slump folds and gravity slide structures in a lower palaeozoic marginal basin sequence the skiddaw group nw england major folds with associated thrust faults and a major olistostrome are described from the skiddaw group a lower ordovician turbidite sequence in the lake district of nw england the style and geometry of the structures are shown to be compatible with their generation as submarine slumps or slide masses although they are much larger than any slump structures hitherto described from britain the predominant strain is shown to be simple shear spatial and temporal variations in strain permit a developmental model to be erected the opposing vergence of the structures across the mapped area indicates a relatively narrow probably fault controlled depositional basin

underlying issues on the selection use and conservation of building limestone an argument is presented that despite popular assumptions many limestones especially the wide range of clastic and in general granular limestones do not decay in a steady and predictable pattern in response to slow dissolution instead these stones especially when used in construction in polluted environments invariably decay episodically through physical breakdown most commonly this is accomplished through a variety of salt weathering mechanisms that if unconstrained can lead to the rapid catastrophic decay of building blocks and their complete loss a process that has driven the extensive programmes of stone replacement that are typical of buildings constructed of these stones in polluted environments especially those rich in sulphur and particulates the most common constraint on accelerated decay has been the rapid development of gypsum crusts that for example could rapidly heal the scars left by contour scaling it is ironic therefore that any reduction in pollution could conceivably lead to increased erosion by retarding this healing process because of this temporal variability of decay and its translation into spatial complexity it is important that further research is undertaken to understand controls on the decay of these important building stones so that future conservation strategies can be appropriately informed on the predictability of decay and the role

preliminary observations on the impact of complex stress histories on sandstone response to salt weathering laboratory simulations of process combinations historic sandstone structures carry an inheritance or a memory of past stresses that the stone has undergone since its placement in a facade this inheritance which conditions present day performance may be made up of long term exposure to a combination of low magnitude background environmental factors for example salt weathering temperature and moisture cycling and superimposed upon these less frequent but potentially high magnitude events or exceptional factors for example lime rendering severe frost events fire the impact of complex histories on the decay pathways of historic sandstone is not clearly understood but this paper seeks to improve that understanding through the use of a laboratory process combination study blocks of quartz sandstone peakmoor from nw england were divided into subsets that experienced different histories lime rendering and removal fire and freeze thaw cycles in isolation and combination that reflected the event timeline of a real medieval sandstone monument in ne ireland bonamargy friary mccabe et al 2006b these subsets were then subject to salt weathering cycles using a 10 salt solution of nacl and mgso4 that represents the every day stress environment of for example sandstone structures in coastal or polluted urban location block response to salt weathering was monitored by collecting drying and weighing the debris that was released as blocks were immersed in the salt solution at the beginning of each cycle the results illustrate the complexity of the stone decay system showing that seemingly small variations in stress history can produce divergent response to salt weathering cycles applied to real world historic sandstone structures this concept may help to explain the spatial and temporal variability of sandstone response to background environmental factors on a single facade and encourage conservators to include the role of stress inheritance when selecting and implementing conservation strategies

weathering effects in an urban environment a case study of tuffeau a french porous limestone abstract a case study is carried out on a highly porous limestone called tuffeau located in an urban environment weathering effects are characterized by several complementary techniques mechanical resistance compressive test imbibition capillarity test mercury intrusion porosimetry chemical analysis inductively coupled plasma optical emission spectrometer icp oes scanning electron microscope sem image analysis and x ray diffraction xrd the results show the different composition of the deteriorated zone of the stone and mainly the presence of high gypsum content in the black crust surface the analysis also shows that the natural penetration of water into this stone under environmental conditions atmospheric precipitation relative humidity and temperature is limited to 20 mm moreover the presence of gypsum is only detected in this limited zone which demonstrates the depth of alteration in this stone finally this study clearly highlights the important role of water movements in the deterioration of stone

an experimental study on the influence of surface finishing on the weathering of a building low porous limestone in coastal environments limestones used as building material are especially prone to weathering in coastal environments due to interactions between sea mist and the carbonate stone subtle variations of the commercial surface finishing may lead to differences in decay patterns and aesthetic properties due to salt crystallization to explore this potentially contrasting behavior tablets of rough and polished low porous limestone were aged in a sea salt spray corrosion chamber to simulate their exposure in a coastal environment different crystallization morphologies and relative proportions of soluble halite and less soluble gypsum salts were observed in the aged rough and polished surface samples these morphologies are ascribed to the microtextural characteristics and the surface pore systems of the diverse rough and polished substrates that in turn influence fluid saline solution transport toward their interior as well as the different salt solubilities interacting with the substrates polished surfaces exhibit little evidence of damage after the ageing test in contrast to the rough samples but do have conspicuous gypsum on the surface together with halite the scarcity of gypsum on the rough surfaces in addition to a more severe change in the porosity system suggests that salts penetrate deeper when the stone surface is not polished potential decay induced by salt crystallization pressure is therefore minimized when the stone surface is polished however polished surfaces show more significant changes in luminosity and chroma after the ageing test and so are less attractive from an aesthetic point of view surface finishing is thus an important feature that needs to be characterized for a better understanding of the weathering behavior of building stones used in coastal environments

depth profile investigations of surface modifications of limestone artifacts by laser induced breakdown spectroscopy the study of the degradation mechanisms of materials constituting historical buildings is very relevant in the context of cultural heritage preservation in this work a limestone sample collected from the masonry blocks of the entrance gate of historic castello svevo bari italy was subjected to depth profile elemental analysis of the ablated black crust and the underlying limestone by double pulse laser induced breakdown spectroscopy the specific elemental components were identified and their concentrations along the sample profile analyzed so allowing to identify the boundary between the weathered and unaltered rock the laser induced plasma stability i e the absence of parameter changes during ablation was verified to be constant and not to affect the elemental peak sizes during the entire depth analysis process when the plasma is confined in the ablation crater

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

building stones used in the architectural heritage of morelia mexico quarries location rock durability and stone compatibility in the monument four different rocks have been used in the architectural heritage of morelia city michoacan state mexico piedra vieja pv is the original building rock whilst tlalpujahua cointzio and jabalina stones tl co and ja respectively are the replacement varieties used in the restoration works during the last decades all of them correspond to rhyolitic ignimbrites quarried close to morelia the new varieties were selected exclusively after aesthetical similarity and no petrophysical criterion was considered in this paper a deep analysis of the weathering process of these rocks during wet dry and salt crystallization cycles is carried out rock decay is defined in terms of linearity and homogeneity ja and tl show nonlinear decay mode and heterogeneous behaviours whilst samples of co and pv weather after linear and homogeneous modes moreover each rock variety shows different decay patterns such as differential erosion pv and tl fractures tl scaling ja and granular disintegration co all these obtained results are discussed according to 1 petrographic factors 2 hydric and mechanical properties and 3 the partial effective pressures reached inside the porous system of each rock during salt crystallization finally a review about the quality of previously published durability estimators is carried out in general terms results reveal that theoretical estimators best fit the visual weathering suffered by the rocks than its mass loss concluding this paper a petrophysical and aesthetical evaluation of the compatibility between both original and replacement building stones used in the architectural heritage of morelia is carried out in order to offer technical recommendations for future restoration works co ignimbrite offers the highest chromatic compatibility with the original building rock pv but its durability is extraordinarily low and consequently its use is not recommended ja and tl are advisable replacement stones although from a petrophysical point of view tl results the most convenient these results highlight the importance of carrying out the selection of building stones for restoration works according to petrophysical criteria instead of using exclusively an aesthetic valuation

low grade metamorphism of the manx group isle of man a comparative study of white mica crystallinity techniques studies have been made in two laboratories on metapelites from the manx group isle of man showing the distribution of white mica crystallinity using the kubler index 2 and the weber index hb rel two isocryst maps which show broadly similar distributions of metamorphic grade are illustrated and a correlation between the laboratories is presented the mineralogy of the fraction in relation to crystallinity has been determined the distribution of metamorphic grade over central and eastern parts of the isle of man as depicted by the kubler index isocryst map is related to subjacent granite plutons but these contact metamorphic effects overprint an earlier largely anchizonal regional metamorphism localized late retrograde effects are related to low temperature hydrothermal mineralization and to cold re working in a large fault zone differences between the maps are largely in the degrees of resolution which stem directly from the different sampling intervals employed comparisons between the maps suggest a sampling interval of 1 2 km is adequate in regions of simpler geology but that an interval of the changes in the mineralogy of the

the occurrence of gypsum in the scaling of stones at the castle of chambord france the main cause of degradation in tuffeau a soft siliceous and clayey limestone extensively used in the construction of the castles of the loire valley in france is scaling the most damaging form of weathering is spalling over time a plaque several centimetres in thickness gradually forms under the stone surface and eventually falls away leaving the resulting new surface powdered hypotheses regarding the initiation and development of such degradation have not yet met scientific consensus the objective of the present paper is to improve existing knowledge of scaling degradation by analysing in situ samples representing different stages of the same degradation process the analysis of the stones at the castle of chambord revealed the presence of gypsum caso4 2h2o mainly located in cracks parallel to the stone surface this gypsum was then studied in terms of its crystal morphology and distribution with depth for comparison purposes another form of scaling identified at the castle of chambord but rarely studied flaking was also examined a first attempt at explaining the origin and formation of the observed gypsum in both scaling processes was conducted by interacting and comparing the characterisation results with historical and environmental data

lichen hotspots raised rock temperatures beneath verrucaria nigrescens on limestone abstract field exposure trials and laboratory experiments are integrated to compare surface and internal temperature changes of limestone with an epilithic verrucaria nigrescens and endolithic verrucaria baldensis covering of lichens and with no lichen cover control blocks with covering of v nigrescens experience both the highest surface and internal temperatures under a direct heating source during daytime and in laboratory experiments spectrophotometer data suggest that the black colour of the v nigrescens thallus plays a significant role in determining the thermal response of the rock surface when direct heating by sun or lamp is absent at nighttime and for a diurnal cycle programmed in an environmental chamber little differentiation occurs between surface and internal temperatures for all surface types compared for all blocks exposed maximum rates of daytime surface temperature change ranged from 1 47 to 3 04 c min 1 and for two of the exposure periods the highest rates of daytime surface temperature change were experienced by blocks with v nigrescens cover the blocks with v nigrescens cover also experience the greatest thermal gradients in both field and laboratory experiments the rates of surface temperature change and thermal gradients experienced beneath v nigrescens in this study could be significant in increasing rock susceptibility to breakdown

seasonal ice speed variations in 10 marine terminating outlet glaciers along the coast of prudhoe land northwestern greenland we present a 3 year record of seasonal variations in ice speed and frontal ablation of 10 marine terminating outlet glaciers along the coast of prudhoe land in northwestern greenland the glaciers showed seasonal speedup initiated between late may and early june and terminated between late june and early july ice speed subsequently decreased from july to september the timing of the speedup coincided with the onset of the air temperature rise to above freezing suggesting an influence of meltwater availability on the glacier dynamics no clear relationship was found between the speedup and the terminus position or the sea ice ice melange conditions these results suggest that the meltwater input to the glacier bed triggered the summer speedup the excess of summer speed june august over the mean for the rest of the year accounted for 0 5 13 of the annual ice motion several glaciers showed seasonal frontal variations i e retreat in summer and advance in winter this was not due to ice speed variations but was driven by seasonal variations in frontal ablation the results demonstrate the dominant effect of glacier surface melting on the seasonal speedup and the importance of seasonal speed patterns on longer term ice motion of marine terminating outlet glaciers in greenland