effects of hydraulic roughness on surface textures of gravel bed rivers field studies of forest gravel bed rivers in northwestern washington and southeastern alaska demonstrate that bed surface grain size is responsive to hydraulic roughness caused by bank irregularities bars and wood debris we evaluate textural response by comparing reach average median grain size d50 to that predicted from the total bank full boundary shear stress t0 bf representing a hypothetical reference condition of low hydraulic roughness for a given t0 bf channels with progressively greater hydraulic roughness have systematically finer bed surfaces presumably due to reduced bed shear stress resulting in lower channel competence and diminished bed load transport capacity both of which promote textural fining in channels with significant hydraulic roughness observed values of d50 can be up to 90 smaller than those predicted from t 0 bf we find that wood debris plays an important role at our study sites not only providing hydraulic roughness but also influencing pool spacing frequency of textural patches and the amplitude and wavelength of bank and bar topography and their consequent roughness our observations also have biological implications we find that textural fining due to hydraulic roughness can create usable salmonid spawning gravels in channels that otherwise would be too coarse

carbon dioxide and radon gas hazard in the alban hills area central italy abstract the sudden and catastrophic or slow and continuous release at surface of naturally occurring toxic gases like co 2 h 2 s and rn poses a serious health risk to people living in geologically active regions in general this problem receives little attention from local governments although public concern is raised periodically when anomalous toxic gas concentrations suddenly kill humans or livestock for example elevated co 2 concentrations have been linked to the death of at least 10 people in the central italian region of lazio over the last 20 years while it was the co 2 asphyxiation of 30 cows in a heavily populated area near rome in 1999 which prompted the present soil gas study into the distribution of the local health risk a detailed geochemical survey was carried out in an area of about 4 km 2 in the ciampino and marino districts whereby a total of 274 soil gas samples were collected and analysed for more than 10 major and trace gas species data were then processed using both statistical and geostatistical methods and the resulting maps were examined in order to highlight areas of elevated risk general trends of elevated co 2 and rn concentrations imply the presence of preferential pathways i e faults and fractures along which deep gases are able to migrate towards the surface the co 2 and rn anomalous trends often correspond to and are usually elongated parallel to the apennine mountain range the controlling structural feature in central italy because of this fundamental anisotropy in the factors controlling the soil gas distribution it was found that a geostatistical approach using variogram analysis allowed for a better interpretation of the data with regard to the health risk to local inhabitants it was found that although some high risk areas had been zoned as parkland others had been heavily developed for residential purposes for example many new houses were found to have been built on ground which has soil gas co 2 concentrations of more than 70 and radon values of more than 250 kbq m 3 it is recommended that land use planners incorporate soil gas and or gas flux measurements in environmental assessments in areas of possible risk i e volcanic or structurally active areas

a contribution of co2 released from mineral springs into overall volume of annual co2 emissions in the slovak republic complex geological and tectonic structure of the western carpathians within the slovak territory has conditioned generation of abundant mineral springs 1782 with various levels of mineralization and chemical types many of them possess a high content of co2 and therefore they may be considered as permanent point sources of co2 they are a part of natural analogues due to this fact an approximate estimation of overall annual volume of co2 has been carried out however such seemingly simple calculation requests an introduction of necessary corrections professional estimates and some limitations based on knowledge and practical experience from a long term monitoring the final result of this process of all considered sources provided volume of around 4 mt of co2 year 1 this amount represents annual co2 emission of standard thermal power plant ca 500 mw and creates practically 10 of the annual slovak co2 production it means that the volume of co2 produced from mineral springs is not a negligible item and may create remarkable share of aggregated emissions in countries of similar geological and hydrogeological structure that is why it should be included in the emission evaluation of the countries concerned

petrology chemistry and texture of modern river sands amazon river system key idea following the spirit of p d krynine the sands of the world s largest tropical river system are studied to reveal much about the general origin of sand and sandstone thin section and chemical study of 95 sand samples from the amazon river system in brazil peru ecuador and colombia a river system with great contrasts in climate and rock types reveals that sands derived from the andes are lithic arenites whereas sands derived from precambrian terrains are much richer in quartz as are sands in rivers draining tertiary molasse sand becomes more mature downstream along the main stem of the amazon solimoes maranon so that a sample analyzed at the mouth does not accurately reflect headwater composition dilution by quartz rich tributaries and quartz rich tertiary outcrops possible differential elimination of rock fragments and even possible weathering on the modern flood plain of the amazon contribute to enhanced maturity downstream we speculate that although data on modern large subarti

gas geochemistry of natural analogues for the studies of geological co2 sequestration geological sequestration of anthropogenic co2 appears to be a promising method for reducing the amount of greenhouse gases released to the atmosphere geochemical modelling of the storage capacity for co2 in saline aquifers sandstones and or carbonates should be based on natural analogues both in situ and in the laboratory the main focus of this paper has been to study natural gas emissions representing extremely attractive surrogates for the study and prediction of the possible consequences of leakage from geological sequestration sites of anthropogenic co2 i e the return to surface potentially causing localised environmental problems these include a comparison among three different italian case histories i the solfatara crater phlegraean fields caldera southern italy is an ancient roman spa the area is characterised by intense and diffuse hydrothermal activity testified by hot acidic mud pools thermal springs and a large fumarolic field soil gas flux measurements show that the entire area discharges between 1200 and 1500 tons of co2 per day ii the panarea island aeolian islands southern italy where a huge submarine volcanic hydrothermal gas burst occurred in november 2002 the submarine gas emissions chemically modified seawater causing a strong modification of the marine ecosystem all of the collected gases are co2 dominant maximum value 98 43 vol iii the tor caldara area central italy located in a peripheral sector of the quiescent alban hills volcano along the faults of the ardea basin transfer structure the area is characterised by huge co2 degassing both from water and soil although the above mentioned areas do not represent a storage scenario these sites do provide many opportunities to study near surface processes and to test monitoring methodologies

middle palaeozoic thrusting in the eastern lachlan fold belt southeastern australia abstract early to middle palaeozoic clastic and volcanic strata in the goulburn bungonia region 150 km southwest of sydney are divided by the n trending yarralaw fault into two domains in the western domain major e w shortening formed folds axial planar cleavage and w dipping contraction faults in all pre upper devonian units this deformation formed an anticlinorium cored by a w dipping thrust system with an overturned e younging limb in the eastern domain upright flattened chevron folds occur in ordovician strata with stratal repetition along steep contraction faults spaced at intervals of 1 km or less zones of tectonic melange occur in the hangingwalls of these faults and have a well developed scaly fabric with a steeply plunging striation overprinting a bedding parallel cleavage in mudstone in interbedded silurian shale and limestone a classical stair step trajectory is recognized for the frome hill fault which duplicates the succession and has undergone back rotation to its present steep dip overall thrusting progressed from east to west with deformation in the eastern domain pre dating intrusion of the early devonian marulan batholith whereas farther west deformation continued into the middle devonian the folds and thrusts in the goulburn bungonia region are part of a major fold thrust zone that extends throughout the eastern lachlan fold belt and which was formed in the middle silurian to middle devonian during a period of plate convergence between gondwana and the palaeo pacific ocean the fold thrust zone is inferred to have an arc frontal arc setting above a w dipping subduction zone and the deformation relates to underthrusting of an allochthonous terrane with major shortening in the hangingwall block

shallow soil co2 flow along the san andreas and calaveras faults california 1 we evaluate a comprehensive soil co2 survey along the san andreas fault saf in parkfield and the calaveras fault cf in hollister california in the context of spatial and temporal variability origin and transport of co2 in fractured terrain co2 efflux was measured within grids with portable instrumentation and continuously with meteorological parameters at a fixed station in both faulted and unfaulted areas spatial and temporal variability of surface co2 effluxes was observed to be higher at faulted saf and cf sites relative to comparable background areas however 13c 23 3 to 16 4 and 14c 75 5 to 94 4 values of soil co2 in both faulted and unfaulted areas are indicative of biogenic co2 even though co2 effluxes in faulted areas reached values as high as 428 g m 2 d 1 profiles of soil co2 concentration as a function of depth were measured at multiple sites within saf and cf grids and repeatedly at two locations at the saf grid many of these profiles suggest a surprisingly high component of advective co2 flow spectral and correlation analysis of saf co2 efflux and meteorological parameter time series indicates that effects of wind speed variations on atmospheric air flow though fractures modulate surface efflux of biogenic co2 the resulting areal patterns in co2 effluxes could be erroneously attributed to a deep gas source in the absence of isotopic data a problem that must be addressed in fault zone soil gas studies

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

natural and industrial analogues for leakage of co2 from storage reservoirs identification of features events and processes and lessons learned instances of gas leakage from naturally occurring co2 reservoirs and natural gas storage sites serve as analogues for the potential release of co2 from geologic storage sites this paper summarizes and compares the features events and processes that can be identified from these analogues which include both naturally occurring releases and those associated with industrial processes the following conclusions are drawn 1 carbon dioxide can accumulate beneath and be released from primary and secondary shallower reservoirs with capping units located at a wide range of depths 2 many natural releases of co2 are correlated with a specific event that triggered the release 3 unsealed fault and fracture zones may act as conduits for co2 flow from depth to the surface 4 improperly constructed or abandoned wells can rapidly release large quantities of co2 5 the types of co2 release at the surface vary widely between and within different leakage sites 6 the hazard to human health was small in most cases possibly because of implementation of post leakage public education and monitoring programs 7 while changes in groundwater chemistry were related to co2 leakage waters often remained potable lessons learned for risk assessment associated with geologic carbon sequestration are discussed

a review of the metallogeny and tectonics of the lachlan orogen future mineral exploration within eastern australia will be enhanced by resolving the tectonic evolution of the lachlan orogen to establish the spatial and temporal terrane distribution of the various mineral deposits the lachlan orogen from north eastern tasmania through to central and eastern new south wales is host to a number of major mineral deposit styles including orogenic gold e g stawell ballarat bendigo volcanic hosted massive sulphide e g woodlawn currawong sediment hosted cu au e g cobar basin deposits porphyry au cu e g cadia parkes cowal and granite related sn e g ardlethan beechworth each of these mineral deposit styles is a sensitive and diagnostic indicator of the prevalent tectonic environment during their formation in this review we briefly summarise the deposit to large scale factors that define the diverse metallogenic evolution of the lachlan orogen this overview is intended to set the scene for subsequent specialist papers published in this thematic issue on the metallogeny and tectonics of the lachlan orogen in south east australia

effects of sediment supply on surface textures of gravel bed rivers using previously published data from flume studies we test a new approach for quantifying the effects of sediment supply i e bed material supply on surface grain size of equilibrium gravel channels textural response to sediment supply is evaluated relative to a theoretical prediction of competent median grain size d9 50 we find that surface median grain size d50 varies inversely with sediment supply rate and systematically approaches the competent value d9 at low equilibrium transport rates furthermore equilibrium transport rate is a power function of the difference between applied and critical shear stresses and is therefore a power function of the difference between competent and observed median grain sizes d9 and d50 consequently we propose that the difference between predicted and observed median grain sizes can be used to determine sediment supply rate in equilibrium channels our analysis framework collapses data from different studies toward a single relationship between sediment supply rate and surface grain size while the approach appears promising we caution that it has been tested only on a limited set of laboratory data and a narrow range of channel conditions

source of the lachlan fold belt flysch linked to convective removal of the lithospheric mantle and rapid exhumation of the delamerian ross fold belt during the cambrian ordovician the paleo pacific margin of gondwana underwent a rapid transition from a site of convergent deformation delamerian ross orogeny to one of sedimentation during which the thick turbiditic sequences of the adjacent basal lachlan fold belt were deposited laser probe 40 ar 39 ar data show that the synkinematic 523 486 ma mid crustal i and s type granites and metamorphic country rocks of the delamerian fold belt were rapidly cooled at 490 485 ma coincident with the intrusion of a suite of high level postkinematic a type granites and gabbros ca 497 481 ma 40 ar 39 ar data on detrital muscovites from the basal sections of the lachlan fold belt provide information on exhumation rather than cooling but yield an age pattern 507 480 ma identical to that of the delamerian fold belt demonstrating that this was the source of the sediments the combined data require that some 15 km of exhumation occurred very rapidly 5 15 mm yr 1 coincident as implied by overlapping ages with the cessation of convergent deformation and partial melting to form the postkinematic magmas this scenario implies a causative link which we infer to have been convective removal of lithospheric mantle following orogenic thickening the model is analogous to the tertiary uplift of the india asia orogen which provided the sediment source for the bengal fan our results suggest that similar processes were important in the evolution of mountain belts at least as far back as the early phanerozoic

diapirism and structural thickening in an early palaeozoic subduction complex southeastern new south wales australia abstract a major problem in the study of subduction complexes has been to distinguish between processes of mud diapirism deformation of unlithified sediments frontal accretion and underplating in the batemans bay area cambro ordovician rocks of the south coast of new south wales eastern australia contain common mud rich melanges that occur amongst an imbricated succession of early to middle ordovician quartz turbidites late ordovician black mudstone and chert cambrian limestone and mafic volcanics an early set of fluidal obliquely trending folds are restricted to the late ordovician black mudstone and chert and probably formed by gravitational down slope movement on a lower trench slope features indicative of deformation of unlithified sediments are still preserved and include mud injections delicate small scale faulting and the absence of grain scale deformation tight to isoclinal north south folds with axial planar west dipping cleavage overprint all units and formed during the younger main phase deformation that post dated early deformation in the prism the melange has been strongly overprinted by this main phase deformation early melange formation is attributed to mud diapirism involving intrusion along early accretionary faults bedding planes and in pipe like features resulting in chaotic outcrop and map patterns

geochemistry of regional aquifer systems hosted by carbonate evaporite formations in umbria and southern tuscany central italy abstract in central italy mesozoic carbonates represent the principal reservoir of freshwater of the region the hydrogeological setting is linked to the geological evolution of the apennine chain and is generally characterised by a lower aquifer and one or more shallower aquifers separated by thin aquicludes in these systems groundwater composition is the result of a complex array of regional and local geochemical processes the main geochemical processes are the dissolution of calcite the influx of deeply derived co2 related to a regional process of mantle degassing dedolomitization and mixing with deep saline fluids the occurrence of saline fluids characterised by a na cl hco3 composition is related to the presence of a deep regional aquifer at the base of mesozoic carbonates the extremely high pco2 values computed for the saline waters suggest that the deep aquifer is also a structural trap for the mantle derived co2 during its ascent towards the surface in central italy geological and geophysical data highlight the presence of two different crustal sectors the eastern sector where the geometry of the apennine thrust belt is still preserved and the western sector where the compressive structures are dislocated by important extensional deformations in the western sector the normal faults disrupting the compressive structures allow the mixing of the deep na cl hco3 fluids with the shallow groundwater causing a salinity increase and the natural deterioration of groundwater quality

provenance of early palaeozoic sandstones southeastern australia part 1 vertical changes through the bengal fan type deposit abstract ordovician strata of the lachlan fold belt in southeastern australia are dominated by a turbidite succession that in its undeformed state was comparable in size to the modern day bengal fan the ancient fan was derived from the northern part of the cambrian ross delamerian orogenic belt that formed at a convergent boundary between plates containing gondwanaland and part of the palaeo pacific ocean respectively substrate to the submarine fan consisted of mafic volcanic rocks with an immature island arc affinity similar to the eocene izu mariana bonin system sandstone compositions determined from several stratigraphically constrained sections demonstrate a uniform framework composition dominated by monocrystalline quartz with less abundant feldspar polycrystalline quartz metamorphic rock fragments sedimentary rock fragments and mica these indicate derivation from a low grade metamorphic terrain up sequence variation is limited to decreasing feldspar and lithic fragments and increasing quartz indicating increased weathering and lowering of topography in the source terrain over time 25 of counted sandstones in the late ordovician interval contain a small component of mafic intermediate volcanic rock fragments that accompanied a change in palaeocurrent direction from eastwards to northwards in the early silurian the ordovician sequence was disrupted by the formation of several major deformation zones between these zones developed several deep marine sedimentary basins that contain a continuous succession from the ordovician into the early silurian early silurian sandstone is similar in composition to underlying early ordovician rocks except that the feldspar component is generally absent early silurian sandstone was derived from uplifted portions of the ordovician sequence and includes texturally inverted types with sandstone containing a bimodal mixture of coarse well rounded quartz and fine angular quartz

nd and sr isotopic signatures of metasedimentary rocks around the south pacific margin and implications for their provenance an nd sr isotope database including c 200 new analyses is presented for palaeozoic and mesozoic metasedimentary successions extending through southeastern australia new zealand west antarctica and the antarctic peninsula to southern south america combining with u pb detrital zircon age data this enables characterization of new zealand terranes especially within the eastern province where there is a progression from westernmost terranes of both volcanic volcaniclastic and accretionary origin with primitive sediment sources to easternmost terranes with mature continental sediment inputs in southern south america west antarctica and the antarctica peninsula similar accretionary complexes have nd model ages principally reflecting mixing of sedimentary material from multiple sources both mature and juvenile a mature gondwana continental provenance dominates in sedimentary basins inboard of the active margin especially in the palaeozoic western province new zealand interior west antarctica and nw argentina and contributes significantly to pre mesozoic sedimentary rocks of patagonia east of the andes along the gondwanaland margin nd systematics for younger late palaeozoic to early mesozoic accretionary complex metasediments reflect younger source inputs notably in the scotia metamorphic complex many of the accretionary complex deposits must involve significant crustal reworking there is no apparent south american equivalent of the primitive provenance of the westernmost accretionary terranes of new zealand

natural analogues a potential approach for developing reliable monitoring methods to understand subsurface co2 migration processes one possible way of mitigating carbon dioxide co2 emissions from fossil fuel combustion is using carbon dioxide capture and storage ccs technology however public perception concerning co2 storage in the geosphere is generally negative being particularly motivated by perceived leakage risks therefore a main issue when attempting to gain public acceptance is ensuring provision of appropriate monitoring practices aimed at providing health safety and environmental risk assessment so that potential risks from co2 storage are minimized naturally occurring co2 deposits provide unique natural analogues for evaluating and validating methods used for the detection and monitoring of co2 spreading and degassing into the atmosphere geological and hydrological structures of the cheb basin nw bohemia czech republic represent such a natural analogue for investigating co2 leakage and offer a perfect location at which to verify monitoring tools used for direct investigation of processes along preferential migration paths this shallow basin dating from the tertiary age is characterized by up to 300 m thick neogene sediment deposits and several tectonically active faults the objectives of this paper are to introduce the co2 analogues concept to present the eger rift as a suitable location for a natural co2 analogue site and to demonstrate to what extent such an analogue site should be used with a case study the case study presents the results obtained from a joint application of geoelectrical measurements in combination with soil co2 concentration and flux determination methods for the detection and characterization of natural co2 releases at gas seeps as part of a hierarchic monitoring concept to highlight discharge controlling structural near surface features was the initial motivation for the application of geoelectrical measurements soil gas concentration and flux measurement techniques are relatively simple to employ and are valuable methods that can be used to monitor seeping co2 along preferential pathways joint interpretation of both approaches yields a first insight into fluid paths and reveals that the thickness and permeability of site specific near surface sedimentary deposits have a great influence upon the spatial distribution of the co2 degassing pattern at surface level

critical shear stress for incipient motion of sand gravel streambeds results of an experimental study of the incipient motion of streambeds composed of sand gravel sediment mixtures are reported and compared with the earlier findings for uniform sediments the experiments were conducted in an 8 m long by 0 30 m wide glass walled tilting flume and an 18 m long by 0 80 1 10 m wide trapezoidal concrete channel a reference transport method is used to define the beginning of bed material movement the experiments demonstrate that the incipient motion of individual size fractions within a mixture is controlled by their relative size with respect to median size intergranular effects mixture standard deviation effect of the shape of grain size distribution absolute value of median size absolute size effect and bed slope effect of relative depth on overall flow resistance the shear stress at incipient motion of median sized grains in mixtures is found to be the same as for uniform sediment of this size the present findings are consistent with available flume and field data a technique for calculating the critical shear stress of different grain sizes in coarse uniform sediments and unimodal weakly bimodal sediment mixtures is proposed

provenance of early palaeozoic sandstones southeastern australia part 2 cratonic to arc switching abstract early palaeozoic strata of the northeastern lachlan fold belt australia consist of an early ordovician sequence adaminaby group of quartz rich turbidites and chert and the conformably overlying late ordovician early silurian coomber formation a mafic volcaniclastic sequence of lithic sandstone and mudstone with mafic volcanic and intrusive rocks analysis of detrital modes from the adaminaby group indicate a uniform quartzose petrofacies q 91 f 2 l 7 composed of deep water quartz and sublithic sandstones derived from the west by contrast the lithic sandstone of the coomber formation represents a volcanolithic petrofacies q 1 f 34 l 65 of mainly intermediate volcanic detritus with a tendency to become more silicic up section these sandstones are considered to be derived from a calc alkaline andesitic basaltic volcanic centre in the eastern lachlan fold belt the change from a quartz rich petrofacies to a volcanolithic petrofacies was sharp with no evidence of mixing this change primarily reflects a rapid outpouring of mafic volcanic material in the late ordovician together with an approximately concurrent eustatic rise in sea level

man made versus natural co2 leakage a 400 k y history of an analogue for engineered geological storage of co2 to evaluate sites for long term geological storage of co2 and optimize techniques for monitoring the fate of injected co2 it is crucial to investigate potential co2 migration pathways out of a reservoir and surface leakage magnitudes for the first time we calculate co2 leakage rates and volumes from ancient fault related travertines and from an abandoned borehole u th dated travertine along two faults near green river utah western united states shows that leakage has occurred in this area for over 400 k y and has switched location repeatedly over kilometer scale distances one individual travertine was active for at least 11 k y modern leakage is predominantly through the active crystal geyser which erupts from an abandoned exploration well using age data and travertine volume we calculate magnitudes and rates of co2 emission fault focused leakage volume is twice as great than diffuse leakage through unconfined aquifers the leakage rate from a poorly completed borehole is 13 times greater than the long term time averaged fault focused leakage although magnitudes and rates of any leakage from future storage sites will be highly dependent on local geology and pressure regime our results highlight that leakage from abandoned wells is likely to be more significant than through faults introduction carbon dioxide could potentially migrate from underground storage sites through boreholes poor cap rocks or faults and fractures storage formation integrity and effects of leaking co2 on the surface environment is commonly investigated stevens et al 2001 kirk 2011 however the overburden between the storage formation and the surface is a poorly studied part of the co2 storage system gaus 2010 understanding flow through potential migration pathways in the overburden such as faults or high permeability strata is crucial for evaluating long term storage security the integrity of well bores and their long term ability to retain co2 has also been recognized as a significant risk to the long term security of geological storage ieaghg 2005 storage operators will be legally required to monitor the fate of injected co2 european commission 2009 effective monitoring and engineered remediation depends on the likely nature of migration pathways through the overburden and on the locations and likely fluxes of co2 shallow leakage pathways cortis et al 2008 benson and hepple 2005 we investigate a unique location in the paradox basin utah western united states where fossil travertine mounds allow us to compare ancient co2 flux via fault associated fracturing and diffuse leakage through an aquifer with modern leakage from abandoned wells the paradox basin hosts at least nine natural co2 accumulations most of which have contained co2 for millennia gilfillan et al 2008 co2 charged springs along the little grand wash lgw and salt wash graben swg normal faults fig 1 demonstrate that co2 is leaking to the surface through fault zones and abandoned wells doelling 1994 the springs are fed from a shallow aquifer overlain by low permeability siltstones and shales and charged by co2 from depth making this setting analogous to heterogeneous and variably permeable overburden above a geological co2 storage site we use u th dating of travertine formed by out gassing of co2 from springwater to determine flow history along the faults combining travertine age and volume allows us to estimate volumes and rates of co2 emission to the surface through time and compare fault focused diffuse and borehole leakage in a single hydrogeological setting

rn he and co2 soil gas geochemistry for the study of active and inactive faults abstract two italian areas characterized by different seismological histories were investigated to enhance the basic knowledge of gas migration mechanisms during earthquakes sharp variations occur in the movement and concentration of some gaseous species due to the evolution of the local stress regime the first area colpasquale is located in the central italian region of marche and provided a good location to study gas migration in a seismically active region the area was devastated by a sequence of shallow earthquakes over a 3 month long period september december 1997 the occurrence of this catastrophic event as well as the long duration of the seismic sequence presented a unique opportunity to study gas migration in a zone undergoing active displacement soil gas surveys were performed 1 day 1 week 1 year and 2 years after the main shock ms 5 6 in the colpasquale area in particular results highlight a change in the rn distribution during the three monitoring years indicating a variation of gas migration that may be linked to the evolution of the stress regime the second study area is located in the campidano graben southern part of sardinia island this area is characterized by seismic quiescence displaying an almost complete lack of historical earthquakes and instrumentally recorded seismicity the consistently low values observed for all analyzed gases suggest that the studied area is likely characterized by sealed non active faults that prevent significant gas migration the comparison of data from both studied areas indicate that soil gas geochemistry is useful to locate tectonic discontinuities even when they intersect non cohesive clastic rocks near the surface and thus are not visible i e blind faults

combined tectonic sediment supply driven cycles in a lower carboniferous deep marine foreland basin moravice formation czech republic the lower carboniferous moravian silesian culm basin mscb represents the easternmost part of the rhenohercynian system of collision related deep water foreland basins culm facies the upper visean moravice formation mf of the mscb shows a distinct cyclic stratigraphic arrangement two major asymmetric megacycles bounded by basal sequence boundary each about 500 to 900 m thick have been revealed the megacycles start with 50 to 250 m thick basal segments of erosive channels overbank successions and slope apron deposits interpreted as lowstand turbidite systems up section they pass into hundred metre thick fine grained low efficiency turbidite systems palaeocurrent data show two prominent directions basin axis parallel ssw nne directions which are abundant in the whole mf and basin axis perpendicular to oblique w e to nw se directions which tend to be confined to the basal parts of the megacycles or channel lobe transition systems in their upper parts based on the facies characteristics palaeocurrent data sandstone composition data and trace fossil distribution data we suggest a combined tectonics sediment supply driven model for the mf basin fill periods of increased tectonic activity resulted in slope oversteepening probably combined with increased rate of lateral w e sediment supply into the basin producing the basal sequence boundary and the subsequent lowstand turbidite systems during subsequent periods of tectonic quiescence the system was filled mainly from a distant southern point source producing the thick low efficiency turbidite systems consistently with the previous models our own sediment composition data indicate a progressively increasing sediment input from high grade metamorphic and magmatic sources up section most probably related to an uplift in the source area and progressive unroofing of its structurally deeper crustal parts the first occurrence of the cruziana nereites ichnofacies in sand rich turbidite systems in the youngest parts of the mf go el to go spi zone supported by rapidly increasing quartz concentrations in sandstones is thought to indicate a transition from generally underfilled to generally overfilled phase in evolution of the mscb basin this transition may be linked to the onset of upper visean phase of northward basin fill progradation assumed by previous authors

accordion vs quantum tectonics insights into continental growth processes from the paleozoic of eastern gondwana the early paleozoic lachlan fold belt of eastern australia is widely regarded as an ancient convergent plate margin beneath which paleo pacific panthalassic oceanic lithosphere was continuously subducted it is cited as the type example of a retreating accretionary orogeny however sandstone compositions the sedimentological nature and timing of chert accumulation and overall stratigraphic architecture are not necessarily consistent with this model we suggest an alternative explanation for growth of gondwanan continental margin oceanic lithosphere outboard of the passive gondwana continental margin was subducted beneath an extensive intra oceanic island arc that now crops out as an allochthonous element macquarie arc within the fold belt once intervening oceanic lithosphere was eliminated this arc collided with and was emplaced upon the gondwana margin recognition of four such events along this margin through the phanerozoic suggests it is a significant mechanism for continental growth

ordovician terranes of the southeastern lachlan fold belt stratigraphy structure and palaeogeographic reconstruction abstract the ordovician of the southeastern lachlan fold belt lfb is represented by two contrasting provinces the molong volcanic province with shoshonitic basalts and shallow marine sediments in the north and a very extensive but relatively thin quartzose flysch chert and black shale sequence elsewhere this paper concentrates on the latter and reviews its stratigraphy correlation sedimentary facies palaeocurrent directions and structure the molong volcanic province contributed insignificant sediment to the surrounding turbidites and there is no evidence that the rise was a fragmented arc as is postulated by most previous workers the rise may have been a hot spot volcano and the southeastern lfb appears to have been a passive margin in the ordovician within the flysch province two terranes are recognized the melbourne terrane in the west and benambra terrane in the east both showing overall upward and eastward fining in the ordovician the boundary is the mount wellington fault zone along which a post ordovician dextral strike slip of up to 400 km is postulated

ordovician contourites in the lachlan fold belt eastern australia abstract the ordovician sequence in the northeastern lachlan fold belt consists of three lithologic units representing an overall fining upward succession from turbidites to black shale the lowest unit dominated by turbidite beds represents a small segment of an extensive ordovician submarine fan sequence that covered much of southeastern australia the overlying unit consists predominantly of ripple bedded sandstone with beds 3 5 cm thick these beds are texturally mature containing heavy minerals mica and silt concentrated on the cross laminae the ripple bedded unit has a mean palaeocurrent trend to 321 which is at 60 to sole marks and almost normal to the trend of ripple cross bedding in the underlying and associated turbidite beds this unit is here interpreted as a sandy contourite sequence that can be attributed to contour currents moving northwards along the eastern margin of gondwana from areas of subpolar downwelling off southern africa and america the two major fining upward successions in the ordovician sequence in southeastern australia may reflect eustatic sea level rises during the middle and late ordovician and thus provide evidence of interglacial periods in the darrawilian and late gisbornian to bolindian the contourites would have accumulated in the latter stages of the glacial periods after sea level had risen sufficiently to cut off major sediment supply to the submarine fan but before the temperature had risen to the extent of preventing deep thermohaline circulation

pyrite and pyrrhotite textures and composition in sediments laminated quartz veins and reefs at bendigo gold mine australia insights for ore genesis the various types textures and compositional zoning of pyrite in the gold bearing saddle reefs quartz veins and surrounding sedimentary rocks provide new information on the potential source and timing of gold and arsenic and related fluid processes responsible for mineralization at bendigo nodular diagenetic pyrite in the black shale tops to sandstone turbidites is enriched in invisible gold and arsenic with mean values of 0 61 ppm au 1 300 ppm as and au ag 1 based on la icpms analyses other elements enriched in the diagenetic pyrite within the organic rich shales are mn zn mo cu v ba ag cd tl co ni bi pb and te in contrast euhedral and growth zoned hydrothermal pyrite in the turbidites and bedding parallel laminated quartz veins contains lower contents of most trace elements but has higher contents of invisible au and as especially on the outermost rim of the pyrite the gold rich pyrite rims generally become thicker a few to hundreds of microns in proximity to the gold bearing saddle reefs pyrite in the reef commonly has the highest levels of invisible au and as and the lowest levels of other trace elements it is characterized by au ag 1 and au pb 0 01 in the deepest stratigraphic levels below known productive gold reefs diagenetic pyrite in the most carbonaceous shales has been replaced by pyrrhotite during metamorphism la icpms analyses reveal that the disseminated pyrrhotite contains similar levels of ni and co to the diagenetic pyrite but is strongly depleted in as and au the spatial relationships between organic rich shales folded bedding parallel laminated quartz veins and gold arsenic bearing saddle reefs combined with the consistent trends in the trace element composition of pyrite hosted by these three geological elements is interpreted to indicate that the black shales were an initial source of au and as and the laminated quartz veins acted as the initial pathways for hydrothermal fluid flow carrying au and as from the source shales to the saddle reefs maximum gold and arsenic input into the reefs principally as free gold plus arsenopyrite occurred late during deformation toward the end of the hydrothermal cycle and is expressed by the au as rich rims to hydrothermal pyrite in the sedimentary host rocks laminated quartz veins and reefs this corresponds with final fold lockup and the development of through going fault arrays linking adjacent anticlines the source of au and as for this final and most economically important fluid flow event is considered to be from carbonaceous shales deeper in the basin where original gold bearing diagenetic arsenian pyrite reacts with organic matter and is converted to pyrrhotite with release of au as and s to the metamorphic fluid

ordovician continental margin terranes in the lachlan orogen australia implications for tectonics in an accretionary orogen along the east gondwana margin 1 four continental margin turbidite black shale terranes of the lachlan orogen in the southern tasmanides of eastern australia formed in two major systems along the east gondwana margin and constrain the ordovician assembly of this accretionary orogen key features are the dissimilar stratigraphies of the adjacent bendigo and melbourne terranes in the western system the dissimilar stratigraphies of the adjacent melbourne and albury bega terranes that reflect juxtaposition of the two systems during the middle devonian and the presence of the albury bega terrane both west and east of the macquarie arc in the eastern system that also includes the ocean floor narooma terrane and igneous ocean crust terrane s repetition of the albury bega terrane either side of the arc requires either rifting or orogen parallel strike slip duplication of a once contiguous package terrane interactions began in the earliest gisbornian with early docking uplift deformation and exchange of detritus amalgamation occurred in the earliest silurian benambran orogeny with accretion in the middle devonian over 40 myr discrete turbidite terranes aligned along the gondwana margin in two systems were converted into a very wide orogen characterized by the along strike juxtaposition of superficially similar terranes

convergence and intraplate deformation in the lachlan fold belt of southeastern australia abstract the lachlan fold belt of southeastern australia is dominated by a widespread oceanic association including cambrian submarine mafic volcanics and an overlying widespread ordovician quartz rich turbidite and black shale succession with scattered mafic to andesitic volcanic centres these rocks are overlain by or in fault contact with deep marine to continental silurian to early carboniferous successions with mafic to silicic volcanics and abundant plutonic rocks major deformation achieved by thrusting and folding affected the fold belt during the silurian to middle devonian and the early carboniferous shortening estimates vary throughout the belt but the widespread ordovician quartz turbidite succession usually has at least 60 shortening which implies an original width of the fold belt of about 1700 km strike slip faulting was important on a local to regional scale but large scale strike slip displacements appear unlikely the large values of shortening are consistent with development of the belt in a convergent margin setting at least for the silurian to carboniferous the nature of the lower crust of the lachlan fold belt has always presented a problem of interpretation but we favour a late proterozoic quasi continental lower crustal layer that has deformed independently of the upper crust by either homogeneous flattening or crustal duplexing during silurian carboniferous convergence and provided a source for silurian devonian granites

annual volcanic carbon dioxide emission an estimate from eruption chronologies continuing interest in the effects of carbon dioxide on climate has been promoted by the exponentially increasing anthropogenic production of co2 volcanoes are also a major source of carbon dioxide but their average input to the atmosphere is generally considered minor relative to anthropogenic input this study examines eruption chronologies to determine a new estimate of the volcanic co2 input and to test if temporal fluctuations may be resolved employing representative average values of 2 7 g cm 3 as density of erupted material 0 2 wt percent co2 in the original melt 60 percent degassing during eruption and an average volume of 0 1 km3 for each of the eruptions in the recently published eruption chronology of hirschboeck 1980 a volcanic input of about 1 5 1011 moles co2 yr 1 was determined for the period 1800 1969 the period 1800 1899 had a somewhat lower input than 1900 1969 which could well be related more to completeness of observational data than to a real increase in volcanic co2 this input is well below man s current co2 production of 4 5 1014 moles co2 yr 1