stable isotope evidence for thermochemical sulfate reduction in the dugald river australia strata bound shale hosted zinclead deposit abstract sulfur isotopes vary along strike and down dip in the mid proterozoic dugald river strata bound shale hosted zinc lead ore deposit australia although the metal grade has been substantially increased at its southern end by tectonism geological relationships indicate that mineralisation occurred during early diagenesis probably in an organic rich shallow water to evaporitic setting muir 1983 cu cu cu pb zn and pb pb zn decrease in the mineralisation northwards independent of the main structural thickening and so are likely to represent a pre deformational primary geochemical dispersion average 34s values in pyrite and sphalerite range from 1 in the south coincident with the highest copper content of the ores to 8 in the north accompanying deposit thinning in contrast adjacent footwall and hangingwall iron sulfide does not exhibit isotopic zonation and has a 34s peak between 3 and 4 n 33 with some values as light as 14 5 whereas overlying dolomites contain 34 s py 5 5 to 17 5 each population is attributed to varying degrees of closed system biogenic sulfate reduction two populations of carbonate carbon isotopes are present the first 13 c 11 to 5 mainly characterises graphitic footwall limestone of the lady clayre dolomite and is interpreted to reflect the metamorphic equilibration of carbonate and organic carbon isotopes the second 13 c 25 to 15 characterises the sulphide lens and its immediate sedimentary host and is most consistent with formation by the oxidation of organic carbon thermochemical sulfate reduction tsr by organic matter is preferred to account for the 34s zonation because of 1 mass balance calculations 2 the 13c values of ore and near ore carbonate 3 the high temperatures likely for ore formation 150 250 c which would have prevented biogenic sulfur reduction but promoted tsr and 4 the trend toward 34sseawater the proposed mineralisation model involves an h2s and metal bearing fluid with 34 s 3 to 0 this fluid ascended into the dugald basin in the south permeating laterally northward through carbonaceous sediments below an evaporitic to shallow marine carbonate platform during this migration the hydrothermal fluid reacted with organic matter and sulfate to form 34s rich sulfide 34 s 8 to 10 by tsr reaction was catalysed by deep sourced h2s biogenic h2s and h2s that evolved by hydrothermal cracking of organic matter the sources of sulfate for the reaction were 1 evaporites locally within the sequence and 2 dissolved sulfate diffusing from surface waters into the diagenetic zone

the role of feedback mechanisms in historic channel changes of the lower rio grande in the big bend region abstract over the last century large scale water development of the upper rio grande in the u s and mexico and of the rio conchos in mexico has resulted in progressive channel narrowing of the lower rio grande in the big bend region we used methods operating at multiple spatial and temporal scales to analyze the rate magnitude and processes responsible for channel narrowing these methods included hydrologic analysis of historic stream gage data analysis of notes of measured discharges historic oblique and aerial photograph analysis and stratigraphic and dendrogeomorphic analysis of inset floodplain deposits our analyses indicate that frequent large floods between 1900 and the mid 1940s acted as a negative feedback mechanism and maintained a wide sandy multi threaded river declines in mean and peak flow in the mid 1940s resulted in progressive channel narrowing channel narrowing has been temporarily interrupted by occasional large floods that widened the channel however channel narrowing has always resumed after large floods in 1990 and 1991 the active channel width of the lower rio grande has narrowed by 36 52 narrowing has occurred by the vertical accretion of fine grained deposits on top of sand and gravel bars inset within natural levees channel narrowing by vertical accretion occurred simultaneously with a rapid invasion of non native riparian vegetation tamarix spp arundo donax which created a positive feedback and exacerbated the processes of channel narrowing and vertical accretion in two floodplain trenches we measured 2 75 and 3 5 m of vertical accretion between 1993 and 2008 in some localities nearly 90 of bare active channel bars were converted to vegetated floodplain during the same period upward shifts of stage discharge relations occurred resulting in over bank flooding at lower discharges and continued vertical accretion despite a progressive reduction in stream flow thus although the magnitude of the average annual flood was reduced between 40 and 50 over bank flooding continued these changes reflect a shift in the geomorphic nature of the rio grande from a wide laterally unstable multi thread river to a laterally stable single thread channel with cohesive vertical banks and few active in channel bars

microbial sulfate reduction in deep sea sediments at the guaymas basin hydrothermal vent area influence of temperature and substrates abstract microbial sulfate reduction was studied by a 35 s tracer technique in sediments from the hydrothermal vent site in guaymas basin gulf of california mexico in situ temperatures ranged from 2 7 c in the overlying seawater to 120 c at 30 cm depth in the hydrothermal sediment sulfate reduction was measured in intact cores of hydrothermal sediment at 3 20 35 50 70 and 90 c the maximum rates of sulfate reduction were found in the upper 0 2 cm of the sediment and ranged from 32 nmol cm 3 d 1 at 90 c to 1563 nmol cm 3 d 1 at 70 c the rates of sulfate reduction rapidly decreased with depth in the upper 0 10 cm of the sediment and the maximal depth integrated rate 0 10 cm was 70 3 mmol so 4 2 m 2 d 1 at 70 c in comparison the sulfate reduction rate in nonhydrothermal sediment from the vent area was 0 85 mmol m 2 d 1 at the in situ temperature of about 3 c the high subsurface rates of sulfate reduction in the hydrothermal vent area was attributed to an enhanced local substrate availability in slurries of hydrothermal sediment incubated at 10 120 c microbial sulfate reduction extended to 102 c and different temperature groups of microbial sulfate reducers had optimum temperatures at around 34 70 and 80 88 c the overall temperature response of thermophilic sulfate reduction was similar in hydrothermal sediment sampled at different sites addition of short chain fatty acids and yeast extract to the sediment slurries stimulated sulfate reduction rates at all incubation temperatures no sulfate reduction was detected in the temperature range from 102 120 c microbial rather than thermochemical sulfate reduction could be a possible source of h 2 s in sulfide deposits with formation temperatures at about 100 c

nitrogen isotope hydrochemistry and denitrification within the chalk aquifer system of north norfolk uk abstract although there has been much debate over the potential health risks of nitrate in drinking water there is a real issue of the costs associated with removing nitrate from drinking water supplies in the chalk aquifer system of north east norfolk modern contaminants of a mainly agricultural origin produce high levels of nitrate 15 mg l no3 n in the unconfined valley areas whereas in confined regions the levels of nitrate are low and commonly below detection limits

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

variscan and post variscan lead zinc mineralization rhenish massif germany evidence for sulfide precipitation via thermochemical sulfate reduction a mechanical decrepitation device coupled with a gas chromatograph has been used to characterize the molecular composition of gaseous and liquid hydrocarbons contained in minerals application of this technique allows the identification of low molecular weight n alkanes and some aromatic hydrocarbons in sulfides and gangue minerals from epigenetic variscan and post variscan lead zinc deposits in the rhenish massif germany based on the analysis of 200 samples variscan and post variscan mineralization can be distinguished by the composition of associated hydrocarbons variscan sulfides and gangue minerals contain high abundancies of methane in contrast n alkanes in the c2 c9 range and aromatic hydrocarbons benzene toluene are dominant in post variscan mineralization the absence of high molecular weight hydrocarbons in ore minerals suggests highly mature gas associated with hydrothermal activity during which hydrothermal fluids caused an increase in thermal maturation of organic matter and the generation of low molecular weight hydrocarbons in the adjacent organic rich rocks the hydrocarbon compositions contained in fluid inclusions of variscan and post variscan minerals are probably governed by the maturation level of the potential source rocks in variscan time tectonic brines t 175 c generated predominantly methane whereas basement brines t 175 c expelled higher molecular weight hydrocarbons wet gases condensates aromatic hydrocarbons from adjacent rocks during the mesozoic event the specific role of hydrocarbons in sulfide precipitation via thermochemical sulfate reduction is indicated by geochemical characteristics of organic matter associated with the plombieres pb zn deposit in eastern belgium intense alteration phenomena were observed in near ore kerogens compared with unaltered kerogens far from the ore body as well as by a very high maturity 5 40 ro a systematic depletion in 12c towards the vein type mineralization high atomic s c ratios 0 49 and by low atomic h c ratios 0 29 the data suggest that hydrothermal solutions caused a drastic increase in the thermal maturation of organic matter within the adjacent wall rock increased thermal maturation resulted in increased 13c values of organic carbon due to the preferential release of 12c the change in the organic matter to a h depleted and s enriched bulk composition in association with sulfide ores strongly suggests that thermochemical sulfate reduction was responsible for organic degradation thus thermochemical sulfate reduction probably triggered base metal sulfide precipitation in variscan and post variscan ore deposits of the rhenish massif finally based on data from this study and previous investigations new genetic models are presented for both variscan and post variscan mineralization in the rhenish massif

sticky business the influence of streambed periphyton on particle deposition and infiltration strong feedbacks exist between physical and ecological components of aquatic systems aquatic plants can alter flow and sedimentation patterns in turn influencing habitat condition and organism responses in this study i investigate the interactions between streambed periphyton particle deposition and infiltration and flow hydraulics to determine the influence of these organisms on the local environment in a series of flume experiments i measured the effects of two contrasting forms of periphyton at several densities and growth stages on near bed hydraulics particle loss from the water column surface deposition and subsurface infiltration data show that periphyton assemblages altered the rate and quantity of particle deposition via several mechanisms including shear stress modification surface adhesion and bed clogging although trends varied for different size classes within a suspension of fine sediment diatoms and algae had distinctly different effects on hydraulics deposition and infiltration in general diatoms increased the rate of decline in suspended particle concentrations relative to non periphyton surfaces by reducing shear stresses and enhancing surface deposition via adhesion increases in diatom biomass however reduced the quantity and depth of particle infiltration presumably by clogging interstitial pore spaces in turn lowering rates of concentration decline in contrast all algal growth stages had slower or similar rates of concentration decline compared to non periphyton conditions due to partial clogging by high biomass and a lack of adhesion at the bed surface clogging effects were counteracted at later growth stages however as late stage algal structures increased shear stresses and downward advection in turn increasing amounts of infiltration compiled data from several field studies and experiments demonstrate a positive relation between periphyton biomass and inorganic mass but also show a wide range in the relation because of external factors such as discharge and suspended sediment concentration my analysis indicates that the decrease in the concentration of suspended particles under controlled conditions is strongly influenced by periphyton structure through direct mechanisms such as adhesion and clogging as well as indirect changes to hydraulics but that external factors in field settings such as discharge and sediment supply may outweigh the effects of periphyton structure

reappraising the geomorphology ecology link this thematic virtual special issue highlights a personal selection of 18 recent 2007 2009 contributions to earth surface processes and landforms these papers provide a flavour of recent research that is concerned with furthering our understanding of the many ways in which the biosphere interacts with the physical and chemical processes of sediment transfer transformation much of this research has focused on understanding the mechanics by which the biota can modulate sediment transport and the strength of earth surface materials often with the aim of applying that knowledge to enhance bioremediation methods of erosion control this work continues to be fundamentally important in enhancing our understanding of earth surface processes but often treats the biosphere and physical world as uncoupled entities this selection therefore also provides samples of work that point to an ongoing but significant disciplinary reappraisal in which it is the interactions between ecological and geomorphological realms that are of primary interest

sulfur in serpentinized oceanic peridotites serpentinization processes and microbial sulfate reduction the mineralogy contents and isotopic compositions of sulfur in oceanic serpentinites reflect variations in temperatures and fluid fluxes serpentinization of 1 ma peridotites at hess deep occurred at high temperatures 200 400 c and low water rock ratios oxidation of ferrous iron to magnetite maintained low o2 and produced a reduced low sulfur assemblage including nife alloy small amounts of sulfate reduction by thermophilic microbes occurred as the system cooled producing low 34s sulfide 1 5 to 23 7 in contrast serpentinization of iberian margin peridotites occurred at low temperatures 20 200 c and high water rock ratios complete serpentinization and consumption of ferrous iron allowed evolution to higher o2 microbial reduction of seawater sulfate resulted in addition of low 34s sulfide 15 to 43 and formation of higher sulfur assemblages that include valleriite and pyrite the high so4 total s ratio of hess deep serpentinites 0 89 results in an increase of total sulfur and high 34s of total sulfur mean 8 in contrast iberian margin serpentinites gained large amounts of 34s poor sulfide mean total s 3800 ppm and the high sulfide total s ratio 0 61 results in a net decrease in 34s of total sulfur mean 5 thus serpentinization is a net sink for seawater sulfur but the amount fixed and its isotopic composition vary significantly serpentinization may result in uptake of 0 4 14 1012 g s yr 1 from the oceans comparable to isotopic exchange in mafic rocks of seafloor hydrothermal systems and approaching global fluxes of riverine sulfate input and sedimentary sulfide output

thermal mechanical and chemical influences on the performance of optical fibres for distributed temperature sensing in a hot geothermal well structural well bore integrity is an important issue for sustainable provision of geothermal energy raman scattering based fibre optic distributed temperature sensing dts can help to monitor the status of a well and therefore help to optimize expensive work over activities this study reports on the installation of a fibre optic cable in the cemented annulus behind the anchor casing in the high temperature geothermal well he 53 hellishei i geothermal field sw iceland although the cable has been damaged during the installation temperature data could be acquired during the entire length of installation down to 261 3 m temperature measurements were performed during the installation in spring 2009 during the onset of a flow test in summer 2009 and after a 8 5 month shut in period in summer 2010 during the flow test maximum temperatures of 230 c were measured after 2 weeks fluid production using optical time domain reflectometry otdr attenuation measurements at 850 and 1 300 nm enabled to identify mechanical thermal and chemical degradation along the optical fibre the observed degradation led to erroneous temperature readings and limits due to the optical budget of the dts system the accessible length of the fibre the characteristics and the influence of the different degradation mechanisms on the accuracy of the dts measurements are discussed and recommendations for an optimized installation are given

unified compression model for venice lagoon natural silts over the last 50 years the city of venice italy has observed a significant increase in the frequency of flooding numerous engineering solutions have been proposed including the use of movable gates located at the three lagoon inlets a key element in the prediction of performance is the estimation of settlements of the foundation system of the gates the soils of venice lagoon are characterized by very erratic depositional patterns of clayey silts resulting in an extremely heterogeneous stratigraphy with discontinuous layering the soils are also characterized by varying contents of coarse and fine grained particles in contrast the mineralogical composition of these deposits is quite uniform which allows us to separate the influence of mineralogy from that of grain size distribution a comprehensive geotechnical testing program was performed to assess the one dimensional compression of venice soils and examine the factors affecting the response in the transition from one material type to another the compressibility of these natural silty clayey soils can be described by a single set of constitutive laws incorporating the relative fraction of granular to cohesive material

geochemical constraints on chemolithoautotrophic metabolism by microorganisms in seafloor hydrothermal systems mixing of hydrothermal fluids and seawater at the ocean floor combined with slow reaction kinetics for oxidation reduction reactions provides a source of metabolic energy for chemolithotrophic microorganisms which are the primary biomass producers for an extensive submarine ecosystem that is essentially independent of photosynthesis thermodynamic models are used to explore geochemical constraints on the amount of metabolic energy potentially available from chemosynthetic reactions involving s c fe and mn compounds during mixing of hydrothermal fluids with seawater for the vent fluid used in the calculations epr 21 n obs the model indicates that mixing environments are favorable for oxidation of h2s ch4 fe2 and mn2 only below 38 c with methanogenesis and reduction of sulfate or s favored at higher temperatures suggesting that environments dominated by mixing provide habitats for mesophilic but not thermophilic aerobes and thermophilic but not mesophilic anaerobes a maximum of 760 cal per kilogram vent fluid is available from sulfide oxidation while between 8 and 35 cal kg vent fluid is available from methanotrophy methanogenesis oxidation of fe or mn or sulfate reduction the total potential for chemosynthetic primary production at deep sea hydrothermal vents globally is estimated to be about 1013 g biomass per year which represents 0 02 of the global primary production by photosynthesis in the oceans thermophilic methanogens and sulfate and s reducers are likely to be the predominant organisms in the walls of vent chimneys and in the diffuse mixing zones beneath warm vents where biological processes may contribute to the high methane concentrations of vent fluids and heavy 34s32s s ratios of vent sulfide minerals the metabolic processes taking place in these systems may be analogs of the first living systems to evolve on the earth

biogeomorphology revisited looking towards the future although biogeomorphological research is well established with many studies on a range of two way interrelations between organisms and geomorphology in different environments there is little consensus over what constitutes biogeomorphology why it might be useful and where it is heading starting with definitions of core biogeomorphic processes we consider the need for future biogeomorphological studies to evaluate the crucial links between bioprocesses biological community dynamics and inorganic earth surface processes five key applications of biogeomorphological research are identified the roles of organisms in environmental reconstruction trace fossil analysis extraterrestrial geomorphology environmental engineering and the built environment some key research directions and methodological challenges for future biogeomorphological research include expanding the spatial and temporal coverage of datasets investigating the role of bioprocesses in landform development tackling scale issues investigating the relevance of nonlinear dynamical ideas to biogeomorphology and developing better sampling and monitoring techniques for bioprocesses

sulfur geochemistry of peridotite hosted hydrothermal systems comparing the ligurian ophiolites with oceanic serpentinites abstract serpentinization processes at slow and ultraslow spreading ridges control the exchange of various elements between seawater and the oceanic lithosphere and play a major role in marine geochemical cycles we use opaque mineral assemblages and sulfur isotope geochemistry to reconstruct variations in fluid fluxes redox conditions and microbial activity prevailing during serpentinization and carbonate precipitation of serpentinites and ophicalcites from an ophiolite sequence in the northern apennines italy we then compare our results with calcite veined serpentinites from the iberian margin formed during the opening of the north atlantic and with serpentinites sampled at the active peridotite hosted lost city hydrothermal field on the atlantis massif near the mid atlantic ridge the sulfide and oxide mineral assemblage of the serpentinites from the northern apennines is dominated by pyrite pentlandite millerite siegenite magnetite and hematite reflecting relatively oxidizing conditions while the sulfur geochemistry reveals a dominance of sulfide sulfur over sulfate sulfur 34 s values of sulfide and sulfate indicate that microbial sulfate reduction leaching and oxidation are the main processes that affected the sulfur isotope signature of these serpentinites the opaque mineralogy in the serpentinites from the northern apennines is similar to that of the iberian margin and the southern wall of the atlantis massif and generally represents the late stages of serpentinization where intense fluid circulation leads to fairly oxidizing conditions and alkaline fluids lead to carbonate precipitation however the mineral assemblages also indicate strong fluctuations in oxygen fugacity likely caused by volume expansion during serpentinization and tectonic activity along a mid ocean ridge additionally local enrichment in 34 s in sulfides suggests that fluids interacted at depth with gabbros and subsequently circulated along shear zones similar to observations along detachment fault surfaces at the atlantis massif our results therefore give further evidence that the ophicalcites and serpentinites from the northern apennines formed in a tectonic setting similar to the atlantis massif we estimate a global annual uptake of seawater sulfate of 5 6 to 12 10 11 g s by serpentinization of ultramafic rocks exposed to seawater on the ocean floor we suggest that the thermal structure of the exposed mantle rocks and in turn the efficiency of microbes to reduce seawater sulfate to sulfide is a major factor controlling the storage of sulfur in serpentinites thus cycling of sulfur in peridotite hosted hydrothermal systems during the jurassic was probably very similar to the processes observed today in systems along the mid atlantic ridge

origin distribution and hydrogeochemical controls on methane occurrences in shallow aquifers southwestern ontario canada abstract natural gas reservoirs in organic rich shales in the appalachian and michigan basins in the united states are currently being produced via hydraulic fracturing stratigraphically equivalent shales occur in the canadian portion of the basins in southwestern ontario with anecdotal evidence of gas shows yet there has been no commercial shale gas production to date to provide baseline data in the case of future environmental issues related to hydraulic fracturing and shale gas production such as leakage of natural gas saline water and or hydraulic fracturing fluids and to evaluate hydrogeochemical controls on natural gas accumulations in shallow groundwater in general this study investigates the origin and distribution of natural gas and brine in shallow aquifers across southwestern ontario an extensive geochemical database of major ion and trace metal chemistry and methane concentrations of 1010 groundwater samples from shallow domestic wells in bedrock and overburden aquifers throughout southwestern ontario was utilized in addition select wells n 36 were resampled for detailed dissolved gas composition 13 c of ch 4 c 2 c 3 and co 2 and d of ch 4 dissolved gases in groundwater from bedrock and overburden wells were composed primarily of ch 4 29 7 98 6 mol of total gas volume n 2 0 8 66 2 mol ar o 2 0 2 3 4 mol and co 2 0 1 2 mol ethane was detected but only in low concentrations 100 in situ saturation were found in bedrock wells completed in the upper devonian kettle point formation middle devonian hamilton group and dundee formation and in surficial aquifers overlying these organic rich shale bearing formations indicating that bedrock geology is the primary control on methane occurrences a few n 40 samples showed na cl br evidence of brine mixing with dilute groundwater however only one of these samples contained high 60 in situ saturation ch 4 the relatively low 13 c values of ch 4 89 9 to 57 3 covariance of d values of ch 4 and h 2 o positive correlation between 13 c values of ch 4 and co 2 and lack of higher chain hydrocarbons c 3 in all but one dissolved gas sample indicates that the methane in groundwater throughout the study area is primarily microbial in origin the presence or absence of alternative electron acceptors e g dissolved oxygen fe no 3 so 4 in addition to organic substrates controls the occurrence of microbial ch 4 in shallow aquifers microbial methane has likely been accumulating in the study area since at least the late pleistocene to the present as indicated by the co variance and range of d values of ch 4 314 to 263 and associated groundwater 19 to 6 d h 2 o

field flume reveals aquatic vegetation s role in sediment and particulate phosphorus transport in a shallow aquatic ecosystem abstract flow interactions with aquatic vegetation and effects on sediment transport and nutrient redistribution are uncertain in shallow aquatic ecosystems here we quantified sediment transport in the everglades by progressively increasing flow velocity in a field flume constructed around undisturbed bed sediment and emergent macrophytes suspended sediment 100 m became dominant at higher velocity steps after a threshold shear stress for bed floc entrainment was exceeded shedding of vortices that had formed downstream of plant stems also occurred on that velocity step which promoted additional sediment detachment from epiphyton modeling determined that the potentially entrainable sediment reservoir 46 g m 2 was similar to the reservoir of epiphyton 66 g m 2 but smaller than the reservoir of flocculent bed sediment 330 g m 2 all suspended sediment was enriched in phosphorus by approximately twenty times compared with bulk sediment on the bed surface and on plant stems indicating that the most easily entrainable sediment is also the most nutrient rich and likely the most biologically active

sub seafloor sulfur cycling in a low temperature barite field a multi proxy study from the arctic loki s castle vent field abstract the loki s castle vent field at the ultraslow spreading arctic mid ocean ridge amor hosts a low temperature venting area which is characterized by microbial mats and numerous up to 1 m tall barite chimneys an actively venting barite chimney yielded 18oso4 and 34sso4 values heavier than ambient seawater and sulfide oxidizing bacteria in microbial mats identified microbial sulfate reduction and sulfide oxidation as the main processes in order to investigate the chemical and microbial structure below the barite field we obtained two gravity cores and present chemical composition e g h2s so42 nh4 dic and stable isotope data for the pore fluids 34sso4 13cdic together with stable isotope 13corg 34s 33s and lipid biomarker data on bulk sediments the gravity core more distant to the high temperature vents shows seawater like pore fluid profiles with only minor vent fluid contribution

geomorphology within the interdisciplinary science of environmental flows article i nfo the field tradition in geomorphology informs beyond studying landforms by also providing a stage for understand ing how geomorphic elements influence the ecology of biota the intersection between fluvial geomorphology and riverine ecology represents an ideal confluence to examine the contribution of the geomorphic field tradition to en vironmental flows and show this area of riverine management as a research frontier for applied geomorphology environmental flows have consisted of a set of ecological based stream flow guidelines designed to inform sustain able water resource management that supports healthy riverine habitats and provides sufficient water supply for society geomorphological understanding is central to environmental flows because it is the interaction between flow form and substrate that influences habitat type condition availability and biotic use across space and time this relationship varies longitudinally laterally vertically overtime and across macro to mesoscale morphologies withintheriverine environment thegeomorphictemplateis therefore asintegralasthe flow wereviewedstudies where field evidence indicated that geomorphology impacts the effectiveness of environmental flow strategies and wemakethecasefortheneedtoincreasegeomorphic considerationsinenvironmental flows although flow iscom monly referred toas themaster variablein environmental flows geomorphologymediatestheeffectsof flow regime on ecological processes concepts and applications from this perspective on the role of geomorphology in riverine ecosystem research will inform the practice policy and implementation of environmental flows

asymmetric growth of collapsed caldera by oblique subsidence during the 2000 eruption of miyakejima japan abstract oblique development of the ring faults reflecting the structural heterogeneities inside the volcano formed many asymmetric structures of miyakejima 2000 ad caldera the asymmetry includes a offset location of the ring faults with respect to the associated shallow magma chamber b unequal outward migration of the caldera wall 600 m at the southeastern rim but only 200 m at the northwestern rim c development of tilted terrace only at the southeastern caldera margin d eruption sites and fumaroles being confined to the southern part of the caldera geophysical data including ground deformation and seismic activity indicates the offset of the location of the magma chamber about 2 km south of the caldera center on the surface the ring faults propagated from the deflating magma chamber obliquely about 30 degrees toward the summit the oblique subsidence of the cylindrical block formed a wider instable zone particularly in the southeastern side of the ring fault that enhanced the larger outward migration of the caldera rim and also caused the formation of the outer half ring fault bordering the tilting slope at the southern part ascending pass of the buoyant magma along the tilted ring faults was concentrated in the southern half of the caldera and consequently the distributions of the eruption sites and fumaroles are localized in the southern half part of the caldera the structure of the miyakejima 2000 caldera with complete development of the ring faults its high roof aspect ratio and oblique subsidence is clearly distinguishable from trapdoor type caldera the oblique development of the ring faults can be controlled by the mechanical contrast between the solidified conduits and surrounding fragile volcanic edifice asymmetric development of the miyakejima caldera shows that the collapsed calderas are potential indicators of the heterogeneous structures inside of the volcano particularly in the case of small size caldera

fluid rock interaction processes related to hydrothermal vein type mineralization in the siegerland district germany implications from inorganic and organic alteration patterns altered wallrocks of vein type pb zn sb mineralization siegerland district rheinisches schiefergebirge have been investigated by a combination of inorganic and organic geochemical methods including major and trace element analysis vitrinite reflectance measurements c isotope and elemental analysis of kerogen alteration features of the siliciclastic pelitic psammitic lower devonian wallrocks are increased k na ratios significant desilicification and relative immobility of a number of elements notably al ti zr cr v wallrock kerogens display elevated vitrinite reflectance values decrease in h c atomic ratios coupled with increase in s c atomic ratios and heavier c isotope compositions compared to the unaltered precursor sedimentary rocks interaction processes between the hydrothermal fluids and the respective wallrocks related to injection of high temperature silica undersaturated solutions are dominated by quartz dissolution coupled with sericitization reactions heat transfer due to fluid infiltration convection and wallrock reactions caused fluid cooling which promoted the sequential deposition of quartz and stibnite sulphosalts within the vein systems hydrocarbons detected in ore assemblages of pb zn and sb mineralization were most probably derived from the lower devonian very low grade meta sedimentary rocks high maturity levels and pronounced typical organic alteration patterns indicate that thermochemical so2 4 reduction tsr played an important role in precipitation of metal sulphides the present study demonstrates that a combination of inorganic and organic investigations on fluid rock interaction processes is particularly useful for deciphering precipitation mechanisms of base metal sulphides

electrical resistivity tomography of vadose water movement cross borehole electrical resistivity tomography ert was used to image the resistivity distribution before and during two infiltration experiments in both cases water was introduced into the vadose zone and the change in resistivity associated with the plume of wetted soil was imaged as a function of time the primary purpose of this work was to study the capabilities and limitations of ert to image underground structure and ground water movement in the vadose zone a secondary goal was to learn specifics of unsaturated flow in a complex geologic setting tomographs of electrical resistivity taken before infiltration image coarser well drained soils sands and gravels as more resistive zones whereas finer grained soils silts and clays which hold more water by capillarity are imaged as more conductive images of changes in resistivity during infiltration show growth of the water infiltration plume with time that is consistent with known geology in the ert images we see the effects of capillary barriers and infer differences between capillary driven flow through fine sediments and gravity driven flow through very permeable sediments images are consistent with numerical flow simulations using hydrological parameter values consistent with soil types inferred from well logs ert can be a useful tool to monitor movement of circuitous moisture fronts in a heterogeneous field setting that would go undetected by borehole measurements

effects of changing channel morphology on vegetation groundwater and soil moisture regimes in groundwater dependent ecosystems abstract channel incision channel widening and excessive floodplain sedimentation are major causes of riparian ecosystem degradation across the country although the causes and consequences of these processes vary significantly the resulting morphology in all cases results in a lower stream stage relative to the floodplain surface for any given discharge this change in channel morphology alters surface water groundwater interactions between the stream and the riparian aquifer and affects the soil moisture and groundwater regimes differentially across the floodplain the distribution of vegetation is altered as the hydrologic regime shifts between the hydrologic niches of potential species we simulate the hydroecologic response of a groundwater dependent ecosystem on the floodplain of an archetypical watershed under three scenarios representing changes in channel morphology a base case a widened channel case and an incised channel case stochastically driven synthetic rainfall records are used to drive a rainfall runoff model of the archetype watershed the resulting hydrograph is transformed to stage via manning s equation for the three channel morphologies considered this stage record is used as a boundary condition for a finite element model simulating 2 dimensional variably saturated groundwater flow in the riparian aquifer the model predicts soil moisture and groundwater regimes lateral to the channel the 7 day moving average high water level is determined for ten growing seasons and used to predict the distribution of three species across the floodplain plant frequency is predicted for carex emoryi an obligate wetland species carex crawei facultative wetland species and carex duriuscula a facultative upland species for each of the channel morphologies considered the frequency is predicted using existing nonlinear parametric species response curves determined empirically for these species using direct gradient analysis results show the sensitivity of the distribution of vegetation on floodplains to channel morphologic changes our linked hydrologic and ecological model provides a solid framework for considering potential hydroecologic impacts of channel disturbance and or restoration on vegetation communities which are often affected by channel degradation and targeted in restoration efforts

the role of prokaryotes in subsurface weathering of hydrothermal sediments a combined geochemical and microbiological investigation a detailed geochemical and microbiological study of a 2 m sediment core from the inactive alvin mounds within the tag hydrothermal field was conducted to examine for the first time the role of prokaryotes in subsurface weathering of hydrothermal sediments results show that there has been substantial post depositional remobilisation of metal species and diagenetic overprinting of the original high temperature hydrothermal minerals and aspects have involved prokaryotic processes prokaryotic enumeration demonstrates the presence of a population smaller than the average for deep sea sediments probably due to the low organic carbon content but not inhibited by and hence adapted to the metal rich environment there was a small but significant increase in population size associated with the active redox boundary in an upper metal sulphide layer 50 70 cm around which active metal remobilisation was concentrated cu au cd ag u zn and zn hence subsurface prokaryotes were potentially obtaining energy from metal metabolism in this near surface zone close association of numbers of culturable mn and fe reducing prokaryotes with subsurface fe2 and mn2 pore water profiles suggested active prokaryotic metal reduction at depth in core cd102 43 to 175 cm in addition a prokaryotic mechanism which is associated with bacterial sulphate reduction is invoked to explain the u enrichment on pyrite surfaces and zn and pb remobilisation in the upper sediment although prokaryotic populations are present throughout this metalliferous sediment thermodynamic calculations indicated that the inferred low ph of pore waters and the suboxic anoxic conditions limits the potential energy available from fe ii oxidation which may restrict prokaryotic chemolithotrophic biomass this suggests that intense prokaryotic fe oxidation and weathering of seafloor massive sulphide deposits may be restricted to the upper portion of the deposit that is influenced by near neutral ph and oxic seawater unless there is significant subsurface fluid flow

induced thermal compaction in cohesive sediments around a borehole heat exchanger laboratory tests on the effect of pore water salinity in closed loop geothermal systems the operation of a borehole heat exchanger bhe affects the thermal equilibrium of the surrounding subsoil this study was part of a large laboratory program undertaken to understand how the cyclic thermal stress induced by a bhe in the subsoil can change sediments mechanical properties if the bhe works in extreme running conditions which induce both freeze thaw cycles and heating processes in the ground this paper presents the results from an experimental laboratory investigation on the effects of different pore water salinity concentrations on the vertical strain induced in a thermally loaded silty clay the considered study case is the historical center of venice italy which provides an example of typical conditions of densely urbanized areas inserted in coastal or transitional environments with abundance of cohesive layers and brackish conditions in the subsoil results show that the irreversible compaction effect induced on sediments increases with higher salinity concentration despite the fact that increasing salt content lowers the sediment freezing point thereby protecting the soil from freezing processes

impacts of subsurface heat storage on aquifer hydrogeochemistry the use of shallow aquifers for subsurface heat storage in terms of energy management and building climatisation can lead to a temperature rise in the aquifer to 70 c and above the influence of temperature changes on individual mineral and sorption equilibria reaction kinetics and microbial activity is largely known however the impact of heating to temperatures as high as 70 c on the aquifer overall system has not been quantified yet temperature related changes in sediment ion exchange behaviour dimension and rates of mineral dissolution and precipitation as well as microbially enhanced redox processes were studied in column experiments using aquifer sediment and tap water at 10 25 40 and 70 c at 70 c a change in sediment sorption behaviour for cations and organic acids was postulated based on temporal changes in ph magnesium and potassium concentration in the experimental solution no clear changes of ph tic and major cations were found at 10 40 c redox zoning shifted from oxic conditions towards nitrate and iron iii reducing conditions at 25 and 40 c and sulphate reducing conditions at 70 c this was attributed to a a temperature related increase in microbial reduction activity and b three times higher release of organic carbon from the sediment at 70 c compared to the lower temperatures the findings of this study predict that a temperature increase in the subsurface up to 25 c and above can impair the usability of ground water as drinking and process water by reducing metal oxides and thus possibly releasing heavy metals from the sediment generally at 70 c where clear cation and organic carbon desorption processes were observed and sulphate reducing conditions could be achieved a site specific assessment of temperature effects is required especially for long term operations of subsurface heat storage facilities

organic rich sediment alteration an experimental and theoretical study at elevated temperatures and pressures organic rich diatomaceous ooze was reacted with sea water at 200 and 300 c 500 bars and an initial fluid sediment mass ratio of 4 to evaluate the role of organic matter in sediment alteration processes at elevated temperatures and pressures decomposition of organic matter during the early stages of reaction dominated alteration and resulted in increased dissolved co2 corganic nh4 and h2s car ylic acids were identified as reaction intermediaries during the transformation of organic matter to ch4 and co2 extensive so42 reduction was observed at 300 c but not at 200 c sediment alteration at 300 c resulted in recrystallization of calcic plagioclase and diatoms to an assemblage containing albite pyrrohotite and quartz in addition to minor anhydrite and mg smectite in contrast sediment alteration at 200 c resulted in only minor anhydrite and mg smectite formation and there was no indication of recrystallization of diatoms to quartz rapid mg fixation during the early stages of alteration resulted in the complete removal of mg from solution at 300 c and partial removal at 200 c production of acidity associated with mg metasomatism was efficiently titrated by thermolytic and oxidative degradation of organic matter resulting in conspicuously low dissolved metal concentrations during the experiments in the later stages of sediment alteration at 300 c albitization of calcic plagioclase caused the continuous release of ca to solution while at 200 c fluid chemistry remained relatively constant speciation calculations for the 300 c experiment indicate an in situ ph of 5 11 and a highly reduced redox state likely controlled by organic matter decomposition experimental results permit us to evaluate fluid mineral equilibria in complex fluids containing high concentrations of dissolved organic species co2 and h2s and constrain better alteration processes in sub sea floor hydrothermal systems at sediment covered spreading centers such as the guaymas basin gulf of california

modified frequency wavenumber algorithm for regional seismograms using filon s quadrature modelling of lg waves in eastern north america summary the main focus of this study is to develop an efficient frequency wavenumber code to synthesize high frequency say 10 hz regional seismograms up to a distance of more than 1000 km in a medium consisting of a large number of crustal layers and investigate effects of regional waveguides on lg waves in this newly developed code the frequency wavenumber response is evaluated by using the filon s quadrature at high frequency and the polynomial approximation of bessei s functions implementing trapezoidal integration at low frequency this has reduced the computation time by several folds compared to the time needed for the trapezoidal integration using this algorithm both broad band seismograms at harvard and short period ectn eastern canadian telemetered network seismograms from 1988 november 25 saguenay earthquake were successfully modelled a moment magnitude of 5 9 was used initially an average waveguide was calibrated to successfully excite the regional pnl and snl waves at hrv its near surface structure constrained by matching the recorded frequency content the crust mantle transition zone was constrained by modelling the strength of the broad band snl waves consisting of sn ssmsnsmssms and ssmssms phases relative to the initial pnl waves the model was modified to consist of thin layers with an alternating high and low velocity distribution to match the high frequency ectn lg waves observed from 300 to 600 km away in addition the effect of a near surface irregular receiver structure on the duration of lg waves was also investigated by convolving its response with the regional lg seismograms initial study suggests this method as viable for modelling the entire lg waves including the coda numerical studies suggest that the shapes and peak amplitudes on lg seismograms depend more strongly on the source depth anelasticity and crustal waveguide than do the pnl seismograms

biogeomorphic interactions in the turtmann glacier forefield switzerland glacier forefields are dynamic environments dominated by active paraglacial processes and simultaneous vegetation succession triggered by glacier retreat since the little ice age while these dynamics are accelerating in the last decades owing to climate change interactions between vegetation and geomorphic processes and components and the resulting patterns are only partly understood using a biomorphic approach based on preexisting geomorphic and glaciological data geomorphic activity was classified and mapped in the turtmann glacier forefield switzerland vegetation and environmental parameters were sampled vegetation analysis was subsequently carried out with vegetation classification and ordination for identifying relationships to environmental parameters a paraglacial impact on vegetation succession could be shown and differentiated according to geomorphic activity on constant terrain age biogeomorphic concepts were then applied to explain these patterns three biogeomorphic succession phases were identified and related to degrees of activity species composition and strength of interactions integrating our results into the paraglacial concept we show how the paraglacial adjustment of a glacier forefield is significantly affected by biogeomorphic interactions

bubble growth processes in magma surrounded by an elastic medium abstract gas bubble growth in magma plays an important role in volcanic explosivity and many previous studies have undertaken theoretical and experimental analyses of gas bubble expansion in melt these previous studies commonly assume constant ambient pressure but it is more natural to assume that the magma is stressed by the crust or volcanic edifices as the volume of gas bubbles increases here we present a bubble growth model that takes into account the elasticity of the surrounding medium we use this model to examine temporal changes in the bubble growth process our model consists of a two dimensional dike filled with compressible viscous melt and numerous tiny gas bubbles we use the cell model proposed by proussevitch et al proussevitch a sahagian d l anderson a t 1993 dynamics of diffusive bubble growth in magmas isothermal case j geophys res 98 22283 22307 to describe the interaction between the numerous gas bubbles and the melt the bubble growth process is formulated by the diffusion equation of volatiles in the melt the mass balance between bubbles and melt and the momentum equation of the melt we also introduce pressure balance equations between the melt and the surrounding elastic medium nishimura t 2004 pressure recovery in magma due to bubble growth geophys res lett 31 using the finite difference scheme we numerically calculate temporal changes in bubble radius and melt pressure within magma subjected to sudden depressurization simulation results show that the elasticity of the surrounding medium strongly controls the bubble growth process under high effective rigidity the final bubble radius is several times smaller than for zero rigidity and the time required for bubble growth is an order of magnitude quicker temporal changes in the melt pressure are particularly dependent on the elasticity of the surrounding medium melt pressure effectively recovers and even exceeds the given pressure drop for conditions of high rigidity and or small initial bubble radius although bubble growth in magma has previously been investigated mainly from geological samples and theoretical perspectives our model can quantitatively evaluate pressure changes in magma that can also be detected by seismic and geodetic measurements

modeling of hydroecological feedbacks predicts distinct classes of landscape pattern process and restoration potential in shallow aquatic ecosystems article i nfo it is widely recognized that interactions between vegetation and flow cause the emergence of channel patterns that are distinct from the standard schumm classification of river channels although landscape pattern is known to be linked to ecosystem services such as habitat provision pollutant removal and sustaining biodiversity the mechanisms responsible for the development and stability of different landscape patterns in shallow vegetated flows have remained poorly understood fortunately recent advances have made possible large scale models of flow through vegetated environments that can be run over a range of environmental variables and over timescales of millennia we describe a new quasi 3d cellular automata model that couples simulations of shallow water flow bed shear stresses sediment transport and vegetation dynamics in an efficient manner that efficiency allowed us to apply the model widely in order to determine how different hydroecological feedbacks control landscape pattern and process in various types of wetlands and floodplains distinct classes of landscape pattern were uniquely associated with specific types of allogenic and autogenic drivers in wetland flows regular anisotropically patterned wetlands were dominated by allogenic processes i e processes driven by periodic high water levels and flow velocities that redistribute sediment relative to autogenic processes e g vegetation production peat accretion and gravitational erosion these anistropically patterned wetlands are therefore particularly prone to hydrologic disturbance other classes of wetlands that emerged from simulated interactions included maze patterned amorphous and topographically noisy marshes open marsh with islands banded string pool sequences perpendicular to flow parallel deep and narrow channels flanked by marsh and ridge and slough patterned marsh oriented parallel to flow because vegetation both affects and responds to the balance between the transport capacity of the flow and sediment supply these vegetated systems exhibit a feedback that is not dominant in most rivers consequently unlike in most rivers it is not possible to predict the channel pattern of a vegetated landscape based only on discharge characteristics and sediment supply the antecedent vegetation pattern and vegetation dynamics must also be known in general the stability of different wetland pattern types is most strongly related to factors controlling the erosion and deposition of sediment at vegetation patch edges the magnitude of sediment redistribution by flow patch elevation relative to water level and the variability of erosion rates in vegetation patches with low flow resistance as we exemplify in our case study of the everglades ridge and slough landscape feedback between flow and vegetation also causes hysteresis in landscape evolution trajectories that will affect the potential for landscape restoration namely even if the hydrologic conditions that historically produced higher flows are restored degraded portions of the ridge and slough landscape are unlikely to revert to their former patterning as wetlands and floodplains worldwide become increasingly threatened by climate change and urbanization the greater mechanistic understanding of landscape pattern and process that our analysis provides will improve our ability to forecast and manage the behavior of these ecosystems published by elsevier b v

a method for measuring the solid particle permittivity or electrical conductivity of rocks sediments and granular materials 1 measurement of the effective dielectric permittivity of porous media provides an elegant method of estimating both the porosity and water content of soils sediments and rocks obtaining accurate estimates of water content can only be achieved if the models relating the measured permittivity to water content work well one of the difficulties with testing physical models describing two and three phase dielectric mixtures saturated and unsaturated systems is obtaining an accurate value for the permittivity of the mineral matrix no direct measurement method has been presented for rocks and soils so the solid permittivity value is often an estimate of 5 essentially remaining a fitting parameter we present a measurement method requiring no preassumed theoretical model the method requires the measurement of the effective permittivity of a granular material immersed in fluids of differing permittivity and interpolation between the range of data points measurements of the permittivity of the mineral matrix of a number of materials are presented including glass beads 7 6 quartz sand 4 7 calcareous seashell fragments 8 9 hematite ore 18 1 tuff 6 0 and a sandy loam soil 5 1 estimates based on using mixing models to obtain the solid permittivity are demonstrated to underestimate the permittivity of hematite ore by between 0 and 45 depending on the model and packing the method is also suitable for measuring the electrical conductivity of granular minerals by changing the electrical conductivity of the bathing solution results for the electrical conductivity of hematite ore 0 040 ds m 1 and carborundum 10 9 ds m 1 are presented

isotopic constraints on fluid evolution and precipitation mechanisms for the boleo cu co zn district mexico stable and radiogenic isotope composition of stratiform cu co zn mineralization and associated sedimentary rocks within the boleo district of the miocene santa rosalia basin baja california sur constrains the evolution of seawater and hydrothermal fluids and the mechanisms responsible for sulfide and oxide deposition stable isotope geochemistry of limestone and evaporite units indicates a strong paleogeographic influence on the chemistry of the water column near shore limestone at the base of the boleo formation is characterized by modified marine carbon 13cpdb 6 0 to 4 4 and oxygen 18osmow 19 5 to 26 2 isotope composition due to the influx of 13c and 18o depleted fluvial water sulfate sulfur isotope composition 34scdt 17 21 to 22 3 and 18osmow 10 7 to 13 1 for basal evaporite and claystone facies are similar to miocene seawater strontium isotopes are less radiogenic than expected for miocene seawater due to interaction with volcanic rocks low s c ratios high mn contents and sedimentological evidence indicate the basin water column was oxidizing the oxygenated basin restricted sulfide precipitation to within the sedimentary pile by replacement of early diagenetic framboidal pyrite and pore space filling by cu co zn sulfides to produce disseminated sulfides quartz mn oxide oxygen isotope geothermometry constrains mineralization temperature between 18 and 118 c sulfur isotopes indicate the following sources of sulfide 1 bacterial sulfate reduction within the sedimentary pile produced negative 34s values 20 in framboidal pyrite and 2 bacterial sulfate reduction at high temperature 80 118 c within the sedimentary pile during the infiltration of the metal bearing brines produced cu co zn sulfides with negative but close to 0 34s values isotope modeling of fluid rock reaction and fluid mixing indicates 1 sedimentary and marine carbonates 13c 11 6 to 3 2 and 18o 19 0 to 21 8 precipitated from basin seawater pore water that variably mixed with isotopically depleted meteoric waters and 2 hydrothermal calcite 13c 7 9 to 4 3 and 18o 22 1 to 25 8 formed by dissolution and replacement of authigenic marine calcite by downward infiltrating metalliferous brine and brine sediment exchange that prior to reaction with calcite had mixed with isotopically depleted pore water the downward infiltration of metalliferous brine is inferred from lateral and stratigraphic metal distributions and from the concentration of cu sulfides along the upper contact of pyrite bearing laminae the co existence and textural relationships among framboidal pyrite base metal sulfides carbonate and mn fe oxides including magnetite within mineralized units are consistent with carbonate replacement and high temperature bacterial reduction within the sedimentary pile occurring simultaneously below a seawater column under predominantly oxygenated conditions

mechanism and rate of denitrification in an agricultural watershed electron and mass balance along groundwater flow paths the rate and mechanism of nitrate removal along and between groundwater flow paths were investigated using a series of well nests screened in an unconfined sand and gravel aquifer intensive agricultural activity in this area has resulted in nitrate concentrations in groundwater often exceeding drinking water standards both the extent and rate of denitrification varied depending on the groundwater flow path while little or no denitrification occurred in much of the upland portions of the aquifer a gradual redox gradient is observed as aerobic upland groundwater moves deeper in the aquifer in contrast a sharp shallow redox gradient is observed adjacent to a third order stream as aerobic groundwater enters reduced sediments an essentially complete loss of nitrate concurrent with increases in excess n2 provide evidence that denitrification occurs as groundwater enters this zone electron and mass balance calculations suggest that iron sulfide e g pyrite oxidation is the primary source of electrons for denitrification denitrification rate estimates were based on mass balance calculations using nitrate and excess n2 coupled with groundwater travel times travel times were determined using a groundwater flow model and were constrained by chlorofluorocarbon based age dates denitrification rates were found to vary considerably between the two areas where denitrification occurs denitrification rates in the deep upland portions of the aquifer were found to range from 0 01 to 0 14 mm of n per year rates at the redoxcline along the shallow flow path range from 1 0 to 2 7 mm of n per year potential denitrification rates in groundwater adjacent to the stream may be much faster with rates up to 140 mm per year based on an in situ experiment conducted in this zone

dissolved gas evidence for denitrification in the lincolnshire limestone groundwaters eastern england abstract high concentrations of dissolved nitrogen gas are present in some groundwaters within the confined zone of the lincolnshire limestone aquifer atmospheric nitrogen sources are shown to be from air equilibration at groundwater recharge and air entrainment during recharge nitrogen arising from these two processes can be identified and quantified by the pattern of noble gas dissolution in the groundwaters nitrogen which is in excess of the amounts due to these two processes is attributed to denitrification the isotopic composition of this nitrogen gas derived from denitrification has variably light 15n values

holocene soil geomorphic surfaces influence the role of salmon derived nutrients in the coastal temperate rainforest of southeast alaska abstract the influence of salmon derived nutrients sdn is widely accepted as a potential factor in the maintenance of aquatic and terrestrial productivity in north american coastal rainforests holocene alluvial landforms are intimately connected with the return of anadromous salmon but the influence of the soils that occupy these landforms and support this important terrestrial aquatic ecological coupling have not been examined in sdn studies we used paleo ecologic information soil resource inventories and measurements of soil morphology to construct a soil geomorphic model for alluvial landforms along salmon spawning channels on prince of wales island southeast alaska usa post glacial sea level rise crustal uplift and subsidence combined with holocene sediment deposition have formed alluvial terraces and floodplains along rivers on prince of wales island these alluvial landforms have soils that are mapped as entisols tonowek soil series and spodosols tuxekan soil series we propose a soil geomorphic model where the spodosols located on terraces are estimated to derive from sediments deposited after the stabilization of landscape approximately 8 kybp to 6 kybp the stability of these soils is reflected through mature soil development with organic matter accumulation and podzolization our model identifies entisols on floodplains developed from alluvial deposition in the latter holocene that have soil morphologic features consistent with recent deposition and limited soil development we used this soil geomorphic model to test the hypothesis that the terrestrial end member value commonly used to quantify nitrogen n loading on soils through stable isotope analysis differs by soil type and found that the two soil types had significantly different n isotopic 15n values more consistent with soil development than sdn loading the use of a soil geomorphic model provides a means to stratify alluvial landforms and constrain the natural variability encountered in studies of riparian nutrient cycles associated with the feedbacks between sdn and terrestrial ecosystems to improve estimates of the fate of sdn in soils and vegetation

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

geochemical modeling of zns in biofilms an example of ore depositional processes the precipitation of nearly pure nanocrystalline zinc sulfides primarily sphalerite and wurtzite within a biofilm dominated by sulfate reducing bacteria of the family desulfobacteriaceae has been observed in the flooded tunnels of an abandoned mine in southwestern wisconsin zns accumulations are limited to biofilms growing on old mine timbers zns deposits which comprise about 20 percent of the volume of the biofilm formed in less than 30 yr from solutions containing only a few milligrams per liter mg l zn 2 a model is proposed wherein sulfate reduction is followed by the formation of aqueous metal sulfide clusters that aggregate to form 1 to 3 nm diameter crystals that are transported and agglomerate to form micron scale aggregates geochemical modeling shows how reduction of sulfate leads to exclusive precipitation of zns until most of the zn 2 is consumed the model also predicts a series of discrete metal sulfide precipitation events that may be used to interpret sulfide mineral paragenesis of low temperature cu pb zn ore deposits for example the paragenesis of essentially monomineralic and mixed sulfide layers in mississippi valley type strataform and strata bound pb zn cu and sedex deposits can be predicted thermodynamically if the rate of aqueous sulfide generation does not outstrip the flux of metals into the system based on the characteristics of zns produced by sulfate reducing bacteria features of ore deposit minerals consistent with a biogenic origin can be identified these include microstructures formed by coarsening of nanophase materials the presence of micron scale spherical aggregates in organic rich microenvironments and spatially heterogeneous patterns of sulfide mineral distribution consistent with local variations in redox potential and activity of sulfate reducing bacteria

subsurface cyclic magma sill expansions in the 2000 miyakejima volcano eruption possibility of two phase flow oscillation 1 step like tilt changes were observed at intervals of dozens of hours during the caldera formation stage occurred during the 2000 miyakejima volcano eruption our analysis suggests that these tilt steps were caused by the cyclic expansion of a subsurface sill like magma plumbing system trending from se to nw of the volcano in the same period a caldera gradually grew at the summit area to a very large 1 6 km in diameter and 450 m in depth the source mechanism of these tilt steps is fairly well explained by a two phase flow instability called a pressure drop oscillation this model indicates that the gas phase capacity in the upper part of the conduit acts as a pump that controls the flux of two phase magma in the sill like reservoir caldera formation as well as magma uplift and descent in the conduit may reflect temporal changes in the intervals between tilt steps which are themselves proportional to the volume of this gas capacity

a reactive transport model for the quantification of risks induced by groundwater heat pump systems in urban aquifers abstract shallow geothermal resource exploitation through the use of groundwater heat pump systems not only has hydraulic and thermal effects on the environment but also induces physicochemical changes that can compromise the operability of installations this study focuses on chemical clogging and dissolution subsidence processes observed during the geothermal re injection of pumped groundwater into an urban aquifer to explain these phenomena two transient reactive transport models of a groundwater heat pump installation in an alluvial aquifer were used to reproduce groundwater solid matrix interactions occurring in a surrounding aquifer environment during system operation the models couple groundwater flow heat and solute transport together with chemical reactions in these models the permeability distribution in space changes with precipitation dissolution reactions over time the simulations allowed us to estimate the calcite precipitation rates and porosity variations over space and time as a function of existent hydraulic gradients in an aquifer as well as the intensity of co2 exchanges with the atmosphere the results obtained from the numerical model show how co2 exolution processes that occur during groundwater reinjection into an aquifer and calcite precipitation are related to hydraulic efficiency losses in exploitation systems finally the performance of reinjection wells was evaluated over time according to different scenarios until the systems were fully obstructed our simulations also show a reduction in hydraulic conductivity that forces re injected water to flow downwards thereby enhancing the dissolution of evaporitic bedrock and producing subsidence that can ultimately result in a dramatic collapse of the injection well infrastructure

hydrothermal petroleum in mineralized mounds at the seabed of guaymas basin petroleum has been dredged from an active hydrothermal mound area in the southern rift of guaymas basin gulf of california this organic matter is composed of gasoline range aliphatic and aromatic hydrocarbons and predominantly residual polar asphaltic material the aliphatic hydrocarbons of two bitumen samples have very different boiling range and composition both samples contain polynuclear aromatic hydrocarbons and olefins which indicate formation at pyrolytic temperatures the overall compositional data indicate an origin from biological detritus by thermal alteration and rapid quenching by hydrothermal removal followed by condensation at the seabed

use of dissolved and vapor phase gases to investigate methanogenic degradation of petroleum hydrocarbon contamination in the subsurface 1 at many sites contaminated with petroleum hydrocarbons methanogenesis is a significant degradation pathway techniques to estimate ch4 production consumption and transport processes are needed to understand the geochemical system provide a complete carbon mass balance and quantify the hydrocarbon degradation rate dissolved and vapor phase gas data collected at a petroleum hydrocarbon contaminated site near bemidji minnesota demonstrate that naturally occurring nonreactive or relatively inert gases such as ar and n2 can be effectively used to better understand and quantify physical and chemical processes related to methanogenic activity in the subsurface in the vadose zone regions of ar and n2 depletion and enrichment are indicative of methanogenic and methanotrophic zones and concentration gradients between the regions suggest that reaction induced advection can be an important gas transport process in the saturated zone dissolved ar and n2 concentrations are used to quantify degassing driven by methanogenesis and also suggest that attenuation of methane along the flow path into the downgradient aquifer is largely controlled by physical processes slight but discernable preferential depletion of n2 over ar in both the saturated and unsaturated zones near the free phase oil suggests reactivity of n2 and is consistent with other evidence indicating that nitrogen fixation by microbial activity is taking place at this site

modified compressibility of cohesive sediments induced by thermal anomalies due to a borehole heat exchanger abstract in ground source heat pump systems gshp a continuous circulation of a fluid inside the exchangers installed in the ground transfers heat between the ground and the building s conditioning system often the carrier fluids are brines consisting of a mixture of water and anti freezing solutions which lower their working temperature in order to improve the heat extraction from the ground during the cold season the international community has already pointed out the importance of assessing a minimum temperature threshold for the brines inside the probes in order to constrain the thermal anomalies induced in the soil this paper analyzes how a borehole heat exchanger could affect the natural consolidation processes of surrounding cohesive layers if the thermal anomaly induces freezing and subsequent heating processes the study case of venice italy is considered where gshp systems could be a very interesting solution for the issues related to the particular configuration of the city center the density of historical buildings and the local regulations venice represents an example of a densely urbanized area with a subsoil characterized by a continuous alternation between cohesive and coarser layers as in most coastal lowland plains the induced thermal settlement and the increased stiffness are measured in a silty clay sampled in the area by means of a special device consisting in a thermostatically controlled oedometer the obtained results contribute to the definition of the environmental hazards connected with the use of gshp systems

bacterial incorporation of relict carbon in the hydrothermal environment of guaymas basin abstract radiocarbon analyses of bulk carbon and individual organic compounds are presented for the hydrothermal environment of the rebecca s roost vent in the southern trough of the guaymas basin hydrothermal field the 14 c values of co 2 and ch 4 in the hottest hydrothermal fluids 317 c are nearly radiocarbon dead 944 and 923 respectively in contrast the 14 c values of sediments and individual fatty acids 418 to 227 obtained from a bacterial mat located south of the vent site are similar to values previously reported for hydrothermal petroleum in this environment and are more depleted in 14 c than overlying waters hydrothermal fluids moving through the sediments appear to supply 14 c of intermediate age to the bacteria this carbon may take the form of or may be supplied by processes similar to the generation of hydrothermal petroleum although the bacterial mat visibly was dominated by beggiatoa spp such mats are known to include numerous other species individual compound data show that preaged carbon is being consumed by the integrated bacterial assemblage values of 13 c and 14 c indicate that petroleum derived carbon is incorporated directly into fresh bacterial biomass subsequently some of this newly synthesized material also is consumed by heterotrophs as eukaryotic sterols from the same sample also have 14 c depleted values 14 c 136 to 110 therefore the entire system may operate as a complex consortium to transform relict carbon back into biomass bacterial consumption of relict carbon occurs despite the ample supply of fresh carbon delivered from the productive overlying water column

preface multiscale feedbacks in ecogeomorphology 1 introductiongeomorphic systems are known to exhibit nonlinear responses tophysical biological feedbacks thornes 1985 baas 2002 reinhardtet al 2010 these responses make understanding and or predictingsystem response to change highly challenging with growingconcerns over ecosystem health a pressing need exists for researchthat tries to elucidate these feedbacks jerolmack 2008 darby 2010 national research council 2010 a session was convened at the fall2008 meeting of the american geophysical union agu to providean outlet for some of this truly interdisciplinary and original research which is central to understanding geomorphic and ecologicaldynamics the session attracted over 39 contributions which weredivided into two well attended oral sessions and a very busy postersession this special issue presents new research from the agu session which highlights clear physical biological feedbacks the aim is tobring together contrasting perspectives on biological and geomorphicfeedbacks in a diversity of physiographic settings ranging fromwetlands and estuaries through rivers to uplands these papershighlight biological and physical feedbacks which involve themodulation or ampli cation of geomorphic processes these paperswill be of interest to a core geomorphology audience and should alsodraw attention from the elds of ecohydraulics hydroecology ecohydrology ecomorphology biogeochemistry and biogeography and biogeomorphology as well as the more traditional elds ofhydrology ecology and biology in this preface to the special issue we a review past contributionsto the emerging eld of ecogeomorphology and related disciplines b provide some context for how this topical special issue came tofruition and c summarize the contributions to this special issue 2 what is ecogeomorphology examples of studies explicitly integrating ecology and geomor phology date back to at least the late 1800s e g cowles 1899 withmore examples appearing in the 1950s e g olson 1958 and 1960s e g hack and goodlet 1960 terms such as ecogeomorphology andbiogeomorphologyonlybecamepopularinthe1990s osterkampandhupp 2010 the 1990 british geomorphology research groupannual meeting thornes 1990 and the 1995 binghamton sympo sium on biogeomorphology hupp et al 1995b were two of the rstsymposiums to emphasize the theme of biogeomorphology ecogeo morphology and biogeomorphology are generally considered syno nyms hupp et al 1995a but they do sprout from slightly differentresearch interests both are part of a larger family of terms thatresearchers have used somewhat inconsistently to describe researchat the interface between some combination of hydrology geomor phologyand orecology biology fig 1 unlikesomeoftheothereco geo hydro combinations in fig 1 the eco or bio root is an adjectivemodifying the noun geomorphology based on the types of researchpublished under these two banners the biogeomorphology commu nity has generally focused more on how chemical and physicalweathering are ampli ed and modulated with biological feedbacks ecogeomorphology is commonly used to describe studies that focusmore on the ampli cation and modulation of erosion and depositionprocesses both are fundamentally concerned with the bidirectionalin uences of biota and landscapes on each other biogeomorphologyis concerned with both the in uence of landforms on plants animalsand micro organisms distribution and development as well as thein uence of those plants animals and micro organisms on earthsurfaceprocessesandthelandformsshapedbythoseprocesses viles 1988 naylor et al 2002 p 4 loosely de ne biogeomorphology asinvolving the cooperation between ecology and geomorphology tostudy two way linkages between ecological and geomorphologicalprocesses murray et al 2008 argue that biomorphodynamics is amore restrictive term than biogeomorphology or ecogeomorphology and that it highlights landscape dynamics in which an explicit twoway coupling i e feedback occurs between biotic and physicalprocesses therelatedzoogeomorphology e g butler 1995 termhasreceived less play but it is worth mentioning that research under thisbanner focuses on examples of animals in uencing geomorphicprocesses and landforms e g beaver salmon burrowing animals etc the term biogeomorphology has been more widely used sinceviles 1988 rst attempted to provide a comprehensive overview ofwhat was at that time an emerging discipline a review of web of

ecogeomorphic feedbacks in regrowth of travertine step pool morphology after dam decommissioning fossil creek arizona abstract the linkages between fluvial geomorphology and aquatic ecosystems are commonly conceptualized as a one way causal chain in which geomorphic processes create the physical template for ecological dynamics in streams with a travertine step pool morphology however biotic processes strongly influence the formation and growth of travertine dams creating the potential for numerous feedbacks here we take advantage of the decommissioning of a hydroelectric project on fossil creek arizona where restoration of caco 3 rich baseflow has triggered rapid regrowth of travertine dams to explore the interactions between biotic and abiotic factors in travertine morphodynamics we consider three conceptual frameworks where biotic factors independently modulate the rate of physical and chemical processes that produce travertine dams combine with abiotic factors in a set of feedback loops and work in opposition to abiotic processes such that the travertine step pool morphology reflects a dynamic balance between dominantly biotic constructive processes and dominantly abiotic destructive processes we consider separately three phases of an idealized life cycle of travertine dams dam formation growth and destruction by erosive floods dam formation is catalyzed by abiotic factors e g channel constrictions and bedrock steps and biotic factors e g woody debris and emergent vegetation from measurements of changes over time in travertine thickness on a bedrock step we find evidence for a positive feedback between flow hydraulics and travertine accrual measurements of organic content in travertine samples from this step show that algal growth contributes substantially to travertine accumulation and suggest that growth is most rapid during seasonal algal blooms to document vertical growth of travertine dams we embedded 252 magnets into nascent travertine dams along a 10 km stretch of river growth rates are calculated from changes over time in the magnetic field intensity at the dam surface at each magnet we record a range of hydraulic and travertine composition variables to characterize the dominant mechanism of growth abiotic precipitation algal growth trapping of organic material or in situ plant growth we find 1 rapid growth of travertine dams following flow restoration averaging more than 2 cm year 2 growth rates decline downstream consistent with loss of dissolved constituents because of upstream travertine deposition but also parallel to a decline in organic content in dam surface material and a downstream shift in dominant biotic mechanism 3 biotic mechanisms are associated with faster growth rates and 4 correlations between hydraulic attributes and growth rates are more consistent with biotic than abiotic controls we conclude that the strong influence of living organisms on rates of travertine growth coupled with the beneficial effects of travertine on ecosystem dynamics demonstrate a positive feedback between biology and geomorphology during our two year study period erosive flood flows occurred causing widespread removal of travertine the temporal distribution of travertine growth and erosion over the study period is consistent with a bimodal magnitude frequency relation in which growth dominates except when large infrequent storms occur this model may be useful in other systems where biology exerts strong controls on geomorphic processes

gas phase formation during thermal energy storage in near surface aquifers experimental and modelling results heating of groundwater by thermal energy storage tes poses a potential for the formation of a separate gas phase necessary boundary conditions potential effects and monitoring feasibility of this process were not focused within previous studies since the formation of a gas phase could change groundwater flow conditions hydrochemistry porous media properties and thus efficiency of tes applications improved understanding of the process is needed the temperature of percolated sediment column tests was adjusted to 10 25 40 and 70 degrees c to quantify temperature induced physical gas phase formation and its effect on electrical resistance gas phase formation its accumulation and effects on hydraulic conductivity heat conductivity and heat capacity were investigated using scenario calculations based on a closed loop borehole tes system at 60 degrees c for different geochemical conditions experimentally quantified degassing ratios were within the expected range of thermodynamic calculations the laboratory time lapse electrical resistivity measurements proofed as a suitable tool to identify the onset and location of the gas phase formation depending on the geochemical conditions hydraulic conductivity in the area of the simulated heat storage site decreased between 60 and up to one order of magnitude in consequence of degassing within the scenario calculations heat conductivity and heat capacity decreased by maximally 3 and 16 respectively the results indicate that gas phase formation as a result of aquifer heating can have pronounced effects especially on groundwater flow conditions and therefore should be considered particularly for nearly or fully gas saturated groundwater and aquifers containing gas sources

low temperature sulphate reduction biological versus abiological sulphate is considered to have been a major source of sulphide in strata bound and stratiform base metal sulphide deposits many of these deposits however appear to have been formed at moderate temperatures 200 c which poses the question by what mechanism s was sulphate reduced to sulphide two modes of reduction have been established experimentally 1 catalysis by sulphate reducing bacteria which at present is only known to occur below ca 100 c and 2 abiological reduction by ferrous iron or organic matter which has only been clearly shown above ca 250 c several attempts have been made to demonstrate abiological reduction below 200 c and some new data are presented here although the results do not exclude the possibility that such a reaction may be geochemically significant there has been no unequivocal demonstration of nett sulphide formation from sulphate at these temperatures recent studies of the microbiology of hydrothermal regions have opened up the prospect of bacterial sulp

disturbance regimes at the interface of geomorphology and ecology geomorphological processes are an integral part of ecosystem functioning and ecosystem functioning affects geomor phological processes increasingly widespread acknowledgement of this simple idea is manifest in a vigorous research community engaged with questions that address the two way interaction between biota and geomorphology at a range of scales and in a variety of terrestrial and aquatic environments geomorphological disturbances are a core element of biogeomorphological interest and although the disciplines of geomorphology and ecology have each developed languages and theories that help to explore model and understand disturbance events little attempt has been made to draw together these approaches following a brief review of these issues we introduce thirteen papers that investigate the interactions and feedbacks between geomorphological disturbance regimes and ecosystem functions these papers reveal the singularity of wildfire impacts the importance of landsliding for carbon budgeting and of vegetation accumulation for landsliding the zoogeomorphic role of iconic and cinderella animals in fluvial geomorphology biophysical interactions in aeolian fluvial and torrential environments and the utility of living ecosystems as archives of geomorphic events most of these papers were first presented in a conference session at the european geoscience union general assembly in 2010 and several others are from recent volumes of earth surface processes and landforms copyright 2012 john wiley sons ltd

generation of short chain acid anions in hydrothermally altered sediments of the guaymas basin gulf of california an initial investigation of the concentration distribution of short chain organic acid anions in hydrothermally altered sediments of the guaymas basin reveals the presence of high concentrations of acetate and propionate relative to normal marine sediments acetate and propionate concentrations appear to vary as a function of sediment temperature and reach concentrations 1100 and 200 m respectively at temperatures 100 c as in previously studied oil field formation waters these acid anions probably play a key role in the generation of co2 and hydrocarbons gases hydrogen ion ph buffering the complexing of aqueous ions and mineral dissolution and precipatation at temperatures 100 c these and other acid anions should be important substrates for heterotrophic bacterial processes including sulfate reduction

fluvial processes and vegetation glimpses of the past the present and perhaps the future abstract most research before 1960 into interactions among fluvial processes resulting landforms and vegetation was descriptive since then however research has become more detailed and quantitative permitting numerical modeling and applications including agricultural erosion abatement and rehabilitation of altered bottomlands although progress was largely observational the empiricism increasingly yielded to objective recognition of how vegetation interacts with and influences geomorphic process a review of advances relating fluvial processes and vegetation during the last 50 years centers on hydrologic reconstructions from tree rings plant indicators of flow and flood frequency parameters hydrologic controls on plant species regulation of sediment movement by vegetation vegetative controls on mass movement and relations between plant cover and sediment movement extension of present studies of vegetation as a regulator of bottomland hydrologic and geomorphic processes may become markedly more sophisticated and widespread than at present research emphases that are likely to continue include vegetative considerations for erosion modeling response of riparian zone forests to disturbance such as dams and water diversion the effect of vegetation on channel and bottomland dynamics and rehabilitation of stream corridors research topics that presently are receiving attention are the effect of woody vegetation on the roughness of stream corridors and hence processes of flood conveyance and flood plain sedimentation the development of a theoretical basis for rehabilitation projects as opposed to fully empirical approaches the effect of invasive plant species on the dynamics of bottomland vegetation the quantification of below surface biomass and related soil stability factors for use in erosion prediction models and the effect of impoundments on downstream narrowing of channels and accompanying encroachment of vegetation bottomland vegetation partially controls and is controlled by fluvial geomorphic processes the purposes of this paper are to identify and review investigations that have related vegetation to bottomland features and processes to distinguish the present status of these investigations and to anticipate future research into how hydrologic and fluvial geomorphic processes of bottomlands interact with vegetation

heat flow hydrothermal circulation and basalt intrusions in the guaymas basin gulf of california abstract the guaymas basin is part of an en echelon series of short seafloor spreading segments in the gulf of california the basin is separated from adjacent deeps by long northwest southeast striking transform faults and divided into subparallel northern and southern troughs which trend northeast to southwest rapid sedimentation 1 to 5 m ka 1 results in a striking morphological contrast between seafloor spreading in the guaymas basin and that in more mature mid ocean settings basalt does not extrude onto the seafloor in the basin as flows and pillows but instead intrudes into a thick sediment layer the presence of relatively unconsolidated sediments lining the floor of the basin make this setting ideal for the study of axial heat flow and the thermal budget of oceanic crustal formation thermal data delineate several modes of heat transfer in both troughs of the basin with negligible heat flow in some areas and values greater than 3 w m 2 in others broad heat flow highs several square kilometers in area result from a combination of deep conductive heat flow slow intergranular fluid circulation and vigorous hydrothermal venting areas of low heat flow between heat flow highs and near normal faults which bound the basin may be indicative of hydrothermal recharge the geometry of faults shallow sills and broad northeast southwest structural trends in the basin largely seems to govern the distribution of heat flow the highest values are clustered within a few isolated zones in each trough with a total area of about 30 km 2 variations in heat flow of two orders of magnitude occur over distances as small as a few hundred meters fourteen hydrothermal vents in the southern trough of the guaymas basin have been sampled directly and found to have temperatures in excess of 250 c locally conductive heat flow at the seafloor is significantly raised in the vicinity of these vents but the general pattern appears to require more deeply seated conductive heat sources the mean heat flow in the southern trough is 453 342 s d mw m 2 a simple analysis of the heat budget in the southern trough suggests that the total intruded section between the top of the magma chamber and the seafloor may be unusually thin perhaps only several hundred meters in thickness

chaos fractals and self organization in coastal geomorphology simulating dune landscapes in vegetated environments complex nonlinear dynamic systems are ubiquitous in the landscapes and phenomena studied by earth sciences in general and by geomorphology in particular concepts of chaos fractals and self organization originating from research in nonlinear dynamics have proven to be powerful approaches to understanding and modeling the evolution and characteristics of a wide variety of landscapes and bedforms this paper presents a brief survey of the fundamental ideas and terminology underlying these types of investigations covering such concepts as strange attractors fractal dimensions and self organized criticality their application in many areas of geomorphological research is subsequently reviewed in river network modeling and in surface analysis amongst others followed by more detailed descriptions of the use of chaos theory fractals and self organization in coastal geomorphology in particular these include self organized behavior of beach morphology the fractal nature of ocean surface gravity waves the self organization of beach cusps and simulation models of ripples and dune patterns this paper further presents a substantial extension of existing dune landscape simulation models by incorporating vegetation in the algorithm enabling more realistic investigations into the self organization of coastal dune systems interactions between vegetation and the sand transport process in the model such as the modification of erosion and deposition rules and the growth response of vegetation to burial and erosion introduce additional nonlinear feedback mechanisms that affect the course of selforganization of the simulated landscape exploratory modeling efforts show tantalizing results of how vegetation dynamics have a decisive impact on the emerging morphology and conversely how the developing landscape affects vegetation patterns extended interpretation of the modeling results in terms of attractors is hampered however by want of suitable state variables for characterizing vegetated landscapes with respect to both morphology and vegetation patterns d 2002 elsevier science b v all rights reserved

on the mechanisms governing dike arrest insight from the 2000 miyakejima dike injection abstract magma stored beneath volcanoes is sometimes transported out of the magma chambers by means of laterally propagating dikes which can lead to fissure eruptions if they intersect the earth s surface the driving force for lateral dike propagation can be a lateral tectonic stress gradient the stress gradient due to the topographic loads the overpressure of the magma chamber or a combination of those forces the 2000 dike intrusion at miyakejima volcano izu arc japan propagated laterally for about 30 km and stopped in correspondence of a strike slip system sub perpendicular to the dike plane then the dike continued to inflate without further propagation abundant seismicity was produced including five m 6 earthquakes one of which occurred on the pre existing fault system close to the tip of the dike at approximately the time of arrest it has been proposed that the main cause for the dike arrest was the fault induced stress here we use a boundary element numerical approach to study the interplay between a propagating dike and a pre stressed strike slip fault and check the relative role played by dike fault interaction and topographic loading in arresting the miyakejima dike we calibrate the model parameters according to previous estimates of dike opening and fault displacement based on crustal deformation observations by computing the energy released during the propagation our model indicates whether the dike will stop at a given location we find that the stress gradient induced by the topography is needed for an opening distribution along the dike consistent with the observed seismicity but it cannot explain its arrest at the prescribed location on the other hand the interaction of dike with the fault explains the arrest but not the opening distribution the joint effect of the topographic load and the stress interaction with strike slip fault is consistent with the observations provided the pre existing fault system is pre loaded with a significant stress released gradually during the dike fault interplay our results reveal how the mechanical interaction between dikes and faults may affect the propagation of magmatic intrusions in general this has implications for our understanding of the geometrical arrangement of rift segments and transform faults in mid ocean ridges and for the interplay between dikes and dike induced graben systems

structural features and genesis of microscopic pores in lacustrine shale in an oil window a case study of the dongying depression the paleogene shale of the dongying depression a continental basin in eastern china is taken as the study subject to examine the microscopic features of lacustrine shale reservoirs in the oil window this study shows that shale pores in this evolutionary stage are present at the micrometer to nanometer scale but fractures commonly have extension distances at the millimeter scale pores and fractures can be divided into three types namely primary pores secondary pores and cracks primary pores commonly have good connectivity at shallow burial depth with the increase of burial depth primary porosity is reduced because of compaction and cementation secondary pores are important in shale including dissolved pores inside grains and at grain edge and dissolution pores inside the hybrid of organic matter om and clay minerals and evaporite minerals including carbonates or sulfates types of cracks were observed bedding fissures dissolution fractures and structural fractures the development of bedding fissures is related to the deposition of shale laminae the formation of dissolution fractures is related to acidic fluids such as organic acids and hydrogen sulfide whereas the formation of structural fractures is jointly controlled by fault development fluid overpressure and lithofacies the pores and fractures in the oil window of lacustrine shale can store and channel oil and gas the hybrid om clay carbonate sulfate and the pores inside are important through the oil window moreover the development of the pores depends not only on hydrocarbon generation but also on the interaction of hydrocarbons and organic acid dissolution this finding has important significance in the accumulation of oil and gas in continental shales

cyclic jerky opening of magma sheet and caldera formation during the 2000 miyakejima volcano eruption 1 nied volcanic observation network at miyakejima volcano central japan repeatedly detected extraordinary step like tilt changes during the 2000 miyakejima eruption associated with these tilt steps broadband seismometers recorded very long pulse waves with a duration of about 50 s during this stage the summit of the volcano collapsed and sank forming a caldera with a depth of about 400 m and a diameter of about 1 6 km in total prior to the tilt steps long period earthquakes were acceleratingly generated in the shallow part of the volcano and the ground tilt changes suggested inflation of the volcanic body the analysis of these data from the tiltmeters and broadband seismometers suggests that the tilt steps and the 50 s pulse packets were caused by the opening of sill sheet like tensile cracks oriented in a se nw direction beneath the volcano with a depth of about 6 8 km and a volumetric change of about 106 107 m3

on the growth of colloform textures a case study of sphalerite from the galmoy ore body ireland abstract colloform textures have been described from many of the world9s sulphide ore deposits and involve formation of distinct microcrystalline layers these textures provide information related to sequential stages of ore formation yet their mechanism of growth is poorly understood this study has analysed a series of colloform samples from the galmoy zn pb mine ireland results indicate that the growth sequence is not always intuitive and layers that appear stratigraphic upon cursory observation may not be the crystal preferred orientation cpo of discrete colloform layers abruptly switches between different orientation axes examination of the same layers using in situ laser sulphur isotope analysis reveals equally striking changes in 34 s signature between end member bacteriogenic 25 and hydrothermal 10 sources although these results combined with petrographic observation allow the determination of a probable growth history there is no correlation between shifting cpo and 34 s signature trace element analysis reveals changes in trace element sequestration between colloform layers cadmium and chlorine rich layers correspond to a hydrothermal sulphur source whereas iron rich layers correspond to a bacteriogenic sulphur source in the absence of alternative mechanisms we suggest that the most likely factors influencing cpo changes are temperature and degree of supersaturation during two fluid mixing

relations among hydrocarbon reservoirs epigenetic sulfidization and rock magnetization examples from the south texas coastal plain this paper focuses on the association between concentrations of iron disulfide fes2 minerals in the shallow subsurface and underlying hydrocarbon accumulations such fes2 concentrations are the result of migration of either h2s or organic constituents from the underlying hydrocarbons the h2s from reservoirs is produced inorganically from sulfate in the reservoir rocks at high temperature 90 c and migrates to shallower beds to react inorganically with iron to form fes2 organic constituents from reservoirs in contrast provide nourishment for sulfate reducing bacteria in shallow relatively cool 90 c beds sandstone in the ray point uranium district in live oak county texas contains abundant fes2 which formed both from deep seated h2s and from h2s produced in the shallow subsurface by bacteria that utilized organic materials from depth deep petroleum reservoirs were physically connected to near surface 100 m beds containing epigenetic fes2 by the oakville fault epigenetic iron sulfide format

dissolved free amino acids in hydrothermal vent habitats of the guaymas basin abstract total dissolved free amino acid dfaa concentrations and molecular compositions were determined in high temperature smoker fluids exit temperatures 152 319 c and interstitial waters of a sediment covered hydrothermal vent system located in the southern guaymas basin gulf of california dfaas were not detected 1 nm in the hot vent fluids a result which probably reflects the instability of these compounds when exposed to the extreme high temperatures and pressures characteristic of hydrothermal fluids ammonium is the principal end product of this thermal catalytic diagenesis hydrothermal vent and non vent control sediments had dfaa concentrations ranging from 5 445 and 10 28 m respectively the dfaa concentrations in both habitats were highest in the near surface region 0 4 cm and decreased at greater depths the depth dependent concentration gradients for hydrothermally impacted sediments were steeper than for the control samples and covaried with total microbial biomass the molecular composition of the hydrothermally impacted samples included most common protein amino acids in addition to aminoglutaric acid glutamate glycine serine and alanine were major constituents of the dfaa pool

causes and spatial distribution of anomalous magnetization in hydrocarbon seepage environments in diagenetic environments containing hydrocarbons the most important magnetic minerals formed appear to be magnetite and pyrrhotite whereas the most important magnetic mineral dissolved or replaced is hematite hence hydrocarbon seepage and migration may result in positive absent or negative anomalous magnetization magnetic contrasts relative to the total magnetization prior to hydrocarbon invasion depending on the amounts of magnetite and pyrrhotite formed relative to the amounts of hematite destroyed where anomalous magnetization is formed by hydrocarbon seepage the magnetic contrasts are located in relatively reducing geochemical plumes such plumes are located above leaking subsurface hydrocarbon accumulations if buoyancy is the predominant driving force for hydrocarbons commonly however migration of the escaping hydrocarbons is dominated by advection hydrocarbon seepage therefore may be vertical or may have any direction other than vertical depending on the position of the leaking hydrocarbon accumulation in the prevailing flow system and on the distribution of high permeability pathways such as carrier beds and faults in these cases magnetic contrasts are deflected or displaced and they are not likely to be vertically above the hydrocarbon source anomalous magnetization magnetic contrasts has been documented from some hydrocarbon seepage environments and can be used for hydrocarbon exploration in association with other surface exploration methods similar magnetic contrasts should also be detectable in core and could be used for evaluation of subsurface proximity to hydrocarbon traps the magnitude and spatial distribution of such magnetic contrasts whether at the surface or in the subsurface depend on geochemical microbial geophysical sedimentologic and hydrogeologic processes these factors must be taken into consideration in aeromagnetic and ground based prospecting for hydrocarbons in particular the use of anomalous magnetization as an exploration tool should always be accompanied by a hydrogeologic study the results of this study suggest that magnetic contrasts could also be used in environmental studies for example to detect hydrocarbons leaking from storage tanks or waste disposal sites on the other hand magnetic contrasts may be generated also by natural and anthropogenic processes that have no genetic relationships to hydrocarbons consequently anomalous magnetization may or may not be genetically related to natural or anthropogenic hydrocarbon accumulations

pressure recovery in magma due to bubble growth 1 pressure recovery in magma subject to sudden depressurization is investigated in terms of the growth of bubbles containing magmatic volatiles assuming conservation of volatile mass and pressure equilibration between the bubbles melt and a surrounding elastic medium the final magma pressure is completely determined by its initial pressure and the magnitude of the pressure drop simulations show that the initial magma pressure is easily recovered or even exceeded when magma containing tiny bubbles is surrounded by a relatively stiff elastic medium under low confining pressure this result suggests that when processes such as magma withdrawal dike intrusion and nearby seismicity decrease the pressure in a magma chamber magma re pressurization can occur without new injection of magma

surface downhole electrical resistivity tomography applied to monitoring of co2 storage at ketzin germany abstractsurface downhole electrical resistivity tomography sd ert surveys were repeatedly carried out to image co2 injected at the pilot storage ketzin germany the experimental setup combines surface with downhole measurements by using a permanent electrode array that has been deployed in three wells two baseline experiments were performed during the site startup and three repeat experiments were performed during the first year of co2 injection by the time of the third repeat approximately 13 500 tons of co2 had been injected into the reservoir sandstones at about 650 m depth field data and inverted resistivity models showed a resistivity increase over time at the co2 injector the lateral extent of the related resistivity signature indicated a preferential co2 migration toward the northwest using an experimental resistivity saturation relationship we mapped co2 saturations by means of the resistivity index method for the latest repeat co2 saturations show values of up to 70 near the injectio

modeling microbial reaction rates in a submarine hydrothermal vent chimney wall the fluids emanating from active submarine hydrothermal vent chimneys provide a window into subseafloor processes and through mixing with seawater are responsible for steep thermal and compositional gradients that provide the energetic basis for diverse biological communities although several models have been developed to better understand the dynamic interplay of seawater hydrothermal fluid minerals and microorganisms inside chimney walls none provide a fully integrated approach to quantifying the biogeochemistry of these hydrothermal systems in an effort to remedy this a fully coupled biogeochemical reaction transport model of a hydrothermal vent chimney has been developed that explicitly quantifies the rates of microbial catalysis while taking into account geochemical processes such as fluid flow solute transport and oxidation reduction reactions associated with fluid mixing as a function of temperature the metabolisms included in the reaction network are methanogenesis aerobic oxidation of hydrogen sulfide and methane and sulfate reduction by hydrogen and methane model results indicate that microbial catalysis is generally fastest in the hottest habitable portion of the vent chimney 77 102 c and methane and sulfide oxidation peak near the seawater side of the chimney the fastest metabolisms are aerobic oxidation of h2 and sulfide and reduction of sulfate by h2 with maximum rates of 140 900 and 800 pmol cm 3 d 1 respectively the maximum rate of hydrogenotrophic methanogenesis is just under 0 03 pmol cm 3 d 1 the slowest of the metabolisms considered due to thermodynamic inhibition there is no anaerobic oxidation of methane by sulfate aom these simulations are consistent with vent chimney metabolic activity inferred from phylogenetic data reported in the literature the model developed here provides a quantitative approach to describing the rates of biogeochemical transformations in hydrothermal systems and can be used to constrain the role of microbial activity in the deep subsurface

expanding frontiers in deep subsurface microbiology abstract the subsurface biosphere on earth appears to be far more expansive and physiologically and phylogenetically complex than previously thought here several aspects of subsurface microbiology are discussed molecular and biogeochemical data as well as characteristics from new isolates suggest that ecosystems below deep sea hydrothermal vents are inhabited primarily by thermophilic archaea and bacteria the void spaces and conduits in basalt at mid ocean ridges and even more so at sediment covered hydrothermal vent sites represent promising hunting grounds for novel chemosynthetic archaea and bacteria as examples we highlight the subsurface microbial communities within the basalt flanks of the juan de fuca ridge off british columbia and the hydrothermal sediments at the guaymas basin in the gulf of california and at middle valley on the juan de fuca ridge in the deep continental subsurface microbial studies have primarily targeted aquifers in basaltic and granitic rock with an almost exclusive emphasis on h2 driven chemolithoautotrophy for example in the subsurface water from lidy hot springs idaho usa h2 consuming methanogenic archaea represent the most populous organisms comprising 95 of all cells besides h2 other potential sources of chemical energy reducing power are considered including abiotically synthesized organic matter and reduced sulfur compounds in addition the well established sequences of redox couples in microbial metabolism are investigated at elevated temperatures using a thermodynamic approach values of peo for 11 common reduction half reactions are tabulated at 25 50 100 and 150 c although many modes of metabolism may be employed by subsurface biota sulfate reduction appears to be one of the more ubiquitous strategies recent studies of sulfate reducing archaea and bacteria in marine and continental systems are reviewed

vegetative impacts on hydraulics and sediment processes across the fluvial system summary vegetation creates a complicated system of feedbacks and linkages across the fluvial system that is realized through river planform shape interactions occur among flow hydraulics sediment deposition and erosion and plant morphology density and biomechanics interest in the interactions and feedback loops between vegetation and the fluvial system has grown extensively in the past few years this interest is partially driven by the popularity of stream restoration activities worldwide that include re vegetation of stream banks and formation of an ecosystem that is intended to encourage the growth of aquatic macrophytes we present a review of the research into the interactions and dependencies between vegetation and the fluvial system to identify hydraulic and sediment dynamics that are consistent around vegetation located in the channel on channel banks and over the floodplain we illustrate process commonalities operating across spatial locations within the fluvial system and highlight some of the current research opportunities and challenges to encourage research collaborations between those working in areas of the fluvial system traditionally viewed as disparate

hydrothermal discharge and alteration in near surface sediments from the guaymas basin gulf of california abstract in the guaymas basin gulf of california hydrothermal fluids discharge onto the seafloor via both direct emanation through hydrothermal spires and diffusely through the sediments the latter mode is the focus of this study short 20 cm sediment cores were taken in zones of diffuse hydrothermal flow for chemical investigation of interstitial fluids and bulk solids the hydrothermal component of the pore fluids was quite variable indicating the heterogenous nature of the near surface flow regimes the bulk solids chemistry indicates that the suite of cores has encountered different amounts of cumulative hydrothermal exposure dissolution of biogenic silica and deposition of large amorphous silica clasts in the sediment are related to the extent of hydrothermal exposure surface enrichments in ba are formed as barite precipitates when ba rich hydrothermal fluids mix with sulfate rich seawater at the seafloor formation of pyrite and removal of mg from the solid phases are also observed effects of hydrothermal flow through these sediments

soil creep the driving factors evidence and significance for biogeomorphic and pedogenic domains and systems a critical literature review abstract soil and regolith creep have been analyzed for at least the last 140 years using many methodological configurations and temporal and spatial scales the general concept of creeping soil and its mechanism first proposed by w m davis and g k gilbert at the end of the 19th century evolved since the 1940s towards theoretical models and precise short and long term field measurements this fruitful epoch continued with results enhanced at the turn of the 20th century by the application of new research methods e g radiometry and a redefinition of the term soil creep to encompass the sum of stochastic shallow subsurface and near surface processes causing net downslope movement of soil or regolith simultaneously another possibility of creep detection was noticed in dendrochronology and since the 1970s in the formally defined discipline of dendrogeomorphology indirect evaluations of creep activity were performed based on tree ring analyses of bent trees this method found many followers but was also heavily criticized as imprecise and lacking in evidence of which kind of tree trunk curvature e g pistol butt like deformation s shape curvature could be ascribed to creep movement from the beginning soil creep was associated with the activity of living organisms on hillslopes however this aspect of creep studies has never been fully developed in spite of the solid foundations and directions of potential studies pointed out by charles darwin at the end of the 19th century in this paper we focus on the historical context of soil creep studies and highlight forest ecosystems as probably the most active environment of biogenic creep mainly due to tree uprooting and other biomechanical effects of living and dead trees root channel infilling tree root mounding etc that are a factors in biotransport in the final sections the position of biogenic creep in the structure of biogeomorphic systems is discussed in relation to such important conceptual frameworks as the biogeomorphic ecosystem biogeomorphic feedback window and ecosystem engineering we also describe several hypotheses that should be carefully tested in the future and propose several research methods that have the ability to further our knowledge about soil creep radiometry laser scanning and soil micromorphology

biogeomorphology past present and future abstract since the 1970s there has been a considerable expansion in biogeomorphological research which considers the complex two way relationships between biological ecological and geomorphological systems over a wide range of spatial and temporal scales advances have been made in theoretical methodological thematic and applied aspects of biogeomorphology a review of key publications and symposia over the period illustrates growth in biogeomorphology with particular advances in quantitative understandings of biogeomorphic interactions in interdisciplinary participation and in theoretical framings theoretical advances have been influenced by the desire to answer four fundamental questions how do ecological and geomorphological systems interact is there a geomorphological signature of life how important is biodiversity to landscape evolution and vice versa how have life and landscape co evolved a review of methodological advances in biogeomorphology confirms the continuing importance of field monitoring and the increasingly tight collaboration between experimental and modelling based research thematically particularly strong progress has been made in disentangling the complex bidirectional biogeomorphic interactions in coastal sedimentary environments and fluvial and riparian systems it is increasingly obvious that variation in ecological traits leads to large differences in biogeomorphic impacts of different species in different circumstances this poses challenges for applications of biogeomorphology to environmental management and conservation seven key topics emerge from this review and provide the basis for a biogeomorphological research agenda to usher in the next 50 yr of progress

burial diagenesis and thermochemical sulfate reduction smackover formation southeastern mississippi salt basin the smackover formation in the southeastern mississippi salt basin has been buried from 3 03 to 6 06 km and subjected to temperatures of 100 to 200c pre hydrocarbon migration burial diagenesis is characterized by precipitation of calcite cement followed by saddle dolomite and late anhydrite these phases formed at temperatures of less than 100c the oxygen isotopic composition of calcite ranges from minus 5 to minus 8 4 pdb and carbon isotopic composition ranges from 3 5 to 6 0 pdb the sulfur isotopic composition of late anhydrites ranges from 18 1 to 19 1 cdt post hydrocarbon migration burial diagenesis is dominated by replacement of previously formed late anhydrite by calcite or calcite plus elemental sulfur and precipitation of post bitumen calcite cement these diagenetic phases formed at temperatures above 150c and are present only in the deep part of the basin the oxygen isotopic compositions of calcites that replace anhydrite range from minus 3 0 to minus 4 0 pdb and carbon isotopic compositions range from minus 2 0 to 4 2 pdb the oxygen isotopic compositions of post bitumen calcites range from minus 3 4 to minus 5 6 pdb and carbon isotopic compositions range from minus 1 6 to minus 16 3 pdb two samples of elemental sulfur have sulfur isotopic compositions of 15 8 and 16 1 cdt the high temperature replacement of anhydrite by calcite more the presence of post bitumen calcite cement the sulfur isotopic composition of sulfates and elemental sulfur and high concentration of hydrogen sulfide indicate that rapid thermochemical reduction of solid sulfates is taking place in the deep part of the mississippi salt basin at temperatures as low as 150c less

geology and geochemistry of the reocin zinc lead deposit basque cantabrian basin northern spain the reocin zn pb deposit 30 km southwest of santander spain occurs within lower cretaceous dolomitized urgonian limestones on the southern flank of the santillana syncline the reocin deposit is one of the largest known strata bound carbonate hosted zinc lead deposits in europe the total metal endowment of the deposit including past production and remaining reserves is 62 mt of ore grading 8 7 percent zn and 1 0 percent pb the epigenetic mineralization consists of sphalerite and galena with lesser marcasite and trace pyrite with dolomite as gangue microprobe analyses of different generations of dolomite revealed nonstoichiometric compositions with various amounts of iron up to 14 mol of feco3 replacement of host dolomite open space filling of fractures and cementation of breccias derived from dissolution collapse are the principal types of ore occurrence detailed cross section mapping indicates a stratigraphic and structural control on the deposit a stratiform morphology is present in the western part of the orebody capa sur whereas mineralization in the eastern part is highly discordant but strata bound barrendera stratigraphic studies demonstrate that synsedimentary tectonic activity related to the rifting of the north atlantic bay of biscay was responsible for variation in sedimentation presence of unconformities including paleokarsts local platform emergence and dolomitization along the n60 fault trend in the reocin area two stages of dolomitization are recognized the first stage is a pervasive dolomitization of the limestone country rocks that was controlled by faulting and locally affected the upper part of the aptian and the complete albian sequence the second dolomitization event occurred after erosion and was controlled by karstic cavities this later dolomitization was accompanied by ore deposition and locally filling of dolomite sands and clastic sediments in karstic cavities the circulation of hydrothermal fluids responsible for sulfide deposition and the infilling of karst cavities were broadly contemporaneous indicating a post albian age vitrinite reflectance data are consistent with previously measured fluid inclusion temperatures and indicate temperatures of ore deposition that were less than 100 c carbon and oxygen isotopic data from samples of regional limestone host rock dolostone and ore stage dolomite suggest an early hydrothermal alteration of limestone to dolostone this initial dolomitization was followed by a second period of dolomite formation produced by the mixing of basinal metal rich fluids with local modified seawater both dolomitization events occurred under similar conditions from fluids exhibiting characteristics of basinal brines the 34s values of sulfides are between 1 8 and 8 5 per mil which is consistent with thermochemical sulfate reduction involving organic matter as the main source of reduced sulfur galena lead isotope compositions are among the most radiogenic values reported for zn pb occurrences in europe and they are distinct from values reported for galena from other basque cantabrian deposits this suggests that a significant part of the lead was scavenged from the local underlying asturian sediments the stratigraphic and structural setting timing of epigenetic mineralization mineralogy and isotopic geochemistry of sulfide and gangue minerals of the reocin deposit are consistent with the features of most of mississippi valley type ore deposits

linking environmental regimes space and time interpretations of structural and functional connectivity connectivity as a concept has been increasingly part of discussions or explanations in hydrology geomorphology and ecology we address recent critiques of this approach by demonstrating how a refinement which distinguishes structural connectivity from functional connectivity can be used to explain patterns observed in very different environmental systems these systems are found in linkages between surface and subsurface flowpaths and the hyporheos in the river don a temperate river channel in yorkshire uk in surface and subsurface fluxes in agricultural land in the uk and in vegetation and surface conditions in a degrading environment at the sevilleta lter site in the semi arid southwest usa first we demonstrate long term geological and structural controls mediated by in channel processes second human organization of landscape elements is a significant control on runoff and erosion so that similar events can produce very different responses and vice versa third linkages between the removal of grass vegetation and runoff and erosion produce non linear and path dependent feedbacks which control the subsequent degradation of the landscape making the process difficult to reverse as a result of these studies we argue that even in cases where connectivity cannot be directly quantified at least at present this limitation does not prevent the concept from being a useful heuristic device for exploring responses of complex systems furthermore this result implies that an increasing need exists for disciplinary connectivity to investigate such systems

hydrocarbons in surface sediments from a guaymas basin hydrothermal vent site petroleum like materials found at the guaymas basin hydothermal vent site gulf of california are derived from pyrolysis of organic matter two characteristics surface sediment cores differing in temperature profiles and other parameters were collected by dsv alvin sectioned and analyzed for hydrocarbons the quantitative and qualitative composition of alkanes steranes diasteranes and triterpanes differed between these cores as well as within sections of the same core these differences apparent for scales of tens of centimeters are related to interactive physical chemical and microbial processes as well as the influence of multiple sources for the petroleum

geomorphic classification of rivers a new methodology applied in an atlantic region galicia nw iberian peninsula the classification of rivers based on geomorphological criteria played in the past a secondary role for management decision making although in the last years they have experienced a shift from the scientific field to that of the technical currently managers require the most simplified form of classifications in order to use them in plans and planning projects management and restoration on the one hand this means that classifications should be directed toward simplifying the diversity of fluvial environments in a number of manageable types and on the other hand to apply to each geomorphic type a management model in this study we have developed a method of geomorphic classification of rivers according to specific stream power variables and median grain size the new method is dynamic ability to readjust and gain robustness with the incorporation of new data and predictive we obtained six types directly from the method although we added a seventh type bedrock rivers for its special singularity each geomorphic type presents concrete values of specific stream power and median grain size which additionally involves a hydraulic geometry adjusted to terms of balance the change from a geomorphic type to another would reflect a geomorphologic imbalance in the form of greater power and sediment size our results have been compared with six commonly used classifications e g rosgen classification system or river styles framework geomorphic classification of rivers stands as a flexible tool that allows the development of a personalized geomorphic classification for rivers of the same geomorphological province through the temporary revision of various sites that act as control points we can learn should the case arise the intensity and geomorphic change of the site geomorphic classification of rivers acts as an alert system for any geomorphologic disturbance its simple application and interpretation facilitate the implementation in the administrative environment or its attachment to other commonly used classifications

mechanisms of step like tilt changes and very long period seismic signals during the 2000 miyakejima eruption insights from kinematic gps during the 2000 eruption of the miyakejima volcano in japan step like tilt changes tc generally accompanied by very long period vlp seismic signals with a pulse like shape and widths of 50 s were repeatedly observed tc vlp events kinematic gps time series for miyakejima were investigated in order to detect displacements associated with these events we found that the kinematic gps time series could be interpreted as the superposition of the following features 1 displacement associated with the tc vlp events the source of which possibly corresponded to a shallow magma chamber represented by an almost vertical ellipsoidal cavity elongated ne sw at a depth of 2 3 km 2 displacement following tc vlp events that may have been caused by exponential type volume decreases of the same magma chamber with a decay constant of approximately half a day and 3 displacements that may be caused by continuous volume decreases of the same magma chamber these features broadly support the piston model of vlp seismic signals in which a vertical piston of solid conduit material intermittently sinks into a magma chamber located a few kilometer beneath the edifice following deflation caused by continuous outflux of magma the volume increase of the magma chamber associated with the tc vlp events was found to be much smaller than that of the collapsed caldera suggesting that most of the mass in the conduit sank into the magma chamber without generating vlp seismic waves or step like tc