karst collapse susceptibility assessment a case study on the amalfi coast southern italy abstract this paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the amalfi coast southern italy and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse in the study area several natural karst caves with volumes varying between 1000 and 10 000 m 3 were inventoried and the most likely genetic processes were identified some of them proved to be remnants of already collapsed caves while others were in precarious stability conditions the caves are usually located upslope or very close to the main populated resorts a detailed geological geomorphological and geostructural study was performed on a very wide deep cave called the saraceno cave on which the resort town of conca de marini has been built the study was carried out through a multidisciplinary approach which included classical field geological observations sometimes requiring the support of rock climbing geologists experts in photogrammetric surveys and terrestrial laser scanning techniques tls tls surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope conca de marini resort furthermore it allowed the thickness of the cave overburden to be determined in detail ground surfaces most susceptible to collapse were also identified in the event of possible widespread collapse several buildings and transportation infrastructures could be involved as the cave is located on a very steep slope a debris avalanche could be triggered in the event of a catastrophic failure and the landslide debris characterized by a presumably high magnitude and velocity could involve a wide slope area down to the coast the failure evolution could be very similar to that which took place in amalfi in the late 19th century

influences on the carbonate hydrochemistry of mound spring environments lake eyre south region south australia abstract mound spring structures composed of tufa precipitated from near ambient temperature spring waters are rare consequently the hydrochemical evolution of the water and the processes that control carbonate deposition in these systems are not well understood this study analysed the water from 3 mound springs in an arid environment in the vicinity of lake eyre south south australia samples were tested for major ion chemistry and stable isotope ratios of water 2 h 1 h and 18 o 16 o most co 2 degasses from water i before emergence as it ascends in the fracture derived spring conduit system below the spring opening and ii after emergence in the turbulent upper tail environment between the spring vent pool and the tail delta however modern carbonate precipitation was generally restricted to tail delta environments spatially disconnected from the areas of strongest co 2 degassing in addition to co 2 degassing and carbonate precipitation evapotranspiration and heterotrophy were inferred to be processes controlling the chemical evolution of water flowing through the tail delta based on considerations of the geometry of the tail delta and evapotranspiration rates it was inferred that infiltration is an important process in determining the tail delta size and hence the morphology of the mound spring environment a reactive transport model was used to assess the importance of these processes for the evolution of carbonate hydrochemistry the model outcomes showed that water loss via evapotranspiration does not significantly affect tufa precipitation despite the springs being located within an arid environment heterotrophy was considered in the model in order to reproduce observed ph and carbonate concentrations highlighting the role of vegetation in controlling the water chemistry the modelling approach adopted here provides a generic framework for the analysis of calcareous spring deposits and places quantitative constraints on data based process conceptualisation

strontium isotopes as tracers to delineate aquifer interactions and the influence of rainfall in the basalt plains of southeastern australia summary to better understand the spatial distribution of groundwater salinisation in western victoria southeast australia the interactions between a surficial basalt aquifer and an underlying extensive palaeodrainage deep lead system were studied using a multi disciplinary approach combining strontium isotope analyses with major ion chemistry and the interpretation of geological and hydrogeological data the strontium isotopes proved particularly useful in delineating flow paths and hydraulic connections between the two aquifers which have contrasting 87sr 86sr ratios the freshest basalt groundwaters lie beneath volcanoes and have 87sr 86sr signatures close to the whole rock strontium isotope ratios of the basalts 0 7045 indicating the strong influence of basalt weathering with increasing distance from the eruption points basalt groundwaters become progressively more saline and the strontium isotope ratios evolve towards the more radiogenic signatures of local rainfall 0 710 0 711 due to the slow addition of infiltration concentrated by evapotranspiration during its passage through the thick clay rich soils developed on the basalt lavas overall the influence of rainwater on the strontium isotope signatures of the basalt groundwater is much greater than that of basaltic weathering indicating that rainwater can play a greater role in determining groundwater strontium composition than is often realised most parts of the palaeodrainage system beneath the basalt are preferentially recharged through the volcanoes as shown by strong downwards hydraulic gradients and groundwater 87sr 86sr ratios similar to the least radiogenic basalt groundwaters however in the northwestern part groundwater 87sr 86sr ratios are closer to those of the source material of the sediments palaeozoic bedrock indicating that here recharge occurs predominantly in the headwaters where the basalts are absent in the southern and western sections of the palaeodrainage system there is an upward flux into the overlying basalts as shown by strong upward hydraulic gradients and elevated strontium isotope signatures in basalt groundwaters this occurs because lateral groundwater flow in the palaeodrainage system is restricted by shallow subsurface basement ridges and ultimately discharges to the surface as salt lakes

a geodynamic model of the southern apennines accretionary prism the apennines comprise a neogen quaternary accretionary prism that shows several anomalies with respect to classic alpine type mountain belts namely i low elevation ii a shallow new moho below the core of the belt iii high heat flow in the internal parts iv mainly sedimentary cover involved in the prism v a deep foredeep and vi a fully developed back arc basin the suction exerted by a relatively eastward migrating mantle can determine the eastward retreat of the subduction zone and an asthenospheric wedging at the retreating subduction hinge heat flow geochemical and seismological data support the presence of a hot mantle wedge underlying the western side of the apenninic accretionary prism a thermal model of the belt with foreland dipping isotherms fits with deepening of the seismicity toward the east mantle volatiles signatures are also widespread in springs along the apennines

the dynamics of back arc extension an experimental approach to the opening of the tyrrhenian sea the e w opening tyrrhenian sea developed after the cretaceous palaeogene alpine collision nearly perpendicular to the motion of the african plate as a back arc of the adria ionian westward subduction three driving mechanisms have been proposed to explain the dynamic evolution of the tyrrhenian apennine system 1 the northward indentation of the african plate 2 the retreating subduction of the adria ionian lithosphere and 3 the gravitational collapse of the alpine post collisional wedge in order to define the relative contribution of each of these mechanisms in the neogene dynamic of the tyrrhenian apennine system we performed 3 d laboratory experiments in which we simulated a retreating subduction process in a compressional regime oriented perpendicularly to the direction of subduction in this framework we also tested the influence of the gravitational collapse of the overriding plate experiments were constructed using dry sand and silicone putties to simulate brittle upper crust and ductile lower crust upper mantle respectively these layers floated on a high density low viscosity glucose syrup which simulated the asthenosphere the main conclusion of our experiments is that large scale continental extension similar to that observed in the tyrrhenian area could be reproduced perpendicular to the shortening direction induced by the indentation of the african plate in this framework extensional processes are indeed possible if the trench retreat velocity is higher than the rate of shortening induced by the advancing african plate our experimental results indicate that this high trench retreat velocity could be explained by the coexistence of the gravitational collapse of the post alpine wedge with a slab pull process linked to the retreating subduction of the adria ionian plate while the first mechanism is predominant in the northern tyrrhenian area the second one seems to be important in the latest stage of extension and oceanic accretion of the southern tyrrhenian area

3 d inversions of magnetic gradiometer data in archeological prospecting possibilities and limitations a vertical gradient magnetic system based on optically pumped cesium sensors has been used to map subtle magnetic anomalies across infilled pit houses and ditches at a medieval archeological site in northern switzerland for estimating the locations and dimensions of these features from the recorded data we have designed and implemented an appropriate inversion scheme tests of this scheme on realistic synthetic data sets suggested that suitable minimum magnetic susceptibility contrasts and smoothing parameters for the inversion may be directly extracted from the data inversions with minimum magnetic susceptibility contrasts generated causative bodies with maximum plausible sizes by using higher magnetic susceptibility contrasts a complete suite of models that matched the data equally well was produced to constrain better the magnetic susceptibility constrast within a selected area of the archeological site shallow samples of topsoil and sediment were analyzed in the laboratory an inversion based o

polyphase out of sequence thrusting and occurrence of marble detritus within the wedge top basin deposits in the mt massico southern apennines insights into the late miocene tectonic evolution of the central mediterranean we present a geological survey of the southwestern sector of the mt massico southern apennines which allowed us to reconstruct the stratigraphy and tectonic architecture of this area the mt massico is a key area to study the out of sequence thrusting stage that affected the southern apennine chain since the late miocene which despite the wide occurrence of these structures in the whole chain is a tectonic process up to now poorly investigated this area deserves to be analyzed also for the occurrence of marble detritus within a wedge top basin deposit representing the only place in the southern apennines where such a kind of metamorphic rocks occurs historically this area is known for the extraction of an ornamental stone named mondragone marble the marble is hosted as olistoliths and clasts within the deposits of the caiazzo fm unconformably covering a jurassic middle miocene succession mostly made of shallow water to deep basin carbonates the wedge top basin deposit mainly consists of a chaotic assemblage of conglomerates olistostromes and olistoliths of meso cenozoic limestones deep basin rocks and marbles embedded in a quartzose matrix the structural setting results from a polyphase deformation related to the superposition of two thrust systems the first thrust system includes a duplex verging to east with the cenozoic carbonates thrusted onto the caiazzo fm and the roof thrust cut by several breaching thrusts the late thrust system encompasses ramp dominated faults verging to the north folds minor thrusts and s c structures are associated with the major compressional structures to date the caiazzo fm and put a temporal constraint to the thrust fault activity we performed a nannoplankton content analysis that furnished for the base of this deposit an age not older than the upper tortonian these out of sequence thrusts hence have acted since the late miocene similar structures are widespread in the southern apennines and are interpreted as the surficial expression of envelopment thrusts formed at deeper structural levels with respect to the thrust front we envisage that the marble and plutonic supply was provided by the mesomediterranean continental crust in the late tortonian when this microcontinent was passing close to the apennine platform domain during its orogenic migration toward se

basement controlled structure and evolution of the queen charlotte basin west coast of canada abstract fault block tectonics usually associated with intracontinental areas characterizes the western part of the north america plate immediately adjacent to the pacific plate the long lived basement supported mosaic of fault bounded blocks controlled the evolution of this part of the west coast of canada since at least the late jurassic manifesting itself strongly in the tertiary this conclusion is based on recently collected geological and geophysical data gravity and magnetic maps and seismic profiles reveal orthogonal fault networks across the region in the tertiary queen charlotte sedimentary basin and on its pre tertiary rim the faults were reactivated and block movements sometimes inverted in the cenozoic similarity of fault networks across the region suggests inheritance of many structures in the basin from earlier time passage of the region over a mantle hot spot in the miocene may have been a partial cause of renewed block movements crosscutting relationships of large faults and their displacement histories onshore preclude regional strike slip faulting in the tertiary tectonic extension within the basin was small maximum 10 the previous model of formation of the queen charlotte basin by continental rifting sensu mckenzie 1978 is negated evolution of the region was not affected fundamentally by plate interactions at the adjacent continental margin in particular by the change from subduction to strike slip regime at 42 ma a similar structural style existed in the area before and after that event

triggering and predisposing factors for flow like landslides in pyroclastic soils the case study of the lattari mts southern italy abstract shallow flowslides debris flows and debris avalanches are rainfall induced landslides consisting in the shear failure of few metres of soils or in some cases even less than a metre which greatly increase downslope in volume and flow velocity the southern italian region of campania has been historically affected by such events involving pyroclastic soils mainly resting on steep carbonate slopes this paper deals with the analysis of factors influencing the occurrence of flow like landslides adopting the lattari mts in campania as a case study the results of two investigation campaigns carried out in the area allowed effective large scale geological and geotechnical characterization to be set up stratigraphic profiles mean physical properties and typical friction angles at the critical state for each soil layer were investigated the effect of suction on peak and critical shear strength whose drop is responsible for soil failure was analysed using detailed information on both the stratigraphic and geotechnical features of the soils involved in past flow like landslides typical triggering models were selected representing locally recurrent geomorphologic conditions at the basin scale the identified models were adopted for slope stability analyses carried out on four cross sections of flowslides occurring prior to the event to back analyse the triggering conditions from the evidence on the triggering mechanisms and the results of analyses the infinite slope approach is not always suitable to model slope stability conditions properly because the onset of landslides is also affected by local topographic and stratigraphic factors

depositional facies and aqueous solid geochemistry of travertine depositing hot springs angel terrace mammoth hot springs yellowstone national park u s a petrographic and geochemical analyses of travertine de positing hot springs at angel terrace mammoth hot springs yellow stone national park have been used to define five depositional facies along the spring drainage system spring waters are expelled in the vent facies at 71 to 73 8c and precipitate mounded travertine composed of aragonite needle botryoids the apron and channel facies 43 728c is floored by hollow tubes composed of aragonite needle botryoids that encrust sulfide oxidizing aquificales bacteria the travertine of the pond facies 30 62 8c varies in composition from aragonite needle shrubs formed at higher temperatures to ridged networks of calcite and aragonite at lower temperatures calcite ice sheets calcified bubbles and aggregates of aragonite needles fuzzy dumbbells pre cipitate at the air water interface and settle to pond floors the prox imal slope facies 28 54 8c which forms the margins of terracette pools is composed of arcuate aragonite needle shrubs that create small microterracettes on the steep slope face finally the distal slope facies 28 30 8c is composed of calcite spherules and calcite feather crys tals despite the presence of abundant microbial mat communities and their observed role in providing substrates for mineralization the com positions of spring water and travertine predominantly reflect abiotic physical and chemical processes vigorous co 2 degassing causes a 12 unit increase in spring water ph as well as rayleigh type covariations between the concentration of dissolved inorganic carbon and corre sponding d 13 c travertine d 13 c and d 18 o are nearly equivalent to aragonite and calcite equilibrium values calculated from spring water in the higher temperature 50 738c depositional facies conversely

structural and petrological analyses of the frido unit southern italy new insights into the early tectonic evolution of the southern apennines calabrian arc system abstract this study provides new data on the deformation and metamorphic evolution of the jurassic to upper oligocene frido unit an ocean continent transition oct unit belonging to the ligurian accretionary complex lac by means of the integration of structural analysis petrological investigations and a revision of the stratigraphical setting the frido unit representing the main metamorphic component of the lower middle miocene lac in southern italy is characterized by a multistage tectonic evolution including i two progressive deformation phases involving the development under relatively high pressure metamorphic conditions of an early cleavage associated with isoclinal folds within the framework of a dominant se ward tectonic transport ii a third deformation stage involving the growth of lower pressure na amphibole along extensional shear surfaces therefore probably marking the onset of tectonic exhumation and iii two very low temperature deformation phases characterized by the development of kink folds and associated thrusts probably related to the late tectonic emplacement of the accretionary wedge onto the outer sectors of the apennine domain with a prevailing tectonic transport first toward the ne and then toward the nw in order to clarify the metamorphic evolution of the frido unit petrologic analyses were focused on its metasedimentary pelitic succession here mineral parageneses including carpholite well documented for the first time in this study and potassic white mica yielded peak pressure of 1 2 1 4 gpa and temperature around 350 c thus indicating a high pressure very low temperature metamorphism and a p t t path characterized by a rapid exhumation without any greenschist facies overprint in comparison with similar units cropping out in northern calabria tuscany and corsica the frido unit experienced one of the coldest burial exhumation histories

cyanobacterial tufa calcification in two freshwater streams ambient environment chemical thresholds and biological processes abstract calcareous freshwater streams near bad urach southwest germany were studied to determine the environmental limits to cyanobacterial calcification daily variations in temperature ph calcium concentration and alkalinity were measured at seasonal intervals from september 1993 to january 1995 in two small woodland streams with lengths of 1 0 and 1 5 km the principal cause of supersaturation in these fast flowing streams is inorganic carbon dioxide outgassing from resurging groundwater locally enhanced by turbulence at waterfalls and cascades photosynthetic uptake of carbon dioxide and temperature effects are negligible nonetheless organic substrates particularly cyanobacteria dominated microbial mats and biofilm significantly localize precipitation by providing suitable nucleation sites precipitation rates on artificial substrates up to 2 2 mm yr on limestone correlate with high saturation index values copper substrates inhibited microbial colonization and received negligible encrustation tufa formation and external calcium carbonate encrustation of cyanobacteria are conspicuous where the annual wateq4f saturation index exceeds 0 8 and are slightly below 0 7 calcium carbonate impregnation of cyanobacterial sheaths has not been observed we infer that in these fast flowing streams cyanobacteria utilize co2 in photosynthesis whereas elsewhere in sluggish freshwater cyanobacteria utilize hco3 leading to sheath impregnation by calcium carbonate even where saturation index is only 0 2 0 3 thus photosynthetic influence on cyanobacterial calcification appears to be negligible in fast flowing co2 rich streams and cyanobacterial calcification takes the form of external encrustation in slow flowing co2 poor streams and lakes cyanobacteria preferentially utilize bicarbonate and sheath impregnation can result modern tropical marine carbonate shelves have saturation indices commonly in the range 0 62 0 82 and cyanobacterial calcification is negligible extrapolation suggests that cyanobacterial calcification could occur in present day seas if saturation index exceeded 0 8 this level corresponding with heavy calcification in the freshwater streams studied may have been widespread in marine environments in the geological past at times when calcified cyanobacteria and environmentally influenced non skeletal calcium carbonate precipitates were abundant

determination of free co2 in emergent groundwaters using a commercial beverage carbonation meter summary dissolved co 2 in groundwater is frequently supersaturated relative to its equilibrium with atmospheric partial pressure and will degas when it is conveyed to the surface estimates of dissolved co 2 concentrations can vary widely between different hydrochemical facies because they have different sources of error e g rapid degassing low alkalinity non carbonate alkalinity we sampled 60 natural spring and mine waters using a beverage industry carbonation meter which measures dissolved co 2 based on temperature and pressure changes as the sample volume is expanded using a modified field protocol the meter was found to be highly accurate in the range 0 2 35 mm co 2 the meter provided rapid accurate and precise measurements of dissolved co 2 in natural waters for a range of hydrochemical facies dissolved co 2 concentrations measured in the field with the carbonation meter were similar to co 2 determined using the ph alkalinity approach but provided immediate results and avoided errors from alkalinity and ph determination the portability and ease of use of the carbonation meter in the field made it well suited to sampling in difficult terrain the carbonation meter has proven useful in the study of aquatic systems where co 2 degassing drives geochemical changes that result in surficial mineral precipitation and deposition such as tufa travertine and mine drainage deposits

ecosystem controlled soil rock pco2 and carbonate weathering constraints by temperature and soil water content carbonate dissolution in soil groundwater systems depends dominantly on ph temperature and the saturation state of the solution with respect to abundant minerals the ph of the solution is in general controlled by partial pressure of co2 pco 2 produced by ecosystem respiration which is controlled by temperature and water availability in order to better understand the control of land temperature on carbonate weathering a database of published spring water hydrogeochemistry was built and analysed assuming that spring water is in equilibrium with the soil water rock atmosphere the soil pco 2 can be back calculated based on a database of spring water chemistry the average soil rock co2 was calculated by an inverse model framework and a strong relationship with temperature was observed the identified relationship suggests a temperature control on carbonate weathering as a result of variations in soil rock pco 2 which is itself controlled by ecosystem respiration processes the findings are relevant for global scale analysis of carbonate weathering and carbon fluxes to the ocean because concentration of weathering products from the soil rock system into the river system in humid high temperature regions are suggested to be larger than in low temperature regions furthermore results suggest that in specific spring samples the hydrochemical evolution of rain water percolating through the soil rock complex can best be described by an open system with pco 2 controlled by the ecosystem abundance of evaporites and pyrite sources influence significantly the chemistry of spring water and corrections must be taken into account in order to implement the inverse model framework presented in this study annual surface temperature and soil water content were identified as suitable variables to develop the parameterization of soil rock pco 2 mechanistically consistent with soil respiration rate findings

physical mechanisms of river waterfall tufa travertine formation waterfall tufa is widely distributed around the world especially in tropical and subtropical karst areas in these areas river water is generally supersaturated with respect to calcite and the precipitation occurs mainly at waterfall and cascade sites development of waterfall tufa has been described as simply being the result of water turbulence we believe however that three physical effects can lead to tufa deposition at waterfall sites aeration jet flow and low pressure effects the three physical effects are induced by two basic changes in the water an accelerated flow velocity and enlargement of the air water interface area these two changes increase the rate of co2 outgassing and the sic so that a high degree of supersaturation is achieved which then induces calcite precipitation these waterfall effects have been simulated in laboratory and field experiments and each of them can accelerate or trigger calcite precipitation field measurements of river water chemistry also show that tufa deposition occurred only at waterfall sites in these experiments and observations waterfall effects play the most important role in triggering and accelerating co2 outgassing rates field and laboratory observations indicate that plants and evaporation also play important roles in tufa formation growth of algae and mosses on tufa surfaces can provide substrates for calcite nucleation and can trap detrital calcite accelerating tufa deposition however the prerequisite for such deposition at waterfall sites is a high degree of supersaturation in river water which is mainly caused by waterfall effects evaporation can lead to supersaturation in sprays and thin water films at a waterfall site and cause the precipitation of dissolved caco3 but the amount of such deposition is relatively small

low angle normal faulting and focused exhumation associated with late pliocene change in tectonic style in the southern apennines italy in the southern apennines low temperature thermochronometry data indicate that exhumation of previous tectonically buried sedimentary units started at around 10 ma and took place mostly during the last 6 ma relatively high exhumation rates are obtained from apatite fission track aft and u th he ahe analysis pointing to a substantial contribution of tectonic processes to rock exhumation besides erosion exhumation rates derived from new apatite u th he data ahe for the last 3 ma are generally lower than rates determined by aft data and almost in line with erosion rates inferred from cosmogenic nuclides and sediment yield thus suggesting that tectonic exhumation was dominant during the older exhumation stages of this region however younger cooling ages in the monte alpi area from both aft and ahe analyses point out focused exhumation during the last 3 ma structural and morphotectonic analyses indicate that fast exhumation occurred specifically in this area where the apulian platform reservoir carbonates elsewhere buried beneath a several kilometer thick allochthonous cover are exposed at the surface as a result of a complex interplay between steep rooted reverse faulting and shallow low angle extension this deformation involved the development of foreland dipping low angle normal faults affecting the allochthonous cover units during the late stages of reverse fault related anticlinal growth in the underlying buried carbonates extension of the region triggered focused exhumation in the footwall of the extensional low angle faults which was followed by widespread crustal extension and associated development of high angle normal faults leading to surface uplift of monte alpi

a geochemical evaluation of perennial spring activity and associated mineral precipitates at expedition fjord axel heiberg island canadian high arctic abstract two groups of perennial springs are observed in the canadian high arctic at expedition fjord on axel heiberg island at colour peak and gypsum hill saline discharge 1 3 2 5 molal nacl produces a variety of calcite travertine and gypsum rich precipitates saturation index calculations of the spring waters at colour peak suggest co 2 degassing from the waters causes calcite precipitation gypsum precipitation dominates at gypsum hill where spring waters have lower alkalinity and higher so 4 concentrations mineral accumulations form both channel and rimstone pool morphologies as a result of varying slope conditions at colour peak confined flow in steep slope areas develop massive structures in contrast to more friable porous accumulations in areas where waters fan out on shallower slopes these morphological variations lead to corresponding varying apparent rates of mineral precipitation mineral precipitation at gypsum hill is far less notable as a result of lower discharge rates and annual degradation by icing formation microscopic observations and geochemical analyses of the channel precipitates at colour peak reveal alternating light calcite spar and dark anhedral microcrystalline calcite combined with organic matter and non carbonate minerals laminae rimstone pools forming in lower sections of spring discharge are composed of accumulations of large euhedral calcite crystals interbedded with allochthonous inputs high concentration of dissolved solids is responsible for slow travertine precipitation rates which occurs during winter this precipitation is further retarded during summer months by the introduction of crystal growth inhibitors such as fe 3 and deposition of organic matter and soil sediments

paleomagnetic and structural evidence for neogene block rotations in the central apennines italy magnetic fabric and paleomagnetic analyses on sedimentary sequences in several structural units in the central apennines ranging from upper cretaceous pelagic carbonates to upper miocene turbidites provide evidence for at least two distinct phases of rotation the first counterclockwise ccw rotation is well recorded in eocene oligocene sediments and does not affect the lower middle miocene sequences the second phase is clearly recorded in lower middle and upper miocene sediments and shows both ccw and clockwise cw rotations in concordance with trends of the different thrust structures we detected three domains characterized by different rotation patterns the westernmost is the southern sabina area an arcuate thrust belt which underwent a cw rotation after the early miocene the second domain is the latium abruzzi carbonate platform where a ccw rotation occurred after the late miocene the third is the marsica area that underwent a cw rotation after the late miocene the magnetic fabric analyses confirm the existence of these different structural provinces and show a strong correlation between the present day strike of the anisotropy of magnetic susceptibility magnetic lineation and the rotations recorded in miocene sediments we attribute present day variations in orientation of the compressional structures in the central apennines to differential rotations about vertical axes due to strike slip faults and out of sequence thrust activity rather than to a change in the stress field orientation we also suggest that this deformation mechanism could be common in other collisional chains around the world

active deposition of calcareous tufa in wessex uk and its implications for the late holocene tufa decline recent publications have suggested that deposition of calcareous tufa and travertine in the british isles has declined since the mid holocene several causal mechanisms have been postulated which include changes in both palaeoenvironmental and palaeoecological conditions results presented here for actively depositing tufa in the wessex region of southwest england suggest that there has been significant under reporting of contemporary tufa deposition this factor must be taken into consideration in any investigation of a possible tufa decline in the late holocene geochemical and environmental conditions at 26 tufa deposition sites are reported in order better to elucidate the climatic and environmental factors which constrain contempor ary tufa deposition and to achieve a better understanding of the controls on holocene deposition

mass balance modeling of mineral weathering rates and co2 consumption in the forested metabasaltic hauver branch watershed catoctin mountain maryland usa mineral weathering rates and a forest macronutrient uptake stoichiometry were determined for the forested metabasaltic hauver branch watershed in north central maryland usa previous studies of hauver branch have had an insufficient number of analytes to permit determination of rates of all the minerals involved in chemical weathering including biomass more equations in the mass balance matrix were added using existing mineralogic information the stoichiometry of a deciduous biomass term was determined using multi year weekly to biweekly stream water chemistry for a nearby watershed which drains relatively unreactive quartzite bedrock at hauver branch calcite hosts 38 mol of the calcium ion ca2 contained in weathering minerals but its weathering provides 90 of the stream water ca2 this occurs in a landscape with a regolith residence time of more than several ka kiloannum previous studies indicate that such old regolith does not typically contain dissolving calcite that affects stream ca2 na ratios the relatively high calcite dissolution rate likely reflects dissolution of calcite in fractures of the deep critical zone of the carbon dioxide co2 consumed by mineral weathering calcite is responsible for approximately 27 with the silicate weathering consumption rate far exceeding that of the global average the chemical weathering of mafic terrains in decaying orogens thus may be capable of influencing global geochemical cycles and therefore climate on geological timescales based on carbon balance calculations atmospheric derived sulfuric acid is responsible for approximately 22 of the mineral weathering occurring in the watershed our results suggest that rising air temperatures driven by global warming and resulting in higher precipitation will cause the rate of chemical weathering in the hauver branch watershed to increase until a threshold temperature is reached beyond the threshold temperature increased recharge would produce a shallower groundwater table and reduced chemical weathering rates copyright 2013 john wiley sons ltd

tectonic burial and young 10 ma exhumation in the southern apennines fold and thrust belt italy in the southern apennines fold and thrust belt thermal indicators record exhumation of sedimentary units from depths locally in excess of 5 km the thrust belt is made of allochthonous sedimentary units that overlie a 6 8 km thick carbonate footwall succession the latter continuous with the foreland apulian platform is deformed by reverse faults involving the underlying basement therefore a switch from thin skinned to thick skinned thrusting occurred as the apulian platform carbonates and the underlying thick continental lithosphere were deformed during the latest shortening stages apatite fission track data showing cooling ages ranging between 9 2 1 0 and 1 5 0 8 ma indicate that exhumation marks these late tectonic stages probably initiating with the buttressing of the allochthonous wedge against the western margin of the apulian platform pliocene pleistocene foreland advancing of the allochthonous units exceeds the total amount of slip that based on cross section balancing and restoration could be transferred to the base of the allochthon from the underlying thick skinned structures this suggests that emplacement of the allochthon above the western portion of the apulian platform carbonates was followed by gravitational readjustments within the allochthonous wedge coeval and partly associated with thick skinned shortening at depth the related denudation processes are interpreted to have played a primary role in tectonic exhumation

calcite supersaturation and precipitation kinetics in the lower colorado river all american canal and east highline canal in situ ph determinations and analysis of major ions in solution indicated that the lower colorado river is supersaturated with respect to calcite throughout the entire daily cycle in both winter and summer although the ion activity product was 4 to 6 times greater than the calcite solubility product there was no detectable precipitation chemical analyses of water samples taken along 350 km of the river and canals from parker dam to the salton sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows laboratory kinetic studies indicated that calcite crystal growth rates with colorado river water are about 30 of the rate for pure ca hco3 waters and about 70 of that for synthetic colorado river water calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite critical supersaturation levels necessary for heterogeneous nucleation do not occur a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime h2co3 levels

extension and compression related basins in central italy during the messinian lago mare event abstract during the messinian lago mare event in the central mediterranean area compression and extension related basins developed as a consequence of the post tortonian evolution of the tyrrhenian apennines system all these syn tectonic sedimentary basins were characterized by different subsidence rates and sedimentary processes several sections located in different tectonic domains from the tyrrhenian to the adriatic margin of the apennine chain have been investigated s valentino in abruzzo citeriore roccamorice penscosansonesco roccacaramanico and le vicenne sections are located in compression related basins foreland basin system while the tolfa blera sections and the sedimentary succession of mondragone 1 well drilled in the garigliano coastal plain are located in extension related basins hinterland or back arc basins the recognition of ostracod assemblages with paratethyan affinities allows them to be referred to the messinian lago mare event loxoconcha djaffarovi zone this result allows us to consider the tyrrhenian rifting the accretion of the apennine thrust belt and the increase in subsidence rate during the flexuration of the foreland domain as synchronous processes due to the same geodynamical process taking into account the thicknesses of the analysed sedimentary basins different total subsidence rates have been computed for both the compression and extension related basins the syn rift basins that developed on the eastern margin of the northern tyrrhenian basin volterra val di fine and tolfa blera basins recorded a mean total subsidence rate of 1 25 mm a whereas higher subsidence rates affected the eastern margin of the central tyrrhenian basin 5 mm a garigliano coastal plain the differences in horizontal stretching and total subsidence rates that affected the tyrrhenian extensional area correspond to different migration rates of the apennine orogenic system in the northern 10 mm a and central apennines 40 mm a this difference in the total syn rift subsidence rate fits in well with the segmentation model of the tyrrhenian apennines system along a nne ssw lithosphere discontinuity which crosses the system from ancona northern apennines to the r selli lineament in the tyrrhenian basin

history of subduction and back arc extension in the central mediterranean summary geological and geophysical constraints to reconstruct the evolution of the central mediterranean subduction zone are presented geological observations such as upper plate stratigraphy hp lt metamorphic assemblages foredeep trench stratigraphy arc volcanism and the back arc extension process are used to define the infant stage of the subduction zone and its latest back arc phase based on this data set the time dependence of the amount of subducted material in comparison with the tomographic images of the upper mantle along two cross sections from the northern apennines and from calabria to the gulf of lyon can be derived further the reconstruction is used to unravel the main evolutionary trends of the subduction process results of this analysis indicate that 1 subduction in the central mediterranean is as old as 80 myr 2 the slab descended slowly into the mantle during the first 20 30 myr subduction speeds were probably less than 1 cm year x1 3 subduction accelerated afterwards producing arc volcanism and back arc extension and 4 the slab reached the 660 km transition zone after 60 70 myr this time dependent scenario where a slow initiation is followed by a roughly exponential increase in the subduction speed can be modelled by equating the viscous dissipation per unit length due to the bending of oceanic lithosphere to the rate of change of potential energy by slab pull finally the third stage is controlled by the interaction between the slab and the 660 km transition zone in the southern region this results in an important re shaping of the slab and intermittent pulses of back arc extension in the northern region the decrease in the trench retreat can be explained by the entrance of light continental material at the trench

the carbonate tectonic units of northern calabria italy a record of apulian palaeomargin evolution and miocene convergence continental crust subduction and exhumation of hp lt rocks in northern calabria italy the metasedimentary succession of the lungro verbicaro tectonic unit preserves mineral assemblages suggesting underthrusting to depths in excess of 40 km internal deformation of these rocks occurred continuously during the following decompression index mineral composition associated with progressively younger tectonic fabrics indicates that a substantial part of the structural evolution took place within the blueschist facies p t field despite their tectonic and metamorphic history the rocks of the lungro verbicaro unit preserve significant sedimentary and palaeontological features allowing correlations with successions included in adjacent thrust sheets and the reconstruction of the mesozoic continental margin architecture the subduction exhumation cycle recorded by the lungro verbicaro unit is entirely of miocene age this portion of the apulia continental palaeomargin was involved in convergence related deformation not earlier than the aquitanian the integration of our results with available constraints on the tectonic evolution of the apennine calabrian arc system suggests that subduction and most of the subsequent exhumation of the lungro verbicaro unit occurred up to langhian time at maximum vertical rates in excess of 15 mm a 1 the exhumation process was then completed at much slower rates 1 in late miocene time as indicated by both apatite fission track data and stratigraphic information

structural and sedimentary features in the tyrrhenian margin off campania southern italy abstract the utilization of multichannel seismic reflection profiles permits the identification of the generally e w trending miocene orogenic and plio quaternary post orogenic features of apennine nw se and anti apennine ne sw trends in the campanian margin the former features are constituted by carbonate and or allochthonous sheets which were thrust mainly towards the north and northeast during the miocene tectogenetic phases the latter are represented by extensional structures which affected the orogenic features during plio quaternary times the anti apennine tectonic trend is responsible for the recent late pliocene quaternary and remarkable block faulting differential subsidence of the southern margin as well as for its present morphology the ragged and disconnected pattern of the allochthonous units over the present day slope and their accumulation underneath the shelf area suggest that they are the result of gravitational gliding tectonics gravity cores and 3 5 khz subbottom profiles indicate that the salerno trough and capri basin areas are characterized by a particular neotectonic mobility this is proved by the thick and coarse grained sediment accumulation from steep relief produced by block faulting this faulting created uplift belts serving as sediment source

sedimentology stratigraphy and tectonics of evolving wedge top depozone ariano basin southern apennines italy the late zanclean wedge top ariano basin located in the external sector of the southern apennines was initially characterized by alluvial and fan delta environments and successively southward of the benevento buonalbergo fault by a gradual drowning with coastal and alluvial plains evolving to shelf and marine coastal settings respectively basin evolution continued with a synsedimentary uplift of different sectors resulting in variations in the drainage pattern and basin shape and ultimately leading to complete basin closure and transition to continental depositional environments early pliocene paleogeography prior to the ariano basin activity is due to regional subsidence and subsequent differential uplifts that resulted from geodynamic processes related to both the downgoing apulian slab and the allochthonous orogenic wedge slab break off and the migration of a tear in the southeastward apulian slab occurred producing a strong subsidence in the external sectors of the southern apennines recorded by the development of the ariano basin subsequently out of sequence synsedimentary thrusting related to thin skinned tectonics occurred in the allochthonous units and unconformably overlying wedge top basin deposits producing northeastward migration of the main depocenters in the ariano basin finally renewed thrusting related to the inversion of pre existing normal faults located in the buried apulian platform and enhanced by regional uplift affected the whole tectonic and sedimentary pile as recorded by deformation of the overlying pliocene deposits

late tertiary quaternary tectonics of the southern apennines italy new evidences from the tyrrhenian slope this paper summarises the results of combined structural and geomorphological investigations we carried out in two key areas in order to obtain new data on the structure and evolution of the tyrrhenian slope of the southern apennines analysis by a stress inversion method angelier j 1994 fault slip analysis and paleostress reconstruction in continental deformation p l hancock ed pergamon press oxford 53 100 of fault slip data from mesozoic to quaternary formations allowed the reconstruction of states of stress at different time intervals by integrating these data with those deriving from the stratigraphic and morphotectonic records chronology and timing of the sequence of the deformation events was obtained the tectonic history of the region can be related to four deformation events structures related to the first event that was dominated by a strike slip regime with a nw se oriented 1 and was active since mid late miocene do not significantly affect the present day landscape as they were strongly displaced and overprinted by subsequent deformation events and or deleted by erosion the second and third events that may be considered as the main responsible for the morphostructural signature of the region are comparable with the stretching phases recognised offshore and considered to be responsible for the opening and widening of the tyrrhenian basin in particular the second event with an e w oriented 3 took place in the late miocene earliest pliocene and was first dominated by a strike slip regime that was also responsible for thrusting and folding since late pliocene it was dominated by an extensional regime that created large vertical offsets along n s to nw se trending faults the third event that was dominated by extension with a nw se oriented 3 started in the early pleistocene and was responsible for formation of the horst and graben structure with ne sw trend that characterises the tyrrhenian margin of the southern apennines the fourth deformation event which is characterised by an extensional regime with a ne sw trending 3 started in the late middle pleistocene and is currently active

tectono stratigraphic and kinematic evolution of the southern apennines calabria peloritani terrane system italy abstract temporal controls such as sedimentation ages in foredeep and wedge top basins combined with information about stratigraphic and metamorphic evolution ages and characterization of magmatic rocks deep structures burial and exhumation histories allowed us to obtain kinematic estimations of the southern apennines calabria peloritani terrane system evolution from the late oligocene to recent calculated thrust front velocities suggest to subdivide the orogenic evolution in main five kinematic stages characterized by different velocity trends nine kinematic complexes from a to i i e sets of tectonic units deformed in the same time range are determined according to foredeep ages these complexes bounded by main regional thrust faults encompass one or more tectonic sub units and successions of different paleoenvironment domains paleogeographic evolution model indicates according to available paleomagnetic data a counterclockwise rotation with a mean angle of 60 for the apennine platform carbonates whereas a mean angle of 20 for the eastern sector of the apennine platform and western side of apulian platform shortening estimations for the apennine successions show values ranging between 55 and 88 and a linear best fit indicating an increase from 60 nw sector to ca 90 se sector such high values are consistent with a deformation dominated by a thin skinned tectonics on the contrary the low value of 28 calculated for mt alpi suggests an exhumation ruled by high angle deep seated structures characterized by limited displacements tectonic vergences referred to middle late miocene late miocene and pliocene middle pleistocene when restored indicate an average eastward tectonic transport finally tectonic evolution is summarized in eleven schematic cross sections and corresponding paleogeographic maps

a late middle pleistocene temperate periglacial temperate sequence oxygen isotope stages 7 5e near marsworth buckinghamshire uk abstract river channel and colluvial deposits near marsworth buckinghamshire record a temperate periglacial temperate sequence during the late middle pleistocene the deposits of a lower channel contain tufa clasts bearing leaf impressions that include acer sp and sorbus aucuparia and containing temperate arboreal pollen attributed to ash dominated woodland the tufa probably formed at the mouth of a limestone spring before being redeposited in a small river whose deposits contain plant remains mollusca coleoptera ostracoda and vertebrate bones of temperate affinities the sediments sedimentary structures and limited biological remains above the lower channel deposits indicate that fluvial deposition preceded climatic cooling into periglacial conditions fluvial deposition recurred during a later temperate episode as shown by the mammalian bone assemblage in stratigraphically higher channel deposits the upper channel deposits are confidently attributed to oxygen isotope sub stage 5e ipswichian on the basis of their vertebrate remains however the age of the lower channel deposits is less clear the mammalian and coleopteran remains in the lower channel strongly suggest correlation with oxygen isotope stage 7 on the basis of their similarities to other sites whose stratigraphy is better known and the clear difference of the lower channel assemblage from well established faunas of ipswichian or any other age by contrast u th dating of the tufa clasts suggests an age post 160 ka bp while aile ile ratios on mollusca point to an ipswichian age and younger four ways of interpreting this age discrepancy are considered the preferred one correlating the lower channel deposits with oxygen isotope stage 7

factors controlling present day tufa dynamics in the monasterio de piedra natural park iberian range spain depositional environmental settings sedimentation rates and hydrochemistry the tufa record and hydrochemical characteristics of the river piedra in the monasterio de piedra natural park ne spain were studied for 6 years the mean discharge of this river was 1 22 m3 s the water was supersaturated with calcium carbonate the hco3 ca2 and tdic concentrations decreased along the 0 5 km long studied stretch whereas the calcite si showed no systematic downstream or seasonal variation over the same stretch several sedimentary subenvironments exist in which four broad types of tufa facies form 1 dense laminated tufa stromatolites 2 dense to porous massive tufa 3 porous coarsely laminated tufa with bryophytes and algae and 4 dense hard laminated deposits in caves the half yearly period thickness and weight of sediment accumulated on 14 tablets installed in several subenvironments showed that the deposition rate was greater in fast flowing river areas and in stepped waterfalls and lower in slow flowing or standing river areas and in spray and splash areas mechanical co2 outgassing is the main factor controlling calcite precipitation on the river bed and in waterfalls but this process does not explain the seasonal changes in depositional rates the deposition rates showed a half yearly period pattern recorded in all fluvial subenvironments persistent over time 5 26 mm 0 86 g cm2 in warm periods 2 26 mm 0 13 g cm2 in cool periods mass balance calculations showed higher calcite mass values in warm 21 58 mg l than in cool 13 68 mg l periods this biannual variation is mainly attributed to the seasonal differences in temperature that caused changes in inorganic calcite precipitation rate and in biomass and the correlative photosynthetic activity tufa sedimentation was therefore controlled by both physicochemical and biological processes the results of this study may help test depositional rates and their environmental controls and thus assess the climatic and hydrological significance of ancient tufas in semi arid conditions in particular in the quaternary

floating rafts of calcite crystals in cave pools central texas u s a crystal habit vs saturation state abstract calcite precipitation at the air water interface in cave pools in central texas u s a produces floating rafts of interconnected low mg calcite crystals with individual crystal habits that range from equant length to width 1 1 to prismatic 4 1 saturation state for the waters ranges from 0 19 to 1 35 sic log iap k equant crystals precipitate from waters with a lower saturation index sic and form rafts with a fused fabric whereas prismatic crystals precipitate from higher sic waters and form rafts with an interlaced fabric the pools contain low magnesium molal mg ca 0 6 calcium bicarbonate and calcium bicarbonate nitrate type waters with temperatures that range from 13 8 c to 20 7 c and ph readings from 6 7 to 8 4 equant euhedral crystals precipitate from water with saturation states close to equilibrium visible defects in the equant crystals include incomplete edges between faces and nearly circular mean diameter 9 m to angular holes in faces the holes apparently result from crystallite growth around foreign objects on the crystal surface such as gas bubbles prismatic crystals precipitate from supersaturated water faces of these subhedral crystals are smaller in area than the faces of the equant crystals no intrafacial circular holes are seen but trigonal intercrystallite pores are common in the prismatic crystals the variety in crystal habits from equant to prismatic is due to preferential growth along one crystallographic axis thus in these cave pools crystal habit is related to the saturation state of the water

oxygen isotope composition of annually banded modern and mid holocene travertine and evidence of paleomonsoon floods grand canyon arizona usa abstract holocene and modern travertine formed in spring fed havasu creek of the grand canyon arizona was studied to determine the factors governing its oxygen isotope composition analysis of substrate grown travertine indicates that calculated calcite formation temperatures compare favorably with measured water temperatures and include silt rich laminae deposited by monsoon driven floods ancient spring pool travertine is dated by u series at 7380 110 yr and consists of 14 travertine silt couplets of probable annual deposition one hundred eighty high resolution 18o analyses of this mid holocene sample average 11 0 pdb the average value for modern travertine is 0 5 lower perhaps because mid holocene temperature was higher or there was proportionally greater summer recharge 18o cyclicity in the mid holocene travertine has average amplitude of 1 9 0 5 pdb slightly less than the inferred modern day annual temperature range of havasu creek the annual temperature range might have been reduced during the 14 yr interval compared to present although other non temperature factors could account for the muted annual variation silt rich laminae within isotopically lower calcite in the modern and mid holocene travertine verifies the seasonal resolution of both samples and suggests that similar temperature precipitation conditions as well as monsoon generated summer floods prevailed in the mid holocene as they do throughout the grand canyon region today

tectonic evolution of the internal sector of the central apennines italy a wide sector of the internal portion of the central apennines which comprises the southern lepini mtns up to the northern simbruini mtns has been investigated through detailed field mapping and integrated with structural analyses a few small productive oil fields and a large number of hydrocarbon seeps and oil impregnations are located in this sector this area offers good opportunities for testing the use of structural fieldwork methodologies in order to highlight oil migrating paths from triassic source rocks and prospecting chances for oil field exploitation the main stages of the structural evolution of the area took place after deposition of the foredeep sediments frosinone fm i e after late tortonian under a stress field characterised by a ne sw trending s1 which was responsible for the early emplacement of major thrust faults present in the area the messinian early pliocene thrust top basin deposits allowed the reconstruction of an in sequence evolution of the thrust system the development of out of sequence thrusting post dates these structures leading to a further strong shortening phase in the area during the pliocene this phase is characterised by a roughly nne ssw trending s1 some peculiar tectonic features evidenced by thrust faults with younger over older relationships and an inversion of the original stacking of thrust sheets developed during this phase successively a block faulting tectonic mainly with ne sw extension stress field occurred and dismembered the compressive tectonic edifice later on up to the middle pleistocene n s to nne ssw trending dextral strike slip faults also acted in the area associated to the strikeslip tectonics are local volcanic centres as well as necks whose compositions show a mantle origin thus indicating deep seating and a possible lithospheric significance of these structures in the light of this study the reduced extension of the productive oil area as well as the spotting of oil seeps may indicate that the migration conditions are not tied to well defined structures but that likely the cross cutting points among structures facilitate the conditions for an upwards rising of oil these conditions in particular are achieved at least in two cases 1 where the late triassic source rocks do not have great depth due to normal or reverse faults or 2 at a major depth when encountered by transcurrent oblique roughly n s trending faults in both cases oil can easily migrate along the damage zone associated to the fault plane q 2004 elsevier ltd all rights reserved

on the tectonic evolution of the ligurian accretionary complex in southern italy unraveling the deformation pattern characterizing the transition from final oceanic subduction stages to early stages of deformation of a foreland continental margin is crucial for a better understanding of the geodynamic processes taking place at convergent plate boundaries in particular the combined role of internal wedge dynamics and continental margin architecture in controlling the tectonic evolution of an accretionary complex during its final emplacement onto the foreland continent is discussed in this study to this purpose we conducted integrated structural stratigraphic and low temperature thermochronometric analyses on the ligurian accretionary complex units exposed in the campania region italy and on continental margin successions located in their footwall as well as on related foredeep and wedge top basin deposits our results point out a series of late early miocene burdigalian shortening events also involving buttressing of the accretionary wedge against the crustal ramp of the foreland continental margin emplacement of the overthickened accretionary complex onto the distal part of the continental margin was followed by horizontal extension and wedge thinning aiding the development of wedge top depocenters extension may have been either related to reduced subduction rates during the middle miocene or to a period of subduction erosion known to have occurred in the northern apennines in the same time frame early miocene nw se shortening recorded by ligurian accretionary complex units was completely unrelated to later late miocene to pleistocene ne directed thrusting in the apennines which was coeval with backarc extension in the tyrrhenian sea therefore our results emphasize the occurrence of a major discontinuity in the neogene geodynamic evolution of the southern apennines the tectonic history of which may be clearly subdivided from a kinematic point of view into pre and syn tyrrhenian backarc extension stages

presentation of magnetic anomaly map data by stereo projection of magnetic shadowgrams coloured magnetic maps published at the 1 1 000 000 scale by the geological survey of canada have been found to be useful aids in support of regional geological mapping and compilation projects however because of the quantization into colour intervals some of the fine detail contained in the original magnetic data is lost these smaller features can be brought out quite effectively with the shaded relief technique although there is an attendant loss of amplitude information which can be recovered by means of stereo shadowgrams a second shadowgram is produced by offsetting the original shadowgram by an amount proportional to the magnetic intensity of each data point and then the offset and original shadowgrams are viewed as a stereo pair an example of the effectiveness of these techniques is the detail that can be seen on the shadowgrams and stereo shadowgrams for the lockhart river imw np 12 13 and the thelon river imw nq 12 13 14 map sheets

co2 outgassing and calcite precipitation in falling spring creek virginia u s a abstract chemical and physical observations are presented to explain the evolution of stream water chemistry along the flow path in warm river cave and falling spring creek mixing of two chemically and thermally distinct waters in the cave defines the initial stream water chemistry all along the flow path the observed composition is influenced by outgassing of co2 the water is supersaturated with respect to co2 both in the subsurface and at the surface of the earth but outgassing is greatest in turbulent stretches of the stream above and at the waterfalls the loss of co2 drives the solution to high degrees of supersaturation with respect to calcite physical evidence for calcite precipitation exists in the rimstone dams observed inside the cave and in the travertine deposits above and below the falls along falling spring creek travertine precipitation in the streambed consumes ca2 and hco 3 with most of the precipitation occurring where the stream experiences the most rapid co2 loss the stream water maintains a significant level of supersaturation with respect to calcite over the entire length of the flow path studied

trigonal dendritic calcite crystals forming from hot spring waters at waikite north island new zealand amorphous silica and calcite form the deposits in the vent and on the discharge apron of waikite spring 100 ws 100 which is located in the waikite geothermal area on north island new zealand these precipitates formed from spring water that has a temperature of 90 c and a ph of 8 1 8 8 the opaline silica is restricted to areas around the vent where cooling and evaporation of the spring water triggered precipitation the calcite deposits in the spring vent and on the discharge apron are formed of large up to 15 cm long asymmetrical dendrite crystals that are characterized by multiple levels of branching branches grew preferentially from the downflow side of their parent branch all branches have a trigonal transverse cross section except in areas where competition for growth space induced merger of neighboring crystals the primary branches of the dendrite crystals are sub perpendicular to the substrate even in areas where the discharge apron slopes at a high angle up to 80 on the steeper parts of the discharge apron the plate like primary branches form the floors of the small terrace pools whereas their distal edges form the rims of the pools growth of these dendrite crystals is attributed to abiotic processes high levels of saturation with respect to calcite were caused by rapid co2 degassing of the sheets of spring water that flowed down the steep discharge apron calcite crystals with different crystal morphologies characterize other springs near this spring the variation in crystal morphologies from spring to spring is attributed to different levels of saturation that are related to the initial pco2 of the spring water upon discharge and the rate of co2 degassing at each spring

neogene quaternary evolution of the central apennine orogenic system italy a structural and palaeomagnetic approach in the molise region abstract we report on new palaeomagnetic and magnetic fabric analyses of mainly upper miocene sedimentary sequences from the external central apennine fold and thrust belt molise area where the principal compressive structures are clearly non coaxial the sampling was carried out on the e w oriented matese frosolone thrust sheet that for its geographical position and structural setting superposition of thrusting strike slip and extensional tectonics since late miocene to present day represents a key structure for the comprehension of the neogene quaternary evolution of the entire molise area palaeomagnetic results suggest that the matese frosolone thrust sheet counterclockwise rotated at least 35 after messinian times these data confirm that the present day trend variability observed in the main compressional structures in the apennine chain can be related to rotations about vertical axes rather than to changes in the stress field orientation at least since late miocene times magnetic fabric analyses indicate that the studied sediments were subjected to very mild deformation suggesting that the surface emergence of the thrust front of the matese frosolone unit is located farther north far from the studied area well defined magnetic lineations of tectonic origin were only observed in sites close to localised belts of strike slip deformation

basin scale and travertine dam scale controls on fluvial travertine jiuzhaigou southwestern china article travertine deposition in fluvialsystemsbuildsdamsandotherformsthatcreatediversityingeomorphicprocesses morphology and associated wetland ecosystems in jiuzhaigou natural reserve sichuan province china we in vestigate the relation between contemporary fluvial travertine morphology slope and water chemistry at the fluvial system scale and at the local scale of large individual dams in order to address two fundamental questions first what factors determine the spatial distribution of such large valley spanning or primary travertine dams second what factors govern smaller but distinctive travertine dams and other secondary travertine morphology present on the sloping downstream side of primary travertine dams through remote sensing analysis and field work we recognize two factors as paramount in controlling spatial distribution of primary fluvial travertine dams watershed scalestepsinthelongitudinalprofile and waterchemistry based on a proxy for dissolved calcite in the steep jiuzhaigou watershed hillslope erosion processes that contribute large boulders to the channel influ ence the majority of the primary dams however two valley spanning primary dams pearl shoals and norilang lakes appear to be dominated by travertine precipitation the submerged upstream sides of these two dams are nearly vertical with heights 30 m slope varies with position along the longitudinalprofilesoverthedownstream sides of these two primary dams because the profile shapes are convex with downstream dam profile lengths 500 m flow encounters secondary travertine morphology organized as an array of travertine bedforms that vary with local channel slope along the convex profiles the secondary travertine bedforms include sequences of repeating patterns including smaller dams that impound correspondingly small waterbodies morphologic differ ences between two types of secondary dams are quantified on the basisof their relative size spacing and the slope on which they form increasing slope is correlated with a decrease in height of secondary travertine bedforms according to a power law where y 0 0053x

calcite precipitation rates in the field measurement and prediction for a travertine depositing stream abstract rates of calcite precipitation from a travertine depositing stream were determined from changes in stream composition between consecutive sampling points and were compared with rates predicted from a laboratory derived rate law plummer et al 1978 the agreement in rates was generally within an order of magnitude and routinely within a factor of 3 least agreement between measured and predicted rates was obtained for sections of flowpath where relatively little change in bulk chemical composition occurred which were the sections with the greatest mass transfer calculation error and for the stream segment including a waterfall which was the section with the greatest error in estimated surface area reaction rate obtained from the mass of calcite precipitated onto seed crystals placed in the stream significantly underestimated the mass transfer rate for the travertine depositing stream of warm river cave and falling spring creek virginia the coupling of equilibrium speciation models with mass balance calculations and simple field measurements allowed successful field based quantification of reaction rates

deep structure of the campanian lucanian arc southern apennine italy abstract recent exploration activities and successful discovery of large oil fields in the upper val d agri area southern apennine italy have encouraged the collection of large quantities of geological and geophysical data and their integration into comprehensive geological models here we present a series of structural profiles based on several hundred kilometres of seismic lines two and three dimensional and the results of many deep wells the best seismic lines have been extensively reprocessed and also tied to magnetotelluric data geological interpretations of those lines have been interactively tested and verified by gravity and magnetic modelling and structural balancing the wells and seismic data demonstrate that the fundamental tracts of the deep architecture of the orogen as it appears today were developed only at the end of the late pliocene the final closure of the ensialic shear zone responsible for the subduction of at least 150 km of continental lithosphere originally underlying the lagonegro basin can be dated as early pliocene the involvement of the inner apulian platform in the core of the belt and the activation of a new and more external left lateral oblique ensialic shear zone can be constrained to the late pliocene pleistocene the seismic profiles clearly show the underthrusting of the outer apulian platform unit beneath the inner apulian platform unit the thick skinned character of the plio pleistocene contractional structures is evident from the structural profiles this geometry is constrained by gravity magnetic data and structural considerations according to the relatively steep angle of dip about 10 of the apulian foreland beneath the chain the structural profiles depict the general architecture of the campanian lucanian arc the apennine platform and lagonegro unit are largely allochthonous and a part of the lagonegro basement could be buried below the apennine platform sole thrust the neogene plastic successions of the apennine platform and lagonegro basin were detached and now outcrop in the bradanic foredeep the inner apulian platform constitutes a huge thrust sheet structured as a wide antiform in the core of the belt its regional culmination roughly corresponds to the val d agri area extensional and transtensional structures cross cut the pre existing compressional structures as shown by the quaternary valleys of vallo di diano and val d agri the profiles shown also highlight the existing contrast between the deep structures in the core of the belt and the tectonic style of the lagonegro liguride and sicilide units these units were in fact subjected to brittle ductile deformation under metamorphic part of liguridi units and deep diagenetic to anchizonal conditions lagonegro units and were affected by a general overthrust shear directed towards the ne the inner apulian platform was on the contrary involved in the thrust belt together with its basement whereas the outer apulian platform affected by a subduction underwent a regional bending with associated normal faulting

miocene unconformities in the central apennines geodynamic significance and sedimentary basin evolution abstract this paper shows the results obtained from an integrated study geology biostratigraphy and geochemistry carried out on the miocene edimentary deposits in central italy in order to define the timing of the sedimentary basin evolution this paper deals also with the causes of the unconformities recorded in these basins in the miocene deposits of the latina valley and the ernici simbruini mts several unconformities which distinguish different stratigraphic sequences have been recognized d 0 d 1 d 2 d 3 and d 4 for each unconformity a general description together with a geodynamical significance is provided in particular d 0 unconformity appears to be related to a regional tectonic event adria europe collision as a consequence the adria lithosphere folded and the area underwent a regional erosive event d 1 d 2 and d 3 unconformities have had a more local tectonic control since they represent the stratigraphic record of the migration of the apennines thrust belt foredeep system d 1 and d 2 unconformities are related to the late tortonian foredeep stage whereas d 3 is linked to the early messinian piggy back stage moreover the d 4 unconformity which took place during the messinian piggy back stage is strictly linked to the sea level drop of the messinian salinity crisis in this paper the genesis and evolution of a late tortonian foreland basin is also stressed latina valley foredeep basin finally taking into account sequence boundaries nannofossil biostratigraphy and geochemistry isotopic data a comparison with the curve of the 3rd order of the relative coastal onlap haq et al 1988 has been attempted in order to distinguish the unconformities controlled either by tectonic or eustatic processes

geochemical evolution of groundwater in the unsaturated zone of a karstic massif using the pco2 sic relationship summary in karstic environments groundwater is strongly influenced by co 2 partial pressure variations of air present in the infiltration zone of these aquifers in order to characterize the geochemical changes in groundwater as it moves through the infiltration zone we monitored various rising springs in the perched karstic aquifer of cussac dordogne france and measured the co 2 partial pressure in air of a nearby cavity the cussac cave for 24 months our method is based on the relationship between the saturation index with respect to calcite sic and the co 2 partial pressure at atmospheric equilibrium with water we distinguished a value for this last parameter when water is at equilibrium with respect to calcite sic 0 called saturation co 2 partial pressure the use of this parameter can provide information on flow conditions and relationships between water air and rock cussac aquifer is a suitable area to apply these methods because of its small size numerous springs and a cave that provides data for co 2 partial pressure condition inside the massif results show that most of the calcium carbonate mineralization is acquired in the epikarst followed by a precipitation phase in the upper part of the infiltration zone groundwater reaches the saturated zone with some degree of saturation depending on co 2 partial pressure variations in air inside the massif

the northward tectonic transport in the southern apennines examples from the capri island and western sorrento peninsula italy we analyzed a thrust fault system located in the western sorrento peninsula and capri island southern italy where several mesoscale structures related to the main thrusts such as riedel shear planes overturned folds minor thrust and back thrust faults suggest a dominant northward tectonic transport major and minor thrust faults generally characterized by a ramp flat geometry involved the mesozoic apennine carbonates the middle miocene foredeep and the unconformable thrust top basin deposits the biostratigraphic analysis of calcareous nannoplankton assemblages on the thrust top basin sediments indicates an age not older than late tortonian we propose that this out of sequence thrusting stage was related to a regional tectonic event widespread in the entire southern apennines probably occurred in the pliocene time simultaneously with the activity of deep seated thrust faults that involved the buried carbonates of the apulian platform these out of sequence thrust faults here referred to as envelopment thrusts were enucleated in a lower structural level with respect to the allochthonous wedge representing the w e segments of large regional arcuate structures

reconciling the elemental and sr isotope composition of himalayan weathering fluxes insights from the carbonate geochemistry of stream waters determining the relative proportions of silicate vs carbonate weathering in the himalaya is important for understanding atmospheric co2 consumption rates and the temporal evolution of seawater sr however recent studies have shown that major element mass balance equations attribute less co2 consumption to silicate weathering than methods utilizing ca sr and 87sr 86sr mixing equations to investigate this problem we compiled literature data providing elemental and 87sr 86sr analyses for stream waters and bedrock from tributary watersheds throughout the himalaya mountains in addition carbonate system parameters pco2 mineral saturation states were evaluated for a selected suite of stream waters the apparent discrepancy between the dominant weathering source of dissolved major elements vs sr can be reconciled in terms of carbonate mineral equilibria himalayan streams are predominantly ca2 mg2 hco3 waters derived from calcite and dolomite dissolution and mass balance calculations demonstrate that carbonate weathering contributes 87 and 76 of the dissolved ca2 and sr2 respectively however calculated ca sr ratios for the carbonate weathering flux are much lower than values observed in carbonate bedrock suggesting that these divalent cations do not behave conservatively during stream mixing over large temperature and pco2 gradients in the himalaya the state of calcite and dolomite saturation was evaluated across these gradients and the data show that upon descending through the himalaya 50 of the streams evaluated become highly supersaturated with respect to calcite as waters warm and degas co2 stream water ca mg and ca sr ratios decrease as the degree of supersaturation with respect to calcite increases and mg2 ca2 and hco3 mass balances support interpretations of preferential ca2 removal by calcite precipitation on the basis of patterns of saturation state and pco2 changes calcite precipitation was estimated to remove up to 70 of the ca2 originally derived from carbonate weathering accounting for the nonconservative behavior of ca2 during riverine transport brings the ca sr and 87sr 86sr composition of the carbonate weathering flux into agreement with the composition of carbonate bedrock thereby permitting consistency between elemental and sr isotope approaches to partitioning stream water solute sources these results resolve the dissolved sr2 budget and suggest that the conventional application of two component ca sr and 87sr 86sr mixing equations has overestimated silicate derived sr2 and hco3 fluxes from the himalaya in addition these findings demonstrate that integrating stream water carbonate mineral equilibria divalent cation compositional trends and sr isotope inventories provides a powerful approach for examining weathering fluxes