic observations of real samples revealed mainly intragranular microcracks in quartz opening of cleavage plains and deformation in mica simulations confirmed that in spite of the high thermal and anisotropic expansion of quartz the microstructure of rocks with large amounts of quartz does not necessarily experience large stresses biotite produces a concentration of stresses along their grain boundaries as a result oof models with 10 biotite showed higher stresses than monomineral ones thermal expansion coefficients of real granites fitted within the limits of the simulated ones proving once more the success of using finite element modeling applied to polymineralic rocks

are open fractures necessarily aligned with maximum horizontal stress abstract fluid flow in fractured rock is an increasingly central issue in recovering water and hydrocarbon supplies and geothermal energy in predicting flow of pollutants underground in engineering structures and in understanding large scale crustal behaviour conventional wisdom assumes that fluids prefer to flow along fractures oriented parallel or nearly parallel to modern day maximum horizontal compressive stress or s hmax the reasoning is that these fractures have the lowest normal stresses across them and therefore provide the least resistance to flow for example this view governs how geophysicists design and interpret seismic experiments to probe fracture fluid pathways in the deep subsurface contrary to these widely held views here we use core stress measurement and fluid flow data to show that s hmax does not necessarily coincide with the direction of open natural fractures in the subsurface 3 km depth consequently in situ stress direction cannot be considered to predict or control the direction of maximum permeability in rock where effective stress is compressive and fractures are expected to be closed chemical alteration dictates location of open conduits either preserving or destroying fracture flow pathways no matter their orientation

satellite tracked drift buoy observations of the near surface flow in the eastern mid latitude north pacific the surface and near surface 30 m currents of the eastern mid latitude pacific obtained from 32 satellite tracked drifting buoys during the period june 1976 through august 1977 are discussed these observations of oceanic currents are merged with and are compared to fleet numerical weather center s daily estimates of surface winds for the same period statistical comparisons of these data sets reveal that the drifters move systematically approximately 30 to the right of the surface wind at approximately 1 5 of the wind speed this relationship between drifter movement and surface winds occurs during the entire period except for the summer months of 1976 when independent of the surface winds the buoy trajectories indicate mesoscale eddy motions with 100 km and 30 day time and space scales respectively drifter liftimes exceeded that of the 9 m diameter parachute drogues set at 30 m depth thus enabling a comparison of the currents derived from the drifter motions at the surface and 30 m these comparisons reveal no systematic difference in the drifter motions with and without drogues these results suggest a rather uniform flow in the upper 30 m during periods of steady winds the estimates of the nature of near surface currents obtained from the drifters differ from those predicted by ekman s classical theory of wind driven flow in that there is no evidence of either a reduction in speed or change in direction of the currents over the upper 30 m

isopycnal eofs in the azores current region a statistical tool fordynamical analysis and data assimilation abstract an empirical orthogonal function analysis of the vertical space time variability of the thermohaline structure of the ocean in summer and fall 1993 in the azores current region has been performed the analysis used data from ctd casts of the semaphore intensive experiment referred to as a seasonally varying climatology the relative merits of depth coordinate and isopycnal coordinate representations have been examined in regard to the quality of identification of physical processes and to the effectiveness of the extrapolation from a sea level anomaly in an attempt to improve the treatment of the vertical dimension in oceanic assimilation problems the isopycnal eofs consistently proved more efficient in capturing the vertical structure of both dominant processes in the area of investigation the variability linked to the mediterranean water and the coherent physical system made up of the azores front and the azores current the isopycnal analysis also proved more robust when meddies mediterra

assessment of physical weathering effects on granitic ancient monuments hamedan iran ancient monuments are significant for the cultural identity of countries and they are also very important from economical point of view there are a lot of environmental damages that affect building materials and monuments therefore the preservation of the monuments has become a vital challenge gradual natural destructive factors including freezing and thawing heating and cooling salt weathering and acidic rainfall play an important role in destruction of monuments in this study for assessment of weathering effects on engineering properties of hamedan granitic monuments heating and cooling up to 600 cycles freezing and thawing up to 300 cycles and salt weathering up to 50 cycles tests have been performed also in order to estimate the deterioration of the ganjnameh inscriptions four inscriptions were prepared and subjected to heating and cooling up to 600 cycles freezing and thawing up to 300 cycles magnesium sulfate salt weathering up to 60 cycles and acidic rain up to 1 year time tests the results showed that when compared with that of salt weathering the effects of heating cooling and freezing thawing weathering were negligible also deterioration effect of magnesium sulfate on weight loss has been observed more remarkably than that of sodium sulfate the deterioration effect of sodium sulfate on loss of engineering properties was evaluated more effectively than that of magnesium sulfate simulation of the ganjnameh inscriptions behavior subjected to the weathering tests indicated that deterioration effect of sulfate solution was more effective than that of other weathering processes

field based experimental determination of the weathering rates of the cappadocian tuffs abstract since the last eruption in the cappadocia region that resulted in the formation of irregular hard thick lava layers on top of the cappadocian tuffs atmospheric processes have preferentially sculptured the tuffs the erosion processes have resulted in some beautiful topographical landscape features the so called fairy chimneys however erosion which is an important factor in the formation of fairy chimneys in the early stages has a negative effect on their future over time the number of visitors to this region has also increased and therefore in addition to natural erosion the effects of localized erosion resulting from tourism at the site have increased in the last few decades the physical mineralogical and mechanical properties of the cappadocian tuffs have been widely investigated in previous studies but their weathering characteristics particularly weathering rate were not determined in these studies determination of the weathering rate of these rocks is mandatory especially for conservation projects which should be urgently applied in order to protect this heritage in this study a comprehensive research program was carried out on the weathering properties of the cappadocian tuffs and the weathering rate was determined in field and laboratory investigations to this purpose a detailed field investigation was performed besides field observations the mineralogical physical and mechanical properties of tuffs were also determined in addition to durability evaluation by the slake durability index test wetting drying and freezing thawing tests were also performed for weathering rate assessment of the cappadocian tuffs in order to account for overburden load on some specific parts of pillars these wetting drying and freezing thawing tests were performed under loads the results obtained from field observations of old man made structures and from laboratory studies show that the weathering rate varies between 0 03 and 0 59 mm year for the esbelli tuff and 0 4 and 2 5 mm year for softer part of the kavak member

currents fronts and eddy fluxes in the canary basin hydrographic data from two cruises in the canary basin meteor 57 july 1981 poseidon 86 april 1982 are analysed with respect to current distribution and lateral heat flux in the azores madeira region the first part of the data base consists of long transects of xbt and g e k measurements between cape finisterre north west spain and the northern canary basin where several year long current meter records exist further information is obtained by thermosalinograph surface data and by expendable current profilers xcp geostrophic currents are derived from xbt profiles using the tight temperature salinity relationship in the depth range of the warmwassersphare the results compare well with the g e k and xcp current observations the second part consists of ctd data from an eddy resolving box shaped ctd survey 500 500 km2 centered at the mooring location 33 n 22 w the observations are supplemented by satellite buoy trajectories horizontal parameter distribution is shown in terms of objectively contoured maps bands of spatially enhanced energetic structures seen in the long transects are further resolved by the box survey as a deep jet like current system cross the canary basin in a west east direction associated with this azores current is a frontal zone with near surface temperature and salinity steps of order 2 k and 0 3 practical salinity units the dynamic topography field can be decomposed into a linear background field a rossby wave and a mesoscale eddy field we find that major contributions to the meridional eddy heat flux are confined to the vicinity of the azores current frontal zone it is shown that the principal balance in the temperature equation is between heating by the mean horizontal advection terms and cooling by the eddy flux divergence

arctic sea ice velocity field general circulation and turbulent like fluctuations 1 using buoy trajectories of the iabp data set we analyze the arctic sea ice velocity field as the superposition of a mean field and fluctuations we study how the mean field can be objectively defined using appropriate spatial and temporal averaging scales depending on the season considered 400 km and 5 months for winter i e approximately all the polar winter duration and 200 km and 2 months for summer i e approximately all the polar summer duration the mean velocity field shows a strong intra annual between winter and the following summer as well as interannual variability the fluctuations i e the remaining part of the velocity field after subtracting the mean field are analyzed in terms of diffusion properties although the arctic sea ice cover is a solid we show that the fluctuations follow the same diffusion regimes as the ones predicted for turbulent flows as observed in geophysical fluids like the ocean or the atmosphere we found that the integral time and the diffusivity of sea ice are in the same ranges as those estimated for the ocean i e 1 5 days in winter and 1 3 days in summer and 0 44 103 m2 s for winter and 0 45 103 m2 s in summer respectively however the statistics of the sea ice fluctuating velocity deviate from classical turbulence theory as they show exponential instead of gaussian distributions sea ice velocity and acceleration are intermittent and both are characterized by a multifractal scaling the oceanic and atmospheric dynamic forcing cannot explain solely the statistical properties of sea ice kinematics and dynamics we argue that sea ice dynamic is significantly influenced by the interplay of multiple fractures that are activated intermittently within the ice pack

the evolution and significance of microfracturing within feldspars in low grade granitic mylonites a case study from the eastern ghats mobile belt india abstract patterns of microfracturing are investigated in plagioclase and k feldspar porphyroclasts formed within granitic mylonites along the boundary of the eastern ghats mobile belt india the mineral assemblage comprising quartz feldspar biotite and hornblende suggests lower greenschist facies conditions during mylonitisation with the contrasting ductile behaviour of quartz and brittle fracturing of feldspars restricting the temperature range during deformation to 300 350 c microfracturing of feldspars takes place by concentration of pure shear within the feldspar rich layers this may reflect strain partitioning into dominantly pure and simple shear due to the competency contrasts between the two major constituent minerals quartz and feldspar the microfractures occur in conjugates here designated t 1 and t 2 with t 1 inclined in the same direction as the s fabric and showing an antithetic sense to the nw verging shear while t 2 is inclined in an opposite sense to the s fabric and displays synthetic shear the direction of maximum compression occurs at high angles to the c fabric and the t 1 and t 2 fractures are the result of pure shear localized into brittle layers within the mylonite with progressive shear the fractures along with their host feldspar grains are rotated theoretical graphs are plotted between bulk shear and the angle of initiation of t 1 and t 2 with respect to c planes for fractures hosted in a circular or elliptical objects the kinematics of these fractures are also analyzed with regard to variations in shear strain and sense of shear along them the sense of shear may vary or remain stable within fractures depending on their initial angle of inclination with respect to the c fabric as t 1 is inclined at low angles to the xy plane and in the same direction as the s fabric it undergoes maximum shear strain compared to t 2 and may even exceed the bulk shear this facilitates breakdown of feldspar porphyroclasts during progressive deformation the t 1 set maintains an antithetic sense of shear even at low angles with the c fabric while t 2 displays a synthetic sense in spite of being at high angles to c the t 1 and t 2 fractures therefore differ significantly from the classic riedel p and y shears where low angle fractures display synthetic shear and high angle ones r show antithetic displacement with respect to the bulk shear sense

micro sheeting of granite and its relationship with landsliding specifically after the heavy rainstorm in june 1999 hiroshima prefecture japan certain types of granite in mountainous areas are microscopically sheeted to a depth of 50 m due to unloading under the stress field that reflects slope morphology micro sheets generally strike parallel to major slope surfaces and gently dip downslope forming cataclinal overdip slopes the cataclinal overdip slope accelerates creep movement of micro sheeted granite which in turn loosens and disintegrates granite via the widening or neoformation of cracks probably in combination with stress release temperature change and changes in water content near the ground surface the surface portion of micro sheeted granite is thus loosened with a well defined basal front which finally slides in response to heavy rain innumerable landslides of this type occurred in hiroshima prefecture western japan following the heavy rainstorm of 29 june 1999 following such landslides the weathering of micro sheeted granite exposed on the landslide scar recommences setting the stage for future landslide

microcracking based rock classification using ultrasonic and porosity parameters and multivariate analysis methods abstract this work aims at presenting a new methodology based on ndt ultrasonic techniques and water porosity measurements to characterize the microcracking state of rocks and classify them in microcracking based equivalent groups the measurements of ultrasonic pulse velocity the attenuation coefficient and the porosity by water saturation under vacuum conditions make it possible to compare and validate all these techniques as good practices to classify aggregates and ornamental stones with regard to their rock matrix compactness beyond the fact that these developments give new approaches to assess the rock microcracking it was shown that these parameters have a direct relationship indeed the classification methodology was applied to a database containing 56 cores coming from blocks sampled in an aggregate production quarry for these cores ultrasonic parameters wave velocity attenuation and anisotropy coefficients and porosity parameters total water crack and pore porosities were measured two multivariate statistical methods principal component analysis and cluster analysis were applied on this database to assess the relationship between all these parameters and to classify the cores into micro structurally similar groups the application of the setup methodology on the core database allows us to study the main correlations between the measured microcracking rock properties on the other hand it was shown that the method can be used as an effective way to characterize the differences in terms of microstructure between rock samples

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

a quasi synoptic survey of the thermocline circulation and water mass distribution within the canary basin shipboard hydrographic measurements and moored current meters are used to infer both the large scale and mesoscale water mass distribution and features of the general circulation in the canary basin we found a convoluted current system dominated by the time dependent meandering of the eastward flowing azores current and the formation of mesoscale eddies at middepths several distinctly different water masses are identified subpolar mode and labrador sea water are centered in the northwest subantarctic intermediate water is centered in the southeast and the saltier warmer mediterranean tongue lies between them mesoscale structures of these water masses suggest the presence of middepth meanders and detached eddies which may be caused by fluctuations of the azores current

observation of the circulation in the newfoundland basin in winter 1997 a hydrographic survey was performed in january february 1997 to document the winter circulation of the north atlantic current system in the newfoundland basin as part of the fronts and atlantic storm tracks experiment fastex eighty seven conductivity temperature depth ctd stations were occupied along a foursection trapezoid which spanned the northwest corner and the branching of the north atlantic current along 358w realistic sea surface temperature analyses were produced every 15 days using all available data collected in this area during the two months of the fastex experiment these maps were combined with sea level anomaly fields from the topex poseidon anders 2 satellites at the same time intervals to analyze the features of the main currents in the area and their evolution these combined analyses providing a coherent overview of the fronts and jets identified along the ship track and the ctd stations are further used to estimate their transports the general pattern is a 15 sv sv 106 m3 s21 transport by the north atlantic current at 478n 438w the existence of a recirculating gyre inside the northwest corner and a complex branching of the circulation associated with significant surface fronts the recirculating gyre forms a closed circulation in which a very deep warm eddy 100 km wide was sampled at the end of february its mixed layer was 800 m deep and its transport was 27 sv along 358w three fronts were identified between 458 and 528n the northern subarctic front the southern subarctic front and the mid atlantic front whose origins are precisely located the currents associated with these fronts transport 26 sv toward the east before crossing the mid atlantic ridge and supplying the eastern part of the north atlantic basin an important transport 14 sv was calculated near 46 8n 378w which mostly fed the current associated with the mid atlantic front

lagrangian observations of the middepth and deep velocity fields of the northeastern atlantic ocean the circulation of the northeastern atlantic ocean at intermediate depths is characterized by watermass transformation processes that involve iceland scotland overflow water isow from the northeast labrador sea water lsw from the west and mediterranean water from the south field observations were carried out with 89 eddy resolving floats rafos and marvor types the data coverage achieved is remarkably high and enables a comprehensive study of the eastern basins between iceland and the azores the trajectories show typical pathways of the water masses involved and the role that the complex bottom topography plays in defining them the isow paths tend to lean against the slopes of the reykjanes ridge and rockall plateau westward escapes through multiple gaps in the ridge are possible superimposed on a sustained southward flow in the eastern basin along the mid atlantic ridge lsw pathways leading to the eastern basins are subject to high variability in flow direction and eddy activity in addition to a selection of characteristic trajectories maps of the horizontal distributions of lagrangian eddy kinetic energy and integral time scales are presented these reveal distinct areas of intensified mixing in the iceland basin as well as the sharp contrast between the subpolar and subtropical dynamics a self contained eddy detection scheme is applied to obtain statistics on individual eddy properties and their abundance it is suggested that much of the intensified mixing can be related to cyclonic activity particularly in the subpolar region

relative contribution of various climatic processes in disintegration of clay bearing rocks abstract the climatic processes of heating and cooling wetting and drying and freezing and thawing affect the disintegration characteristics of clay bearing rocks shales claystones mudstones and siltstones to varying degrees although heating and cooling wetting and drying and freezing and thawing are known to be the main processes responsible for physical disintegration of rocks under natural conditions most of the previous investigators have used methods based only on water content variations e g jar slake slake index and slake durability index tests to assess the disintegration of clay bearing rocks such assessments may not be adequate to explain the field behaviour of clay bearing rocks subjected to a full range of climatic processes in order to evaluate the combined effects as well as relative contributions of various climatic processes on the disintegration behaviour samples of selected clay bearing rocks consisting of 5 6 particles each weighing 85 150 g were subjected to multiple cycles of heating and cooling wetting and drying and freezing and thawing these treatments resulted in fragmentation of samples with fragments ranging from 50 to 2 mm and finer in dimensions a new approach referred to as the disintegration ratio and defined as the area under the grain size distribution curve of the disintegrated material to the total area encompassing all grain size distribution curves of the samples was used to account for fragmentation into varying sizes statistical analyses were performed to investigate the relationship between fragmentation mineralogical composition and physical properties

causes of scaling on bush hammered heritage ashlars a case study plaza mayor of madrid spain masons have traditionally used granite anisotropy to cut and lay the stone scaling a common type of granite decay is observed worldwide this study explored the relationship between weathering and cut planes in heritage ashlars specifically in the stone on madrid s plaza mayor whose construction dates back to 1590 the 71 rectangular granite columns that support its porticoes are oriented towards the four cardinal points all 71 have one exposed side that faces the square one protected side facing inward and two semi protected sides perpendicular to the other two the sides of the columns are also oriented to the points of the compass this study aimed to identify the prevailing orientation of scaling if any in the granite ashlars and to determine how this process is affected by climate microclimate orientation use hewing and exfoliation microcracks all four sides of the 71 columns were mapped 284 in all to analyse scaling height distribution and orientation the findings showed that the microcracks are vertically oriented and decline in density and length with depth from the surface scaling was observed on the lower ashlars in the columns to a maximum depth of 3 mm determining the direction of exfoliation microcracks is imperative to understanding decay mechanisms in granite ashlars and sculptures and that information must be taken into consideration when applying conservation treatments

artificial weathering of spanish granites subjected to salt crystallization tests surface roughness quantification for hundreds of years two types of granite zarzalejo and alpedrete from the madrid region spain have been extensively used as building stones fresh specimens of both stone types have been sampled from their respective quarries and subjected to sodium sulphate salt crystallization test sct the resulting physical and chemical weathering patterns have been characterized by polarized light optical and environmental scanning electron microscopy water absorption under vacuum conditions and mercury intrusion porosimetry techniques were used to determine the pre and post sct porosity and pore size distribution the following non destructive techniques were performed to assess stone durability and decay ultrasound velocity us and surface roughness determination sr of intra and inter granular quartz feldspar and biotite minerals at the centre as well as at the corners and edges of specimen surfaces before the sct us values were lower and sr values higher in zarzalejo zar than alpedrete alp granite after sct the us values declined while sr rose in both types of granites with greater average differences in zar than alp for both parameters feldspar and biotite and their inter granular contacts were found to be the weakest and therefore the most decay prone areas of the stone the initial sr parameters were generally higher and rose more steeply after sct at the corners and around the edges of the specimens while behaviour was found to be similar in the two types of granite variations were greater in zar the less durable and more decay prone of the two surface roughness measurement of mineral grains in granite stones is a very useful in situ non destructive technique for quantifying salt crystallization mediated physical and chemical weathering the resulting quantification of decay and of related durability provides insight into the future behaviour of this type of stone commonly used in historic buildings

weathering of marbles and granites in marine environment petrophysical properties and special role of atmospheric salts the aim of this paper was to study the weathering mechanism of marbles and granites exposed to the marine environment at the delos archaeological site alterations as granular disintegration contour scaling and alveolus formations can be observed either at the base of blocks and columns or at the median high zones of monuments a white marble which originated from naxos island had a weak porosity 0 2 its porous network was organized into two subnetworks of rectilinear and sinuous cracks which limited capillary transfer to 10 cm the granite which originated from delos island had a relatively high porosity 2 15 and had a well connected system of cracks and microporous zones of weathered minerals this homogeneous network allowed good capillary transfer for long distances 1 2 m for the marble as for the granite evaporation occurred mainly at depth in the stone and encouraged its deterioration this damage depends on the dissolution and crystallization of salts which occur in cycles first by the capillary transfer of water and salt from the ground when the stones are located near the sea this processes can explain the deterioration of the marble and the granite bases and the decay of granite on all its surfaces second by fixation of water vapor by sea salt deposited on the stone by wind this phenomenon can explain the degradations observed on the median high parts of monuments in marble and granite even though for the granite the first mechanism was more active

differences in the quality of polishing between sound and weathered granites aesthetic characteristics are important when rocks are used as construction materials among all the surface finishes available the polished finish is the one which best enhances the rock attractiveness colour c roughness r and gloss g are surface properties usually used to assess the rock polishing in this research the crg properties were assessed in polished samples of three ornamental granites with different textures and physical mechanical properties one weathered and two sound c was evaluated in cie l a b and cie l c abhab systems r with ra and rz parameters and g using the 20 60 and 85 geometries the weathered granite presents a noticeable colour variation especially in the b parameter while the sound ones have a more homogeneous colour sound and more textural homogeneous granites have a low surface roughness and high gloss which are uniformly distributed the weathered granite shows a higher surface roughness and lower gloss with scattered distribution the mineral contacts are the main cause of the surface irregularities the results show the interdependence between the crg properties and stress the importance of the polishing process for enhancing the aesthetic characteristics of the granites crg properties could be used for quality control in granite processing plants thus avoiding noticeable differences in the facades of buildings particularly when weathered granites are used

drifting buoy trajectories in the north atlantic current despite intensive research there are still large gaps in our knowledge of the north atlantic current which is considered to be the link between the gulf stream off the east coast of north america and the anomalously warm surface waters off northwestern europe in the classical scheme given in fig 1 which was constructed by dietrich1 on the basis of data obtained during 1957 58 the current is seen to comprise several branches two important difficulties arise from this interpretation first the data for the area east of newfoundland are not sufficient to define the causes of why the branching of the north atlantic current is stationary in its source area over the slope off grand banks2 second rapid surveys of the oceanic temperature structure by means of expendable sondes and increasingly of long term moored instrumentation and satellite tracked drifting buoys3 have revealed that the oceanic current field is dominated by mesoscale eddies and meanders rather than by large scale steady flows we report here two experiments using satellite tracked buoys which address these difficulties our results clarify the pathway of the north atlantic current and confirm that the current indeed consists of mesoscale eddies and meanders

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

thermal fatigue and thermal shock in bedrock an attempt to unravel the geomorphic processes and products widespread acceptance in science at large notwithstanding the ability of thermal stresses to produce thermal fatigue tf and or thermal shock ts in bedrock and coarse debris in the field is often doubted commonly called insolation weathering in geomorphology the results of questionable laboratory experiments have led many geomorphologists to consider terrestrial temperatures to be inadequate to generate thermally induced stresses leading to rock failure the exceptions are the action of fire or lightning we comprehensively survey the general scientific literature on tf and ts while rigorously scrutinizing that relating to geomorphology findings indicate theoretical and experimental information is adequate to establish the feasibility of tf and ts in rock stemming from rock temperatures monitored in the field while ts may exhibit fracture patterns that are uniquely diagnostic those of tf lack any such attributes it would appear unlikely that tf can prepare or weaken rock to increase the likelihood of ts the question of whether widespread polygonal versus rectilinear cracking is diagnostic of ts is presently an open one as possible explanations invoke process es and or host material s and consequently to assign palaeoenvironmental significance to such fracture patterns is premature at this time further geomorphological laboratory research into tf and ts is merited as sufficient theoretical underpinning already exists however laboratory experimentation needs to be much more rigorously defined and executed and is faced with significant hurdles if it is to be effectively linked to field observations

the role of thermal stress fatigue in the breakdown of rock in cold regions abstract many geomorphological studies have ignored the role of thermal stress fatigue engineers have long maintained that thermal stress is an effective process physicists and the ceramics industry have provided a theoretical foundation to explain the nature and mode of operation of thermal breakdown recent geomorphological studies have shown the importance of thermal stress in cold regions by means of high frequency rock temperature data which can identify rates of temperature change in excess of 2 c min 1 the occurrence of weathered material in cold but dry regions can be explained by thermal stress shock differential radiation receipts on slopes of varying orientation and gradient can exert a very strong effect

permanent strain of thermal expansion and thermally induced microcracking in inada granite 1 i made measurements of the permanent strain of thermal expansion compressional wave velocity and density of microcracks of inada granite which was subjected to slow and homogeneous temperature change under atmospheric pressure the permanent strain implying the cumulative amount of newly generated microcracks and the opening of preexisting microcracks appeared distinctly at a temperature between 100 and 125 c and increased almost exponentially in the range from 200 c to immediately before the temperature of transition in quartz 573 c as the peak temperature of the thermal cycle was elevated at 600 c the strain increased further the density of the microcracks was heightened as the peak temperature increased moreover the said trend coincided with that of the crack density parameter estimated from the compressional wave velocity at the same time the maximum width of the microcracks which was determined by microscopic observation and the average width increment of the microcracks calculated from the permanent strain and microcrack density showed a similar trend using the mercury intrusion porosimetry method the average width increment of the microcracks coincided with the equivalent width of the microcracks measured there are two causes of thermally induced microcracking the mismatching of the coefficients of thermal expansion between the adjacent mineral grains and the decrepitation of the fluid inclusions the density of the fluid inclusion microcracks showed a remarkable increase starting from the peak temperature of 300 c at temperatures equal to or higher than 400 c the fluid inclusion microcracks accounted for approximately 35 of all the intragranular cracks

morphology and mineralogy of weathering crusts on highly porous oolitic limestones a case study from budapest black crusts are very common on limestones in polluted urban environments but white crusts are less frequently developed on the soft porous and inherently weak oolitic limestone of budapest both crusts are frequent and indeed white ones are more common on the stone walls of the studied fortress in this paper black and white crusts and the host rock have been described using morphological criteria mineralogical analyses xrd dta elements analyses microprobe and micro morphological sem tests the analyses have shown that on white crusts the surface dissolution is combined with the precipitation of gypsum and calcite in the pores and accumulation of gypsum on the underside of the crust thin white crusts are removed by a combination of salt crystallisation gypsum and frost action while very thick stone layers scale off due to freeze thaw cycles black crusts are enriched in gypsum relative to white crusts gypsum accumulates on the crust surface and signs of dissolution have not been observed airborne particulates flyash silt sized quartz and organic debris adhere to the crust surface of sheltered black crusts these particles are later incorporated into the expanding gypsum crystals that are visible on the underside of the crust the host rock also contains gypsum but it is washed off the surface when the crust is removed further exposure of the host rock may lead to the dissolution of calcite crystals as it is observed by sem the micro environment influences the crust formation and adherence of the crusts on frequently wet and dry surfaces crust removal is more common the crust serves as a protective layer on the stone surface but this protection is temporary since trigger mechanisms such as salt crystallisation or frost action can cause rapid surface loss

surface circulation in the eastern north atlantic from drifters and altimetry a description of the near surface circulation and its properties is the result of the analysis of a drifting buoy data set in the eastern north atlantic between the iberian peninsula the azores and the canary islands world ocean circulation experiment tropical ocean global atmosphere experiment drifters equipped with holey sock drogues centered at 15 m depth collected a total of 14 4 years of data the drifters sampled a rather inhomogeneous velocity field with a weak mean flow regime and eddies of different scales they meandered southward everywhere in the study region except in the iberian coastal transition zone north of 41degreesn where they headed northward the near surface mean velocity field obtained from the drifter data set shows all important mean currents including the poleward portugal coastal countercurrent during the fall winter and early spring off western and northern iberia the southward portugal coastal current the slow offshore southward flow of the portugal current during the whole year the southwestward canary current and the eastward azores current which extends to the vicinity of the african coast near the gulf of cadiz maps of the eddy kinetic energy field were obtained from the drifters and from satellite altimetry it provides the largest part of the total kinetic energy the rate of dispersion is estimated from the lagrangian statistics of the drifting buoys the dispersion of the drifters in the study region is well modeled by a simple description of eddy diffusion assuming homogeneous turbulence ensemble mean diffusivities k and the langrangian integral length scales and timescales l and t were obtained for the zonal and meridional directions the sea surface temperature measured along the drifter trajectories is used to produce estimates of the eddy diffusivity which is compared with the diffusivity estimates obtained from the theory of taylor the eddy diffusivity is found to be approximately proportional to the eddy kinetic energy discrete eddies and meanders were observed using drifters and altimetry in order to map and describe their geographical distribution and characteristics in the eastern north atlantic

near surface circulation in the southern gulf of cadiz abstract we have used several data sets expandable bathythermograph sections buoy trajectories current meter moorings and surface wind stress to investigate the temporal variation of the upper thermocline north atlantic central waters circulation patterns in the southern gulf of cadiz the main data set consists of eight expandable bathythermograph sections two per season running between the strait of gibraltar and cape beddouza just offshore the continental slope and approximately parallel to the morocco coastline a salinity temperature polynomial obtained from historical conductivity temperature depth data is used to infer dynamic properties salinity density dynamic height geostrophic velocity and transport dynamic heights are calculated referred to the 1027 25 kg m 3 neutral density surface which we justify is a good reference level for this section these observations are then combined with a process oriented one layer quasigeostrophic model for the northeastern corner of the north atlantic subtropical gyre with modified eastern boundary conditions the results indicate the existence of about 1 sv onshore transport all year long into a 300 km long coastal transition zone off morocco which must follow south as a narrow current during winter the flow is zonal towards the slope and recirculates south as a very narrow jet of less than 100 km width during summer the flow probably becomes more intense but is deflected southeastward before reaching the slope such that the onshore geostrophic transport into the coastal transition zone decreases and the recirculating band widens

north atlantic ocean surface currents 1 close to 1800 surface drifters are used to investigate the 15 m circulation of the north atlantic ocean the data are used to describe structures of the average eulerian circulation and of the associated eddy variability the data resolve scales on the order of 50 km which have hitherto not been systematically described in particular near shelf breaks and near the most intense currents the gulf stream the north atlantic current nac and the frontal currents of the subpolar gyre this reveals a complex series of quasi permanent eddies meanders and recirculation patterns gulf stream intensity is portrayed as changing abruptly near 54 w east of which it is identified as two current branches centered near 39 and 41 5 n the northern one connecting more directly with the nac and the southern one with the recirculation gyre and the azores current ac many features of the currents are controlled by topography in particular currents are often intensified near shelf breaks or parallel to ridges in the subpolar gyre however the largest northward branch of the nac in the icelandic basin is located near the deepest bathymetry not near steep bathymetry other currents in particular in the subtropical gyre are less clearly related to topography for instance the ac is featured as a zonal eastward current extending far west of the mid atlantic ridge mar to at least 55 w and possibly 63 w in the interior and away from topographic features the eddy kinetic energy eke is the largest where the mean currents are the largest in the subpolar gyre there are striking differences in eke between southward flowing currents the labrador and east greenland current and the northward flowing currents west greenland current and branches of the nac which have higher eke the areas of weakest variability are located in the southwest part of the subpolar gyre northeast of iceland and in the eastern atlantic south of 45 n the ac eddies and the mesoscales south of the canary islands transect this eastern eddy desert drifter trajectories are used as realizations of lagrangian particles in the vicinity of current cores these illustrate the variety of paths or connections between different current systems and demonstrate cross stream dispersions

meandering of the subtropical front south east of the azores a subtropical front was observed in the area south and southeast of the azores during cruises of fs meteor and fs poseidon in early 1982 the front has a basically west east extension with considerable meandering observed meso scale eddies are found on both sides the overall flow pattern corresponds to earlier results on geopotential differences in the upper northeast atlantic but the baroclinic transport of the order of 107 m3 s 1 is found to be concentrated in a 60 km wide jet we suggest here that the current band is part of the gyre circulation resulting from a branching of the north atlantic current

on the persistence of weathering abstract the term weathering has been in use for a very long time but it has come to mean different things to different people and hence as scientific short hand it no longer functions here we question the tenets underpinning the most common usage of the term and note that the climate process linkage implicit to the term is often missing and amounts to misdirection rather than climate as the primary driver behind specific weathering processes it is argued that rock properties constitute the dominant control further a case is made for reconsideration of our present bipartite mechanical chemical division of weathering processes and of the weathering processes currently deemed to be those that occur as process studies become evermore reductionist in nature so the functionality of the term comes more and more into question the linkage between process and landform the scaling up attribute is seen as a current weakness and one that will become more confusing as reductionist approaches continue as a way forward it is suggested that weathering stripped of specific preconceived notions of specific processes be envisaged as a function of energy transfer and be investigated in that light identification of new processes as well as restructuring of known processes particularly when considering weathering on other planets is a potential outcome of such an approach with a process foundation rooted in energy transfer rock decay provides a better umbrella term and liberates researchers from the inescapable conceptual baggage implicit to the term weathering

alteration of plagioclase to nepheline in the khariar alkaline complex se india constraints on metasomatic replacement reaction mechanisms abstract at the khariar alkaline complex in southeastern india some tholeiitic amphibolites inter layered with syenite and nepheline syenite show microtextural evidence of fenitization typical metasomatic textures include the replacement of plagioclase by vein nepheline and albitic plagioclase or by symplectitic nepheline albite na al rich clinopyroxene whole rock mass balance calculations indicate that the fenitized variants gained alkalis na k some large ion lithophile elements sr rb and ba and high field strength elements like zr and hf during the metasomatic exchange the plagioclase replacement textures can be explained by a fluid mediated coupled dissolution reprecipitation process whereby the infiltration of alkali bearing fluid along grain boundaries and deformation induced intragranular fractures led to the dissolution of the host plagioclase along an inward moving reaction interface na ions were introduced and ca 2 ions removed by the fluid phase the al and si released from the breakdown of the anorthite component of the plagioclase combined with na from the fluid to precipitate nepheline albitic plagioclase or na al rich clinopyroxene reaction enhanced cracking during metasomatism due to local volume changes in the alteration zone produced a hierarchical system of fractures mass balance calculations using the volume proportion of phases in the plagioclase replacement zones show that sio 2 and al 2 o 3 were broadly conserved during the replacement there was significant loss of cao ca 73 and huge gains of na 2 o and k 2 o these results indicate that alkali and alkaline elements na k and ca were exchanged freely between the fluid phase and the reaction zone whereas si and al released during plagioclase dissolution were consumed in the replacement zone itself to form nepheline and albite rich plagioclase or na al rich clinopyroxene the trace element and sr nd isotope signature of the rocks indicate that the fenitizing fluids were derived from the nepheline syenites

the fate of coccoliths at 48 n 21 w northeastern atlantic abstract as part of the joint global ocean flux study program jgofs north atlantic bloom experiment nabe coccolithophore fluxes were recorded over one year period from april 1989 to april 1990 three vertically moored sediment traps synchronized on a 14 day interval were deployed at 48 n 21 w at three water depths at 1 2 and 3 7 km sea floor at 4 4 km we present the results on the vertical variability of coccolith and coccosphere fluxes through the water column calcium carbonate was the largest component of the total mass flux followed by particulate organic matter and opal coccolith and coccosphere seasonal fluxes followed the seasonality of the biogeochemical particle fluxes at all three depths with maxima occurring during the spring particle bloom the decrease in correlation between coccosphere and coccolith fluxes with depth from r 0 98 at 1 km depth to 0 60 at 3 7 km depth documents that disaggregation of the coccospheres occurs during settling in the deeper part of the water column between 1 and 3 7 km water depth annual coccosphere and coccolith fluxes were 1 5 108 and 0 9 10 11 m 2 year 1 respectively at 1 km depth or 3 1 108 and 1 4 10 11 m 2 year 1 including the spring 1990 episode for the 3 7 km trap the corresponding values were 0 5 108 and 1 1 1011 0 6 108 and 1 1 1011 including the partially recorded spring 1990 episode the slight increase in coccolith numbers with water depth can be explained by coccosphere disintegration and lateral influx nevertheless selective dissolution of delicate coccolith species from 1 to 3 7 km water depth occurs e g relative abundances of oolithothus fragilis coccoliths decrease from 3 at 1 km to less than 0 5 at 3 7 km water depth emiliania huxleyi gephyrocapsa muellerae calcidiscus leptoporus and coccolithus pelagicus constitute from 65 at 1 km depth to 95 at 3 7 km depth of the total coccolith assemblages the same four coccolith taxa dominate the fossil assemblages in the underlying surface sediments selective dissolution continues in the sediments most notably the abundance of the solution resistant species c leptoporus increases from 10 to 15 in the trap samples to 15 40 in the sediments annual flux of calcium carbonate in sediment trap samples accounts for about 60 of the total annual mass flux with the coccolith fraction m being about 45 of the annual carbonate flux mean value of 41 at 1 km and 50 at 3 7 km water depth the correlation between the m caco 3 and the calculated coccolithophore and calcisphere caco3 fluxes decreases with depth r 0 92 at 1 km and r 0 86 at 3 7 km indicating that partial dissolution and fragmentation of the delicate less calcified coccolithophore and planktic foraminifera species occurs during settling this fine fragmentation of biogenic caco3 can contribute to the m fraction causing the decrease of correlation with the calculated caco3 fluxes being based only on the flux of intact coccoliths and calcispheres

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

mean circulation and eddy kinetic energy in the eastern north atlantic sixty two satellite tracked buoys have been released in the northern part of the western and central north atlantic during 1981 and 1982 by the institut fur meereskunde universitat kiel federal republic of germany additionally six buoys deployed in spring 1980 by the bedford institute have been taken over mean values and variances about the mean have been calculated for 3 by 3 areas the mean velocities confirm the large scale gyre circulation as deduced from hydrographie data and numerical models the center of the gyre is located at about 33 n eddy kinetic energy decreases east and southward and is concentrated along the north atlantic current it appears that the north atlantic current polar front is the main source of eddy kinetic energy for the northern north atlantic whereas the mid atlantic ridge is no source of eddy energy eddy kinetic energy along the north atlantic current decreases from about 1000 cm2 s 2 near newfoundland to 300 cm2 s 2 west of scotland a homogeneous pool of low eddy kinetic energy less than 100 cm2 s 2 appears in the central north atlantic east of the mid atlantic ridge the level increases towards the european and african shelf where the mean southward flow also becomes stronger the results concern the upper ocean

thermal stress induced microcracking in building granite abstract microcracking induced by wide fluctuations in temperature affects granite quality and durability making the stone more vulnerable to decay determining the extent of that effect is not always straightforward however given the excellent durability of these materials four types of construction granite quarried in the region of madrid spain and frequently used in both the built heritage and in de novo construction alpedrete cadalso de los vidrios colmenar viejo and zarzalejo were exposed to 42 thermal cycles 105 20 c une en 14066 2003 petrographic and petrophysical properties were analysed using both destructive and non destructive techniques microcracking generated in the granite stones by 42 thermal cycles had barely any impact on their petrophysical properties which are the parameters normally assessed to establish material quality and durability their petrographic properties which are not generally assessed in this type of studies were affected however this study contends that petrographic analysis is needed to objectively quantify the actual quality and durability of the most highly resistant materials when petrophysical studies are inconclusive petrographic and fluorescence microscopy along with fractography are among the most prominent techniques for petrographic exploration thanks to the deployment of these techniques mineral microcracking could be monitored throughout the present tests conducted the microscopic findings revealed substantial micro textural and microstructural change in and around the granite minerals which play a prominent role in decay the findings showed that pre existing microcracks coalesced and generated further microcracking as decay progressed microcracking was most intense in zarzalejo granite due to its textural characteristics determined by its high feldspar content microscopic observation revealed that the microstructure of feldspar minerals with their crystallographic anisotropies and secondary mineral phases favoured microcrack development zarzalejo granite exhibited lower quality and durability than colmenar viejo and cadalso de los vidrios granites which were more resistant to heat treatment

upper ocean eddy transports of heat potential vorticity and volume in the northeastern north atlantic vivaldi 1991 abstract mesoscale eddies in the northeast north atlantic were investigated using the seasoar towed ctd and adcp data from the 1991 vivaldi cruise these data cover an area of 1700 km 1500 km between 39 and 54 n and between 35 and 10 w to maximize statistical significance but retain the possibility of determining north south gradients statistics of eddy quantities were calculated separately for the northern and southern halves of the cruise area the mean flow in the south is essentially zero in the north the flow is dominated by the north atlantic current nac with a mean speed of 6 5 cm s 1 the eddy kinetic energy in the south 205 cm2 s 2 is however only slightly less than in the north 272 cm2 s 2 the eddy momentum transports or reynolds stresses u show a poleward decrease corresponding to an acceleration of the mean eastward flow associated with the nac of 0 03 cm s 1 day 1 the eddy heat transports u t are not significantly different from zero in the south but show a clear po

modeling postbreakup landscape development and denudational history across the southeast african drakensberg escarpment margin 1 we employ a numerical surface processes model to study the controls on postbreakup landscape development and denudational history of the southeast african margin apatite fission track data presented in the companion paper suggest that the drakensberg escarpment formed by rapid postbreakup river incision seaward of a preexisting drainage divide located close to its present position and subsequently retreated at rates of only 100 m m y 1 numerical modeling results support such a scenario and show that the prebreakup topography of the margin has exerted a fundamental control on subsequent margin evolution the rheology of the lithosphere lithological variations in the eroding upper crust and inland base level falls provided secondary controls a relatively low flexural rigidity of the lithosphere te 10 km is required to explain the observed pattern of denudation as well as the observed geological structure of the southeast african margin lithological variations have contributed to the formation of flat topped ridges buttressing the main escarpment as well as major fluvial knickpoints both these features have previously been interpreted as supporting significant cenozoic uplift of the margin an inland base level fall possibly related to back cutting of the orange river drainage system and occurring 40 50 m y after breakup explains the observed denudation inland of the escarpment as well as the development of inland drainage parallel to the escarpment our model results suggest that in contrast to widely accepted inferences from classical geomorphic studies the southeast african margin has remained tectonically stable since breakup and escarpment retreat has been minimal 25 km

historical position of the north atlantic current the path of the north atlantic current nac within the newfoundland basin is determined from the historical hydrographic database 1910 1988 horizontal probability distributions for dynamical and property front locations on specific volume anomaly surfaces are derived from an analysis of all available hydrographic stations in the basin these probability distributions indicate where the fronts were most likely to have been observed in the past they are observed to exhibit a pattern of stationary meanders with troughs located over the southcast newfoundland rise over the newfoundland seamounts and to the east of the flemish cap the width of the nac s envelope varies from 300 km over the southeast newfoundland rise temporal subsamples of the historical data indicate that the path and meander patterns are persistent features for all seasons and for the four decades between 1950 and 1990

a three dimensional ocean mesoscale simulation using data from the semaphore experiment mixed layer heat budget a primitive equation model is used to simulate the mesoscale circulation associated with a portion of the azores front investigated during the intensive observation period iop of the structure des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore experiment in fall 1993 the model is a mesoscale version of the ocean general circulation model ogcm developed at the laboratoire d oceanographie dynamique et de climatologie lodyc in paris and includes open lateral boundaries a 1 5 level order turbulence closure scheme and fine mesh resolution 0 11 for latitude and 0 09 for longitude the atmospheric forcing is provided by satellite data for the solar and infrared fluxes and by analyzed or reanalyzed for the wind atmospheric data from the european centre for medium range weather forecasts ecmwf forecast model the extended data set collected during the iop of semaphore enables a detailed initialization of the model a coupling with the rest of the basin through time dependent open boundaries and a model data comparison for validation the analysis of model outputs indicates that most features are in good agreement with independent available observations the surface front evolution is subject to an intense deformation different from that of the deep front system which evolves only weakly an estimate of the upper layer heat budget is performed during the 22 days of the integration of the model each term of this budget is analyzed according to various atmospheric events that occurred during the experiment such as the passage of a strong storm this facilitates extended estimates of mixed layer or relevant surface processes beyond those which are obtainable directly from observations surface fluxes represent 54 of the heat loss in the mixed layer and 70 in the top 100 m layer while vertical transport at the mixed layer bottom accounts for 31 and three dimensional processes account for 14

numerical modeling of meander and eddy formation in the azores current frontal zone abstract numerical experiments with an 11 level primitive equation finite difference model in a periodic channel are performed to analyze the properties of unstable finite amplitude disturbances in an idealized azores current release of available potential energy due to baroclinic instability occurs preferentially on scales of about 100 km with a theoretical growth time of 8 days at larger times the combined effect of friction and nonlinear transfer between internal and external depth integrated mode and the distribution of energy among different wavenumbers of the initial disturbance determine the scale of the meandering jet cold water tongues with a meridional scale of several hundred km found in satellite images and hydrographic surveys east of the azores are prescribed as initial disturbances they develop into pairs of troughs and ridges dominated by cyclonic vortices on the poleward flank of the jet phase propagation is downstream at 2 4 km day 1 extremely strong frontogenetic enhancement o

on the reasons for the formation and variability of the azores current abstract recent studies have shown that the formation of the well defined zonally oriented azores current may be the result of water mass transformation associated with the mediterranean outflow in the gulf of cadiz as the denser mediterranean water descends down the continental slope it entrains overlying north atlantic central water it is believed that the azores current then forms as part of the horizontal recirculating gyre generated through the plume mechanism in this study the authors further explore this hypothesis by performing a series of numerical experiments these experiments are based on a high resolution general circulation model that includes the mediterranean sea and that realistically simulates the water mass exchange through the strait of gibraltar and the transport and variability of the azores current the authors show that the divergence of the relative vorticity flux and the planetary vorticity flux associated with planetary waves are the main factors determining the variab

warm water pathways transports and transformations in the northwestern north atlantic and their modification by cold air outbreaks 1 this paper presents a numerical study of the warm water pathways transports and water mass transformation in the newfoundland basin region and an investigation of the rectification effects of a series of cold air outbreaks caos on the above processes an initial mean state simulation was compared with observations and showed good agreement then repeated cao events were explicitly included in the surface fluxes and illustrated the following rectification effects the thermal regime of the entire baroclinic layer was impacted as the thermocline deepened and the temperature anomaly was noticeable down to 500 m different mechanisms were responsible for the propagation of the temperature anomaly at different stages during the onset of the cao vertical diffusion propagated the temperature anomaly downward near the surface then vertical advection further propagated the anomaly downward between cao events to about 500 m depth with caos the north atlantic current carried more warm water and its pathway in the northwest corner shifted towards the southeast the volume averaged mean and eddy kinetic energy increased by 30 and 20 respectively and the water mass transformation rate in the newfoundland basin was doubled the gulf stream carried more heat but heat transport to the eastern basin decreased owing to the increase in heat release to the atmosphere

a seasonal signal in ocean currents to abyssal depths long term 9 32 month current meter records from the eastern north atlantic 41 n 59 n suggest that remote from the influence of the western boundary current eddy kinetic energy ke at all depths is principally a function of wind stress and stratification generated during the winter and early spring propagating to abyssal depths and decaying to a minimum in late summer although this seasonal variation in ke has not previously been described from the midlatitude ocean some theoretical basis for it is presented

coccolithophore export production species composition and coccolith caco3 fluxes in the ne atlantic and abstract coccolithophores were examined in two sediment traps deployed for one year april 1989 to april 1990 at approximately 1 km water depth in the subtropical ne atlantic at 34 n 21 w station nabe 34 and in the temperate ne atlantic 48 n 21 w station nabe 48 as part of the jgofs north atlantic bloom experiment nabe at both stations maximum coccolith and coccosphere fluxes were recorded during local spring bloom periods the average coccolith and coccosphere fluxes at nabe 34 were 1 12 10 9 m 2 d 1 and 4 90 10 6 m 2 d 1 respectively at this station coccoliths from 51 taxa were identified a marked seasonal change was noticed in relative abundances of emiliania huxleyi and deep photic zone species e huxleyi dominated during spring while in late autumn the coccolith assemblage was dominated by florisphaera profunda and the coccosphere assemblage by g flabellatus and algirosphaera spp emiliania huxleyi was the most abundant species in the overall coccolith and coccosphere assemblages with 69 and 64 respectively at nabe 48 the average daily fluxes were significantly lower with 3 88 10 8 coccoliths m 2 d 1 and 8 45 10 5 coccospheres m 2 d 1 and only 36 taxa were recorded in the trap samples emiliania huxleyi was the dominant species in the coccolith assemblage throughout the year with 72 and showed maximum fluxes during spring 1990 coccolithus pelagicus exhibited a distinct seasonal pattern with maximum fluxes in early june 1989 probably related to the development of a mesoscale cyclonic eddy in the vicinity of the trap site holococcolithophore fluxes were highest during maximum sea surface temperatures in summer the coccosphere assemblage was dominated by gephyrocapsa spp syracosphaera spp and e huxleyi estimated caco3 fluxes of coccoliths coccospheres and calcareous dinophytes were compared with the caco3 content in the fine m fraction the annual mass estimated caco3 flux of coccoliths and coccospheres was 5 1 g m 2 yr at nabe 34 and 2 7 g m 2 yr at nabe 48 and that of calcareous dinophytes 0 9 and 0 1 g m 2 yr respectively these summed mass estimated values contributed on average only 55 at nabe 34 and 60 at nabe 48 to the fine fraction caco3

growth of exfoliation joints and near surface stress orientations inferred from fractographic markings observed in the upper aar valley swiss alps abstract granitic rock mass of the upper aar valley grimsel area switzerland contains distinct generations of exfoliation joints which formed during different stages of the pleistocene subparallel to distinct glacial valley palaeotopography the bulk of exfoliation joints shows prominent common fractographic features 1 radial plumose structures with distinct plume axes 2 arrest marks superimposed by plumose striations and 3 gradually developing en echelon fringe cracks multiple arrest marks reveal that exfoliation joints formed incrementally and together with the absence of hackle fringes suggest stable i e subcritical fracturing conditions smooth transitions from plumose structures on the parent plane to en echelon fringe cracks combined with non systematic stepping senses of fringe cracks suggest local vs temporal stress field variations assuming that plume axes formed parallel to the maximum principal compressive stress 1 enables us to infer near surface palaeostress orientations and compare them with classical borehole based in situ stress data the majority of plume axes suggest 1 persistently subhorizontal to slightly inclined 1 orientations at trough valley slopes and 2 near surface variability of 1 orientations originating from topographic perturbation caused by glacial valley erosion superimposed on the regional stress field our investigations of fracture surface morphologies yield unique insights into exfoliation fracture formation such as directional trends of fracture propagation and associated palaeostress orientations within alpine valley slopes

eddy kinetic energy in the north atlantic from surface drifters one hundred ten satellite tracked freely drifting buoys measured velocities and trajectories of the near surface currents in the north atlantic mean velocity values and the velocity variance about the mean were calculated for different regions a horizontal map of eddy kinetic energy was prepared on a 2 2 grid between latitudes 20 and 55 n maximum eddy energy 3000 cm2 s 2 coincides with the high speed gulf stream jet where it begins large amplitude meanders near 37 n 67 w a tongue of high eddy energy coincides with the stream s path eastward and around the grand banks into the newfoundland basin where values of 1000 cm2 s 2 are found a weaker tongue extends eastward across the mid atlantic ridge near 45 n a second weak extension reaches southeastward from the stream and crosses the mid atlantic ridge between 30 and 35 n north and south of the stream eddy energy diminishes rapidly reaching an e folding at 300 km from the axis values of 200 cm2 s 2 were observed in the mid gyre region and 100 cm2 s 2 in the eastern north atlantic and north equatorial current although the gross distribution of eddy energy is similar to that determined from ship drift measurements there are significant differences eddy energy from drifters amounts to about twice the value measured by ship drift in the gulf stream and one half the ship drift values in the mid gyre it is suggested that these differences are due to the horizontal averaging of mesoscale motion and the errors in navigation both of which are problems with the ship drift technique

on the geographical variability of the upper level mean and eddy fields in the north atlantic and north pacific abstract all available historical expendable bathythermograph data are used to compute means and standard deviations in temperature for the upper 500 m in the north atlantic and north pacific to take advantage of marked spatial differences in data coverage a variable grid scheme is employed both surface and subsurface annual mean temperature distributions agree well with published maps of these quantities climatological mean temperature salinity and salinity depth curves are used to infer salinities for the mean temperature profiles in order to compute 0 500 db inferred dynamic height and its standard deviation these mean curves are also used to compute eddy potential energy at 300 m the maps of mean annual inferred dynamic height agree well with traditional dynamic height maps and appear similar to the maps of mean temperature at 400 m the north atlantic eddy potential energy distribution is similar to an earlier calculation maps of the standard deviations in inferred dynamic height also represent

methods for measuring rock surface weathering and erosion a critical review studies of rates processes and modes of rock surface and near surface deterioration and also hardening are central to rock weathering and building stone research conservation and management there is a need to measure and monitor weathering at the rock atmosphere interface to facilitate understanding of climatic environmental and lithological controls on the evolution and development of surface weathering features this paper reviews long established and recently developed field and laboratory methods used by geomorphologists to monitor and measure the impact of weathering and erosion on physical and mechanical properties of exposed rock surfaces and their immediate subsurface key advances are highlighted their application to multi scalar understanding and modelling of rock surface weathering in different contexts is discussed and potential future advances to provide new insights into rock weathering durability and materials conservation are identified in highlighting key advantages and disadvantages of a wide range of methods to the broader earth science community the paper aims to contribute to further innovative thinking across disciplines to develop new methods for measuring and monitoring rock weathering

evidence for exhumation of a granite intrusion in a regional extensional stress regime based on coupled microstructural and fluid inclusion plane studies an example from the velence mts hungary abstract a new approach the fluid inclusion plane technique coupled with fluid inclusion microthermometry and field measurements have been applied to demonstrate the exhumation and relative vertical displacements of an allochthonous permian granite intrusion velence mts which was situated in the middle triassic at the western end of the neotethys rift system the pressure and the temperature conditions during the permian fluid flow 350 c and 2 kbar in the granite were considerably higher than during the triassic fluid flow it is suggested that the exhumation of the velence mts along with the regional fluid flow can be connected to the passive pre rift phase of the northern adriatic block during the middle late triassic the variations in homogenization temperatures of triassic regional fluid inclusion assemblages between the blocks of the granite as well as variations in the fluid inclusion plane orientations suggest a post triassic vertical segmentation and relative block rotation of the granite

the influence of the characteristics of quartz and mineral deterioration on the strength of granitic dimensional stones it is important to have a thorough knowledge of the petrographic characteristics of rocks to evaluate and understand their mechanical behavior this paper deals with the influence of the texture and the mineral characteristics of nine portuguese granites employed as dimensional stones this study evaluates different mineral characteristics such as mineral deterioration grain size quartz fissuration and the contacts between quartz and others mineral groups the main differences in the studied granites were identified clarifying the relationship between the petrographic characteristics the consequences on their respective mechanical behavior were subsequently evaluated the physical and textural characteristics of quartz in the studied granites have proven to be very important for understanding the behavior of granitic rocks under compressive stress uniaxial compressive strength values are not proportional to the quartz feldspar ratio or quartz content and there is a tendency for strength to decrease with the increase in quartz this could be related to the increase in quartz quartz contacts and the decrease in the rock capacity for accommodating the deformation