the interrelation of glaciotectonic and glaciodepositional processes within the glacial environment abstract in recent years it has been recognised that ice sediment coupling occurred beneath the quaternary ice sheets that advanced over the soft sediments of lowland areas this paper looks in detail at the effects of this coupling on the sediments which results in glaciotectonic deformation and also discusses the interaction of deformation and deposition within the subglacial environment two types of glaciotectonic deformation are discussed that are produced by the active movement of ice 1 proglacial tectonics at the margin which include compressive fold styles such as listric thrusts and faults and open folding 2 subglacial tectonics formed beneath the glacier which include fold styles resulting from simple shear and represent a soft rock purely dynamic shear zone styles of deformation associated with stagnant ice are also investigated we argue that glaciotectonic deformation is a common phenomenon and an integral part of geological record from continental ice sheets it is suggested that zones of deformation within the sediment are related to similar zones of strain in the ice sheet and complex deformation sequences are produced by the superimposition of these differing styles upon one another as the ice sheet advances and retreats it is also argued that subglacial deposition and deformation are related and that on soft beds underformed till is rare whilst deformed till is very common

the accuracy of rainfall estimates by radar as a function of range high spatial resolution data were collected for nearby convective storms by using a volume scanning weather radar with 200m resolution and for stratiform events by using a high resolution 20m vertically pointing radar errors in the estimation of rainfall by the scanning radar due to the radar beam intersecting or overshooting features such as the bright band were simulated by using these high resolution images it was found that these effects define a maximum useful range for the radar that is a strong function of the prevailing meteorological conditions e g bright band height intense cell diameter and height sudden changes in bright band height over short times and the large scatter observed in its thickness limit the accuracy with which corrections for the vertical profile of reflectivity may be precalculated in stratiform rain events a scheme for using a vertically pointing radar to produce these corrections in real time is proposed the convective events show enough significant storm to storm variability that caution is required in extending the useful range of the radar too far

microstructural interpretations of modern and pleistocene subglacially deformed sediments the relative role of parent material and subglacial processes analysis of till micromorphology represents a relatively new technique that has been used most frequently to infer the importance of subglacial shear in till genesis this study aims to calibrate the technique by comparing pleistocene tills from united kingdom with a modern till the upb till from beneath ice stream b west antarctica despite the fact that all of the tills examined have been interpreted as deforming bed deposits the modern till has significantly less abundant and diverse microstructures than those found in the pleistocene tills seventeen examined thin sections of the upb till contain recognisable microstructures over only 0 30 of individual thin section area the most common microstructures are i birefringent clay patterns that are interpreted as shear zones and ii adherent matrix structures which we interpret as uncomminuted remnants of the parent glacial glaciomarine diamictons fourteen thin sections of the pleistocene tills were covered by microstructures in 10 95 of their area the pleistocene microstructures include birefringent clays and adherent matrix structures as in the upb till but also laminations and deformed pods made of chalk and sorted sediments we conclude that the same till forming process i e subglacial deformation may result in distinctly different till micromorphology this is a consequence of the fact that microstructural characteristics are strongly influenced by factors other than shear deformation we identify three controls that may be important for forming contrasting microstructural assemblages i strain magnitude ii the degree of heterogeneity of parent material and iii relative importance of sediment sorting by flowing water in the subglacial environment thus till micromorphology is sensitive to multiple factors which with proper calibration may enhance the existing capability to interpret past subglacial conditions from microstructures copyright 2001 john wiley sons ltd

striated clast pavements products of deforming subglacial sediment studies of modern glaciers have recently drawn attention to the importance of subglacial sediment deformation to glacier dynamics and processes inferences regarding the probable shear strength of this sediment imply that large clasts may in some cases sink to underlying rigid sediment where abrasion by overlying deforming sediment could occur this scenario provides a formative mechanism for striated clast pavements commonly described from the base of fine grained massive diamictons associated with the late pleistocene laurentide ice sheet such a mechanism indicates that at the time of formation of clast pavements overlying diamictons associated with pavements had a low yield strength 0 5 kpa and were deforming mechanically like a debris flow clast pavements may therefore be an important criterion for recognition of sediments deposited by subglacial deformation transport

styles of subglacial glaciotectonic deformation within the context of the anglian ice sheet a substantial proportion of the glacial sediments of east anglia england are chaotic and highly deformed this has been attributed to a direct glaciotectonic deformation or b slumping of glaciomarine sediments we show that interpretation a leads to a classification of subglacial glaciotectonic deposits into sites of constructional deformation where little or no erosion of the preglacial deposits has occurred and styles of deformation are preserved moving up in the sequence and excavational deformation where substantial erosion of preglacial sediments has occurred and deformational styles are superimposed on each other by using glaciological and geotechnical theory we show that the expression of these deformational styles in east anglia is a natural response to the stress fields imposed by the ice sheet and that in consequence their spatial relationships are explicable the depth of deformation is related to the geotechnical properties of till and substrate the stress and effective stress fields and found to be consistent with observations

mud volcano eruptions and earthquakes in the northern apennines and sicily italy abstract the relations between earthquakes and the eruption of mud volcanoes have been investigated at the pede apennine margin of the northern apennines and in sicily some of these volcanoes experienced eruptions or increased activity in connection with historical seismic events showing a good correlation with established thresholds of hydrological response liquefaction to earthquakes however the majority of eruptions have been documented to be independent of seismic activity being mud volcanoes often not activated even when the earthquakes were of suitable magnitude and the epicentre at the proper distance for the triggering this behaviour suggests that paroxysmal activity of mud volcanoes depends upon the reaching of a specific critical state dictated by internal fluid pressure and implies that the strain caused by the passage of seismic waves can activate only mud volcanoes in near critical conditions i e close to the eruption seismogenic faults such as the pede apennine thrust often structurally control the fluid reservoirs of mud volcanoes which are frequently located at the core of thrust related folds such an intimate link enables mud volcanoes to represent features potentially suitable for recording perturbations associated with the past and ongoing tectonic activity of the controlling fault system

the relationship between drumlins and other forms of subglacial glaciotectonic deformation this paper brings together the field data from 33 drumlins to show the relationship between drumlin formation and other subglacial deforming bed processes it is shown that there is a drumlin structure continuum a depositional which are similar to flutes formed by sediment flowing into the low pressure area behind a large obstacle and these conditions are mostly found within rock cored drumlins b deformational which contain different styles of deformation associated with a relatively weak core including stoss side deformation including both small and large scale brittle and ductile deformation stoss and lee side deformation compressive deformation and extensional deformation c erosional which consist of either truncated stratified sequences or homogeneous tills with distinct ice flow patterns furthermore it is suggested that if more sediment enters the deforming layer than can be removed then there will be net subglacial deposition which will result in the build up of a deforming bed till but if more sediment leaves the deforming layer then net erosion will occur under net erosional conditions any obstacle to flow may be left behind as a drumlin thus although individual drumlins have different internal structures they are formed associated with subglacial net erosion 0 1997 elsevier science ltd all rights reserved

deformation till in the great lakes region implications for rapid flow along the south central margin of the laurentide ice sheet structural and lithologic data indicate that while deposited under actively moving ice considerable portions of three muddy calcareous subglacial tills in the great lakes region probably experienced some component of ductile deformation viscous till flow and ductile shear are invoked to explain a combination of features such as recumbent isoclinal folds unlithified sediment clasts mixed ostracode shells reversed stone lee ends girdle and transverse fabrics irregular stone pavements fine striae following stone curves and inconsistent stone striae and a axes deforming fine textured subglacial till is considered as a subhorizontal shear zone rheologically layered with associated structures in descending order ductile e g isoclinal folds brittle ductile e g fissility and brittle e g till wedges rheology would be controlled mainly by till pore water content matrix texture and stone content spatial and temporal superposition of rheologies and subglacial processes probably occur

radiocarbon dating of residual organic matter in travertine formed along the yumoto fault in oga peninsula northeast japan implications for long term hot spring activity under the influence of earthquakes abstract radiocarbon dating was performed on trace amounts of organic matter included in travertines formed along the yumoto fault in oga peninsula ne japan the reliability of the dating method was confirmed by the consistency of ages obtained with the stratigraphy of the travertine mound and the ratio of carbon stable isotopes the radiocarbon chronology of the travertines shows that 1 the hot springs at oga have been active for approximately 29 000 years with average depositional rates ranging from 0 24 to 1 75 mm yr and 2 the principal hot spring activity has migrated southward with time variations in the accumulation rates and the progressive migration of the main focus of the hot spring activity imply irregular spring behaviour this behaviour has not been influenced by paleoclimate but may have been controlled by the earthquakes that occur frequently in the region around oga peninsula

comment on first records of syn diagenetic non tectonic folding in quaternary thermogene travertines caused by hydrothermal incremental veining by billi et al tectonophysics 700 701 2017 60 79 abstract billi et al 2017 proposed a new interpretation for the origin and internal structure of thermogene travertine deposits on the basis of evidence from two quarries located in southern tuscany italy they interpreted some travertine beds as calcite veins and argued that undulating travertine beds formed by syn diagenetic i e non tectonic folding that was caused by laterally confined volume expansion caused by incremental veining they assumed that such a process causes changes to the rock properties including porosity reduction rock strengthening and age rejuvenation the interpretations by billi et al 2017 challenge and question the current understanding and interpretation of thermogene travertine deposits this understanding based on numerous studies since the 1980s is that these deposits form from thermal water flowing downslope and precipitating calcium carbonate here we explain how the comparison with active depositional systems is essential for the understanding the origin of structures in older inactive travertine deposits such as those studied by billi et al 2017 we further argue that the three dimensional setting of travertine deposits should be taken into account in order to discuss the possible development of secondary structures indeed travertine deposition on slopes typically leads to the formation of terraced morphologies with pools bordered by rounded rims and separated from each other by steep walls the resulting three dimensional structures can be misinterpreted as asymmetric folds in two dimensional views i e in saw cut walls of quarry in this paper we debate the interpretations offered by billi et al 2017 and their criteria to recognise syn diagenetic non tectonic folds in travertine deposits and explain why many of their ideas are questionable

the mechanics of subglacial sediment an example of new transitional behaviour a series of isotropic compression tests and drained and undrained triaxial compression tests have been performed on glacial sediment from iceland langjokull sediment which is well graded is thou

the effect of grain texture on the occurrence of microstructural properties in subglacial till in this paper we examine whether till grain size affects the range and occurrence of micromorphological features associated with subglacial shear our till samples were collected from two glaciers in iceland and varied in texture from a coarse sandy clast rich till fjallsjokull to a fine grained silty sandy till vestari hagafellsjokull we found a wide range of deformational microstructures that included skelsepic plasmic fabric intraclasts of pre existing eroded bedrock basalt and weathered clay and mini shear zones between clasts we classified our micromorphological data into three classes rotational intermediate and linear in addition to these observations we performed extensive microfabric analysis at different scales on all of our samples we found that the coarse grained till contained a greater number and variety of microstructures than the fine grained till in addition the fine grained till showed a distinct lack of rotational structures that we attribute to the lack of significantly sized clasts in the matrix we argue that the varied texture of the coarse grained till provides a greater degree of perturbation within the shearing layer and so more distinct microstructures form in a more fine grained till shearing is more homogeneous since there are less perturbations in the matrix and this leads to a more singular kind of microstructure our observations suggest that subglacial shear occurs within a multi layered patchwork of different grain sizes competence and pore water pressures it is these factors that are so crucial in determining the occurrence and type of microstructural evidence we see in subglacial tills

towards improved radar estimates of surface precipitation rate at long range a method has been developed for estimating surface precipitation rates using reflectivities measured with a radar scanning at several different angles of elevation in each pixel of a radar image an idealized profile of the reflectivity factor is constructed each profile is defined in terms of three unknowns the reflectivity in the rain beneath the melting layer and the slope of the profile of the reflectivity in each of two layers above the melting layer in these layers above the melting layer it is necessary to invoke assumptions of horizontal homogeneity in the shape of the profile simple parametrizations are used for low level orographic growth and for the bright band and the profile is diagnosed with the help of non radar information the difference between the idealized and observed profiles is expressed as a single value for an entire radar image the difference is minimized by iteration and this avoids using complicated methods of inversion a simulation experiment was carried out for 15 different cases in most of them the incorporation of data from several elevation angles reduced bias errors at long range the new method was then used on real radar data in typical frontal rainfall it showed no consistent improvement because it avoids using corrections which can otherwise become detrimental at long ranges however the new method gave improved results when reflectivity profiles were atypical unresolved spatial variability of the reflectivity profile continues to be a problem

identification and uncertainty estimation of vertical reflectivity profiles using a lagrangian approach to support quantitative precipitation measurements by weather radar 1 this paper presents a novel approach to estimate the vertical profile of reflectivity vpr from volumetric weather radar data using both a traditional eulerian as well as a newly proposed lagrangian implementation for this latter implementation the recently developed rotational carpenter square cluster algorithm rocasca is used to delineate precipitation regions at different reflectivity levels a piecewise linear vpr is estimated for either stratiform or neither stratiform convective precipitation as a second aspect of this paper a novel approach is presented which is able to account for the impact of vpr uncertainty on the estimated radar rainfall variability results show that implementation of the vpr identification and correction procedure has a positive impact on quantitative precipitation estimates from radar unfortunately visibility problems severely limit the impact of the lagrangian implementation beyond distances of 100 km however by combining this procedure with the global eulerian vpr estimation procedure for a given rainfall type stratiform and neither stratiform convective the quality of the quantitative precipitation estimates increases up to a distance of 150 km analyses of the impact of vpr uncertainty shows that this aspect accounts for a large fraction of the differences between weather radar rainfall estimates and rain gauge measurements

earthquake triggered soft sediment deformation structures seismites in travertine deposits abstract earthquakes related soft sediment deformations seismites are relevant structures to help reconstructing the palaeoseismicity in a region nevertheless although seismites have been described for a large variety of palaeo environments and stratigraphic settings they are rare and in some cases ambiguous structures in this paper we document for the first time impressive seismites affecting a latest quaternary travertine deposit located in southern tuscany serre di rapolano italy these structures are extremely relevant as seismites have been never described for this kind of terrestrial deposits the seismites developed within a 2 5 m thick stratigraphic succession made of alternating terrigenous and carbonate sediments embedded within the travertine deposits earthquake produced liquefaction and fluidization of some terrigenous levels and the injection of fluidized silty sediments dykes and sills into carbonate and terrigenous levels slumped levels and associated decollement surfaces produced highly non cylindrical folds overall induced by the loss of brittle shear strength along the basin slopes the occurrence of these soft sediment deformations implies an important seismic event that took place in a time spam encompassed between 84 8 and 48 92 5 08 ka in an area characterized by low seismicity and scarce knowledge of its seismotectonic setting their spectacular exposition and preservation in saw cuts of an abandoned quarry cava oliviera quarry highlights their relevance and importance

substrate geology controlling different morphology sedimentology diagenesis and geochemistry of adjacent travertine bodies a case study from the sanandaj sirjan zone western iran abstract a travertine fissure ridge and travertine mound are situated 800 m from each other at the western margin of the active tectono volcanic sanandaj sirjan zone western iran despite their close proximity the two geobodies show a difference in morphology lithofacies lithotypes diagenesis and geochemistry petrographic analysis of the fissure ridge carbonates revealed homogeneous sparitic fabrics with dendritic structures reflecting precipitation under fast flowing conditions from calcite supersaturated spring water the mound carbonates are much more heterogeneous and display dominantly micritic fabrics with mainly volcanic clasts reflecting a lower energy flow regime and lower calcite saturation in contrast to the limited diagenetic overprint of the fissure ridge carbonates the more porous mound carbonates are affected by dissolution cementation and formation of mn fe oxide hydroxides attesting of a strong control on porosity by early diagenetic processes the widespread bright luminescent calcite phases especially in sparitic fabrics within both geobodies display high mn concentrations in calcite indicating suboxic precipitation conditions the overlapping 87sr 86sr signatures and 13c signatures point to a mixture of co2 that dominantly originated from dissolution of the marine carbonate qom formation oligo miocene the different 18o signatures indicate different upwelling systems caused by different substrate settings the fissure ridge formed on a hard and brittle limestone substrate with precipitation from dominantly subsurface sourced fluids the mound travertine formed on top of fairly unconsolidated and fractured volcanic strata the depleted 18o signatures and impure micrite dominated fabrics of the mound travertine reflect precipitation from thermal water that mixed with surrounding groundwater this difference is also reflected in a different calculated precipitation temperature that varies between 4 and 21 c for the mound versus 25 50 c for the fissure ridge our findings show that subsurface geology exerts a major control on precipitation processes resulting in differences in travertine morphology sedimentology diagenesis and geochemistry despite that the travertine bodies occur adjacent to each other

weertman regelation multiple refreezing events and the isotopic evolution of the basal ice layer a simple model is developed to s imulate the isotopic fractionation which accompanies weertman regelation at the bed of temperate based glaciers the fractionation equations of jouzel and souchez 1 982 are applied to multiple refreezing events over measured glacier bed profiles and mass balance is maintained as the basal ice and meltwater produced at one bedrock hummock enter the next s imulation results indicate that undeformed regelation ice layers are on the order of millimetres to centimetres thick often being completely melted at the stoss face of certain hummocks and exceptionally reaching a thickness in excess of 1 0 cm neither the internal morphology nor the isotopic composition of these layers is constant but both vary down glacier in accordance with bedrock configuration a glacier wide fractionation process is identified whereby heavy isotopes are preferentially removed fro m the basal meltwater film and incorporated into the basal ice this process might go some way to explaining the anomalously light isotopic composition measured in base flow waters leaving some glaciers vertical isotope profiles through undeformed basal ice layers are reconstructed and show that significant isotopic excursions can occur at a scale of millimeteres while the range of isotopic compositions within such m ulti layered regelation ice is greater than that which would occur in ice produced by a single refreezing event in circumstances where the regelation system is disrupted by removal of film waters into a network of linked cavities i t is found that the remaining basal ice may be significantly enriched in heavy isotopes relative to the composition of the initial mass inputs to the system heavy isotope enrichment of this m agnitude and consideration of the thickness of the basal ice layers concerned may explain the absence of recorded basal ice samples heavy enough to h ave been formed in equilibrium with subglacial precipitates sampled at one of the sites glacier de tsanfleuron and reported in an earlier paper

physical conditions at the base of a fast moving antarctic ice stream boreholes drilled to the bottom of ice stream b in the west antarctic ice sheet reveal that the base of the ice stream is at the melting point and the basal water pressure is within about 1 6 bars of the ice overburden pressure these conditions allow the rapid ice streaming motion to occur by basal sliding or by shear deformation of unconsolidated sediments that underlie the ice in a layer at least 2 meters thick the mechanics of ice streaming plays a role in the response of the ice sheet to climatic change

the deforming bed debris rich basal ice continuum and its implications for the formation of glacial landforms flutes and sediments melt out till abstract there are two potentially important shear zones at the base of the glacier the deforming layer and or the debris rich basal ice layer these two layers have a significant effect on glacier motion and glacial erosional depositional and sedimentary processes however it is shown that most of the processes operating within these two layers are very similar this includes compression at the ice margin longitudinal extension and simple shear upglacier similar styles of shear zone and associated fabric development and similar incorporation transport and depositional processes in the past many criterion have been developed to identify distinct deposition from the deforming layer and the debris rich basal ice layer however if the processes within these layers are similar then it makes the distinct identification of these two separate layers in the geological record very difficult however it is also shown that the main differences between the two layers include rates of sediment movement processes and preservation potential the later is very important as it appears that the two layers are interconnected and that material is melted out from the debris rich basal ice to form a significant component of the deforming layer in this way the final depositional imprint is from the deforming layer and there is little likelihood of the debris rich basal ice layer being preserved undeformed this is demonstrated from modern glacial environments pleistocene flute studies and studies of pleistocene melt out tills from the u k u s a and germany

fractal dimensions of diamictic particle size distributions simulations and evaluation it has been proposed that deformation tills have fractal particle size distributions reflecting scale invariant debris comminution processes numerical simulations however show that fractal dimensions m typical of deformation tills can be produced by the mixing of gaussian parent populations analogous to the mechanical mixing of coarse medium and fine grained sorted sediments the simulated distributions have high r2 values 0 98 and narrow 95 confidence limits indicating that fractal analysis cannot distinguish diamictons that have been created by shearing from those formed by other mechanisms such as the mixing of preexisting sediments the fractal dimensions of diamictons reflect the relative amounts of coarse and fine material in the distribution but are not uniquely diagnostic of particular genetic processes

plateau versus fissure ridge travertines from quaternary geothermal springs of italy and turkey interactions and feedbacks between fluid discharge paleoclimate and tectonics abstract morphologically different deposits of thermal travertines are known worldwide but what factors controlled their morphology volume and growth for tens of thousands of years is only partially understood two main morphotypes of quaternary thermal travertines are reconsidered here to understand the reasons for their differential growth the fissure ridge travertines of denizli basin western turkey and the travertine plateau of tivoli central italy for comparable longevities and average vertical deposition rates the main differences between the studied travertines are as follows 1 volume of the travertine plateau is about one hundred times larger than each fissure ridge 2 despite a larger volume the travertine plateau does not produce relief whereas the fissure ridges produce a characteristic prominent topography 3 the travertine plateau grew primarily through lateral progradation whereas the fissure ridges through vertical aggradation 4 travertine deposition occurred in different environments principally low energy flat or shallow environments at tivoli and high energy inclined environments at denizli 5 the growth of the tivoli plateau occurred in a subsiding basin whereas the fissure ridges were not influenced by significant subsidence 6 c and o isotope signatures from the two studied travertines are different 7 despite similar annual precipitations the present water discharge in the tivoli area is about ten times greater than that of the denizli basin u series ages from the two deposits are correlated with paleoclimate oscillations at regional and global scales geological field evidence together with paleoclimate correlations suggest that in both the study cases the main body of travertine deposits the bedded travertine grew preferentially when the water table was high warm and or humid periods conversely when the water table was depressed cold and or dry periods the tivoli travertine underwent partial erosion and the denizli ridges were cut by axial veins and lateral sill like structures filled by banded sparitic travertine a comparative model is proposed where the main factor driving the difference in the morphostratigraphic architecture of fissure ridges and travertine plateaus is the volume of water discharge a high discharge rate resulted in the precipitation of caco3 far away from the springs hence driving the lateral progradation of the tivoli plateau a reduced discharge rate caused travertine precipitation close to the springs thus causing the vertical aggradation of the denizli fissure ridges paleoclimate oscillations must have controlled the amount of fluid discharge which in turn must have influenced the opening of the feeding fractures by an increased pore pressure

hydrothermal fluids circulation and travertine deposition in an active tectonic setting insights from the kamara geothermal area western anatolia turkey abstract coexistence of thermal springs travertine deposits and tectonic activity is a recurring feature for most geothermal areas although such a certainty their relationships are debated mainly addressing on the role of the tectonic activity in triggering and controlling fluids flow and travertine deposition in this paper we present the results of an integrated study carried out in a geothermal area located in western anatolia turkey nearby the well known pamukkale area denizli basin our study focused on the relationships among hydrothermal fluids circulation travertine deposition and tectonic activity with particular emphasis on the role of faults in controlling fluids upwelling thermal springs location and deposition of travertine masses new field mapping and structural kinematics analyses allowed us to recognize two main faults systems nw and ne trending framed in the neogene quaternary extensional tectonic evolution of western anatolia a geo radar gpr prospection was also provided in a key area permitting us to reconstruct a buried fault zone and its relationships with the development of a fissure ridge travertine deposit kamara fissure ridge the integration among structural and geophysical studies fluids inclusion geochemical isotopic data and 230 th 238 u radiometric age determination on travertine deposits depict the characteristics of the geothermal fluids and their pathway up to the surface hydrological and seismological data have been also taken in account to investigate the relation between local seismicity and fluid upwelling as a main conclusion we found strict relationships among tectonic activity earthquakes occurrence and variation of the physical chemical features of the hydrothermal fluids presently exploited at depth or flowing out in thermal springs in the same way we underline the tectonic role in controlling the travertine deposition making travertine mainly banded travertine a useful proxy to reconstruct the seismological history of an area as well as the characteristics of the parent geothermal fluids adding an effective tool for geothermal exploration tasks

hydrothermal co2 degassing in seismically active zones during the late quaternary natural co2 discharges are abundant in turkey as evident from ongoing deposition of recent terrace mound travertines and emplacement of significant travertine vein and breccia deposits in fractured damage zones of active fault systems we report high precision u series age data for the vein carbonates combined with important field observations and geochemical data to evaluate the travertine veining and co2 degassing history in seismically active areas field evidence suggests that travertine filled veins and associated breccias represent hydrothermal eruption products which probably formed by hydraulic fracturing in response to overpressure of co2 rich fluids stable isotope and ree data support the field observations and indicate that travertine veins formed as thermogene deposits from rapidly ascending co2 rich fluids travertine veins from the kirsehir geothermal field give u series ages in a range from 10 6 0 3 ka to 86 16 1 24 ka with a majority of ages failing between 10 6 0 3 and 11 3 0 2 ka vein samples from the pamukkale geothermal field yield u series ages between 21 1 0 1 ka and 73 6 0 6 ka two major age groups are evident in pamukkale that cluster coherently around 21 ka and 25 ka a large number of travertine veins we dated by high precision u series technique coincide with times of cold dry climate events this is different from surface sinter deposits in geothermal fields which more frequently form during warm and wet periods we propose that a significant reduction in surface discharge of co2 by spring or geothermal waters during dry climate periods may promote oversaturation of co2 in deep reservoirs host rock fracturing in response to seismic shaking and fluid overpressure results in rapid exsolution and expansion of the dissolved gas and may lead to hydrothermal eruptions crown copyright c 2009 published by elsevier b v all rights reserved

the off fault deformation on the north anatolian fault zone and assessment of slip rate from carbonate veins abstract discrepancies in earthquake characteristics between geodetically determined and geologically observed slip rates are prominent for the eastern part of the north anatolian fault naf zone we investigated the spatial distribution of deformation across a naf fault segment near erzincan ne turkey through field observations of physiographic features along the principle fault and a carbonate filled fissure system we propose that distributed deformation across the principal fault in a stretching zone caused sigmoidal simple shear rotation of the carbonate filled fissure system displacement data of that sigmoidal fissure using isotopic age data of the carbonate fill indicates an off fault deformation rate of 15 90 3 19 mm per year for the holocene which corresponds to at least 50 of the geodetically estimated annual slip across the fault it is critical to take the distributed deformation into account for determining earthquake characteristics of active fault systems

till fabric associated with deformable beds this paper investigates the development of till fabric associated with glaciers overlying deformable beds first the till fabrics from both modern and ancient soft bed and hard bed subglacial environments are investigated and then soft bedded sites with specific strain histories are examined the results indicate that lodgement tills had a strong fabric whilst there is a wide range of much weaker fabric strengths associated with soft bed tills it is suggested from a theoretical study of soft bed till deposition that longitudinal and vertical processes in the subglacial deforming layer are important in fabric development field sites were chosen to isolate these two factors and fabrics investigated in areas of known relative shear strain and known relative thickness of the deforming layer the results indicate that 1 for a fixed deforming layer fabric strength does increase with increasing deformation except at very high strains where the development of a transverse fabric can lead to a reduction in the overall fabric strain and 2 lodgement tills and soft bed tills associated with a thin deforming layer have a high fabric strength whilst soft bed tills associated with a thick deforming layer have a low fabric strength where the deforming layer is thin clasts are oriented parallel with the glacier direction either by lodging against a hard bed or ploughing against a soft bed however where the deforming layer is thicker and shear strains are high melt out processes encourage a parallel fabric but the increased shear strain and changes in the deforming layer thickness cause the clasts to develop both a parallel and transverse fabric these processes combine to reduce the overall fabric strength till fabric studies are a further sedimentological technique to separate the depositional processes associated with a homogeneous till

a sedimentological and isotopic study of the origin of supraglacial debris bands kongsfjorden svalbard hubbard b glasser n f hambrey m j etienne j l 2004 a sedimentological and isotopic study of the origin of supraglacial debris bands kongsfjorden svalbard journal of glaciology 50 169 157 170 rae2008

aragonite laminae in hot water travertine crusts rapolano terme italy small 5 30 m aggregates of aragonite needles occur in calcite crystal crusts of present day hot water slope travertines at rapolano terme in tuscany italy the aggregates are mainly concentrated in irregular wispy and dark laminae which cross cut calcite crystal feathers to create a pervasive millimetre scale banded appearance in the deposit they also occur less commonly scattered irregularly through the calcite layers the aragonite needle aggregates are in the form of crosses fascicles sheaf shaped bundles or dumbbell shaped rosettes and spherulites locally irregular masses of needles also occur the fascicles rosettes and spherulites have hollow centres which resemble microbial components fungal spores bacterial colonies and pollen suggesting that the aragonite crystals are biotically nucleated the lamination is interpreted to reflect diurnal control stimulation of microbial activity during daylight concentrates cells in laminae and promotes aragonite calcification calcite feather crystals although traversed by the aragonite aggregate laminae have a clear appearance under the light microscope they form more or less continuously through the diurnal cycle by abiotic precipitation the constant association of aragonite with organic nuclei irrespective of whether the latter are in laminae or scattered through the calcite layers supports a biotic control on aragonite formation lamination in pleistocene travertines is superficially similar to that in the present day deposits but is diagenetically altered in the pleistocene deposits the calcite feathers appear dark under the light microscope and the aragonite aggregates where they are not altered to dark calcite are dissolved together with parts of the adjacent spar calcite and therefore appear light coloured

fluid mixing in carbonate aquifers near rapolano central italy chemical and isotopic constraints chemical major and trace elements and isotopic compositions dd and d 18 o in waters and d 13 ci n co 2 and 3 he 4 he in gases of natural thermal 11 and cold 39 fluids spring waters and gases discharging from a tectonic window of mesozoic limestones in central italy have proved to be the result of mixing processes inside the limestone formations the limestones provide a preferential route for subsurface fluid migration and they gather both descending cold ca hco3 b depleted groundwaters and rising convective ca so4 hco3 co2 saturated b rich thermal waters atmospherically derived descending gas components n2 ne he dissolved in rainfall that infiltrates the limestone system mix with n2 ne he depleted hot rising waters boron in the liquid phase and n2 and ne in the gas phase are the most useful elements to trace the mixing process the deeper gas samples recognised in the area are associated with the hotter waters emerging in the area in spite of being depleted in ne and he and light hydrocarbons they have the higher measured 3 he 4 he ratios suggesting a contribution of mantle 3 he to the gas phase this contrasts with deep circulation in the crust which would lead to increased concentration of 4 he in the deeper gases paradoxically there is more relative concentration of 4 he in the more air contaminated gas samples than in the deeper gas samples a similar paradox exists when the d 13 co f co 2 in the deeper gas samples is considered the shallower air contaminated gas samples although they should be affected by the addition of soil 13 c depleted organic c have d 13 ci n co 2 more positive than the deeper gas samples recognized since any deep hydrothermal source of co2 should generate co2 with more positive values of d 13 c than those measured at surface a multiple single calcite precipitation process from hydrothermal solutions with c isotopic fractionation along the rising path inside the mesozoic limestone formations is proposed 2002 elsevier science ltd all rights reserved

till beneath ice stream b 3 till deformation evidence and implications most of the velocity of ice stream b near the upstream b camp upb west antarctica appears to arise from deformation of a seismically detected subglacial till layer that averages 6 m thick available evidence indicates that the entire thickness of this till layer is deforming and is eroding subjacent bedrock into flutes parallel to ice flow and hundreds of meters across the resulting till flux beneath upb is equivalent to an average erosion rate of about 0 4 mm yr 1 in the catchment area and suggests that till deltas tens of kilometers long have been deposited at the grounding line during the holocene such deltas should be characterized by partial ice till decoupling across a water film and by a small ice air surface slope they may have been discovered by recent geophysical work

origin and diagenesis of quaternary travertine shrub fabrics rapolano terme central italy millimetre to centimetre sized arborescent shrub like calcite precipitates are common constituents of hot water travertine shallow pool deposits of quaternary age at rapolano terme tuscany italy in the presently forming travertines the shrubs consist of apparently random associations of i micrite aggregates and ii subhedral to euhedral rhombic spar crystal aggregates in thin section the micrite aggregates appear dark and the spar rhomb aggregates light giving the shrubs a mottled appearance travertines are basically produced by caco3 precipitation due to degassing and evaporation of the spring waters although biological influence may also stimulate precipitation the formation of masses of erect shrubs rather than dense crystal crusts that form on slopes is probably due to limited water flow in the pool environments microbes including bacteria and diatoms are important influences on shrub microfabric and external shape the micrite aggregates are associated with bacteriform bodies seen as tiny rods and spheres the micrite precipitates around these bodies and in adjacent biofilm spar rhomb precipitation appears to be external to the biofilm and may be related to the presence of diatoms which are locally closely associated with the spar rhombs although an essentially inorganic origin particularly for the more euhedral rhombs cannot be ruled out in the older quaternary travertines the original microfabric of the shrubs has been diagenetically altered the original mottled appearance of the shrubs has become uniformly dark and micritic and the evidence for the dual micritic and spar rhomb origin of the shrubs is obscured or destroyed spar micritization of the shrubs is probably due to abiotic and locally biotic dissolution previous studies did not recognize the diagenetic micritization and attributed shrub formation entirely to bacterial activity

lateral and vertical variations in sedimentology and geochemistry of sub horizontal laminated travertines cakmak quarry denizli basin turkey abstract the laterally extensive sub horizontal laminated travertine deposits outcropping in the cakmak quarry denizli basin turkey allows reconstructing their three dimensional geobody architecture based on field observations detailed petrographic and geochemical analyses stable carbon and oxygen isotopes major and trace elements the most important controlling porosity permeability parameters in this lacustrine dominated facies in relation to microfacies and diagenetic modifications were constrained sedimentological analyses and the observed architectural geometries allowed to subdivide the sub horizontal carbonate succession into three main depositional units these units in turn based on macro and microscopic observations were subdivided into nine dominant lithotypes reflecting an overall shrub flat and a marsh pool depositional setting the shrub flat facies mainly comprises dendritic shrub crusts boundstone pustular grainstone and clotted micrite mudstone to boundstone in contrast the marsh pool environment is dominated by coated reed rudstone to boundstone cryptalgal silty bioclast rich bioturbated mudstone and peloidal packstones the diagenetic study revealed that the sediments were affected by dissolution cementation sparmicritization recrystallization and local formation of fe oxi hydroxides and chalcedony among the diagenetic products in particular the calcite cements were investigated applying micro analysis of stable carbon and oxygen isotopes accordingly the co variation between the obtained isotopic values and the elemental concentrations sr mg na and s point to a thermogene fluid system that likely circulated through the subsurface limestones dolomites and evaporites of the lycian nappes these findings ensure an in depth understanding of continental carbonate deposition i e sub aqueous travertines in the context of a lacustrine depositional system

characterization of pebble fabrics in modern terrestrial glacigenic sediments pebble fabric data are available from several facies of glacigenic sediments deposited by modern glaciers where sedimentary processes can be observed or inferred with relatively little ambiguity over 100 samples from contemporary environments illustrate fabrics characterizing melt out till deformed and undeformed lodgement till sediment flow deposits and ice slope colluvium lodgement till fabric variability is related to the two layer structure of these sediments a structureless friable upper layer with low shear strength and high consolidation coefficient overlying a very compact material of horizontal platy structure fabric strength assessed by eigenvalue analysis is weaker and pebble dip is more dispersed in the upper structureless horizon stronger fabrics in the lower platy horizon may be primary depositional fabrics which are destroyed by subglacial shearing to give weaker fabrics in the upper horizon alternatively upper horizon fabrics may be characteristic of all recently deposited lodgement tills with stronger fabrics developing at depth by dewatering and consolidation there is a general reduction in fabric strength and an increase in particle dip associated with the transition from melt out tills through undeformed and deformed lodgement tills to sediment flow deposits and ice slope colluvium there is however considerable overlap in the fabric strengths characteristic of sediment flow deposits and deformed lodgement tills fabric data from modern glacial sedimentary facies are used to assist in interpreting the mode of deposition of some quaternary glacial sediments relatively strong fabrics characteristic of melt out tills and undeformed lodgement tills are more likely to be diagnostic of genesis than weaker fabrics associated with deformed sediments

pleistocene holocene tectonic reconstruction of the ballik travertine denizli graben sw turkey de formation of large travertine geobodies at intersecting grabens abstract travertine geobodies have been identified as potential reservoir analogues to carbonate build ups in pre salt hydrocarbon systems to investigate travertine geobody deformation faults were mapped in 35 travertine quarries that excavate the ballik travertine i e a c 12 5 km2 large travertine geobody that precipitated at the intersection of the ne margin of the denizli basin and neighbouring baklan graben sw turkey this travertine precipitated from cooling carbonate saturated thermal spring waters that resurfaced along the margin fracture fault network and through neogene unconsolidated underlying sediments from the denizli basin floor to the uplifted graben shoulders fault orientation is dominantly wnw ese oriented with major basin faults showing a left stepping trend along the upper denizli margin travertine is only deformed by extensional normal faults along the lower margin travertine starts with a subhorizontal facies but evolves to a travertine facies formed by a sloping topography with a domal architecture paleostress inversion of fault slip data reveals that an early pleistocene nne ssw extensional transtensional phase initiated the wnw ese oriented graben facing normal fault network in the middle pleistocene the ballik fault network was left lateral strike slip reactivated because it acted as a transfer zone between the nw se extending neighbouring baklan basin and nw se extension along ne sw oriented margin faults of the dghs in this stress configuration travertine precipitated along the sw margin fault of the baklan graben after strike slip reactivation a late pleistocene to current nne ssw extensional stress regime reinstalled during which margin faults widened and active travertine precipitation moved to more central parts of the dghs as different tectonic regimes affect graben intersections reservoir analogues can have a complex deformation history driven by fault reactivation and recurrent stress permutations this study concludes that large travertine geobodies can form at graben intersections because of their susceptibility to enhanced fluid flow through the complex fault fracture network

on subglacial stone pavements in till four pavements from central and western canada display uneven pavement surfaces abundant tilted and inverted stones reversed lee ends fine crossing striae in various directions weak striae around curves worn facets distributed evenly on rounded stones and till fabric girdles collectively inconsistent with the popular concept of stones firmly held in till being abraded by overriding ice based on these data new models are offered that involve stone rotation in viscously deforming till to produce deformation pavements in the specific model increased pore water pressure under moving ice locally mobilizes previously formed lodgment and or erosional pavements into deformation pavements in the more general model stones released from the sole of a wet based glacier rotate interact and settle into a viscous suspension zone in deforming till according to velocity density and viscosity gradients stone axes and striae settle into various orientations following dewatering and till stiffening conceptu

linking co2 degassing in active fault zones to long term changes in water balance and surface water circulation an example from sw turkey abstract calcite veins are commonly found at shallow depth a few metres below the surface in damage zones of active normal fault systems in southwest turkey although earlier studies demonstrated the link between the vein formation and seismicity the association of near surface carbonate precipitation with climate driven hydrological conditions water table amount of precipitation and evaporation and water discharge is poorly understood in this study using the u th dating method we investigate the timing of vein formation and the interrelationship between tectonic and climatic related hydrological processes carbonate precipitation is interpreted to occur as a result of sudden pressure drops and co2 release after earthquake induced fracturing vein formation mostly occurred during glacial periods which coincide with slow growth rates and higher oxygen isotope values of speleothems from the eastern mediterranean region we relate these episodes to reduced winter rainfall due to the decrease in westerly flow in sw turkey these somewhat drier conditions influenced the chemical composition of circulating water creating conditions conducive to carbonate precipitation and sealing of damage zones these conditions also facilitated co2 accumulation and overpressure build up in the rupture zones failure of the faults resulted in the release of large volumes of co2 rich fluids and the generation of shallow carbonate veins it is proposed that during phases of increased winter rainfall co2 is advected to the surface and discharged as passive degassing when meteoric water circulation is enhanced while regional tectonics is the ultimate driver of fault activity and fracture formation climate driven near surface hydrological changes may have played an important role in modulating co2 rich fluid circulation and surface discharge

mineralogical crystal morphological and isotopic characteristics of smooth slope travertine deposits at reshuitang tengchong china abstract reshuitang is an important active hydrothermal area in the tengchong geothermal field and is characterized by many hot springs and their associated deposits detailed mineralogical crystal morphological and stable isotopic investigations of the smooth slope fossil travertines at reshuitang and hydrochemical studies of two active springs around the fossil travertines were conducted to study their genesis the results show that 1 the modern springs discharge waters with high temperature 70 c near neutral ph 6 3 8 34 and high saturation indices of calcite and aragonite 2 the fossil travertines contain calcite and small amounts of mn fe oxides halite thenardite and non carbonate debris 3 the calcite include ray crystals dendrite crystals platy crystals and spike crystals and 4 13c and 18o of the fossil travertines at reshuitang range from 1 59 to 0 87 and 6 48 to 7 80 respectively according to comparison between the travertines at reshuitang and other travertines in tengchong all these travertines are thermogene travertines with a large contribution of mantle degassing to their parent co2 but are formed at different temperatures the fossil travertines at reshuitang similar to those at shuzhishi are formed at high temperatures near 100 c which results in weak microbial activities during the formation of the fossil travertines most of the calcite crystals at reshuitang were non equilibrium products precipitated directly from the spring waters during the deposition process while the spike crystals originated from diagenetic dissolution of large calcite crystals comparison between the fossil travertines at reshuitang and other smooth slope travertines from other areas shows these smooth slope travertines have different lithofacies and fabrics in smooth slope environments temperature may control the distribution and development of microbes and the intensity of co2 degassing and consequently cause the precipitation of contrasting fabrics and lithofacies

growth of fissure ridge travertines from geothermal springs of denizli basin western turkey fissure ridge travertines grown from geothermal springs of denizli basin southwestern turkey are investigated through stratigraphic structural geochemical and geochronological methods with the aim of understanding the growth of these elongate mound shaped structures two main types of travertine deposits are recognized 1 bedded travertines which grew as flowstone on sloping surfaces and form the bulk of fissure ridges and 2 banded travertines which grew as veins within the bedded travertine chiefly along its central feeding conduit stratigraphic and structural observations shed light on the bedded banded travertine relationships where the banded features grew through successive accretion phases crosscutting the bedded travertine or forming sill like structures the bedded and banded travertines alternated their growth as demonstrated by complicated crosscutting relationships and by the upward suture in places of banded travertine by bedded travertine that was in turn crosscut by younger banded travertine the bedded travertine is often tilted away from the central axis of the fissure ridge thus leaving more room for the central banded travertine to form u series ages confirm the bedded banded travertine temporal relationships and show that the growth of the studied fissure ridges lasted up to several tens of thousands of years during quaternary time the banded travertine was deposited mainly during cold events possibly in coincidence with seismic events that might have triggered the outflow of deep geothermal fluids c and o stable isotope and rare earth element data indicate a shallow feeding circuit for the studied structures with a fluid component deriving from a deeper geothermal circuit a crack and seal mechanism of fissure ridge growth is proposed modulated by the interplay of local and regional influencing factors and mechanisms such as geothermal fluid discharge paleoclimate tectonics and the progressive tilting of bedded travertine limbs over a soft substratum creating the necessary space for the central veins to grow

particle and aggregate mobility in till microscopic evidence of subglacial processes abstract microscopic studies of tills show that the deforming bed of glaciers is made up of minute rotational elements or wheels consisting of a nucleus alone or a nucleus with spiralling arms of fine grains these fine grains can move from one wheel to the next providing a process of high grain mobility within a deforming subglacial till recognition of this process explains a variety of glacial distribution patterns i e the mineralogical reflection of subjacent lithologies in the till matrix the side by side occurrence of far travelled erratics and locally derived matrix and the shape of geochemical anomalies

subglacial till formation microscale processes within the subglacial shear zone abstract this was a study of subglacial deformation till genesis from a modern temperate glacier at skalafellsjokull iceland detailed microscale properties of till samples from scanning electron microscope sem and thin section analysis were examined from a glacial site with in situ subglacial process monitoring and an exposed subglacial surface in the foreland two lithofacies were examined a grey sandy till derived from the ash and basalt and a silty reddish brown till derived from oxidized paleosols and or tephra layers these also represented a clay content continuum from low 0 3 to high 22 3 the evolution from debris to subglacial till was investigated this included a reduction in grain size 21 for grey lithology 13 reddish brown lithology and reduction in rounding ra 32 for the grey lithology 26 for the reddish brown lithology and the quantification and analysis of the different grain erosion comminution processes in the resultant till it was shown that the microstructures within a till were dependent on shear strain and glaciological conditions deformation history the low clay content tills were dominated by linear structures lineations and boudins and anisotropic microfabric whilst the higher clay content tills were dominated by rotational structures turbates and plaster and isotropic microfabric these results are important in our understanding of the formation of both modern and quaternary tills and informs our reconstruction of past glacial dynamics

bowl shaped basin related to low angle detachment during continental extension the case of the controversial neogene siena basin central italy northern apennines abstract this paper deals with the tectonic evolution of a bowl shaped neogene basin siena basin located in the inner northern apennines and developed during an articulated tectonic evolution this basin was controversially interpreted by different authors as graben half graben or thrust top basin structural and stratigraphic data from the basin substratum and filling sediments integrated with the interpretation of reflection seismic profiles and borehole logs highlight that the siena basin consists of a tectonic depression with a complex internal architecture such a basin developed on a multilayered substratum deeply affected by extensional tectonics since the middle miocene extensional detachments produced a widespread thinning of the basin substratum and superimposed on contractional structures developed during the northern apennines collisional events extensional detachments accommodated within weak horizons and gave rise to the lateral segmentation of most competent stratigraphic horizons sediments filling the siena basin mainly deposited on the ligurian units the topmost tectonic units forming the tectonic pile in the gap between two laterally segmented geological bodies made up of the triassic siliciclastic succession of the verrucano group such a lateral segmentation produced a synformal structural depression not delimited by faults filled by late serravallian late messinian marine to continental sediments which deposited during the extensional faulting from the latest early pliocene to the middle pliocene the architecture of the basin was modified by an high angle normal fault system which affected the eastern side of the basin and produced new accommodation space for marine sediments in sum the siena basin consists of a sin tectonic basin developed on the hanging wall of staircase extensional detachments later affected by high angle normal to oblique faults the latter faults defined a half graben during the latest evolution of the basin the tectonic evolution of the siena basin made it possible to point out some differences with respect to the types of bowl shaped basins related to extensional detachments and named as supradetachment basins

subglacial comminution in the deforming bed inferences from sem analysis this study investigates the variations in erosional processes beneath briksdalsbreen a norwegian valley glacier with a thin coarse grained deforming bed the subglacial zone was investigated in situ close to the central glacial flow line site a and close to the valley wall site b via boreholes the till was collected using two different sediment samplers and the bed was examined using a borehole video camera in order to evaluate how representative borehole sampling was of the subglacial environment the results from in situ subglacial samples were compared with random samples taken from an exposed subglacial surface in the glacier foreland as well as a sample taken from the site after glacier retreat the results indicated that the texture of the exposed subglacial surface was similar to in situ samples from subglacial site b close to the valley wall and that the samples collected with the small sediment sampler had the closest fit sem analysis revealed eroded quartz grains at both sites as a result of rotation abrasion and fracture the samples from close to the valley wall were very poorly sorted with evidence for rounding and preservation of pre weathered surfaces which suggest that a relatively simple pattern of erosion from crushing to rotation dominated however the till from the centre of the glacier was better sorted more angular and with few pre weathered surfaces we suggest that this results from a more complex glacial erosional history associated with greater strain and longer residence time within the deforming layer when compared with other deformation tills it was confirmed that there is a relationship between grain size and erosional style clay rich tills show little comminution fine sand rich tills generate a significant silt component whilst the coarse sand rich tills at briksdalsbreen showed complex deformational styles but no significant silt component

genesis and diagenesis of travertine futamata hot spring japan abstract genetic and diagenetic processes of travertine were examined at futamata hot spring where both active and inactive subfossil and fossil travertines are present geochemical and geomicrobiological analyses of active travertines reveal that abiotic process of caco3 precipitation is predominant photosynthetic inhibition of caco3 precipitation occurs at the upstream while the cyanobacterial population is low in the downstream resulting in photosynthesis induced caco3 precipitation only in the midstream nonetheless microorganisms have an effect upon depositional fabrics and filamentous cyanobacteria possessing non acidic sheaths contribute to the particle trapping binding and the generation of pore space both active and inactive travertines are mainly composed of calcite however active travertine in the up midstream also contains some aragonite due to high rates of co2 degassing active and subfossil travertines are characterized by domal topography and relatively high flow rates are assumed due to the dominance of slope facies on the other hand fossil travertines are characterized by fissure ridge topography and relatively low flow rates are assumed due to the dominance of crest and marsh facies the elemental composition of travertines primarily reflects their constituent minerals and the active travertines consisting of both aragonite and calcite show higher sr ba na and k contents whereas travertines consisting solely of calcite show higher mg and mn contents due to elevated mn content bright cathode luminescence is exhibited by the primary calcite of active travertines most fossil travertines have experienced prominent diagenetic alteration in the vadose zone and are commonly cemented and recrystallized in addition to meteoric water percolating hot spring water was also involved in the diagenetic process combined with the results of u th dating our results suggest that the formation of fissure ridge travertines at futamata hot spring began approximately 20 thousand years ago ka via fault activity which terminated at around 7 ka and the domal travertines were formed by hot spring water discharging from several vents

calcite veining and feeding conduits in a hydrothermal system insights from a natural section across the pleistocene golemezli travertine depositional system western anatolia turkey abstract linking the architecture of structural conduits with the hydrothermal fluids migrating from the reservoir up to the surface is a key factor in geothermal research a contribution to this achievement derives from the study of spring related travertine deposits but although travertine depositional systems occur widely their feeding conduits are only rarely exposed the integrated study carried out in the geothermal golemezli area nearby the well known pamukkale area denizli basin western anatolia turkey focused on onyx like calcite veins banded travertine and bedded travertine well exposed in a natural cross section allowing the reconstruction of the shallower part of a geothermal system the onyx like veins represent the thickest vein network 150 m so far known new field mapping and structural kinematic analyses allowed to document a partially dismantled travertine complex bedded travertine formed by proximal fissure ridges and distal terraced pools depositional systems the banded calcite veins wnw trending and up to 12 m thick developed within a 200 m thick damaged rock volume produced by parallel fault zones th u dating indicates a long lasting middle late pleistocene fluids circulation in a palaeo geothermal system that due to its location and chemical characteristics can be considered the analogue of the nearby still active pamukkale system the isotopic characteristics of the calcite veins together with data from fluid inclusions analyses allow the reconstruction of some properties i e temperature salinity and isotopic composition and processes i e temperature variation and intensity of degassing that characterized the parent fluids and the relation between degassing intensity and specific microfabric of calcite crystals elongated microsparite micrite bands controlled by changes fluctuations of the physico chemical fluid characteristics

palaeomagnetic and rock magnetic properties of travertine its potential as a recorder of geomagnetic palaeosecular variation environmental change and earthquake activity in the sicak cermik geothermal field turkey travertine the product of incremental growth of inorganic carbonate is potentially a high resolution recorder of geomagnetic palaeosecular variation psv when it incorporates small amounts of ferromagnetic material it grows most regularly in regions of neotectonic activity where geothermal waters feed into extensional fissures and deposit successive layers of carbonate as fissure travertine the same waters spill out onto the surface to deposit bedded travertine which may incorporate wind blown dust including ferromagnetic particles tectonic travertine deposits are linked to earthquake activity because the geothermal reservoirs are reset and activated by earthquake fracturing but tend to become sealed up by carbonate deposition between events this study investigates whether sequential deposition can identify cycles of psv and provide a means of estimating rates of travertine growth and earthquake frequency the palaeomagnetic record in three travertine fissures from the socak cermik geothermal field in central anatolia and nearby bedded travertines dated up to 360 000 years in age u th are investigated to evaluate magnetic properties and relate the geomagnetic signature to earthquake induced layering sequential sampling of bedded travertine from the margins earliest deposition to centres of fissures last deposition identifies directional migrations reminiscent of psv thermal demagnetisation shows that goethite pigment is not a significant remanence carrier instead hematite and more rarely magnetite is the carrier magnetic susceptibility of fissure travertine is proportional to the calcite aragonite ratio two frequency susceptibility analysis identifies a ferromagnetic content in bedded travertine dominated by fine superparamagnetic grain sizes whereas the fissure travertine has mostly single and multidomain grain sizes a difference interpreted to reflect contrasting energies of the two environments plus atmospheric input in the bedded travertine fissure travertine possesses strong lineated anisotropy of magnetic susceptibility ams with horizontal kmax axes oriented along the fissure axes and kint and kmin distributed within the orthogonal plane this is explained by rolling of ferromagnetic grains up the side of the fissure during repeated water ejection until fixed by the host carbonate precipitation in contrast bedded travertine has low magnitude ams with near neutral ellipsoid shapes controlled by settling of grains during weak outflow from the axis of the fissure ridge the source of the magnetic minerals in the fissure travertine is probably in material washed down by meteoric waters from the local terra rossa soil and concentrations of these minerals and hence magnetic susceptibility could be a signature of pluvial environments fissure travertine is a reliable recorder of the ambient field when layered although bedded travertine is found to exhibit inclination shallowing on the assumption that psv cycles record periods of 1 2 ky layering in the travertine identifies resetting of the geothermal system by earthquakes every 50 100 years in this region travertine precipitation occurs at rates of 0 1 0 3 mm year on each side of the

a hypothesis on the relative roles of crushing and abrasion in the mechanical genesis of a glacial sediment relatively new techniques of optical microscopy and interferometry have been used combined with fractal and modal analyses to study possible deformation mechanisms in glacial sediment from langjokull iceland previous studies have shown that the langjokull till has reached an ultimate grading during deposition and transport the results presented here add information on the deformation mechanisms that it may have suffered until and after reaching this ultimate grading the modal and fractal analyses suggest high mechanical weathering this is supported by the shape and texture of particles determined using the different imaging techniques of laser scanning optical microscopy combined with three dimensional image construction interferometry and scanning electron microscopy the larger particles have highly weathered surfaces indicating severe abrasion to their surface during transport the finer particles show less abrasion stamp and higher angularity they also bear evidence of relatively fresh fractures this seems to indicate that as the sediment became better distributed during transport breakage moved from the larger to the smaller particles with the larger grains only suffering abrasion this supports the hypothesis of fractal breakage in this type of soil

a melting layer model and its use in correcting for the bright band in single polarization radar echoes a new dynamic microphysical model of the melting layer is presented developed from a previous model this new model is applied to obtain vertical reflectivity profiles vrps and vertical attenuation profiles vaps through the melting layer which both allow for and neglect propagation effects the model profiles are compared with measured profiles at a range of different frequencies in particular a detailed comparison was made for frequencies in the x band the vrps are used to generate relations between bright band peak intensity and surface rainfall rate r0 at frequencies in the s c and x bands relations between other model bright band parameters and r0 are found to be more complicated functions of model input parameters the model profiles are also applied to the problem of correcting for the radar bright band in the meteorological office s radar data early results from three detailed case studies seem promising however the technique has yet to be tested in an operational environment

a multi methodological approach to reconstruct the configuration of a travertine fissure ridge system the case of the cukor quarry suttő gerecse hills hungary abstract travertines are continental carbonates that precipitate from spring waters mainly due to co2 degassing they are widely quarried as building stone which has led to numerous often abandoned travertine quarry outcrops these and other outcrops however merely represent the surface expressions of the complex architecture of travertine bodies and their deep rooted feeding systems integration of field observations and geochemical analyses with crucial subsurface geophysical data is required in order to fully understand travertine systems and their relationship to the local geological framework such a multi methodological approach is illustrated here for the case of the abandoned cukor quarry radio magnetotelluric rmt and electrical resistivity tomography ert surveys provide unique insights into local tectonics geobody architecture and the topography preceding travertine deposition altogether the lens shaped isolated domal geobody with spring proximal lithofacies and subvertical bedding in addition to the contrasting geochemistry and age with surrounding travertine enabled the unequivocal reconstruction of the dismantled cukor fissure ridge this study illustrates the high potential of this multi methodological approach on poorly exposed strongly weathered quarried and tectonically deformed travertine bodies and provides information on the complex feeding system beneath travertine deposits their reconstruction can be interpreted in light of the neo tectonic expression of regional uplift helps to complete the regional tectonic history and provides insights into older landscapes that lack preservation or would no longer be immediately recognized at the surface

evolution of subglacial overdeepenings in response to sediment redistribution and glaciohydraulic supercooling received 16 august 2012 revised 18 december 2012 accepted 15 january 2013 1 glaciers erode bedrock rapidly but evacuation of sediments requires efficient subglacial drainage networks if glaciers erode more rapidly than evacuation proceeds a protective subglacial till layer can form to armor the bed where glaciers cross overdeepenings local closed depressions the bed slope opposes the ice surface and lowers the hydraulic potential gradient that drives water flow here we present results of a dynamic distributed model of coupled basal water flow and sediment transport to show how overdeepenings evolve over the course of a melt season we use steady state calculations as well as numerical simulations to understand how alluvial bed erosion alters overdeepenings numerical results from a modified form of the spring hutter equations show behaviors that cannot be inferred from either local or steady state calculations in general opposition of surface and bed slopes lessens sediment transport regardless of ice accretion from glaciohydraulic supercooling drainage efficiency strongly affects erosion and deposition rates results show characteristic behaviors of flow through overdeepenings such as overpressured water systems and accretion rates compatible with field measurements simulations that start with overdeepened glacier configurations progress out of a freezing regime where glaciohydraulic supercooling occurs this progression indicates that glacier hydrology is more strongly affected by erosion and deposition than by freezing from glaciohydraulic supercooling we discuss how this outcome affects glacier erosion and sediment transport under modern and past ice sheets

studying travertines for neotectonics investigations middle late pleistocene syn tectonic travertine deposition at serre di rapolano northern apennines italy middle late pleistocene tectonic activity has been inferred through studies on travertine deposits exposed in a tract of the hinterland northern apennines a detailed study on the relationships between tectonics and travertine deposition coupled with 230th 234u age determination of travertines at cava oliviera quarry located close to serre di rapolano village southern tuscany northern apennines allowed us to recognise pleistocene faults whose activity has been referred to 157 24 ka at least travertine deposition was tectonically controlled by wsw ene striking oblique and normal faults associated to a main fault named as the violante fault this structure dissected a regional normal fault known as the rapolano fault early middle pliocene in age which bounded the eastern side of the pliocene siena basin and gave rise to space accommodation for clayey and sandy marine sediments hydrothermal circulation and related travertine deposition was favoured by the damaging enhancement due to the fault fault intersection tectonic activity has been also documented by deformation recorded by travertines which suggest a main tectonic event between 64 5 and 40 5 ka the tectonic activity described for the study area agrees with the quaternary tectonic evolution documented in the surrounding areas e g mt amiata and mt vulsini as well as the tyrrhenian margin of the central apennines indicating that a widespread tectonic activity affected the inner part of the apennines until the latest quaternary

notes and correspondence polarimetric radar observation of multiple freezing levels abstract an unusual multiple freezing level event observed with polarimetric radar during the second phase of the improvement of microphysical parameterization through observational verification experiments improve 2 field program is described the event occurred on 28 november 2001 when a warm front moved over the oregon cascade mountains as the front approached an elevated melting layer formed above a preexisting melting layer near ground continued warming of the lower atmosphere eventually dissipated the lower melting layer the polarimetric measurements are used to estimate the height of the freezing levels document their evolution and deduce hydrometeor habits the measurements indicate that when the two freezing levels were first observed melting was incomplete in the upper melting layer and characteristics of particles that passed through the two melting layers were similar as warming progressed the character of particles entering the lower melting layer changed possibly becoming ice pell

possible microbial effects on stable carbon isotopes in hot spring travertines recent and older early holocene to pleistocene hot spring travertine carbonates from central italy have two distinctive macrofabrics crystalline crusts and shrubs crystalline crusts are laminated slope deposits that formed abiotically following co 2 degassing from spring water the formation of shrub travertine irregular dendritic precipitates from pool environments is controversial and has been attributed to both abiotic and microbial processes oxygen isotope variation in our travertines can be explained by abiotic processes mainly co 2 degassing in contrast our carbon isotope data cannot be wholly explained by abiotic co 2 degassing invoked in earlier studies because photosynthesis is known to preferentially remove 12 c leaving ambient waters enriched in 13 c this fractionation should be recorded in delta 13 c values of microbially influenced travertine our shrub carbon isotope values are between 0 5 per thousand and 6 0 per thousand larger than values for associated abiotic precipitates and this difference is probably caused by microbial activity these isotope data support previous visual evidence that some shrub fabrics are microbially influenced

travitonics using travertines in active fault studies abstract late quaternary travertines deposited from hot springs can reveal much about the neotectonic attributes and histories of structures on the basis of field studies in the aegean region turkey and greece the northern apennines italy and the basin and range province usa we conclude that the following relationships are of predictive value i travertine deposits are preferentially located along fracture traces either immediately above extensional fissures or in the hanging walls of normal faults ii the locations of many travertine fissure ridge deposits coincide with step over zones relay ramps between fault segments networks of intersecting tensional fissures reflecting the complex strains experienced in such settings are probably responsible for enhancing hydrothermal flow iii the morphology of travertine deposits overlying extensional fissures is controlled by the rheology of the underlying materials tufa cones towers pinnacles form on former and present lake floors where fissures underlie unconsolidated sediments whereas fissure ridges develop where fissures cut bedrocks at the surface iv fissure ridges comprise outwardly dipping bedded travertine flanking a central tensional fissure filled by vertically banded travertines fissures can be used to infer local stretching directions v where there are travertines datable by the u series method it is possible to calculate time averaged dilation and lateral propagation rates for individual fissures vi most fissures cutting fissure ridges comprise self similar angular segments with fractal dimensions in the range 1 00 1 12 the properties of bedded travertine combined with stress perturbations at fissure tips probably being responsible for such similar fractal dimensions being inferred from such a wide range of locations fissures gradually increasing in width with depth are products of continuous fracture dilation in contrast to those that form during episodic dilation which display stepped increases of width with depth vii travertine deposited from springs along fault zones accumulate in terraced mounds sited down slope of the spring line viii many post depositional fractures cutting travertine deposits are locally oriented at right angles to deposit margins and ix systematic joints in travertines are restricted to those parts of eroded sheet deposits that have been exhumed

geomorphological consequences of a glacier advance across a paraglacial rock avalanche deposit abstract glacial reworking of paraglacial rock slope sediment has been inferred from long deglaciated terrains to contribute significantly to glacial sediment transfer at feegletscher switzerland we provide the first description of the geomorphological consequences of glacier advance across paraglacial rock avalanche sediment this produced a small arcuate end moraine that encloses a zone of hummocky debris the sedimentology of these landforms is conditioned by rock avalanche sediment and can be differentiated from purely glacial sediments indicating that the contribution of glacially reworked rock avalanche debris may be recognisable in deglaciated terrain remarkably much of the overridden rock avalanche debris has maintained its angularity and delicate brecciation features despite up to 40 years of glacial action we suggest that the surface carapace facies of the rock avalanche deposit comprising large openwork blocks limited the effectiveness of glacial erosion processes the carapace facies will have resisted significant erosion by the relatively thin glacier because of its high shear strength and because it was able to transmit subglacial meltwater efficiently thus enhanced debris transfer associated with reworking of paraglacial rock avalanche sediment should not necessarily be expected during the initial stages of glacier advance

deformation of till beneath ice stream b west antarctica the behaviour and possible instability of the west antarctic ice sheet depend fundamentally on the dynamics of the large ice streams which drain it model calculations show that most ice stream velocity arises at the bed1 2 and radar sounding has shown the bed to be wet3 but the basal boundary condition is not well understood seismic evidence from the upstream b camp upb on the siple coast of west antarctica4 shows that the ice stream there rests on a layer of unconsolidated sediment averaging 5 or 6 m thick in which the water pressure is only 50 kpa less than the overburden pressure because this thin layer occurs well inland beneath an active ice sheet and rests on a surface showing flutes4 characteristic of glacial erosion5 we presume that it is glacial till we propose here that deformation within the till is the primary mechanism by which the ice stream moves and we discuss implications of this hypothesis

grain textural analysis across a range of glacial facies a technique proposed by hooke and iverson 1995 to identify deformed subglacial sediments is reviewed and tested based on two main objectives first an investigation of whether the fractal dimension can distinguish between non deformed and deformed facies for which we compare supraglacial and subglacial facies explicitly second an evaluation of whether the fractal dimension can be used as a diagnostic criteria to discriminate between different styles and degrees of basal deformation this is tested using a range of sediments from the deformation continuum suggested by hart and boulton 1991b sixteen subglacial samples were selected from quaternary sites in england and three supraglacial samples from the modern haut glacier d arolla switzerland the mean fractal dimension for the subglacial diamicton matrix facies was 2 92 similar to findings of 2 90 by hooke and iverson 1995 for their basal tills the supraglacial facies displayed a mean fractal dimension of 2 83 which is unusually high for facies which are assumed to be undeformed a mann whitney u test showed that fractal dimensions of supraglacial and subglacial diamicton matrix facies were not significantly different no significant difference was found between the fractal dimensions of the different tectonic facies within the subglacial group it may be impossible to separate the subglacial and supraglacial facies because of complex debris paths within the glacier grain fracture or parent lithology may affect the particle size distribution of subglacial facies

freezing rate effects on the physical characteristics of basal ice formed by net adfreezing a number of theoretical and empirical studies have indicated that many individual characteristics of ice formed by processes of net basal adfreezing may be sensitive to the rate of propagation of the freezing front through the reservoir concerned the effects of freezing rate on the the stable isotope chemistry and crystallography of ice in addition to the disposition and character of included debris and gas are reported unidirectional freezing through a cylindrical reservoir containing various water sediment mixtures has been conducted in the laboratory and the resulting cores analysed for debris and gas disposition and ice crystal size and fabric the data lend support to inferences drawn from studies concerned with specific ice properties and an idealized suite of characteristics is developed which may be diagnostic of basal ice formed by net adfreezing

radar estimates of rainfall rates at the ground in bright band and non bright band events summary the major error in estimating precipitation rates at the ground from radar arises from the change in radar reflectivity z with height in stratiform precipitation z rises in the bright band where the snow is melting and then falls steeply in the dry ice above in regions of vigorous convection containing graupel the bright band is absent and the fall in z with height is less marked if accurate estimates of surface precipitation are to be made based upon radar observations taken within or above the bright band it is important to use a correction scheme which uses a different vertical profile of reflectivity vpr for the two precipitation types using a large radar data set this work addresses the issue of vpr variability by constructing average vertical profiles and sorting them into snow and graupel categories using the value of the linear depolarization ratio at the melting layer these observations show that convection is often embedded within stratiform precipitation and some convective showers containing snow have bright bands as a result the use of an average profile over the whole region scanned by radar leads to only marginal improvement in rain estimates instead this work proposes that a bright band correction should always be applied unless the value of z at 1 5 km above the bright band exceeds 30 dbz in which case a convective vertical profile of 2 dbz km should be used this z threshold indicates that graupel only forms when the ice water content exceeds 0 35 gm which has implications for ice parametrization schemes in mesoscale models

sedimentary processes at the base of a west antarctic ice stream constraints from textural and compositional properties of subglacial debris samples of sediments from beneath ice stream b at camp upb west antarctica provide the first opportunity to study the relationship between sediment properties and physical conditions in a sub ice stream environment piston coring in holes bored by hot water drilling yielded five 1 3 m long undisturbed subglacial sediment cores we analyzed granulometry composition and particle morphology in these cores the upb cores are composed of a clay rich unsorted diamicton containing rare marine diatoms sedimentary particles in these cores bear no evidence of the recent crushing or abrasion that is common in other subglacial sedimentary environments the presence of reworked diatoms and their state of preservation as well as the relative spatial homogeneity of this diamicton suggest that the upb cores sampled a several meter thick till layer and not in situ glacimarine sediments the till does incorporate material recycled from the subjacent poorly indurated tertiary glacimarine sediments of the ross sea sedimentary basin which extends beneath this part of the west antarctic ice sheet we propose that the lack of significant comminution in the upb till is ultimately due to its setting over these easily erodible clay rich source sediments the resulting fine grained till matrix inhibits glacial comminution because it facilitates buildup of high pore water pressures and hinders interparticle stress concentrations our observations are consistent with the conjecture that subglacial deformation of weak fine grained tills does not produce significant comminution of till debris elson 1988 based on our findings we hypothesize that extensive layers of weak till may develop preferentially where ice overrides preexisting poorly indurated fine grained sediments since such weak till layers create a permissive condition for ice streaming sub glacial geology may have an indirect but strong control over the location extent and basal mechanics of ice streams

are u th dates correlated with historical records of earthquakes constraints from coseismic carbonate veins within the north anatolian fault zone u th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late quaternary crustal deformations in this study for the first time we correlate u th ages of travertine deposits in coseismic fissures along the north anatolian fault zone with records of paleoseismological studies supported by historical earthquake catalogued data u th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major holocene earthquakes our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the north anatolian fault zone the periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies at least six of the periods correspond to the earthquakes reported in the historical catalogues the age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern north anatolian fault zone with a mode at 130 330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault recorded events in carbonate veins indicate a close epicenter d vi paleoearthquakes our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques this tool has advantages over traditional paleoseismological methods for the understanding of long term earthquake behavior particularly for prehistoric late pleistocene events which cannot be dated easily by traditional paleoseismological methods

microscopic evidence of subglacial deformation abstract subglacial deformation is by now a well established process however recognition of this process in pleistocene tills is not always clear studies of thin sections of pleistocene tills show that there are a variety of microscopic features caused by deformation this paper gives a review of microscopic evidence for subglacial deformation and starts with a case where deformation could be established macroscopically then traces the microscopic features through planar and rotational movements which are described and separated accordingly attention is also given to features caused by crushing of grains and sediment dewatering these studies indicate that almost all basal tills show evidence of subglacial deformation rather than sedimentary derivation this implies that if we want to understand subglacial processes such tills should be described in tectonic rather than sedimentary terminology

drainage through subglacial water sheets 1 subglacial drainage plays an important role in controlling coupling between glacial ice and underlying bed here we study the flow of water in thin macroporous sheets between ice and bed previous work shows that small perturbations in depth of a nearly parallel sided water film grow unstably because these areas have enhanced viscous dissipation that leads to enhanced melting of an ice roof we argue that in the presence of bed protrusions bridging a water sheet downward motion of the ice roof can stabilize this sheet stability results when the rate of roof closure increases faster with water depth than the rate of viscous dissipation we therefore modify existing theory to include protrusions that partially support the overlying glacier differences in the pressure on protrusions relative to water pressure drive roof closure the mechanisms of both regelation and creep normal to the bed close the overlying ice roof and decrease the ice bed gap in order to account for multiple protrusion sizes along the bed for instance resulting from an assortment of various sized sediment grains we incorporate a method of partitioning overburden pressure among different protrusion size classes and the water sheet partitioning is dependent on the amount of ice protrusion contact and therefore water depth this method allows prediction of roof closure rates we then investigate stable steady sheet configurations for reasonable parameter choices and find that these steady states can occur for modest water depths at very low effective pressures as is appropriate for ice streams moreover we find that multiple steady sheet thicknesses exist raising the possibility of switches between low and high hydraulic conductivity regimes for the subglacial water system

tectonic control on travertine and calcareous tufa deposition in a low temperature geothermal system sarteano central italy this paper presents an integrated study directed toward an understanding of the tectonic control on the hydrothermal circulation and resulting deposition of middle late pleistocene travertine in a low temperature geothermal field of southern tuscany located in the sarteano area central italy the study area is characterized by thermal springs c 25 c and related continental carbonate deposits structurally controlled by sw ne trending oblique to strike slip faults dissecting previous normal faults sedimentological stratigraphical data and 230 th 234 u radiometric age determination for the travertine indicate that continental carbonates were deposited in a tectonically controlled perched spring system from 268 22 ka at least to the present the hydrothermal system is and was characterized by meteoric waters with a minor contribution from fluids of deeper origin meteoric waters infiltrated to depth through tectonically damaged zones of mesozoic and cenozoic carbonate rocks and overheated as a result of localized anomalous geothermal gradient then fluids enriched in bicarbonate sulphate moved up along highly fractured rock masses at the intersection between strike slip faults and normal faults this paper highlights the use of continental carbonates in the reconstruction of palaeohydrothermal systems in terms of the location of the main conduits for hydrothermal fluid flow age of faulting and physical properties of hydrothermal fluids

evaluating the geogenic co2 flux from geothermal areas by analysing quaternary travertine masses new data from western central italy and review of previous co2 flux data abstract quantification of carbon fluxes between solid earth and its atmosphere is necessary to understand the global geological carbon cycle some of the main co2 contributors are metamorphism and magmatic mantle degassing co2 is discharged from active and quiescent volcanoes fault zones geothermal systems and co2 rich groundwater here a new method for the estimation of the geogenic flux of co2 from tectonically active regions based on the volume composition and age of travertine deposits is proposed the method is applied to the travertine deposits of western central italy where travertine deposition is driven by degassing of co2 charged groundwater results show that the study areas are characterized since middle pleistocene by diffuse co2 degassing processes with time averaged co2 fluxes ranging between 1 24 0 12 106 mol y 1 km 2 and 1 38 0 42 106 mol y 1 km 2 these values are of the same order of magnitude of carbon dioxide fluxes measured by different methods in western central italy and are higher than the global baseline co2 flux from high heat flow regions the review of the available 234u 230th and 14c data shows that the co2 degassing processes that affects western central italy nowadays were already active at least 350 ka ago proving that this region is a globally relevant case for the study of earth degassing considering the widespread occurrence of travertine deposits in tectonically active areas worldwide the proposed approach can be used as a reliable tool to estimate the co2 flux in different geodynamic settings within system earth

criteria to distinguish between subglacial glaciotectonic and glaciomarine sedimentation i deformation styles and sedimentology abstract this paper compares and contrasts the sedimentology and structural geology of a quaternary glaciomarine site melabakkar asbakkar iceland and a quaternary subglacial glaciotectonic site west runton uk research suggests that the glaciomarine environment is dominated by sedimentary processes related to sediment supply water content and distance from the glacier margin glaciotectonic deformation however is dominated by deformational processes related to effective pressure shear strain nature of the subglacial material and distance from the glacier margin from this study a series of criteria are suggested to distinguish both quaternary and contemporary glaciotectonic and glaciomarine environments in addition the paper also discusses the subsequent effects of glaciotectonic deformation on a primary glaciomarine site due to a glacial readvance

travertine deposition and faulting the fault related travertine fissure ridge at terme s giovanni rapolano terme italy in this paper we describe an example of travertine fissure ridge development along the trace of a normal fault with metre displacement located in the eastern margin of the neogene quaternary siena basin in the terme s giovanni area rapolano terme italy this morphotectonic feature 250 m long 30 m wide and 10 m high formed from supersaturated hot waters 39 9 c flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than late pleistocene 24 3 ka a straight continuous fissure with a maximum width of 20 cm occurs at the top of the ridge along its crest hot fluids flow from cones mainly located at the extremities of the ridge where travertine is depositing the travertine fissure ridge shows an asymmetrical profile since it buries the fault scarp the difference in height of slopes corresponds to the vertical displacement of the normal fault fissuring of the recent travertine deposits along the strike of the crestal fissure as well as recent hydrothermal circulation lead us to believe that the terme s giovanni normal fault may be currently active on the whole the terme s giovanni fissure ridge can be defined as a travertine fault trace fissure ridge adding a helpful example for studying the relationship between faulting and travertine deposition

subglacial till a physical framework for its properties and processes the continuum theory of mixtures provides a framework around which present knowledge of subglacial till can be organized the proposed framework is provisional in two senses the constitutive description of till will require improvement and not all potentially significant processes have been included till is treated as a three component mixture of water clasts coarse grained solids and fine grained matrix solids these components obey mass balance equations and their behavior is subject to constitutive relations that describe such processes as darcian water transport fine grained sediment transport consolidation shear deformation dilatancy and comminution five state variables uniquely determine the compressibility permeability shear strength and other physical properties numerical solutions of the state evolutions equations illustrate that the properties of till are highly responsive to changes in the subglacial environment

relating permeability to the structural setting of a fault controlled hydrothermal system in southeast oregon usa 1 it is generally accepted that high permeability pathways are required to bring hydrothermal fluids to the surface from depth at elevated temperatures and these pathways are commonly associated with faulting the orientation and mode of fractures that develop as a result of fault slip are dependent on the state of stress and the geometry of the fault system which in turn control the near fault permeability structure we hypothesize that temperature data collected in fault controlled hydrothermal systems may be used to delineate the extent of the near surface breakdown region of the controlling fault and may provide insight regarding the fault geometry and stress field here we present a geostatistical analysis of 1550 ground and spring temperature measurements in an area of active hydrothermal discharge located at mickey hot springs in southeast oregon indicator kriging was used to treat heterogeneity across the site prior to in category simulation of temperature as a continuous variable the analysis indicates that zones of high medium and low temperature at the site arise from different physical mechanisms which we propose are related to the underlying modes of fracturing and the dominant mechanisms of heat and mass transport i e by advection or diffusion the findings of this study suggest that thermal hydrologic data of the type presented here may be useful for understanding fault zone characteristics and for developing conceptual models of fault controlled fluid flow

earthquake impact on fissure ridge type travertine deposition the role of travertine fissure ridges in reconstructing tectonics and related earthquakes is a challenging issue of recent debate directed at delineating historical prehistorical seismic records indeed direct measurements on a travertine fissure ridge immediately after a seismic event have never been previously performed we describe the co and post seismic effects of a m 3 6 earthquake on fluid flow and travertine deposition in a geothermal area of tuscany italy direct observation allows us to demonstrate that thermal spring re activation is directly influenced by transient seismic waves therefore providing a basis for reconstructing seismic events in the past