developments in monitoring and modelling small scale river bed topography recent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography flow hydraulics and sediment transport although understanding of the behaviour of dynamic river channels has been increased markedly through detailed within channel process studies less attention has been given to the accurate monitoring and terrain modelling of river channel form using three dimensional measurements however such information is useful in two distinct senses firstly it is one of the necessary boundary conditions for a physically based deterministic modelling approach in which three dimensional topography and river discharge drive within channel flow hydraulics and ultimately spatial patterns of erosion and deposition and therefore channel change secondly research has shown that an alternative means of estimating the medium term bedload transport rate can be based upon monitoring spatial patterns of erosion and deposition within the river channel this paper presents a detailed assessment of the distributed monitoring and terrain modelling of river bed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey the availability of increasingly sophisticated terrain modelling packages developed for civil engineering application allows the representation of topographic information as a landform surface intercomparison of landform surfaces allows visualization and quantification of spatial patterns of erosion and deposition a detailed assessment is undertaken of the quality of the morphological information acquired this allow some general comments to be made concerning the use of more traditional methods to monitor and represent small scale river channel morphology

promise performance and current limitations of a magnetic bedload movement detector understanding fluvial bedload transport and its geomorphic implications is hampered by the paucity and low accuracy of field derived transport data tunnicliffe et al hydrological processes 2000 14 2631 2643 described the bedload movement detector bmd a magnetic induction system for measuring bedload movement in gravel bed rivers based on a sensor that produces signals when its magnetic field is enhanced by a passing particle we conducted two types of laboratory experiments to attempt to calibrate the bmd system 1 rotating platter experiments were designed to relate sensor response curves to particle properties and 2 flume experiments were designed to measure particle speed and permit computation of a calibrated model physically based relations were derived amongst particle volume speed and magnetic content and signal integral amplitude and width the calibrated relations demonstrate a basis to estimate sediment flux in gravel bed rivers but they require independent knowledge of particle magnetic susceptibility over the course of the experiments a number of weaknesses in the sensor design and performance were identified and suggestions are made to improve the system the high spatial and temporal resolution of data that magnetic sensors of bedload movement are likely to offer makes them valuable to consider for sediment transport measurements in both the field and laboratory copyright 2009 john wiley sons ltd

geochemistry and isotopes of fluids from sulphur springs valles caldera new mexico abstract detailed geochemistry supported by geologic mapping has been used to investigate sulphur springs an acid sulfate hot spring system that issues from the western flank of the resurgent dome inside valles caldera the most intense activity occurs at the intersection of faults offsetting caldera fill deposits and post caldera rhyolites three geothermal wells in the area have encountered pressures 4 8000 mg l these conditions cause argillic alterations throughout a large area non condensible gases consist of roughly 99 co 2 with minor amounts of h 2 s h 2 and ch 4 empirical gas geothermometry suggests a deep reservoir temperature of 215 to 280 c comparison of 13 c and 18 o between caco 3 from well cuttings and co 2 from fumarole steam indicates a fractionation temperature between 200 and 300 c by decarbonation of hydrothermally altered paleozoic limestone and vein calcite in the reservoir rocks tritium concentrations obtained from steam condensed in a mudpot and deep reservoir fluids baca 13 278 c are 2 1 and 1 0 t u respectively suggesting the steam originates from a reservoir whose water is mostly 50 yrs old deuterium contents of fumarole steam deep reservoir fluid and local meteoric water are practically identical even though 18 o contents range through 4 thus precipitation on the resurgent dome of the caldera could recharge the hydrothermal system by slow percolation from analysis of d and 18 o values between fumarol steam and deep reservoir fluid steam reaches the surface either 1 by vaporizing relatively shallow groundwater at 200 c or 2 by means of a two stage boiling process through an intermediate level reservoir at roughly 200 c although many characteristics of known vapor dominated geothermal systems are found at sulphur springs fundamental differences exist in temperature and pressure of our postulated vapor zone we propose that the reservoir beneath sulphur springs is too small or too poorly confined to sustain a true vapor dominated system and that the sulphur springs system may be a dying vapor dominated system that has practically boiled itself dry

determination of the bedload transport rate in a small proglacial high arctic stream using direct semi continuous measurement abstract the article presents the results of a 34 day series of direct semi continuous measurements of the bedload transport performed during the melt season 2013 in the scott river catchment nw part of the wedel jarlsberg land spitsbergen the daily variability of the bedload transport rates and its relation to the dissolved and suspended load were analysed in two cross sections located in the lower course of a proglacial gravel bed river the bedload flux was measured by means of two 4 module sets of river bedload traps rbt in the research period a total of 34 day long samples of bedload and 34 water samples for the determination of the dissolved and suspended load were collected in each of the two cross sections 200 m apart the measurements showed longitudinal and temporal variability of bedload flux and the remaining components solutions suspensions corresponding with changes in water discharge the mean daily bedload flux qb in consecutive measurement cross sections xs amounted to 124 kg d 1 xs i and 59 kg d 1 xs ii respectively and showed high variability and an evident relationship with temperature the unequal bedload flux of the two measuring stations xs i and xs ii suggests aggradation within the alluvial fan that separates the two reaches the volume and rate of bedload flux were determined by the frequency of the occurrence of flood flows during which approximately from 59 xs i to 77 xs ii of total bedload was discharged the highest recorded daily values constituted 12 of total bedload flux through the cross section below the alluvial fan the river discharged approximately 6 million cubic meters m m3 of water 3 t of bedload lb 2238 t of suspended load ls and 613 t of dissolved load ld the relationships between the three components of the load suggest a 500 fold excess of suspended load and a 100 fold excess of dissolved load in relation to bedload flux high temporal and latitudinal variability of the bedload transport rate resulted in changes in the channel morphology and during floods also the floodplain

spectral and geological study of the sulfate rich region of west candor chasma mars sulfates have been discovered by the omega spectrometer in different locations of the planet mars they are strongly correlated to light toned layered deposits in the equatorial regions west candor chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates a detailed study coupling mineralogy derived from omega spectral data and geology derived from hrsc imager and other datasets leads to some straightforward issues the monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material it likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments or during hydrothermal alteration at depth because it is typically found on outcrops that are eroded and steep polyhydrated sulfates that match any ca na fe or mg sulfates with more than one water molecule are preferentially present on less eroded and darker outcrops than outcrops of kieserite these variations can be the result of a diversity in the composition and or of the rehydration of kieserite on surfaces with longer exposure the latter possibility of rehydration in the current or recent atmosphere suggests the low surface temperatures preserve sulfates from desiccation and also can rehydrate part of them strong signatures of iron oxides are present on sulfate rich scarps and at the base of layered deposits scarps they are correlated with tes gray hematite signature and might correspond to iron oxides present in the rock as sand size grains or possibly larger concretions that are eroded and transported down by gravity at the base of the scarp pyroxenes are present mainly on sand dunes in the low lying terrains pyroxene is strongly depleted or absent in the layered deposits when mixed with kieserite local observations favor a spatial mixing with dunes over layered deposits sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation either in an intermittent lacustrine environment or by hydrothermal fluid circulation both possibilities require the presence of sulfur rich groundwater to explain fluid circulation the elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2 5 km above datum only 1 km below the plateau surface

on the origin of gypsum in the mars north polar region 1 we describe the distribution and concentration of the largest martian gypsum deposit discovered to date by the mars express omega observatoire pour le mineralogie l eau les glaces et l activite imaging spectrometer its relationship to the late amazonian aged north polar dunes in which it is found and its likely origin gypsum has not been discovered anywhere within the north polar region outside of the olympia undae dune sea in the areas of highest gypsum a concentration 35 pure gypsum grains of a few tens of micrometers in size mixed with 65 millimeter sized gypsum grains containing dark spectrally featureless inclusions best fit the omega observations the gypsum rich dunes contain no significant average albedo temperature or morphological anomalies we propose that water emanating from nearby channels carved during melting of the polar layered deposits infiltrated the eastern end of the polar dune sea percolating through the dunes deposits of gypsum resulted from a combination of direct in situ alteration of sulfide and high calcium pyroxene bearing dunes and from formation of evaporitic gypsum crystals in the pore spaces of these dunes this gypsum deposit formed in a unique local environment and is disconnected from sulfate forming events elsewhere on mars which are thought to have occurred much earlier during the late noachian and hesperian by various means sulfates have not been discovered in any other collection of dunes on mars

efflorescence as a source of hydrated sulfate minerals in valley settings on mars abstract a distinctive sulfur cycle dominates many geological processes on mars and hydrated sulfate minerals are found in numerous topographic settings with widespread occurrences on the martian surface however many of the key processes controlling the hydrological transport of sulfur including sulfur sources climate and the depositional history that led to precipitation of these minerals remain unclear in this paper we use a model for the formation of sulfate efflorescent salts mg ca na sulfates in the rio puerco watershed of new mexico a terrestrial analog site from the semiarid southwest u s to assess the origin and environmental conditions that may have controlled deposition of hydrated sulfates in valles marineris on mars our terrestrial geochemical results s 34 of 36 0 to 11 1 show that an ephemeral arid hydrological cycle that mobilizes sulfur present in the bedrock as sulfides sulfate minerals and dry wet atmospheric deposition can lead to widespread surface accumulations of hydrated sulfate efflorescences repeating cycles of salt dissolution and reprecipitation appear to be major processes that migrate sulfate efflorescences to sites of surface deposition and ultimately increase the aqueous so 4 2 flux along the watershed average 41 273 metric tons yr we suggest that similar shallow processes may explain the occurrence of hydrated sulfates detected on the scarps and valley floors of valles marineris on mars our estimates of salt mass and distribution are in accord with studies that suggest a rather short lived process of sulfate formation minimum rough estimate 100 to 1000 years and restriction by prevailing arid conditions on mars

fluid generation and pathways beneath an active compressional orogen the new zealand southern alps inferred from magnetotelluric data 1 forty one wideband magnetotelluric mt soundings were collected in a 150 km long transect across the southern alps of the central south island of new zealand an active compressional orogen decomposed mt impedance tensors vertical magnetic field relations and reconnaissance soundings at two locations off line imply an approximately two dimensional geometry here with average regional geoelectric strike of n40 e similar to surface geologic trends two independent two dimensional inversion algorithms were applied to the mt data and both imply a concave upward u shaped middle to lower crustal conductive zone beneath the west central portion of the island the average conductivity of this zone in the strike direction appears to be much higher than that required across strike and may represent anisotropy or along strike conductive strands narrower than the transverse magnetic cross strike mode mt data can resolve the deep crustal conductor under the southern alps is interpreted to represent mainly a volume of fluids arising from prograde metamorphism within a thickening crust fluid interconnection and electrical conduction are promoted by shear deformation the conductor rises northwestward toward the trace of the alpine fault but attains a near vertical configuration at a depth of 10 km and reaches close to the surface 5 10 km inland of the fault trace itself the transition to vertical orientation at this depth is interpreted to occur as fluids ascend across the brittle ductile transition in uplifting schist and approach the surface through induced hydrofractures the high grade schist becomes resistive after depletion of fluids and continues to extrude toward the alpine fault shallow extensions of the deep high conductivity are coincident with modern hydrothermal veining and gold mineralization interpreted to be of deep crustal provenance to the southeast high conductivity also reaches the surface coincident with a major back thrust fault zone of the doubly vergent southern alps orogen which also exhibits evidence for expulsion of high temperature fluids the higher conductivity inferred along strike possible anisotropy could reflect more efficient fluid interconnection in this higher strain direction as well as possible contributions by sheared fluid deposited graphite conductivity of the uppermost mantle of the south island is low consistent with advection of cold mantle lithosphere into the underlying asthenosphere as suggested by p wave delay studies

a new tracer technique for measuring bedload in natural channels summary with a new tracer technique using permanent magnets measurements of coarse material bedload transport were made in a fiumara in calabrien south italy the movement of magnetic cobbles was determined by recording disturbances of the magnetic field at a measuring site

the spatial and temporal patterns of aggradation in a temperate upland gravel bed river intensive field monitoring of a reach of upland gravel bed river illustrates the temporal and spatial variability of in channel sedimentation over the six year monitoring period the mean bed level in the channel has risen by 0 17 m with a maximum bed level rise of 0 5 m noted at one location over a five month winter period these rapid levels of aggradation have a profound impact on the number and duration of overbank flows with flood frequency increasing on average 2 6 times and overbank flow time increasing by 12 8 hours this work raises the profile of coarse sediment transfer in the design and operation of river management specifically engineering schemes it emphasizes the need for the implementation of strategic monitoring programmes before engineering work occurs to identify zones where aggradation is likely to be problematic exploration of the sediment supply and transfer system can explain patterns of channel sedimentation the complex spatial seasonal and annual variability in sediment supply and transfer raise uncertainties into the system s response to potential changes in climate and land use thus there is a demand for schemes that monitor coarse sediment transfer and channel response copyright 2009 john wiley sons ltd

pool spacing in forest channels field surveys of stream channels in forested mountain drainage basins in southeast alaska and washington reveal that pool spacing depends on large woody debris lwd loading and channel type slope and width mean pool spacing in pool riffle plane bed and forced pool riffle channels systematically decreases from greater than 13 channel widths per pool to less than 1 channel width with increasing lwd loading whereas pool spacing in generally steeper step pool channels is independent of lwd loading although plane bed and pool riffle channels occur at similar low lwd loading they exhibit typical pool spacings of greater than 9 and 2 4 channel widths respectively forced pool riffle channels have high lwd loading typical pool spacing of 2 channel widths and slopes that overlap the ranges of free formed pool riffle and plane bed channel types while a forced pool riffle morphology may mask either of these low lwd loading morphologies channel slope provides an indicator of probable morphologic response to wood loss in forced pool riffle reaches at all study sites less than 40 of the lwd pieces force the formation of a pool we also find that channel width strongly influences pool spacing in forest streams with similar debris loading and that reaches flowing through previously clear cut forests have lower lwd loading and hence fewer pools than reaches in pristine forests

tracking channel bed resiliency in forested mountain catchments using high temporal resolution channel bed movement abstract this study uses continuous recording load cell pressure sensors in four high elevation 1500 1800 m sierra nevada headwater streams to collect high temporal resolution bedload movement data for investigating the channel bed movement patterns within these streams for water years 2012 2014 data show an annual pattern where channel bed material in the thalweg starts to build up in early fall peaks around peak snow melt and scours back to baseline levels during hydrograph drawdown and base flow this pattern is punctuated by disturbance and recovery of channel bed material associated with short term storm events a conceptual model linking sediment sources at the channel margins to patterns of channel bed fill and scour in the thalweg is proposed building on the results of martin et al 2014 the material in the thalweg represents a balance between sediment supply from the channel margins and sporadic conveyor belt like downstream transport in the thalweg the conceptual model highlights not only the importance of production and transport rates but also that seasonal connectedness between the margins and thalweg is a key sediment control determining the accumulation rate of sediment stores at the margins and the redistribution of sediment from margins to thalweg that feeds the conveyor belt disturbance and recovery cycles are observed at multiple temporal scales but long term the channel beds are stable suggesting that the beds act as short term storage for sediment but are in equilibrium interannually the feasibility of use for these sensors in forested mountain stream environments is tested despite a high failure rate 50 load cell pressure sensors show potential for high temporal resolution bedload measurements allowing for the collection of channel bed movement data to move beyond time integrated change measurements where many of the subtleties of bedload movement patterns may be missed to continuous and or real time measurements this type of high temporal resolution data provides insight into short term cycles of bedload movement in high gradient forested mountain streams

the timing and magnitude of coarse sediment transport events within an upland temperate gravel bed river this paper describes the application of a new instrument to continuously measure bedload transport an impact sensor to a 72 km2 test catchment in the yorkshire dales northern england data from a network of impact sensors are linked to repeat surveys of channel morphological response to get a better understanding of the conditions that lead to sediment generation and transfer results suggest certain areas of the catchment act as key sediment sources at the annual time scale with material being quickly delivered to the lower parts of the catchment along the steep bedrock channel sediment transfer within the tributaries occurs in significantly smaller magnitudes than within the main channel but it moves more frequently and at different times of the year with transfer rates being strongly conditioned by larger scale valley geomorphology the lower 5 6 km reach sees a significant reduction in gradient and a widening of the valley this permits significant accumulation within the channel which has persisted for many years this lower reach is very sensitive to changes in sediment supply and there is good agreement between changes in bedload transport data and the surveyed channel response these observations have major implications for how river management projects should be developed in upland environments especially those where large scale geomorphological controls have a major impact upon the sediment transfer process evidence suggests that where river management restricts lateral movement of the channel and transfer of sediment into floodplain storage changes in sediment supply can lead to areas of severe accumulation acceleration of bank erosion and exacerbated flood risk

mineralogy of juventae chasma sulfates in the light toned mounds mafic minerals in the bedrock and hydrated silica and hydroxylated ferric sulfate on the plateau 1 juventae chasma contains four light toned sulfate bearing mounds denoted here as a d from west to east inside the trough mafic outcrops at the base of the mounds and in the wall rock and light toned layered deposits of opal and ferric sulfates on the plateau hyperspectral visible near infrared compact reconnaissance imaging spectrometer for mars crism spectra were used to identify monohydrated and polyhydrated sulfate phs outcrops of layered material on the bright mounds most of the monohydrated sulfate signatures closely resemble those of szomolnokite feso4 h2o characterized by a water band near 2 08 m while some areas exhibit spectral features more similar to those of kieserite mgso4 h2o with a band centered closer to 2 13 m the largest phs outcrops occur on the top of mound b and their spectral features are most consistent with ferricopiapite melanterite and starkeyite but a specific mineral cannot be uniquely identified at this time coordinated analyses of crism maps mars orbiter laser altimeter elevations and high resolution imaging science experiment images suggest that mounds a and b may have formed together and then eroded into separate mounds while mounds c and d likely formed separately mafic minerals low ca pyroxene high ca pyroxene and olivine are observed in large 2 10 km wide outcrops in the wall rock and in smaller outcrops 50 500 m across at the floor of the canyon most of the wall rock is covered by at least a thin layer of dust and does not exhibit strong features characteristic of these minerals the plateau region northwest of juventae chasma is characterized by an abundance of light toned layered deposits one region contains two spectrally unique phases exhibiting a highly stratified terraced pattern crism spectra of one unit eroded into swirling patterns with arc like ridges exhibit a narrow 2 23 m band assigned to hydroxylated ferric sulfate a thin layer of a fractured material bearing an opaline silica phase is observed at the contact between the older plateau unit and the younger hydroxylated ferric sulfate bearing light toned layered deposits hydrothermal processes may have produced an acidic environment that fostered formation of the hydrated silica and hydroxylated ferric sulfate units

spectral reflectance and morphologic correlations in eastern terra meridiani mars the mars express observatoire pour la mineralogie l9eau les glaces et l9activite omega hyperspectral image data covering eastern terra meridiani indicate the ubiquitous presence of molecular water in etched terrain materials that disconformably overlie heavily cratered terrains and underlie the hematite bearing plains explored by the opportunity rover identification of crystalline water in kieserite mgso4 h2o is linked to materials exposed in a valley and plateau to the north of hematite bearing plains the mineralogical similarities between the etched terrain deposits examined with omega data and the layered rocks examined by opportunity imply that the ancient aqueous environments inferred from analyses of the rover data extend over regional scales

evaluating the role of sulfide weathering in the formation of sulfates or carbonates on mars orbital and landed missions to mars have revealed complex sulfate and fe oxide bearing mineralogical assemblages which have been interpreted as the result of a late planet wide acidic period due to large so2 emissions however this global scenario does not explain the recent discovery of hesperian and noachian aged carbonates in several regions because they should have been dissolved by the acidic conditions nor the restriction of sulfate occurrences in preferential regions here we present the results of a 4 year long experimental study designed to test the impact of fe sulfides pyrrhotite fe0 9s on the weathering of basaltic silicates olivine clino and orthopyroxene under an early martian like co2 rich atmosphere our weathered silicate sulfide mixtures showed complex parageneses containing elemental sulfur hydrated sulfates gypsum hexahydrite jarosite and fe oxy hydroxides olivine only samples produced nesquehonite an mg carbonate precursor of hydromagnesite and magnesite these secondary phases are similar to those observed in the martian sulfate and carbonate bearing deposits therefore we propose a geochemical model in which on the one hand martian sulfates mainly formed from weathering of sulfide enriched basalts producing locally acidic environments and on the other hand carbonates were preserved and could even have formed in regions initially devoid of sulfides thereby resolving the apparent paradox arising from the possible coeval formation of the two types of minerals these results raise doubts on the need for a global acidic event to produce the sulfate bearing assemblages suggest that regional sequestration of sulfate deposits is due to regional differences in sulfide content of the bedrock and pave the way for reevaluating the likelihood that early sediments preserved biosignatures from the earliest times

metamorphism water from stone where the pacific and australian tectonic plates collide under the south island of new zealand large quantities of aqueous fluid are produced but how does this happen geophysical and petrological data indicate that it may not be as we thought

an electromagnetic device for automatic detection of bedload motion and its field applications a new sensor for the continuous and unmanned detection and recording of bedload motion is described the sensor acts in the same fashion as a conventional metal detector but is elongate and installed permanently in the bed of an alluvial channel artificial clasts are labelled with short lengths of ferrite rod and are seeded upstream from the sensor replacing bed particles the entrainment of seeded clasts takes them over the sensor where they distort the magnetic field and produce a change in inductance that is detected and recorded a field installation demonstrates the value of the sensor by revealing for the first time in coarse grained alluvium the spasmodic nature of particle motion reminiscent of kinematic waves it also illustrates the importance of pebble clusters in delaying particle entrainment

recent 1999 2003 canadian research on contemporary processes of river erosion and sedimentation and river mechanics contributions by canadian fluvial geomorphologists between 1999 and 2003 are discussed under four major themes sediment yield and sediment dynamics of large rivers cohesive sediment transport turbulent flow structure and sediment transport and bed material transport and channel morphology the paper concludes with a section on recent technical advances during the review period substantial progress has been made in investigating the details of fluvial processes at relatively small scales examples of this emphasis are the studies of flow structure turbulence characteristics and bedload transport which continue to form central themes in fluvial research in canada translating the knowledge of small scale process related research to an understanding of the behaviour of large scale fluvial systems however continues to be a formidable challenge models play a prominent role in elucidating the link between small scale processes and large scale fluvial geomorphology and as a result a number of papers describing models and modelling results have been published during the review period in addition a number of investigators are now approaching the problem by directly investigating changes in the system of interest at larger scales e g a channel reach over tens of years and attempting to infer what processes may have led to the result it is to be expected that these complementary approaches will contribute to an increased understanding of fluvial systems at a variety of spatial and temporal scales

high resolution measurement of bedload transport a bedload movement detector of novel design was installed in a gravel bed stream as a component of the ongoing research on sediment transport dynamics in the stuart takla experimental watersheds in north central british columbia canada the device is designed to collect information on the patterns and timing of bedload transport during a flood event the device is based on a passive magnetic sensor that produces signals of 10 2 to 10 5 v as its magnetic field is disturbed by passing clasts a series of 82 sensors is housed in an aluminum beam placed across the stream inserted such that its surface is flush with the gravel bed the device can be raised or lowered to compensate for bed aggradation and scour a data acquisition system gathers voltage signals from the sensors at rates of 30 to 100 hz this device is sensitive enough to record the movement of most volcanic metamorphic granitic and ultramafic clasts larger than a few millimetres o ne ell creek watershed is a 68 km2 tributary basin of the middle river drainage system in the northern headwaters of the fraser river bedload transport generally occurs twice a year in the stuart takla streams once during spring floods and again during salmon spawning activity bedload moved only during two days in 1998 at the peak of the relatively small nival flood in may nevertheless the device detected at least 3 106 passing clasts a continuous record of bedload transport was obtained showing a pulsating pattern of activity seemingly independent of stage lateral movement of the transport zone and a sudden onset of bed movement with a tapered cessation we anticipate that more sophisticated calibration of the sensors and accelerated sampling rates will provide detailed information on the size and or velocity and magnetic permeability of particles moving over the device and will contribute to a better understanding of bedload transport copyright 2000 john wiley sons ltd

coarse bedload transport in a mountain river coarse bedload transport dynamics are investigated utilizing hydrodynamic and sediment transport data obtained in an extensively instrumented study reach located in squaw creek montana usa during 1991 and 1992 a number of discrete bedload transport events associated with the daily rise and fall in stream discharge were investigated data show that initiation of sediment transport was accompanied by a reduction in bed roughness and by changes in bulk hydraulic parameters for larger discharges coarser fractions of the bed material mobilized and bedload transport rates and average hydraulic parameters stabilized as discharge reduced mobile coarse particles became less frequent and deposited fine particles were removed resulting in an increase in bed roughness these observations are attributed to the downstream translation of bar sediments during the passage of a hydrograph bedload pulses were aperiodic but spatially variable flow turbulence and velocity profile data obtained during low flows allowed comparison between average bed shear stress and apparent bed roughness estimates obtained using different approaches 1998 john wiley sons ltd

phyllosilicates and sulfates at endeavour crater meridiani planum mars 1 phyllosilicates have been identified on the martian surface from orbit and are hypothesized to have formed under wet non acidic conditions early in the planet s history exposures of these minerals have not yet been examined by a landed mission using mars reconnaissance orbiter data we report the detection of phyllosilicate bearing outcrops that may be accessible by the mars exploration rover opportunity currently exploring meridiani planum the phyllosilicates are associated with layered polygonally fractured rocks exposed in the rim of the 20 km diameter crater endeavour these rocks may have formed via regional or global scale processes of aqueous alteration that predated the period of acid sulfate formation recorded in the rocks that opportunity has studied to date detailed characterization by opportunity could better constrain the conditions under which these phyllosilicates formed hydrated sulfates are also detected from orbit in the plains adjacent to endeavour s rim providing the first opportunity for ground truth of these detections

sulfur cycle in the valles caldera volcanic complex new mexico letter 2 aqueous sulfate budget and implications for hydrological transport on early mars abstract there is a large disagreement about what sulfur sources participated in formation and transport of aqueous sulfate so 4 2 on early mars previous geochemical models mainly focused on volcanic degassing and atmospheric deposition via acid rainfall generally it is unclear whether chemical weathering of sulfur mineralization present in volcanic bedrock might have been an important source of aqueous so 4 2 on mars therefore we selected the watershed of valles caldera to better constrain the quantities fluxes of so 4 2 from chemical weathering compared to direct oxidation of hydrothermal sulfur rich h2s gases and atmospheric deposition our results show that in the presence of various oxidants e g oxygen metals the so 4 2 contributions from these sources significantly vary between dry and wet seasons in the dry seasons of nov 2012 and may 2013 the aqueous so 4 2 flux from bedrock weathering was the highest 5992 to 8142 kg month 81 of total flux with minor so 4 2 contributions from atmospheric deposition 1110 to 1508 kg month 15 and hydrothermal h2s gas emission 314 to 404 kg month 4 conversely in the wet season mar 2014 the bedrock weathering showed so 4 2 fluxes of 4070 kg month 34 and gas emission of 6088 kg month 51 compared to smaller inputs from atmospheric deposition 1796 kg month 15 the volume of water interacting with a particular sulfur reservoir appears to define the amount flux of so 4 2 transported in the aqueous system of active volcanoes while h2s emission more effectively increased so 4 2 fluxes in surface water under wet conditions the so 4 2 fluxes from chemical weathering only slightly varied between investigated wet and dry seasons we demonstrate that in addition to hydrothermal sulfur emissions the chemical weathering should be included in geochemical source to sink models of sulfur cycles on mars particularly when assuming prevailing dry surface conditions in the past

the concept of transport capacity in geomorphology the notion of sediment transport capacity has been engrained in geomorphological and related literature for over 50 years although its earliest roots date back explicitly to gilbert in fluvial geomorphology in the 1870s and implicitly to eighteenth to nineteenth century developments in engineering despite cross fertilization between different process domains there seem to have been independent inventions of the idea in aeolian geomorphology by bagnold in the 1930s and in hillslope studies by ellison in the 1940s here we review the invention and development of the idea of transport capacity in the fluvial aeolian coastal hillslope debris flow and glacial process domains as these various developments have occurred different definitions have been used which makes it both a difficult concept to test and one that may lead to poor communications between those working in different domains of geomorphology we argue that the original relation between the power of a flow and its ability to transport sediment can be challenged for three reasons first as sediment becomes entrained in a flow the nature of the flow changes and so it is unreasonable to link the capacity of the water or wind only to the ability of the fluid to move sediment secondly environmental sediment transport is complicated and the range of processes involved in most movements means that simple relationships are unlikely to hold not least because the movement of sediment often changes the substrate which in turn affects the flow conditions thirdly the inherently stochastic nature of sediment transport means that any capacity relationships do not scale either in time or in space consequently new theories of sediment transport are needed to improve understanding and prediction and to guide measurement and management of all geomorphic systems

geological context of water altered minerals in valles marineris mars 1 greater than 15 000 km2 of the layered deposits within valles marineris are associated with water altered minerals yet their origin and history of alteration remain a mystery there are numerous competing hypotheses for the formation of the interior layered deposits including aeolian lacustrine and volcanic recent orbiter spectroscopic data have indicated that water has played a role in their geological history thermal emission spectrometer tes measurements have revealed significant crystalline hematite bearing deposits within valles marineris typically related to interior layered deposits these hematite deposits found with a wide range of albedo values are associated with relatively steep bedrock exposures but can also be seen downslope on flat surfaces where they may be a lag deposit more recently observatoire la mineralogie l eau les glaces et l activite omega data have shown hydrated sulfates covering more than 13 000 km2 area of valles marineris sulfates are found in numerous topographic settings and geological units but are typically located along the flanks of interior layered deposits and nearby low lying floor units here we study the detailed morphologies of hematite and sulfate bearing units such as mantled wall units mass wasting blocky deposits massive floor deposits and tectonically altered floor units all of these terrains have diverse erosional styles and varied crater populations in both hematite and sulfate bearing units occasionally found in conjunction with one another formation processes require contributions from water the results indicate a wide range of diversity within an individual mineral class between mineral classes and also among morphological types the diversity of geological settings and properties suggest that any single unified formation mechanism is improbable

sulfates in the north polar region of mars detected by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer observed the northern circumpolar regions of mars at a resolution of a few kilometers an extended region at 240 e 85 n with an area of 60 kilometers by 200 kilometers exhibits absorptions at wavelengths of 1 45 1 75 1 94 2 22 2 26 and 2 48 micrometers these signatures can be unambiguously attributed to calcium rich sulfates most likely gypsum this region corresponds to the dark longitudinal dunes of olympia planitia these observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains

fluid and deformation regime of an advancing subduction system at marlborough new zealand newly forming subduction zones on earth can provide insights into the evolution of major fault zone geometries from shallow levels to deep in the lithosphere and into the role of fluids in element transport and in promoting rock failure by several modes the transpressional subduction regime of new zealand which is advancing laterally to the southwest below the marlborough strike slip fault system of the northern south island is an ideal setting in which to investigate these processes here we acquired a dense high quality transect of magnetotelluric soundings across the system yielding an electrical resistivity cross section to depths beyond 100 km our data imply three distinct processes connecting fluid generation along the upper mantle plate interface to rock deformation in the crust as the subduction zone develops massive fluid release just inland of the trench induces fault fracture meshes through the crust above that undoubtedly weaken it as regional shear initiates narrow strike slip faults in the shallow brittle regime of interior marlborough diffuse in width upon entering the deeper ductile domain aided by fluids and do not project as narrow deformation zones deep subduction generated fluids rise from 100 km or more and invade upper crustal seismogenic zones that have exhibited historic great earthquakes on high angle thrusts that are poorly oriented for failure under dry conditions the fluid deformation connections described in our work emphasize the need to include metamorphic and fluid transport processes in geodynamic models

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time

using sediment impact sensors to improve the morphological sediment budget approach for estimating bedload transport rates constructing a sediment budget from morphological channel change typically measured using repeat cross sectional surveys has proven a useful technique for estimating mean bedload transport rates in gravel bed rivers we apply and suggest improvements to the approach using new data sources from an intensely monitored 5 6 km reach of an upland gravel bed river in northern england sediment impact sensors were placed in the bed to record the instantaneous passage of grains during transport events these sensors provide valuable information for the budget including 1 a downstream budget limit from which the rest of the budget can be calculated 2 estimates of sediment input from tributaries and 3 a better indication of active transport time used in the calculation of average transport rates further information collected from field studies include estimates of lateral inputs from the banks using field surveys and bank erosion pins and estimates of the variability of sediment porosity from bed grain size distributions budget calculations for different locations and time periods demonstrate large spatial and temporal variabilities in bedload transport rates over a short distance 3 km whilst some uncertainty in the new data sources remains this work highlights some limitations of the traditional budget approach and some potential solutions in particular the value of sediment impact sensors for sediment transport studies

spatial pattern of flow competence and bed load transport in a divided gravel bed river a 14 month continuous record of the spatial variation in the incidence and magnitude of bed load transport was provided by nine pit traps sunk into the bed of a 21 m wide upland gravel bed river the bed load data are related to a simultaneous record of average bed shear stress derived from the depth slope product the study reach is straight and includes a small low relief mid channel bar which represents the divide between two zones of markedly different bed structure and stability he bed of the left channel and bar tail is loose with an open framework while that of the bar head and right channel is tightly interlocking and well imbricated bed surface grain size is similar throughout the reach the two zones of contrasting bed structure have a strong influence on the threshold of sediment movement c and consequently the spatial pattern of bed load transport entrainment thresholds for the tightly structured bed are up to seven times higher than those for the loosely structured bed sediment transport is therefore most frequent in the left channel and over the bar tail where flows with excess shear stresses c peaking at 8 c constitute 19 of the flow record this is in marked contrast to the right channel and bar head where excess shear stresses of maximum 1 4 c total only 1 3 of the flow record however despite the marked difference in the magnitude and duration of competent flows between the two contrasting bed areas little difference in bed load yield is observed between the nine traps when averaged over the 14 month study period this study shows that different zones of bed structure and stability in a channel will control the incidence and spatial pattern of bed load transport but not necessarily the medium and long term bed load yield this has important implications for local and short term bed load sampling programs and the numerical modeling of sediment budgets and zone to zone bed load transfer