stable chlorine isotopes in the palo duro basin texas evidence for preservation of permian evaporite brines experimental evaporation of seawater yields brines with 37cl from 0 0 initial to 0 9 in the palo duro basin brines with 37cl values overlapping the 0 1 to 0 4 range of halite evaporite can be generated by a set of processes including dissolution of halite in meteoric water such brines occur above and below an evaporite aquitard brines with 37cl values of 0 4 to 1 0 in the evaporite aquitard and in a deep brine aquifer cannot be generated by dissolution of halite considered with br and cl content d and noble gas content the 37cl data indicate that such brines originated as evapoconcentrated seawater high br evaporite brine formed directly from seawater on the eastern side of the basin whereas low br evaporite brines on the western side formed after an influx of meteoric water at the time of evaporite formation there has not been detectable vertical flow of meteoric water across the evaporite aquitard strata beneath the evaporite contain compartments that have been isolated geochemically since the permian

the nature and pattern of debris liberation by salt weathering a laboratory study a laboratory simulation of salt weathering was used to ascertain the effects of sodium sulphate and sodium carbonate under negev conditions using a single immersion technique three main points were addressed what are the grain size and textural characteristics of the debris liberated from limestones and a sandstone what do scanning electron microscope observations of the weathered samples tell us about the decay processes involved and how does the rate of debris liberation change during the course of 100 cycles the grain size characteristics of the liberated debris tended to be multimodal and were related to the original petrological characteristics of the rock large amounts of fines were produced which are believed to be analogous to the rock flour of arid areas blistering was also observed scanning electron microscope analysis revealed differences in the style of attack for different rock types and salt treatments and revealed the pattern of salt crystallization in pores and the nature of cracking the rate of debris liberation tended to decline or remain constant through time the reasons for this remain obscure but it is evident that diurnal cycles of temperature and humidity change can cause continuing rock weathering long after the initial input of salt to the rock has taken place

honeycomb development on alexander island glacial history of george vi sound and palaeoclimatic implications two step cliffs mars oasis w antarctica abstract analysis of three generations of glacial deposits and of a range of geomorphic features including widespread honeycombs and tafonis at two step cliffs mars oasis 71 52 s 68 15 w provides new insights into the geomorphological evolution of west antarctica with special respect to alveolar weathering at two step terrace indicators of the inherited character of cavernous weathering were found such as 97 non flaking and varnished backwalls and 80 tafoni floors that are till covered and or sealed by lithobiontic coatings based on the ne predominant aspect of the alveolized boulder faces tafoni initiation is attributed to coastal salt spray weathering by halite coming from the george vi sound during the 6 5 ka bp open water period the present day activity of these inherited cavities is restricted to roof flaking attributed to a combination of processes involving thermal stresses this 6 5 ka bp phase of coastal alveolization is the first step of a six stage holocene geomorphological scenario that includes alternatively phases of glacial advance or stationing and phases of vegetal colonization and or rock weathering and aeolian abrasion on the deglaciated outcrops this geomorphic scenario is tentatively correlated with the available palaeoenvironmental record in the antarctic peninsula region with two potential geomorphic indicators of the holocene optimum being identified 1 clusters of centimetric honeycombs facing the sound marine optimum at 6 5 ka bp 2 salmon pink lithobiontic coatings preserved inside cavities and at the boulder surface terrestrial optimum at 4 3 ka bp

atmospheric gas in modern and ancient halite fluid inclusions a screening protocol abstract halite possesses great potential for hosting and storing information vital to the reconstruction of earth s ancient climate seawater chemistry and evolving atmosphere here we propose a screening protocol that not only distinguishes between primary and secondary halite but also identifies fluid inclusions that carry original gas trapped during the primary crystallization process an integrated multi analytical protocol is presented for sample preparation petrographic evaluation analytical measurements and distinguishing original gases and contents from contaminants the screening protocol starts with the visual inspection of halite for primary chevron and hopper features and or milky appearance then petrography is used to distinguish between primary and secondary diagenetic crystal fabrics and inclusions the trace element and isotope geochemistry speak directly to the composition of the depositional and or diagenetic fluids and to the formation in marine non marine or diagenetic settings furthermore rare earth elements and redox sensitive elements may address the redox conditions of the salt pan flat brines whereas microthermometry helps characterize the depositional diagenetic environment s temperature finally gas extracted by quadrupole mass spectrometer from gas bubbles in fluid inclusions is screened with concomitant ch4 co2 and ar contents to distinguish and quantify organic matter decomposition contributions and with 40ar 36ar to monitor modern atmospheric gas diffusion leakage issues and thus contamination of the primary gas contents our test case shows that halite collected from cores is well suited in maintaining its original mineralogical texture chemistry and gas content our integrated screening protocol suggests that the 815 myr old halite from the tonian browne formation of the officer basin australia formed under atmospheric conditions of about 10 9 po2 back calculation or 9 6 po2 mean calculation the coeval neoproterozoic gypsum collected in outcrop from minto inlet victoria island canada underwent some mineralogical alteration however experiments suggest that depositional gypsum from outcrop core may have potential of retaining vestiges of original gas in fluid inclusions

the major ion composition of permian seawater abstract the major ion mg2 ca2 na k so42 and cl composition of permian seawater was determined from chemical analyses of fluid inclusions in marine halites new data from the upper permian san andres formation of texas 274 272 ma and salado formation of new mexico 251 ma analyzed by the environmental scanning electron microscopy esem x ray energy dispersive spectrometry eds method along with published chemical compositions of fluid inclusions in permian marine halites from north america two formations of different ages and the central and eastern european basins eight formations of four different ages show that permian seawater shares chemical characteristics with modern seawater including so42 ca2 at the point of gypsum precipitation evolution into mg2 na k so42 cl brines and mg2 k ratios 5 permian seawater however is slightly depleted in so42 and enriched in ca2 although modeling results do not rule out ca2 concentrations close to those in present day seawater na and mg2 in permian seawater are close to slightly below their concentrations in modern seawater permian and modern seawater are both classified as aragonite seas with mg2 ca2 ratios 2 conditions favorable for precipitation of aragonite and magnesian calcite as ooids and cements the chemistry of permian seawater was modeled using the chemical composition of brine inclusions for three periods lower permian asselian sakmarian 296 283 ma lower permian artinskian kungurian 283 274 ma and upper permian tatarian 258 251 ma parallel changes in the chemistry of brine inclusions from equivalent age evaporites in north america central europe and eastern europe show that seawater underwent secular variations in chemistry over the 50 million years of the permian modeled so42 concentrations are 20 mmol per kg h2o mmolal and 19 mmolal in the asselian sakmarian and artinskian kungurian with higher concentrations in the upper permian tatarian 23 mmolal modeled ca2 is at or above its concentration in modern seawater throughout the permian mg2 is close to slightly below its concentration in modern seawater 55 mmolal in the asselian sakmarian 52 mmolal and tatarian 52 mmolal but slightly higher than modern seawater in the artinskian kungurian 60 mmolal mg2 ca2 ratios are 3 5 total range 2 7 to 5 5 in the lower permian and rose slightly to 3 7 total range 3 1 to 5 8 in the upper permian primarily due to decreases in ca2 these results are consistent with models that predict oscillations in the major ion composition of phanerozoic seawater on the basis of changes in the midocean ridge river water flux ratio driven by changes in the rate of midocean ridge crust production the permian was characterized by low sea levels icehouse conditions and southern hemisphere glaciation such conditions analogous to the present ice age and the similarities between permian seawater and modern seawater all suggest that general phanerozoic supercycles driven by mantle convection and global volcanicity also control the major ion chemistry of seawater

variability in sulfur isotope records of phanerozoic seawater sulfate the s of seawater sulfate reflects processes operating at the nexus of sulfur carbon and oxygen cycles however knowledge of past seawater sulfate s values must be derived from proxy materials that are impacted differently by depositional and post depositional processes we produced new timeseries estimates for the s value of seawater sulfate by combining 6710 published data from three sedimentary archives marine barite evaporites and carbonate associated sulfate with updated age constraints on the deposits robust features in multiple records capture temporal trends in the s value of seawater and its interplay with other phanerozoic geochemical and stratigraphic trends however high frequency discordances indicate that each record is differentially prone to depositional biases and diagenetic overprints the amount of noise quantified from the variograms of each record increases with age for all s proxies indicating that post depositional processes obscure detailed knowledge of seawater sulfate s s value deeper in time

geochemistry of formation waters from the wolfcamp and cline shales insights into brine origin reservoir connectivity and fluid flow in the permian basin usa abstract despite being one of the most important oil producing provinces in the united states information on basinal hydrogeology and fluid flow in the permian basin of texas and new mexico is lacking the source and geochemistry of brines from the basin were investigated ordovician to guadalupian age reservoirs by combining previously published data from conventional reservoirs with geochemical results for 39 new produced water samples with a focus on those from shales salinity of the ca cl type brines in the basin generally increases with depth reaching a maximum in devonian median 154 g l reservoirs followed by decreases in salinity in the silurian median 77 g l and ordovician median 70 g l reservoirs isotopic data for b o h and sr and ion chemistry indicate three major types of water lower salinity fluids 100 g l isotopically heavy o and h water in leonardian permian to pennsylvanian reservoirs 2 3 2 km depth is evaporated late permian seawater water from the permian wolfcamp and pennsylvanian cline shales which are isotopically similar but lower in salinity and enriched in alkalis appear to have developed their composition due to post illitization diffusion into the shales samples from the cline shale are further enriched with nh 4 br i and isotopically light b sourced from the breakdown of marine kerogen in the unit lower salinity waters 3 km depth which plot near the modern local meteoric water line are distinct from the water in overlying reservoirs we propose that these deep meteoric waters are part of a newly identified hydrogeologic unit the deep basin meteoric aquifer system chemical isotopic and pressure data suggest that despite over pressuring in the wolfcamp shale there is little potential for vertical fluid migration to the surface environment via natural conduits

linking lacustrine cycles with syn sedimentary tectonic episodes an example from the codo formation late aptian northeastern brazil the codo formation exposed in the eastern grajau basin northeastern brazil consists mostly of black shales limestones and evaporites arranged into several shallowing upward cycles formed by progradation of lake deposits three ranks of cycles are distinguished the lower rank cycles correspond to millimetric interbeddings of bituminous black shales with evaporites calcimud stones or peloidal wackestone packstone grey green shale with calcimudstone peloidal wackestone packstone or ostracodal wackestone grainstone and ostracodal wackestone grainstone and or calcimudstones with cryptomicrobial mats and ooidal pisoidal packstones the intermediate rank cycles average 1 7 m in thickness and are formed by complete and incomplete cycles complete cycles show a transition from central to intermediate and then to marginal facies associations and include two types c1 cycle with central lake deposits consisting of evaporites and black shales and c2 cycle with central lake deposits formed by grey green shale complete cycles were produced by the upward gradation from central to marginal environments of the lake or saline pan sabkha system incomplete cycles are those where at least one facies association is lacking having been formed by successions either with central and intermediate facies associations i1 or intermediate and marginal facies associations i2 the higher rank cycles are on average 5 2 m thick and consist of four depositional units that display shallowing upward successions formed by complete and incomplete intermediate rank cycles that vary their distribution upward in the section and are bounded by sharp surfaces while the lower rank cycles display characteristics that reveal their seasonal signature detailed sedimentological characterization and understanding of stratal stacking patterns related to the intermediate and higher rank cycles support a genesis linked to syn sedimentary tectonic activity this is particularly suggested by the high facies variability limited lateral extension and frequent and random thickness changes of the intermediate rank cycles additionally the four higher rank cycles recognized in the codo formation match with stratigraphic zones having different styles of soft sediment deformation structures attributed to seismic activities therefore the several episodes of lake shallowing recorded in the codo formation are linked to seismic pulses that alternated with sediment deposition this process would have created significant changes in the lake water level and resulted in sharply bounded successions with upward gradation from deeper to relatively shallower facies associations

cavernous weathering in the capitol reef desert utah tafoni and honeycomb weathering are abundant in sandstones at capitol reef national park cavities are particularly common in talus blocks resting on alkali rich soil in vertical walls of desert washes and in sandstones containing calcareous cement chemical analyses x ray diffraction data and field observations suggest that salt weathering is the most important cause of disintegration but dissolution of calcite cement also occurs in calcareous sandstones cavernous weathering at capitol reef produces cavities similar in appearance to features found in arkose outcrops along the coast of northwest washington even though the environmental conditions at these two locations are very different

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

dolomite in permian paleosols of the bravo dome co2 field u s a permian reflux followed by late recrystallization at elevated temperature abstract lower permian abo tubb subsurface strata of northeastern new mexico u s a consist of 30 to 120 m of fluvial and eolian deposits containing numerous dolomitic paleosols dolomite in the abo tubb interval occurs in discrete intervals interpreted as paleosols on the basis of recognizable horizonation and the presence of associated features such as ped structures and rhizoliths the dolomite commonly forms veins rhizoliths and discrete and coalesced nodules petrographic analysis indicates four dolomite types present in paleosol horizons microsparitic pseudospherulitic clear cement and cloudy inclusion rich cement microsparitic dolomite constitutes most of 70 the dolomite and is stoichiometric with relatively low sr and na and elevated fe and mn pseudospherulitic dolomite forms 15 of the dolomite and consists of stoichiometric microspar and spar with abundant fluid inclusions low sr na and fe and elevated mn clear dolomite cement constitutes approximately 12 of the dolomite and is finely to coarsely crystalline with a relatively calcian composition low sr and na and elevated fe and mn the cloudy cement forms a minor 2 phase of very coarsely crystalline rhombs with a calcian composition low sr and na values and relatively high fe and mn all dolomite types exhibit a mottled texture of moderate to bright orange and red luminescence fluid inclusion analysis was not possible on the most common microsparitic dolomite type but analyses on the coarser varieties reveal homogenization temperatures typically ranging from 70 c to 110 c and final melting temperatures of ice ranging from 20 c to 34 c suggesting fluids of high 25 by weight salinity bulk rock carbon and oxygen isotopes of carbonate nodules and rhizoconcretions from four paleosol profiles most commonly exhibit mean values typically ranging between 3 to 5 5 vpdb and 0 5 to 2 8 vpdb respectively sulfur isotopes were analyzed for the overlying cimarron anhydrite interval and an anhydrite nodule near the base of the study interval both samples yielded similar results suggesting that brines that precipitated the cimarron anhydrite also influenced the study interval the dolomite in the abo tubb interval is interpreted to have precipitated in multiple stages solid calcite microinclusions in microsparitic and pseudospherulitic dolomite suggest that pedogenensis and groundwater penecontemporaneous with early permian deposition led to precipitation of calcite rather than dolomite oxygen and sulfur isotope data indicate dolomitization from later reflux of brines associated with deposition of the overlying leonardian cimarron anhydrite petrographic relations and elevated temperatures and salinities recorded by the fluid inclusions in the coarse dolomite are consistent with recrystallization of the earlier dolomite and precipitation of dolomite cement from warm saline fluids of a possible tertiary hydrothermal origin just predating migration of mantle derived gas into the bravo dome reservoir these findings offer insight into questions about the climate significance of dolomite in paleosols origin of dolomite in hydrothermally altered hydrocarbon reservoirs and the long term effect of co2 sequestration in saline aquifers the results show that dolomitic nodules in paleosols may form as replacements of paleosol calcite long after the paleosol formed primary pedogenic dolomite would undoubtedly have climatic and paleoenvironmental significance but recognizing it as forming during soil formation as opposed to later dolomitization is key in establishing that significance also this study provides an example of high temperature recrystallization of low temperature dolomite a process hotly debated in discussions of dolomitized hydrocarbon reservoirs with evidence for hydrothermal fluid flow finally as a natural co2 reservoir the bravo dome system shows that the long term result of dissolution of co2 into brines is predominantly carbonate mineral dissolution

the origin of honeycomb weathering honeycomb weathering occurs throughout the world but the origin remains a matter of controversy wind erosion exfoliation frost shattering and salt weathering have been proposed as explanations although few attempts have been made to substantiate these hypotheses with chemical or mineralogical studies chemical analyses and field observations indicate that honeycomb weathering in coastal exposures of arkosic sandstone near bellingham washington results from evaporation of salt water deposited by wave splash microscopic examination of weathered surfaces show that erosion results from disaggregation of mineral grains rather than from chemical decomposition thin walls separating adjacent cavities seem to be due to protective effects of organic coatings produced by microscopic algae inhabiting the rock surface cavity walls are not reinforced by precipitation of elements released by weathering as has often been suggested at other locations honeycomb weathering develops rapidly and can be observed on surfaces that were planar less than a century ago

cavernous weathering dynamical instability and self organization cavernous weathering may be conceptualized as a self reinforcing process characterized by positive feedback within the weathering system a morphometric study of caverns in the valley of fire state park nevada usa demonstrates the applicability of a dynamically unstable or conditionally unstable model of cavernous weathering systems outcrop surfaces displaying caverns tend to show increasing fragmentation of the surface in the early stages of cavernous weathering succeeded by convergent evolution of the surface in which caverns tend to grow and coalesce a paradoxical relationship exists between the weathering system output at the scale of individual forms and the outcrop scale caverns tend toward minimum interior surface area by developing a spheroidal form yet the outcrop surface tends toward maximum exposed surface area by increasing the degree of fragmentation of the surface copyright 2004 john wiley sons ltd

strontium isotopic signatures of oil field waters applications for reservoir characterization the 87sr 86sr compositions of formation waters that were collected from 71 wells producing from a pennsylvanian carbonate reservoir in new mexico display a well defined distribution with radiogenic waters up to 0 710129 at the updip western part of the reservoir grading downdip to less radiogenic waters as low as 0 708903 to the east salinity 2800 50 000 mg l displays a parallel trend saline waters to the west pass downdip to brackish waters elemental and isotopic data indicate that the waters originated as meteoric precipitation and acquired their salinity and radiogenic 87sr through dissolution of upper permian evaporites these meteoric derived waters descended perhaps along deeply penetrating faults driven by gravity and density to depths of more than 7000 ft 2100 m the 87sr 86sr and salinity trends record influx of these waters along the western field margin and downdip flow across the field consistent with the strong water drive potentiometric gradient and tilted gas oil water contacts the formation water 87sr 86sr composition can be useful to evaluate subsurface flow and reservoir behavior especially in immature fields with scarce pressure and production data in mature reservoirs sr isotopes can be used to differentiate original formation water from injected water for waterflood surveillance strontium isotopes thus provide a valuable tool for both static and dynamic reservoir characterization in conjunction with conventional studies using seismic log core engineering and production data roger barnaby has conducted stratigraphic studies of carbonates and siliciclastics in outcrop and subsurface for 15 years he holds a ph d from virginia polytechnic institute and a b s degree from east carolina university barnaby has worked on sedimentary successions of the gulf coast permian basin alaska north slope middle east and caspian region he maintains interests in carbonate diagenesis and geochemistry gregg oetting received an m a degree in geology in 1995 from the university of texas at austin he is the author of six publications concerning geochemical and strontium isotopic variations in edwards aquifer groundwaters for the past seven years oetting has traded energy futures for leading merchant energy concerns he works for an independent consulting business in houston texas guoqiu gao received his b s and m s degrees in geology from central south university hunan china and his ph d in geology from the university of texas at austin he works for a major oil company in houston texas his current interests lie in the field of geoscience computing

multivariate probability distribution for some intact rock properties a multivariate probability distribution model for nine parameters of intact rocks including unit weight porosity n l type schmidt hammer hardness rl shore scleroscope hardness sh bra

the role of rock surface hardness and internal moisture in tafoni development in sandstone the development of cavernous weathering features such as tafoni remains poorly understood in particular the roles played by internal moisture and case hardening remain unclear in this study electric resistivity tomography ert has been used to map moisture distribution within inner walls of tafoni developed in sandstone and an equotip device used to measure rock surface hardness as a proxy measure of the degree of weathering and case hardening seven large tafoni in the golden gate highlands national park south africa varying in size and degree of development have been monitored a dynamic relationship between surface hardness degree of weathering and internal moisture regimes has been found we propose a new conceptual model which illustrates the complex interaction between case hardening and internal moisture and suggests a new direction for cavernous weathering research copyright 2011 john wiley sons ltd

weathering at high latitudes on the carboniferous old red sandstone petrographic and geotechnical investigations jedburgh abbey church scotland a case study weathering processes and intensity vary according to the predominant environmental conditions as well as the rock s physical and geotechnical properties in a given area jedburgh abbey church has been taken as a representative historical building constructed from carboniferous old red sandstone at humid pre glacial region the research aims to examine weathering processes and intensity under the environmental conditions of high relative humidity and low temperature and to determine the output of weathering through an examination of the rock s petrological and geotechnical properties

complex weathering in drylands implications of stress history for rock debris breakdown and sediment release abstract weathering studies have often sought to explain features in terms of a prevailing set of environmental conditions however it is clear that in most present day hot desert regions the surface rock debris has been exposed to a range of weathering environments and processes these different weathering conditions can arise in two ways either from the effects of long term climate change acting on debris that remains relatively static within the landscape or through the spatial relocation of debris from high to low altitude consequently each fragment of rock may contain a unique weathering related legacy of damage and alteration a legacy that may greatly influence its response to present day weathering activity experiments are described in which blocks of limestone sandstone granite and basalt are given stress histories by subjecting them to varying numbers of heating and freezing cycles as a form of pre treatment these imposed stress histories act as proxies for a weathering history some blocks were used in a laboratory salt weathering simulation study while others underwent a 2 year field exposure trial at high mid and low altitude sites in death valley california weight loss and ultrasonic pulse velocity measurements suggest that blocks with stress histories deteriorate more rapidly than unstressed samples of the same rock type exposed to the same environmental conditions laboratory data also indicate that the result of imposing a known weathering history on samples by pre stressing them is an increase in the amount of fine sediment released during salt weathering over a given period of time in comparison to unstressed samples

tafoni on coastal slopes south devon u k cavernous weathering tafoni development occurs on coastal slopes in greenschist bedrock at elevations up to 40 m above sea level the freshly weathered surfaces of the cavern interiors are irregular in morphology discordant to major rock structure formed by substantially weakened rock and associated with granular weathering debris the weathering debris contains soluble elements in proportions similar to those present in seawater and the penetration of elements associated with sea salts into the weathering surface to estimated depths of at least 0 1 0 2 m is indicated by the presence of chlorine scanning electron microscopy and microprobe analyses suggest that rock breakdown occurs principally through limited chemical weathering at grain boundaries the mechanism for the emplacement of marine salts within sheltered rock surfaces in the tafoni is postulated to be a combination of dry deposition under turbulent atmospheric conditions and wetting by coastal fog

bromide distribution characteristics of different zechstein 2 rock salt sequences of the southern permian basin a comparison between bedded and domal salts the bromide profile of the bedded zechstein 2 rock salts in the southern permian basin is characterized by a continuous increase in the bromide contents from base to top indicating progressive evaporation of sea water former studies have suggested that the bromide distribution in domal salts is more irregular raising such questions as whether there is a causal relationship between bromide distribution and deformation related processes or whether various halite types with different primary bromide contents account for such irregularities in this study the bromide distribution of a defined stratigraphic section hauptsalz of the zechstein 2 was investigated in three salt deposits with bedded salt teutschenthal compared with domal salts morsleben and gorleben furthermore two different halite types kristallbrocken matrix were distinguished during sampling comparison between the locations reveals that i the characteristic trend of the bromide profile was generally preserved in both the bedded and the more intensely deformed domal salts ii the dispersion of bromide contents along the running average curve is lower in domal salt especially in the lower half of the hauptsalz and iii the kristallbrocken are absent in the lower half of the hauptsalz of morsleben and gorleben the absence of the kristallbrocken and the lower dispersion of the bromide contents in the domal salts are clear indications for the influence of salt migration related processes on the bromide distribution characteristics it shows that these processes are associated with a redistribution of bromide which eventually results in a homogenization of the originally varying bromide contents on the other hand preservation of the characteristic trend in the bromide profiles indicates that large scale brecciation folding processes or circulating bromide rich fluids played only a minor role during the formation of the salt domes selective sampling of the kristallbrocken and matrix halite displays a disparity in bromide content that is not consistent between the studied locations these specific phenomena might be related to different depositional locations in the zechstein basin or to post depositional processes

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

a preliminary scanning electron microscope study of honeycomb weathering of sandstone in a coastal environment honeycomb weathering has been observed in a carboniferous sandstone at a coastal location near ballycastle on the north coast of northern ireland specimens of this sandstone have been analysed by x ray diffraction scanning electron microscopy and energy dispersive spectrometry results reveal that calcium sulphate gypsum is the only salt present and is found only at and immediately below the rock surface sem observations suggest that crystallization of salts in pores could easily dislodge quartz grains to promote granular disintegration whilst etching of quartz grain surfaces attests to chemical weathering activity within the rock however the reason for the development of the honeycomb pattern is not known

biogenic origin of coastal honeycomb weathering honeycomb weathering occurs in two environments in late cretaceous and eocene sandstone outcrops along the coastlines of south west oregon and north west washington usa and south west british columbia canada at these sites honeycomb weathering is found on subhorizontal rock surfaces in the intertidal zone and on steep faces in the salt spray zone above the mean high tide level in both environments cavity development is initiated by salt weathering in the intertidal zone cavity shapes and sizes are primarily controlled by wetting drying cycles and the rate of development greatly diminishes when cavities reach a critical size where the amount of seawater left by receding tides is so great that evaporation no longer produces saturated solutions encrustations of algae or barnacles may also inhibit cavity enlargement in the supratidal spray zone honeycomb weathering results from a dynamic balance between the corrosive action of salt and the protective effects of endolithic microbes subtle environmental shifts may cause honeycomb cavity patterns to continue to develop to become stable or to coalesce to produce a barren surface cavity patterns produced by complex interactions between inorganic processes and biologic activity provide a geological model of self organization surface hardening is not a factor in honeycomb formation at these study sites salt weathering in coastal environments is an intermittently active process that requires particular wind and tidal conditions to provide a supply of salt water and temperature and humidity conditions that cause evaporation under these conditions salt residues may be detectable in honeycomb weathered rock but absent at other times honeycomb weathering can form in only a few decades but erosion rates are retarded in areas of the rock that contain cavity patterns relative to adjacent non honeycombed surfaces copyright 2010 john wiley sons ltd

marine to nonmarine facies transition in permian evaporites of the palo duro basin texas geochemical response the late paleozoic palo duro basin evolved from a marine to nonmarine environment as it was infilled the evaporitic part of the sequence leonardian through ochoan is composed of regressive carbonate anhydrite halite cycles that displaced open marine environments toward the south during basin filling systematic vertical changes in evaporite geochemistry through the evaporite section include increasing 87sr 86sr ratios and decreasing altered from marine 34s in anhydrite decreasing recycled bromide content of the halite and increasing meteoric influence on the stable isotopic composition of fluid inclusions in halite geochemical changes correspond to changes in evaporite sedimentology and document the evolution from marine dominated to partly nonmarine evaporites geochemical tracers when used with sedimentological and facies analysis provide reliable indicators of the sources of water and solutes in an anhydrite halite facies tract perennial intermittently stratified and ephemeral brine pool conditions affect the amount of synsedimentary recycling variable rates of reflux and marine recharge control residence times of brines in the depositional environment these are two key processes in relating evaporite geochemistry to depositional environment

an upper aptian saline pan lake system from the brazilian equatorial margin integration of facies and isotopes facies and isotope sr and s data were combined in order to discuss the genesis and palaeohydrology of an upper aptian evaporite succession formed during the initial development of an intra continental rift from northern brazil comparison of facies distribution between two investigated areas shows i stable well stratified and hypersaline lakes with periods of anoxia and closure in the eastern margin of the basin where there was evaporite precipitation only in central lake environments and ii more ephemeral conditions in the eastern margin of the basin where a saline pan complex developed and evaporite precipitation took place mainly in marginal salinas and surrounding mudflats in both areas expansion contraction cycles developed as sedimentation took place accompanied by a decrease and then an increase in 87 sr 86 sr and d 34 s isotope values this combined with the wide distribution of sr and s isotope data within individual depositional cycles as well as petrographic and scanning electronic microscopic sem images led to the conclusion that diagenesis was not enough to obscure the primary geochemical signature a non marine brine source is suggested by 87 sr 86 sr ratios between 0ae707824 and 0ae709280 which are higher than those from upper aptian sea water i e between 0ae70720 and 0ae70735 the d 34 s value varies from 16ae12 to 17ae89 in the eastern margin of the basin which is in disagreement with upper aptian marine values 13 to 16 both geochemical tracers were influenced by facies characteristics and thus a model is provided where 87 sr 86 sr values respond to changes in expansion and contraction

rates and patterns of bedrock denudation by coastal salt spray weathering a seven year record rapid surface lowering of bedrock is taking place in the supratidal zone by salt spray weathering a seven year run of data demonstrates a mean rate of lowering of 0 625 mm a 1 considerable variation exists in annual point lowering values within measurement sites although between site variation is not significant aggregate year to year variations in surface lowering are not significant spatial variation in individual point values may be compensated by temporal variation over an 11 year period there is a marked summer maximum in surface lowering rate and this is strongly correlated with monthly air temperature spatially and temporally episodic swelling of the rock surface is demonstrated this does not correlate statistically with any available climatic variable and is deemed to be a real and largely stochastic phenomenon it is interpreted as rock bursting at the granular scale due to haloclasty the processes most likely to be responsible for the observed rapid denudation are crystallization and thermal expansion of halite both of which are enhanced by high summer temperatures

new challenges for tafoni research a new approach to understand processes and weathering rates cavernous tafoni type weathering is a common and conspicuous global feature creating artistic sculptures which may be relevant for geochemical budgets weathering processes and rates are still a matter of discussion field evidence in the type locality corsica revealed no trend of size variability from the coast to subalpine elevations and the aspect of tafoni seems to be governed primarily by the directions of local fault systems and cleavage and only subordinately by wind directions or the aspect of insulation rem analysis of fresh tafone chips confirmed mechanical weathering by the crystallization of salts as conchoidal fracturing of quartz is observed the salts are only subordinately provided by sea spray as calcium and sodium sulfates rather than halite dominate even close to the coast characteristic element ratios compare well with aerosols from mixed african and european air masses sulfates are largely derived from sahara dust indicated by their sulfur isotopic composition salt crystals form by capillary rise within the rock and subsequent crystallization in micro cracks and at grain boundaries inside rain protected overhangs siderophile bacteria identified by raster electron microscopy rem analysis of tafone debris contribute to accelerated weathering of biotite and tiny sulfide ore minerals by applying 10be exposure dating weathering rates of large mature tafone structures were found to be about an order of magnitude higher than those on the exposed top of the affected granite blocks copyright 2010 john wiley sons ltd

formation of quartz silt during humid tropical weathering of dune sands abstract quartz dune sand grains in northeast australia break down in situ under humid tropical weathering conditions to form substantial amounts of silt fragmentation appears to occur primarily due to silica solution along microfractures and dislocation structures in grains which have experienced tectonic deformation prior to deposition the surface textures of quartz grains viewed with the sem exhibit a close dependency on crystallographic properties in the b and c horizons of some weathered late pleistocene dunes silt forms up to 10 of the bulk sediment local remobilisation of such deposits by wind allows selective removal of the silt which is later deposited as a thin surficial sheet in more sheltered areas downwind these observations provide further evidence that weathering processes provide a major mechanism of silt formation and are an important factor to be considered in relation to the origin of loess and siltstones

experimental investigation of silt formation by static breakage processes the effect of temperature moisture and salt on quartz dune sand and granitic regolith weathering simulations carried out using a climatic cabinet have demonstrated that diurnal temperature and humidity variations typical of those occurring in warm desert environments are ineffective in causing static breakage of quartz dune sand and polymineralic regolith sand grains wetting and drying combined with temperature variations was also found to be a relatively ineffective weathering process these results suggest that crack tip processes are insignificant where mineral grains are not subject to static loading sodium sulphate weathering was found to cause slight damage to quartz dune sand grains and major damage to first cycle regolith grains feldspars and mica in the regolith sands were more susceptible to salt action than quartz salt weathering of the regolith sands produced substantial quantities of silt in the size range typically found in natural loess deposits

some aspects of lithological and exogenic control of sandstone morphology the świetokrzyskie holy cross mts case study poland abstract various morphologies of cliffs built of different quartzose rocks in the wietokrzyskie holy cross mts upland region central poland from cambrian quartzites and devonian quartzitic sandstones to triassic and jurassic porous sandstones were described in order to examine the constraints of their lithological and spatial occurrence the quantitative study of the occurrence of these morphologies on cliffs makes it possible to distinguish two principal groups of morphologies angular relief produced by rock splitting crumbling typical of quartzites indurated in silica and of open porosity less than 1 5 and morphologies developed due to granular disintegration and exfoliation of sandstones of open porosity higher than 1 5 among the relief types of this second group morphology reflecting sedimentary and diagenetic structures as well as smooth surfaces are the most common and are referred to sandstones of a wide range of porosity whereas honeycombs and surfaces suffering fast granular decay and scaling are characteristic of rocks of specific porosity respectively 5 8 and 3 5 8 the occurrence of honeycombs on rock surfaces is also conditioned by exogenic factors sun wind and rain since this morphology tends to occur on cliffs with aspects ranging from south east through south to west north west

application of an s shaped curve model to the temporal development of tafoni of salt weathering origin to describe temporal change in tafone development an s shaped curve equation is proposed z zc 1 n 1 exp t n exp 1 1 n t where z is observed tafone depth zc is ultimate tafone depth t is time and n and are constants the applicability of this model is examined using tafone data selected from seven sites which are categorized into three different salt weathering environments a spray splash dominant occasionally wave affected supra tidal zone aerosol affected coastal regions and inland desert areas the results indicate that the equation can well describe tafone development in each of these environments an investigation based on the values of n and determined through a best fit of the equation to the data suggests that n characterizes site specific environmental conditions and reflects the magnitude of factors controlling the recession mechanism of tafone surfaces it is found that 1 the maximum rate of tafone growth dramatically decreases from supra tidal through coastal to desert environments and 2 the growing mode of tafoni is different depending on the environmental settings the erosional force to facilitate the development of tafoni at supra tidal sites is estimated to be about 400 times greater than that in the general coastal area copyright 2011 john wiley sons ltd

micro environmental change as a trigger for granite decay in offshore irish lighthouses implications for the long term preservation of operational historic buildings following automation of lighthouses around the coastline of ireland reports of accelerated deterioration of interior granite stonework have increased significantly with an associated deterioration in the historic structure and rise in related maintenance costs decay of granite stonework primarily occurs through granular disintegration with the effective grusification of granite surfaces a decay gradient exists within the towers whereby the condition of granite in the lower levels is much worse than elsewhere the lower tower levels are also regions with highest relative humidity values and greatest salt concentrations data indicate that post automation decay may have been triggered by a change in micro environmental conditions within the towers associated with increased episodes of condensation on stone surfaces this in turn appears to have facilitated deposition and accumulation of hygroscopic salts e g nacl giving rise to widespread evidence of deliquescence in the lower tower levels evidence indicates that the main factors contributing to accelerated deterioration of interior granite stonework are changes in micro environmental conditions salt weathering chemical weathering through the corrosive effect of strongly alkaline conditions on alumino silicate minerals within the granite and finally the mica rich characteristics of the granite itself which increases its structural and chemical susceptibility to subaerial weathering processes by creating points of weakness within the granite this case study demonstrates how seemingly minor changes in micro environmental conditions can unintentionally trigger the rapid and extensive deterioration of a previously stable rock type and threaten the long term future of nationally iconic operational historic structures