environmental factors controlling the δ13c and δ18o variations of recent fluvial tufas a 12 year record from the monasterio de piedra natural park ne iberian peninsula abstract a 12 year study 2000 2012 of the stable isotopes of recent fluvial tufas has been performed in the monasterio de piedra natural park river piedra ne iberian peninsula an area of mediterranean climate with intense tufa deposition since the pleistocene the biannual monitoring of the tufa calcite 13c and 18o signatures and of the water 18o value has demonstrated a clear seasonal pattern for the tufa calcite oxygen isotope composition with less negative values for cool periods which is consistent with regional temperature oscillations the tufa calcite 13c values only occasionally exhibit a pattern which is inconclusive and opposite to the 18o clear pattern the water 18o signature has a distinct seasonal pattern also opposite to the tufa calcite 18o clear pattern the temperature calculations from the tufa calcite 18o values and average water 18o values agree with the seasonal pattern of measured water temperatures with a mean difference of 2 3 c between the calculated and measured temperatures the anomalous values recorded for both the water and the tufa calcite oxygen isotope composition during a two year period are characterized by smoothing of the seasonal variations of the tufa calcite and by reversal of the water pattern there is also an increase in the differences between the measured and estimated temperatures the detected anomaly is roughly synchronous with a change in the isotopic signature of the regional precipitation 18o values this contribution demonstrates that tufas in this depositional and climatic context are good indicators of seasonal temperature oscillations and that tufas can also record other interannual environmental changes such as variations in the isotopic composition of precipitation these results can be extrapolated to ancient tufa systems developed in similar contexts which would expand the potential of tufas as high resolution records of paleoenvironmental conditions

an experimental and computer simulation study of erosion on a mine tailings dam wall mine tailings dams pose a signi cant risk to the environment if not correctly designed built and maintained the effect of erosion on a back lled and capped earthen dam wall was examined by construction of an analogue in an experimental model landscape simulator the ability of a computer based erosion model to simulate erosion processes on the experimental structure was examined the experimental landscape simulator uses a rainfall simulator to create overland ow and erode an arti cial soil at the commencement of rainfall erosion occurred rapidly with deep gullies developing on the dam wall batter the gullies developed by downcutting with consequent bank collapse and slumping and followed ow lines towards their source a physically based erosion model siberia was used to simulate erosion on the experimental dam wall erosion and consequent development of the experimental structure were modelled by siberia the ability of siberia to model incision and landscape development in the experimental setting was further examined by use of a simple one dimensional experimental catchment the laboratory experiment and computer simulations demonstrated that erosion on the tailings dam is driven by concentrated runoff and that runoff control is crucial to the long term stability of such structures the study demonstrates that computer based erosion models can be used to predict how erosion occurs on the experimental landscapes examined thus providing con dence in their use and application copyright 2004 john wiley sons ltd

a physical explanation of the cumulative area distribution curve a physical explanation for the behavior of the cumulative area distribution cad based on the tokunaga channel network model is given the cad is divided into three regions the first region for small areas is dependent on hillslope flow accumulation patterns and represents the catchment average of the hillslope flow accumulation in the diffusive erosion dominated areas upstream reaches of the catchment the second region represents that portion of the catchment dominated by fluvial erosion this region is well described by a log log linear power law which results from the scaling properties of the channel network the scale exponent b is highly sensitive to a parameter of the tokunaga stream numbering scheme the exponentb converges to 0 5 for higher order tokunaga networks for parameters consistent with topological random networks small networks have lower values ofb which asymptotic converges tob 0 5 as the catchment scale increase the third region reflects the lowest reaches of the channel network the scale of the catchment and is a boundary effect an explicit analytical solution to the scaling properties in the second region is derived on the basis of the tokunaga network model the cumulative distribution of drainage area is the percent age of the catchment that has an area per unit width draining through a point which is greater than or equal to a given area it is a geomorphologic measure that characterizes part of the catchment hydrology and is a measure commonly used by geo morphologists and hydrologists to characterize the scale invari ant structure of channel networks tarboton et al 1989 ro driguez iturbe et al 1992 inaoka and takayasu 1993 la barbera and roth 1994 this cumulative area distribution cad characterizes the scaling properties of drainage area the cad and its scaling properties are key components in the development of physically based models that link geomorphol ogy and hydrology perera 1997 ibbitt et al 1997 perera 1997 showed that slope of the cad in both the hillslope and channel domains is important for describing the geomorphic impact on subsurface saturation excess runoff generation using a digital elevation model dem of a catchment the drainage path through and the drainage area per unit width of each point in the catchment can be computed for a grided dem the cumulative area a is determined as the number of pixels within the catchment which have drainage area a num ber of pixels draining through greater than or equal to some specified drainage area a

concentric crater fill in utopia planitia history and interaction between glacial brain terrain and periglacial mantle processes abstract at martian mid to high latitudes the surfaces of potentially ice rich features including concentric crater fill lobate debris aprons and lineated valley fill typically display a complex texture known as brain terrain due to its resemblance to the complex patterns on brain surfaces in order to determine the structure and developmental history of concentric crater fill and overlying latitude dependent mantle ldm material brain terrain and polygonally patterned ldm surfaces are analyzed using hirise images from four craters in utopia planitia containing concentric crater fill brain terrain and mantle surface textures are classified based on morphological characteristics 1 closed cell brain terrain 2 open cell brain terrain 3 high center mantle polygons and 4 low center mantle polygons a combined glacial and thermal contraction cracking model is proposed for the formation and modification of the brain terrain texture of concentric crater fill a similar model related to thermal contraction cracking and differential sublimation of underlying ice is proposed for the formation and development of polygonally patterned mantle material both models require atmospheric deposition of ice likely during periods of high obliquity but do not require wet active layer processes crater dating of brain terrain and mantled surfaces suggests a transition at martian mid latitudes from peak glacial conditions occurring within the past 10 100 my to a quiescent period followed by a cold desert periglacial period during the past 1 2 my

invariance and scaling properties in the distributions of contributing area and energy in drainage basins a the cumulative probability distributions for stream order stream length contributing area and energy dissipation per unit length of channel are derived for an ordered drainage system from horton s laws of network composition it is shown how these distributions can be related to the fractal nature of single rivers and river networks finally it is shown that the structure proposed here for these probability distributions is able to fit the observed frequency distri butions and their deviations from straight lines in a log log plot

lineated valley fill lvf and lobate debris aprons lda in the deuteronilus mensae northern dichotomy boundary region mars constraints on the extent age and episodicity of amazonian glacial events abstract in order to assess the nature degradational processes and history of the dichotomy boundary on mars we conducted a detailed morphological analysis of a 70 000 km 2 region of its northern portion north central deuteronilus mensae south of lyot in the vicinity of sinton crater this region is characterized by the distinctive sinuous 2 km high plateau scarp boundary outlying massifs to the north and extensive fretted valleys dissecting the plateau to the south these features represent the first order modification and retreat of the dichotomy boundary and are further modified by processes that form lineated valley fill lvf in the fretted valleys and lobate debris aprons lda along the dichotomy scarp and surrounding the outlying massifs we use new high resolution image and topography data to examine the nature and origin of lvf and lda and to investigate the climatic and accompanying degradational history of the escarpment on the basis of our analysis we conclude that 1 lvf and lda deposits within the study region are comprised of the same material show integrated flow patterns and originate as debris covered valley glaciers a significant amount of ice hundreds of meters is likely to remain today beneath a thin cover of sublimation till 2 there is depositional evidence to suggest glacial highstands at least 800 m above the present level implying previous conditions in which the distribution of ice was much more widespread this is supported by similar deposits within many other areas across the dichotomy boundary 3 the timing of the most recent large scale activity of the lda lvf in this area is about 100 500 million years ago similar to ages reported elsewhere along the dichotomy boundary 4 there is evidence for a secondary but significantly limited phase of glaciation the deposits of which are limited to the vicinity of the alcoves similar later phases have also been reported elsewhere along the dichotomy boundary 5 modification of the fretted valleys of the dichotomy boundary has been substantial locally but we find no evidence that the amazonian glacial epochs caused retreat of the dichotomy boundary of the scale of tens to hundreds of kilometers our findings support the results of an analysis just to the east of the study region and of studies carried out elsewhere along the dichotomy boundary that find further evidence for the remnants of debris covered glaciers and extensive valley glacial land systems

seasonal patterns of carbon chemistry and isotopes in tufa depositing groundwaters of southwestern japan abstract annually laminated carbonates known as tufas commonly develop in limestone areas and typically record seasonal patterns of oxygen and carbon isotope compositions 18o values are principally controlled by seasonal changes of water temperature whereas 13c values are the result of complex reactions among the gaseous liquid and solid sources of carbon in the system we examined the processes that cause the seasonal patterns of 13c in groundwater systems at three tufa depositing sites in southwestern japan by applying model calculations to geochemical data underground inorganic carbon species are exchanged with gaseous co2 which is mainly introduced to the underground hydrological system by natural atmospheric ventilation and by diffusion of soil air these processes control the seasonal pattern of 13c which is low in summer and high in winter among the three sites we investigated we identified two extreme cases of the degree of carbon exchange between liquid and gaseous phases for the case with high radiocarbon composition 14c and low pco2 there was substantial carbon exchange because of a large contribution of atmospheric co2 and a small water mass for the other extreme case which was characterized by low 14c and high pco2 the contribution of atmospheric co2 was small and the water mass was relatively large our results suggest that at two of the three sites water residence time within the soil profile was longer than 1 year our results also suggested a short residence time less than 1 year of water in the soil profile at the site with the smallest water mass which is consistent with large seasonal amplitude of the springwater temperature variations the 14c value of tufas is closely related to the hydrological conditions in which they are deposited if the initial 14c value of a tufa depositing system is stable 14c chronology can be used to date paleo tufas

calibration of the calcite water oxygen isotope geothermometer at devils hole nevada a natural laboratory abstract the 18 o of ground water 13 54 0 05 and inorganically precipitated holocene vein calcite 14 56 0 03 from devils hole cave 2 in southcentral nevada yield an oxygen isotopic fractionation factor between calcite and water at 33 7 c of 1 02849 0 00013 1000 ln calcite water 28 09 0 13 using the commonly accepted value of calcite water t of 0 00020 k 1 this corresponds to a 1000 ln calcite water value at 25 c of 29 80 which differs substantially from the current accepted value of 28 3 use of previously published oxygen isotopic fractionation factors would yield a calcite precipitation temperature in devils hole that is 8 c lower than the measured ground water temperature alternatively previously published fractionation factors would yield a 18 o of water from which the calcite precipitated that is too negative by 1 5 using a temperature of 33 7 c several lines of evidence indicate that the geochemical environment of devils hole has been remarkably constant for at least 10 ka accordingly a re evaluation of calcite water oxygen isotopic fractionation factor may be in order assuming the devils hole oxygen isotopic value of calcite water represents thermodynamic equilibrium many marine carbonates are precipitated with a 18 o value that is too low apparently due to a kinetic isotopic fractionation that preferentially enriches 16 o in the solid carbonate over 18 o feigning oxygen isotopic equilibrium

gully channel and hillslope erosion an assessment for a traditionally managed catchment understanding landscape features such as gullying and soil erosion is an important issue in the long term dynamics and evolution of both natural agricultural and rehabilitated i e post mining landscapes considerable research has been undertaken examining the initiation movement and overall dynamics of such features this study reports on a series of 34 gully heads and other erosion features such as scour holes five in total located in channels in a catchment largely undisturbed by european activity in the northern territory australia over a 5 year period 2002 2007 during this period the erosion features were monitored for their headward advance retreat enlargement or in filling the erosion features ranged in depth from 0 2 m to 1 5 m and widths of 0 3 m to 8 m hillslope erosion was also monitored using erosion pins the catchment was subject to a range of rainfall regimes including extreme rainfall and a category 5 cyclone and also was burnt every second year so that all grass cover was removed according to traditional management practice the results of this monitoring show that the erosion features have changed little during this 5 year period a remote sensing assessment found no relationship between erosion feature morphology and hillslope erosion the monitored gullies heads and scour holes appear to be resilient landscape features yet have a morphology that suggests they are ready for rapid headward movement and expansion leading to a destabilisation of the catchment hillslope erosion was found to be related to wetness indices derived from a digital elevation model significant linkages were found between hillslope erosion and change in erosion feature depth indicative of a strong hillslope channel coupling copyright 2010 commonwealth of australia

ice and debris in the fretted terrain mars viking moderate and high resolution images along the northern highland margin were studied monoscopically and stereoscopically to contribute to an understanding of the development of fretted terrain results suport the hypothesis that the fretting process involved flow facilitated by interstitial ice the process apparently continued for a long period of time and debris apron formation shaped the fretted terrain in the past as well as the present interstitial ice in debris aprons is most likely derived from ground ice obtained by sapping or scarp collapse debris aprons could have been removed by sublimation if they consisted mostly of ice or by deflation if they consisted mostly of debris to remove the debris wind erosion was either very intense early in martian history or was intermittent perhaps owing to climatic cycles the location of debris aprons in two midlatitudinal belts can be attributed to atmospheric conditions that permit ice to remain in the ground at moderate depth in those latitudes and climatic factors that permit temperatures to be warm enough for ice to flow channels have minimum gradients of 5 8 m km which permits flowing ice to deform by dislocation creep at exceedingly low strain rates alternately ice charged debris may have been buoyed by brines by analogy with the fretted channels ice could have flowed through the outflow channels if the atmospheric pressure was somewhat higher in the past and permitted ice to exist in the equatorial area

the influence of temperature ph and growth rate on the δ18o composition of inorganically precipitated calcite abstract the oxygen isotope composition of carbonate minerals varies with temperature as well as other environmental variables for carbonates that precipitate slowly under conditions that approach thermodynamic equilibrium the temperature dependence of 18 o uptake is the dominant signal and the measured 18 o content can be used as a paleotemperature proxy in the more common case where carbonate minerals grow in a regime where they are not in isotopic equilibrium with their host solution their oxygen isotope compositions are a convolution of multiple environmental variables here we present results from calcite growth experiments demonstrating the occurrence of large 2 non equilibrium oxygen isotope effects under conditions relevant to biogenic calcite growth and many natural inorganic systems we show that these non equilibrium effects vary systematically with ph and crystal growth rate an isotopic ion by ion crystal growth model quantifies the competing roles of temperature ph and growth rate and provides a general description of calcite water oxygen isotope fractionation under non equilibrium conditions the crystal growth model results show that 1 there are both equilibrium and kinetic contributions to calcite oxygen isotopes at biogenic growth rates 2 calcite does not directly inherit the oxygen isotope composition of dic even at fast growth rates 3 there is a kinetically controlled variation of about 1 per ph unit between ph 7 7 and 9 3 at constant growth rate for inorganic calcite as well as biogenic calcite and 4 extreme light isotope enrichments in calcite in alkaline environments are likely due to disequilibrium among dic species in aqueous solution the model can be extended to 13 c uptake into carbonates as well as clumped isotopes but additional data are needed to constrain the kinetic fractionation factors for carbon isotopes the experimental and model results constitute an important step in separating the relative influence of inorganic and biologic processes on isotopic fractionation and may aid the development of new paleoproxies based on non equilibrium effects

modification of the dichotomy boundary on mars by amazonian mid latitude regional glaciation 1 restoration of the dichotomy boundary to its original position to assess its origin requires a thorough knowledge of processes responsible for its degradation and retreat the unique fretted terrain located along the deuteronilus protonilus mensae northern mid latitude portion of the boundary has been long held to provide clues to dichotomy degradation processes we use new spacecraft data to show that fretted valleys display a multitude of characteristics typical of integrated valley glacial systems on earth multiple theater headed alcove like accumulation areas sharp arete like ridges typical of glacial erosion converging patterns of downslope valley flow valley lineation patterns typical of folding and shear wrap around features indicative of flow around obstacles and broad piedmont like lobes as the valley fill extends out into the northern lowlands the single integrated system containing these features covers about 30 000 km2 and is one of dozens of fretted valleys along the dichotomy boundary in this region these relationships suggest that the boundary area was subjected to very large scale regional glaciation during the amazonian recognition and documentation of this important late stage process provides information critical to reconstructing the original dichotomy boundary

lithospheric flexure and the evolution of the dichotomy boundary on mars 1 the boundary of the martian crustal dichotomy in the eastern hemisphere is one of the most striking topographic features on the planet the long wavelength topography of much of the boundary is expressed by a broad rise and an arched ramp that slopes downward from the southern highlands into the northern lowlands and often ends in a steep scarp lithospheric flexure of the southern highlands for both a continuous and broken plate boundary with the northern lowlands lithosphere is modeled we find that the long wavelength topography of the boundary is best fit by a lithospheric deflection profile of a broken lithosphere for reasonable values of the flexural parameter the lithosphere near the dichotomy boundary may have been weakened by tectonic stress associated with the formation of the crustal dichotomy by subcrustal transport caused by overturn of an early magma ocean

climatic variations in mis 11 recorded by stable isotopes and trace elements in a french tufa la celle seine valley marine isotope stage mis 11 palaeoclimate has so far been documented in marine and ice sheet isotopic records however excepting some lacustrine pollen records very little is known about palaeoclimatic conditions in continental areas this study uses geochemical records in calcareous tufa deposits from rivers as a basis for reconstructing temperate palaeoclimatic conditions tufa deposits are now proven to record high quality palaeoclimatic information in recent to holocene deposits work on older interglacial tufas is just starting and in this paper we present the first comprehensive results from a mis 11 tufa the tufa comes from the seine valley la celle northern france geochemical data in the tufa calcite are interpreted to record primarily air temperature do and humidity dc and mg ca and sr ca the combined data identify a warm and wet climatic optimum followed by two temperature decreases associated with oscillations in humidity these marked climatic variations recorded through the la celle profile are strongly coherent with the palaeoenvironmental reconstructions from malacological data the abrupt climatic and environmental events recorded could be related to short term degradation of vegetation cover in europe which is itself controlled by global palaeoclimatic events

stable isotope geochemical study of pamukkale travertines new evidences of low temperature non equilibrium calcite water fractionation abstract in this paper we present the first detailed geochemical study of the world famous actively forming pamukkale and karahayit travertines denizli basin sw turkey and associated thermal waters sampling was performed along downstream sections through different depositional environments vent artificial channel and lake terrace pools and cascades of proximal slope marshy environment of distal slope 13 c travertine values show significant increase from 6 1 to 11 7 pdb with increasing distance from the spring orifice whereas the 18 o travertine values show only slight increase downstream from 10 7 to 9 1 pdb mainly the co 2 outgassing caused the positive downstream shift 6 in the 13 c travertine values the high 13 c values of pamukkale travertines located closest to the spring orifice not affected by secondary processes suggest the contribution of co 2 liberated by thermometamorphic decarbonation besides magmatic sources based on the gradual downstream increase of the concentration of the conservative na k cl evaporation was estimated to be 2 5 which coincides with the moderate effect of evaporation on the water isotope composition stable isotopic compositions of the pamukkale thermal water springs show of meteoric origin and indicate a local meteoric water line of denizli basin to be between the global meteoric water line craig 1961 and western anatolian meteoric water line imsek 2003 detailed evaluation of several major and trace element contents measured in the water and in the precipitated travertine along the pamukkale mm section revealed which elements are precipitated in the carbonate or concentrated in the detrital minerals former studies on the hungarian egerszalok travertine kele et al 2008a b 2009 had shown that the isotopic equilibrium is rarely maintained under natural conditions during calcite precipitation in the temperature range between 41 and 67 c in this paper besides the detailed geochemical analyses along downstream sections we present new evidences of non equilibrium calcite water fractionation in lower temperature range 13 3 to 51 3 c our measurements and calculations on natural hot water travertine precipitations at pamukkale and egerszalok revealed that the 18 o travertine is equal with the 18 o hco3 at the orifice of the thermal springs which means that practically there is no oxygen isotope fractionation between these two phases high rate of co 2 degassing with rapid precipitation of carbonate could be responsible for this as it was theoretically supposed by o neil et al 1969 thus for the determination of the deposition temperature of a fossil travertine deposit we propose to use the water bicarbonate oxygen isotope equilibrium fractionation instead of the water travertine fractionation which can result 8 9 c difference in the calculated values our study is the first detailed empirical proof of o neil s hypothesis on a natural carbonate depositing system the presented observations can be used to identify more precisely the deposition temperature of fossil travertines during paleoclimate studies

mg isotope fractionation during calcite precipitation an experimental study abstract experimental precipitations of calcite and other carbonate minerals were performed under various conditions of ph temperature and solution mg ca to determine the mg partition coefficient and mg isotope fractionation fifteen experiments were performed at ph ranging from 7 41 0 07 to 8 51 0 39 temperature ranging from 16 2 0 7 to 26 5 0 3 c and mg ca solution ranging from 0 11 to 0 52 mol mol the apparent mg partition coefficient between calcite and solution d mg spans a large range of values from 0 018 0 014 to 0 15 0 11 and carbonate mg isotope fractionation 26 mg ranges from 2 53 0 25 to 1 33 0 14 and does not correlate with either ph or temperature the range in d mg and 26 mg suggests non equilibrium partitioning controlled by the processes of calcite growth i e mixing between calcite grown at equilibrium and fluid inclusions and entrapment of a surface mg rich calcite layer in isotopic equilibrium with the solution the equilibrium mg isotope fractionation between inorganic calcite and solution is estimated to be 2 13 0 24 additional mg elemental and isotopic fractionations are observed to occur during biogenic formation of calcite due to variable removal of mg by the organisms high mg calcite corals foraminifera of seawater mg from their calcification medium

intrinsic and extrinsic controls of spatial and temporal variations in modern fluvial tufa sedimentation a thirteen year record from a semi arid environment sedimentological and hydrochemical parameters of the river piedra north east spain were monitored every six months from 1999 to 2012 at 24 sites at which tablets were installed all along the river the river water is of hco3 so4 ca type and is notably influenced by inputs from upstream karstic springs tufa deposition was first detected 8 km downstream of these springs and greatly increased from there primarily along the steeper stretch i e within the monasterio de piedra natural park then deposition decreased through the most downstream stretch with smaller ground water inputs the spatial evolution of the tufa thickness with parallel variations of pwp plummer wigley parkhurst rates was thus determined by the river water pco2 which was controlled by ground water inputs and by the river bed slope five fluvial subenvironments and seven sedimentary facies were characterized the water flow conditions are the primary factor responsible for the distinct deposition rates of facies mainly through co2 outgassing stromatolites and moss tufa and alga tufa had the highest rates whereas loose tufa formed in slow flowing water and tufa of spray areas had thinner deposition a six month pattern in the deposition rate was detected through thickness measurements that pattern was parallel to the seasonal pwp rates the increased deposition during warm periods spring and summer mean 5 08 mm compared with cool periods autumn and winter mean 2 77 mm is linked chiefly to temperature which controlled the seasonal changes in the physico chemical and biological processes this finding is supported by a principal components analysis seasonal variations of insolation and day duration also contributed to such a deposition pattern large discharge events which provoked erosion of tufa deposits and dilution of water caused the reversal of the seasonal deposition rate pattern stromatolites are likely to preserve the most complete sedimentary record although tufas are a potentially sensitive record of climate related parameters erosion is an intrinsic process that may overwhelm the effects of such parameters this issue should be considered in palaeoclimatic studies based on the tufa record particularly in semi arid conditions

modelling landscape evolution geomorphology is currently in a period of resurgence as we seek to explain the diversity origins and dynamics of terrain on the earth and other planets in an era of increased environmental awareness yet there is a great deal we still do not know about the physics and chemistry of the processes that weaken rock and transport mass across a planet s surface discovering and refining the relevant geomorphic transport functions requires a combination of careful field measurements lab experiments and use of longer term natural experiments to test current theory and develop new understandings landscape evolution models have an important role to play in sharpening our thinking guiding us toward the right observables and mapping out the logical consequences of transport laws both alone and in combination with other salient processes improved quantitative characterization of terrain and process and an ever improving theory that describes the continual modification of topography by the many and varied processes that shape it together with improved observation and qualitative and quantitative modelling of geology vegetation and erosion processes will provide insights into the mechanisms that control catchment form and function this paper reviews landscape theory in the form of numerical models of drainage basin evolution and the current knowledge gaps and future computing challenges that exist copyright 2010 john wiley sons ltd

oxygen isotope variations in rainfall drip water and speleothem calcite from a well ventilated cave in texas usa assessing a new speleothem temperature proxy abstract measurements of the oxygen isotopic composition 18o value of rainfall drip water and associated calcite grown on artificial substrates and in a natural speleothem at multiple drip sites in a well ventilated cave in central texas were conducted to investigate the potential use of speleothem 18o for quantitative temperature reconstructions from 2009 to 2011 rainfall 18o varied by 11 5 10 5 to 1 0 v smow whereas drip waters had a much narrower range of 0 3 4 7 to 4 4 v smow this contrast indicates that mixing processes along flow paths in the vadose zone above the cave produce a well homogenized water reservoir that supplies drip water to the cave the 18o values for calcite grown on substrates over the same time period show seasonal variations summer 6 winter 3 that are strongly correlated with surface air temperatures ta at all three monitored sites r2 0 88 0 96 p

mars global surveyor observations of martian fretted terrain the martian fretted terrain between latitudes 30 and 50 n and between 315 and 360 w has been reexamined in light of new mars orbiter camera moc and mars orbiter laser altimeter mola data from mars global surveyor much of the terrain in the 30 50 latitude belt in both hemispheres has a characteristic stippled or pitted texture at moc 1 5 m scale the texture appears to result from partial removal of a formerly smooth thin deposit as a result of sublimation and deflation a complex history of deposition and exhumation is indicated by remnants of a former thicker cover of layered deposits in some hollows and on some slopes particularly those facing the pole are smooth textured deposits outlined by an outward facing escarpment throughout the study area are numerous escarpments with debris flows at their base the escarpments typically have slopes in the 20 30 range at the base of the escarpment is commonly a deposit with striae oriented at right angles to the escarpment outside this deposit is the main debris apron with a surface that typically slopes 2 3 and complex surface textures suggestive of compression sublimation and deflation the presence of undeformed impact craters indicates that the debris flows are no longer forming fretted valleys contain lineated fill and are poorly graded they likely form from fluvial valleys that were initially like those elsewhere on the planet but were subsequently widened and filled by the same mass wasting processes that formed the debris aprons slope reversals indicate that downvalley flow of the lineated fill is minor the ubiquitous presence of breaks in slope formed by mass wasting and the complex surface textures that result from mass wasting deflation and sublimation decreases the recognizability of the shorelines formerly proposed for this area

testing of the siberia landscape evolution model using the tin camp creek northern territory australia field catchment the siberia landscape evolution model was used to simulate the geomorphic development of the tin camp creek natural catchment over geological time measured hydrology erosion and geomorphic data were used to calibrate the siberia model which was then used to make independent predictions of the landform geomorphology of the study site the catchment located in the northern territory australia is relatively untouched by europeans so the hydrological and erosion processes that shaped the area can be assumed to be the same today as they have been in the past subject to the caveats regarding long term climate fluctuation a qualitative or visual comparison between the natural and simulated catchments indicates that siberia can match hillslope length and hillslope profile of the natural catchments a comparison of geomorphic and hydrological statistics such as the hypsometric curve width function cumulative area distribution and area slope relationship indicates that siberia can model the geomorphology of the selected tin camp creek catchments copyright 2002 environmental research institute of the supervising scientist commonwealth of australia

equilibrium vs kinetic fractionation of oxygen isotopes in two low temperature travertine depositing systems with differing hydrodynamic conditions at baishuitai yunnan sw china abstract in order to understand the behavior of oxygen isotopic fractionation and obtain more reliable paleoclimatic data from surficial travertine deposits the hydrochemistry carbonate precipitation rates and the temporal and spatial variations in 18 o values of the modern travertine in two low temperature travertine depositing systems canal and pool with differing hydrodynamic conditions at baishuitai yunnan sw china were investigated during the warm rainy season may 24 to november 2 in 2010 it was found that the oxygen isotopic composition of travertine in the two systems showed distinct controlling mechanisms mainly due to different carbonate precipitation rates and water residence times for the canal system with fast flow large deviations between the calculated and measured temperatures indicated that travertine precipitated out of isotopic equilibrium this was due to rapid carbonate precipitation with intense co 2 degassing 18 o travertine values and water temperature increased downstream 1 and 4 c respectively while 18 o water values remained relatively stable it was shown that the 18 o values of travertine in the canal system recorded the 18 o values of dissolved carbonates hco 3 which also increased along the canal controlled by rayleigh distillation effects in contrast in the pools system with slow flow oxygen isotopic equilibrium between dissolved carbonates hco 3 and h 2 o was achieved and the 18 o travertine values did not display spatial variations calculated water temperatures using the equilibrium fractionation factors of coplen 2007 were identical to the measured ones which indicates that travertine in such pools system is suitable for the reconstruction of paleo precipitating temperatures finally by comparing these two systems we have obtained a simple criterion to determine the suitability of travertine to estimate temperatures the 18 o value of baco 3 precipitated from water samples is compared with the theoretical 18 o value of dissolved carbonate calculated using water temperature and 18 o water to check if the oxygen isotopes of the dissolved carbonate are in equilibrium with the water

the influence of kinetics on the oxygen isotope composition of calcium carbonate paleotemperature reconstructions rely on knowledge of the equilibrium separation of oxygen isotopes between aqueous solution and calcium carbonate although oxygen isotope separation is expected on theoretical grounds the temperature dependence remains uncertain because other factors such as slow exchange of isotopes between dissolved co2 species and water can obscure the temperature signal this is problematic for crystal growth experiments on laboratory timescales and for interpreting the oxygen isotope composition of crystals formed in natural settings we present results from experiments in which inorganic calcite is precipitated in the presence of 0 25 m dissolved bovine carbonic anhydrase ca the presence of dissolved ca accelerates oxygen isotope equilibration between the dissolved carbon species co2 h2co3 hco3 co32 and water thereby eliminating this source of isotopic disequilibrium during calcite growth the experimental results allow us to isolate for the first time kinetic oxygen isotope effects occurring at the calcite water interface we present a framework of ion by ion growth of calcite that reconciles our new measurements with measurements of natural cave calcites that are the best candidate for having precipitated under near equilibrium conditions our findings suggest that isotopic equilibrium between calcite and water is unlikely to have been established in laboratory experiments or in many natural settings the use of ca in carbonate precipitation experiments offers new opportunities to refine oxygen isotope based geothermometers and to interrogate environmental variables other than temperature that influence calcite growth rates

power law distributions of discharge mass and energy in river basins river networks constitute dissipative systems with many spatial degrees of freedom previous work by mandelbrot 1983 and bak et al 1987 1988 1990 suggests that such systems will follow power law distributions in their mass and energy characteristics it is shown that this is the case for river networks where the exponent in the distribution p x x x is approximately equal to 0 45 and 0 90 for discharge and energy respectively in the case of several networks analyzed in north america when these variables are calculated for each individual link throughout the drainage network an explanation of the values of is offered based on the fractal structure of rivers and on principles of energy expenditure in river basins

a comparison of srtm and high resolution digital elevation models and their use in catchment geomorphology and hydrology australian examples the recently released shuttle radar topography mission srtm 3 arc second digital elevation data set provides a complete global coverage of the earth s land surface in this paper we examine the srtm data for three catchments in australia over a range of climates geology and resultant geomorphology to test this new data set the srtm data are compared with high resolution digital elevation models we use basic hydrological and geomorphological statistics and descriptors such as the area slope relationship cumulative area distribution and hypsometric curve along with strahler and networking statistics the above measures describe the surface morphology of a catchment therefore integrating catchment geology climate and vegetation the srtm data were also assessed as input into the siberia landscape evolution and soil erosion model as were runoff properties using a wetness index the results demonstrate that the 90 m srtm data provide a poor catchment representation hillslopes appear as a linked set of facets and display little of the complex curvature that is observed in high resolution data while catchment area slope and area elevation hypsometry properties are largely correct catchment area relief and shape as measured by the width function are poorly captured by the srtm data also results in working statistics are also variable the large grid size of the srtm data also results in incorrect drainage network patterns and different runoff properties consequently care must be used for quantitative assessment of catchment hydrology and geomorphology as in all cases srtm derived catchment area is incorrect and smaller digital elevation grid sizes are required for accurate catchment wide assessment while only a limited number of catchments have been examined we believe our findings are applicable to other areas

geomorphic analysis of lobate debris aprons on mars at mars orbiter camera scale evidence for ice sublimation initiated by fractures 1 lobate debris aprons known to be geomorphic landform indicators of the presence of ground ice are of special interest for future missions devoted to the research of water on mars lobate debris aprons in fretted terrains of deuteronilus and protonilus mensae 35 50 n show typical convex shapes interpreted to be the result of viscous deformation at the scale of mars orbiter camera moc high resolution images the surface of these debris aprons shows complex patterns with small pits and buttes these patterns can be explained by the mantling of dust the accumulation of interstitial ice and the subsequent removal of ice by sublimation the sublimation of the ground ice is especially initiated and accelerated by subsurface heterogeneities like fractures theoretical quantification of sublimation rates therefore minimizes sublimation which is not a homogeneous process at least over the landforms studied crater counts show that the sublimation occurred in the last tens of millions of years up to the recent past in the point of view of future searching of subsurface ice only surface layers are submitted to sublimation favoring the conservation of ground ice in deeper layers since the formation of the landform the geophysical survey of lobate debris aprons would give interesting insights into the subsurface distribution of ice and its seasonal variations especially in order to measure current sublimation of ground ice

seasonal temperatures from δ18o in recent spanish tufa stromatolites equilibrium redux this study focuses on recent debate over the value of stable isotope based environmental proxies recorded in riverine tufa stromatolites we recovered a 12 year record 1999 2012 of river bed tufa stromatolites in the river piedra ne spain along with a partly overlapping 15 year record 1994 to 2009 of accumulations in a drainage pipe both deposits formed in water with near identical physico chemical parameters measured water temperature tw data and near constant 18owater composition allowed selection of an equilibrium palaeotemperature equation that best replicated actual temperatures we found as other have that both the epstein et al 1951 and kim o neil 1997 formulas for tw calculation from equilibrium calcite 18o compositions were appropriate for the river piedra where tufa deposition rates are high means between 5 6 and 10 8 mm in six months 18ocalcite in both the river and the pipe deposits record essentially the full actual seasonal tw range only the coldest times tw 10oc when calcite precipitation mass decreased to minimum are likely to be unrepresented an effect most noticeable in the pipe where depositional masses are smaller and below sample resolution while we cannot rule out kinetic effects on 18ocalcite based calculated tw the good fit between measured tw and 18ocalcite calculated tw indicates that temperature is the principal control textural and deposition rate variability between the river and pipe settings are caused by differences in flow velocity and illumination in the river calcification of growing cyanobacterial mat occurred throughout the year producing composite dense and porous laminae whereas in the pipe discontinuous cyanobacterial growth in winter promoted more abiogenic calcification high resolution 18ocalcite data from synchronous pipe and river laminae show that reversals in tw occur within laminae not at lamina boundaries a pattern consistent with progressive increase in calcite precipitation rate as cyanobacterial growth re established in spring

the use of digital elevation models in the identification and characterization of catchments over different grid scales this study examines the ability of well known hydrological and geomorphological descriptors and statistics to differentiate between catchments with spatially varying geology size and shape subject to the same climate in the northern territory australia the effect of digital elevation model grid resolution on these statistics is also examined results demonstrate that catchment descriptors such as the area slope relationship cumulative area distribution and hypsometric curve can differentiate between catchments with different geology and resultant morphology but catchment network statistics are insensitive to differences in geology examination of the effects of digital elevation model grid scale demonstrates that while considerable catchment information can be gained at digital elevation grids greater than 10 m by 10 m hillslope and hydrological detail can be lost geomorphic descriptors such as the area slope relationship cumulative area distribution width function and strahler statistics were shown to be sensitive to digital elevation model grid scale but the hypsometric curve was not consequently caution is needed when deciding on an appropriate grid resolution as well as the interpretation and analysis of catchment properties at grid scales greater than that for optimal hillslope and area aggregation definition copyright 2005 john wiley sons ltd

stable isotopes of holocene calcareous tufa in southern poland as paleoclimatic indicators abstract the isotopic composition of oxygen in freshwater calcareous tufa seems to be a sensitive indicator of past climatic changes results of measurements of c 18 o and c 13 c in tufa samples dated with the 14 c method are used to reconstruct holocene climatic changes in southern poland values of c 18 o obtained on tufa samples from four sites raclawka rzerzu nia trzebienice sieradowice representing different hydrodynamic conditions of tufa sedimentation seem to form a selfconsistent series these values with some simplifying assumptions concerning the course of tufa sedimentation were therefore used to estimate mean annual temperatures in the interval ca 9500 2000 yr b p when the resulting curve of thermal changes in southern poland is compared with changes of deposition and erosion of tuffaceous sediments and with results of other methods of reconstruction of paleoclimate in central europe a reasonable agreement among the different specific methods is seen

origin of annual laminations in tufa deposits southwest japan abstract laminated tufas and a tufa depositing stream in sw japan shirokawa ehime prefecture were studied monthly over a 3 yr period a series of samples from the tufa clearly reveals the pattern of annual laminations the annual layering pattern was primarily controlled by changes in the rate of calcite precipitation as calculated from water chemistry the concentration of dissolved caco 3 which correlates with the precipitation rate was high in summer autumn and low in winter spring owing to changes in the partial pressure of co 2 in underground air regular seasonal changes in underground pco 2 probably resulted from two temperature dependent processes the diffusion of soil co 2 and the ventilation of underground air these changes in addition to water temperature changes altered the precipitation rate which has a clear seasonal pattern especially in the lower stream the seasonal precipitation rate was high in summer autumn and low in winter spring which is consistent with the seasonal lamination pattern seen in the tufas the textures of collected samples show that the laminations consist of densely calcified summer autumn june october laminae and lightly calcified winter spring november may laminae we infer that the increased precipitation rate stimulated thick calcite encrustation on cyanobacterial filaments to produce the dense textures this interpretation is supported by the lowered organic inorganic carbon production ratio in summer autumn seasonal variations in cyanobacterial assemblages are present but do not reflect the seasonal lamination pattern because the relevant processes are temperature dependent the seasonal lamination pattern at shirokawa is thought to generally apply to other laminated tufas deposited in temperate climates however a reversed pattern can result from local and climatic circumstances dense laminae were deposited in winter near the source of the spring at shirokawa because calcite precipitation was high owing to low underground pco 2 in winter reversed patterns reported from northwestern europe were probably influenced by seasonal rainfall which is reflected in hydrological conditions

implications of the saltation abrasion bedrock incision model for steady state river longitudinal profile relief and concavity the saltation abrasion model predicts rates of river incision into bedrock as an explicit function of sediment supply grain size boundary shear stress and rock strength here we use this experimentally calibrated model to explore the controls on river longitudinal profile concavity and relief for the simple but illustrative case of steady state topography over a wide range of rock uplift rates we find a characteristic downstream trend in which upstream reaches are close to the threshold of sediment motion with large extents of bedrock exposure in the channel bed while downstream reaches have higher excess shear stresses and lesser extents of bedrock exposure profile concavity is most sensitive to spatial gradients in runoff and the rate of downstream sediment fining concavity is also sensitive to the supply rate of coarse sediment which varies with rock uplift rate and with the fraction of the total sediment load in the bedload size class variations in rock strength have little influence on profile concavity profile relief is most sensitive to grain size and amount of runoff rock uplift rate and rock strength influence relief most strongly for high rates of rock uplift analysis of potential covariation of grain size with rock uplift rate and rock strength suggests that the influence of these variables on profile form could occur in large part through their influence on grain size similarly covariation between grain size and the fraction of sediment load in the bedload size class provides another indirect avenue for rock uplift and strength to influence profile form copyright 2008 john wiley sons ltd

a methodology for calculating the spatial distribution of the area slope equation and the hypsometric integral within a catchment 1 the area slope relationship and the hypsometric curve are well known catchment descriptors the main shortcoming of traditional area slope and hypsometry extraction methods is their limited ability to represent heterogeneity within the catchment here we present a new methodology for explicit calculation of the spatial distribution at a pixel scale within a catchment of the area slope parameters and the hypsometric integral this method allows us to create a quantitative representation of the area slope equation and the hypsometric integral which can potentially be used in a variety of geomorphologic applications the results show that the spatial distribution of both the area slope equation and the hypsometric integral are noisy at the pixel scale in order to reduce the noise three averaging techniques were examined subcatchment scale averaging was found to be the best at identifying the spatial distribution of the area slope equation and hypsometric integral at the subcatchment scale the spatial distribution of the area slope equation and the hypsometric integral approximated the spatial distribution of soil morphological and geological units of the goulburn river catchment in eastern australia the spatially distributed area slope results were tested using manually extracted subcatchment average area slope values and found to be well correlated the spatially distributed hypsometric integral was also well correlated with landform concavity and convergence the subcatchment scale averaging of the spatially distributed area slope equation and hypsometric integral is shown to be a promising tool for producing spatially distributed data the techniques are demonstrated on a catchment that has marked spatial variation in soils and geology the results show that the spatially explicit maps can potentially identify the spatial extent of these soil types and geological features and agrees well with existing soil maps

origin of the martian global dichotomy by crustal thinning in the late noachian or early hesperian the marked dichotomy in topography surface age and crustal thickness between the northern lowland and southern upland of mars has been explained as due to an initially inhomogeneous crust a single mega impact event several overlapping large basin impacts and first order convective overturn of the martian mantle all of the published hypotheses propose that the dichotomy was formed early in martian history before the end of the primordial heavy bombardment a primordial origin is inherent in the initial crustal inhomogeneity hypothesis and required for both impact hypotheses endogenic hypotheses are not so constrained geological data indicate episodes of fracturing and faulting in the late noachian and the early hesperian this fracturing and faulting occurred primarily within the northern lowland and along the boundary between lowland and highland igneous activity also peaked in the late noachian and early hesperian these data suggest a tectonic event near the noachian hesperian boundary characterized by enhanced heat loss and extensive fracturing including formation of the faults that define much of the highland lowland boundary we argue that the major result of this tectonic event was formation of the dichotomy by thinning of the crust above a large convection cell or plume

continuous 60 year stable isotopic and earth alkali element records in a modern laminated tufa jaruga river krka croatia implications for climate reconstruction abstract a continuous 60 year record 1938 1998 of stable isotope compositions of carbon and oxygen as well as trace metal mg sr ba concentrations in a laminated calcite crust precipitated in a short artificial tunnel on a non equilibrium groundwater fed karstic river is presented chemical and isotopic records have been compared to hydrometeorological data available for the last 48 years an attempt is made to relate isotopic and geochemical variations in the crust to environmental parameters such as temperature precipitation and changes in vegetation cover as well as to postdepositional recrystallisation of the older crust material isotopic composition of the crust is largely influenced by non equilibrium precipitation which favours the incorporation of isotopically depleted c and o into the carbonate furthermore because of the complicated hydrological situation there is no observable correlation between the stable oxygen isotope composition of water and temperature the result is that the 18 o isotopic thermometers overestimate the measured precipitation temperatures temperatures calculated from mg ca ratios of water and the carbonate match the 18 o palaeotemperatures within 2 4 c in the older part of the crust precipitated before the onset of industrial pollution of the river it was demonstrated that the application of mg palaeothermometry in natural systems where the mg ca ratio of water is influenced not only by temperature but also by other environmental parameters such as precipitation surface runoff groundwater retention time and anthropogenic influences is subject to a large uncertainty up to 10 c

channel network simulation models compared with data from the ashley river new zealand this paper compares the ability of two channel network simulation models to simulate the channel network properties of the ashley river in the foothills of the southern alps of the south island of new zealand the basin was chosen because it contains a large scale topographic feature a central ridge the simulation of which would provide a measure of each model s ability to handle spatial nonuniformities the two models assessed were the optimal channel network ocn model and a catchment evolution model siberia catchment evolution model the ability of these models to replicate observed geomorphic statistics and relationships was assessed the models were also compared against each other to assess their relative suitability for simulating the observed geomorphology model performance was gauged using the single valued measures of catchment convergence hypsometric integral and energy expenditure by the network and plots of the width function the slope of the cumulative area diagram and the hypsometric curve of basin topography the effects of different forcings were examined the basic forcing was one in which the climate and the geological and tectonic properties of the basin were assumed to be unchanging in both space and time the first variant on the basic forcing looked at what happens when there is a permanent spatial gradient in the rainfall over a basin with spatially uniform geological and tectonic properties the second variant considered the effects of constant spatially uniform rainfall on a basin in which spatially variable tectonic uplift is occurring neither model adequately simulated the observed geomorphology when the spatially nonuniform tectonic forcing was ignored when spatially nonuniform tectonic effects at length scales of tens of kilometers were simulated siberia performed more satisfactorily the effect of nonuniform rainfall was found to be small for both models the performance of the ocn as gauged by single valued measures improved markedly when energy expenditure calculations were consistent with the geometric length of flow paths

stable isotopic and elemental characteristics of recent tufa from a karstic krka river south east slovenia useful environmental proxies tufa samples from 16 consecutive barrages along a 13 km section of a groundwater fed krka river slovenia were analysed for their petrographical mineralogical elemental and stable carbon 13c and oxygen 18o isotope composition to establish their relation to current climatic and hydrological conditions waters constantly oversaturated with calcite and the steep morphology of the krka riverbed stimulate rapid co2 degassing and subsequent tufa precipitation the carbon isotope fractionation 13c between dic and tufa in the krka river evolves toward isotopic equilibrium being controlled by continuous co2 degassing and tufa precipitation rate downstream the 13c increased from 1 9 to 2 5 vienna peedee belemnite however since tufa precipitation rates remain similar downstream the major controlling factor of carbon isotope exchange is most probably related to the continuous 12co2 degassing downstream leaving the carbon pool enriched in 13c in the case of oxygen the isotope fractionation was found to be from 1 0 to 2 3 smaller than reported in the literature the observed discrepancies are due to different precipitation rates of calcite deposits as krka tufas on cascades grow relatively faster compared to slowly precipitated calcite deposits in cave or stream pools due to non equilibrium oxygen isotope exchange between krka tufa and water the 18o proxy showed from 1 2 to 8 2 c higher calculated water temperatures compared to measured water temperatures demonstrating that 18o proxy based temperature equations are not reliable for water temperature calculations of fast growing tufa on cascades because mg is bound to the terrigenous dolomite fraction in the krka tufa samples the mg ca was also found to be an unreliable temperature proxy yielding over up to 20 c higher calculated water temperatures this article is protected by copyright all rights reserved

stable isotope characterisation of recent aragonite travertine deposits associated with the fitero thermal waters spain the travertines of the fitero thermal springs with more than 98 of aragonite in most of the samples are studied in this paper the main objective is to improve the general understanding of aragonite precipitation since the deposits of almost pure aragonite are very scarce this study presents a complete mineralogical and isotopic characterisation including the evaluation of the 18o and 13c fractionation during precipitation as valuable information for paleoclimate and paleoenvironmental studies samples of a laminated travertine deposit constituted by almost pure aragonite were taken from a pipe discharging water at 40 c waters suffered an important co2 outgassing as suggested by the geochemical calculations and the 13c values of travertines and waters this outgassing triggers the oversaturation and precipitation of carbonate phases temperature seems to be the main factor controlling the precipitation of aragonite or calcite as checked by studying another travertine sample with higher calcite content various 18o isotope fractionation equations for aragonite and calcite were used the results indicate that precipitation took place close to equilibrium according to some of these equations the fact that the equilibrium is maintained in a natural system with an important co2 loss is surprising however it can be explained by an hco3 water oxygen isotopic equilibrium and a direct transfer of the hco3 isotope signal to the carbonate without fractionation due to the fast co2 loss and precipitation finally considering other natural aragonite samples a fractionation equation is defined for natural aragonite in the temperature range between 23 and 80 c

the use of a landscape simulator in the validation of the siberia landscape evolution model transient landforms siberia is a physically based model for the geomorphic evolution of landforms it is essential that the siberia model be tested or validated against controlled landform development previous studies have demonstrated that siberia is able to simulate declining equilibrium landforms and in this paper we examine siberia s ability to simulate landforms as they evolve to their declining equilibrium form these landscapes are termed transient landforms landscapes generated by siberia were compared to those produced by a physical model experimental model landforms at stages of evolution comparison of the experimental landscapes with the simulated landscapes using total mass hypsometric curve width function cumulative area distribution and area slope demonstrate that siberia can simulate the experimental model landscape during development i e transient landscapes copyright 2002 john wiley sons ltd

the interaction between hydrology and geomorphology in a landscape simulator experiment an experimental landscape simulator has been developed which uses a rainfall simulator to create overland flow and erosion the simulator uses rainfall sprinklers that eliminate rainsplash and an artificial soil which has little cohesion experimental landscapes developed in the simulator evolved according to howard s headward growth model elements of glock s model could be identified during evolution i e initiation and maximum extension but other stages of this model were not observed i e extension and integration the horton concept of cross grading and micropiracy and stream piracy was not observed despite the dominance of overland flow nor the groundwater headward growth mechanism proposed by dunne the latter due to experimental design which eliminated any perched groundwater table the experimental apparatus produced model landscapes that are scaled down analogues of real world processes copyright 2001 john wiley sons ltd

speleothem calcite farmed in situ modern calibration of δ18o and δ13c paleoclimate proxies in a continuously monitored natural cave system abstract understanding the relationships between speleothem stable isotopes 13 c 18 o and in situ cave forcing mechanisms is important to interpreting ancient stalagmite paleoclimate records cave studies have demonstrated that the 18 o of inorganically precipitated low temperature speleothem calcite is systematically heavier than the 18 o of laboratory grown calcite for a given temperature to understand this apparent offset rainwater cave drip water groundwater and modern naturally precipitated calcite farmed in situ were grown at multiple locations inside hollow ridge cave in marianna florida high resolution micrometeorological air chemistry time series and ventilation regimes were also monitored continuously at two locations inside the cave supplemented with periodic bi monthly air gas grab sample transects throughout the cave cave air chemistry and isotope monitoring reveal density driven airflow pathways through hollow ridge cave at velocities of up to 1 2 m s 1 in winter and 0 4 m s 1 in summer hollow ridge cave displays a strong ventilation gradient in the front of the cave near the entrances resulting in cave air that is a mixture of soil gas and atmospheric co 2 a clear relationship is found between calcite 13 c and cave air ventilation rates estimated by proxies pco 2 and 222 rn calcite 13 c decreased linearly with distance from the front entrance to the interior of the cave during all seasons with a maximum entrance to interior gradient of 13 c caco3 7 a whole cave hendy test at multiple contemporaneous farming sites reveals that ventilation induces a 1 9 0 96 13 c offset between calcite precipitated in a ventilation flow path and calcite precipitated on the edge or out of flow paths this interpretation of the hendy test has implications for interpreting 13 c records in ancient speleothems calcite 13 c caco3 may be a proxy not only for atmospheric co 2 or overlying vegetation shifts but also for changes in cave ventilation due to dissolution fissures and ceiling collapse creating and plugging ventilation windows farmed calcite 18 o was found to exhibit a 0 82 0 24 offset from values predicted by both theoretical calculations and laboratory grown inorganic calcite unlike 13 c caco3 oxygen isotopes showed no ventilation effects i e 18 o caco3 appears to be a function of growth temperature only although we cannot rule out a small effect of unmeasured gradients in relative humidity evaporation accompanying ventilation our results support the findings of other cave investigators that water calcite fractionation factors observed in speleothem calcite are higher that those measured in laboratory experiments cave and laboratory calcite precipitates may differ mainly in the complex effects of kinetic isotope fractionation combining our data with other recent speleothem studies we find a new empirical relationship for cave specific water calcite oxygen isotope fractionation across a range of temperatures and cave environments 1000 ln 16 1 10 3 t 1 24 6 with a fractionation temperature dependence of 18 o t 0 177 c lower than the currently accepted 0 206 c

chemical and stable isotope composition of recent hot water travertines and associated thermal waters from egerszalok hungary depositional facies and non equilibrium fractionation abstract combined petrographical mineralogical geochemical and stable isotope analyses were conducted on an actively forming egerszalok travertine mound to determine the factors that govern carbonate precipitation and thus influence the use of travertines in paleoclimate reconstruction stable isotope analyses of oxygen carbon and hydrogen demonstrate both biological and abiological factors to control travertine deposition processes of morphology related outgassing had major effects upon isotopic composition continuous co 2 degassing and temperature change of the thermal water between the spring orifice and distal parts of the system caused stable carbon and oxygen isotope compositions of the precipitating travertines to increase from 2 7 to 4 3 relative to v pdb and from 10 5 to 14 7 relative to v smow respectively the travertines at the spring orifice t 67 c are composed of almost pure calcite with a 13 c value of 2 7 relative to v pdb enabling classification as intermediate between thermometeogene and thermogene in lower temperature water away from the spring orifice various amounts of aragonite 5 35 with higher sr concentrations precipitate from solution this phenomenon is exceptional in hot spring carbonate deposits and could be explained by fast carbonate precipitation due to the morphology related outgassing oxygen and hydrogen isotope measurements of the thermal water confirmed evaporation to be causing limited kinetic isotope fractionation however 18 o values of the travertine do show isotope shifts away from the equilibrium fractionation curve which is most probably related to the rapid calcite precipitation and transportation along the flow path our data closely follow the temperature 18 o calcite water relationship observed for other travertine localities this is slightly displaced from the experimental curve and determines an empirical travertine curve our study shows that this shift may result in an approximately 8 c difference in paleotemperature calculations depending upon which fractionation curve is used

oxygen isotope fractionation in travertine depositing pools at baishuitai yunnan sw china effects of deposition rates abstract travertine 18o values can be used to reconstruct paleo temperatures if the oxygen isotope fractionation factors between travertine and water are accurately understood for this purpose the 18o values of pool travertine and its parent water and the deposition rates of the calcite were investigated at baishuitai yunnan sw china over the course of the full hydrological year april 23 2006 april 25 2007 the results show that the travertine water isotope fractionation factors are close to the commonly accepted equilibrium line of kim and o neil 1997 this differs from the results obtained by yan et al 2012 who found that the oxygen isotope fractionation factors in the travertine depositing pools were close to the line suggested as equilibrium relationship by coplen 2007 the average calcite deposition rate 2 30 mg cm 2 d 1 in the present study is six times larger than that 0 38 mg cm 2 d 1 in yan et al 2012 if slower calcite precipitation leads to equilibrium oxygen isotopic fractionation then the results of this study support the results of coplen 2007 that indicate that the equilibrium fractionation factor may be greater than the commonly accepted one derived by kim and o neil 1997 the relationship between oxygen isotope fractionation factor and calcite deposition rate in our study also agrees with the results of dietzel et al 2009 who found that the kinetic isotope effect favors preferential incorporation of 16o in solid calcite as the calcite deposition rate increases there was a threshold for calcite precipitation rate control on oxygen isotopic equilibrium in our case of travertine depositing pools when the calcite deposition rate was lower than 0 38 mg cm 2 d 1 oxygen isotopic equilibrium between calcite and water was attained therefore calcite deposition rate is a potentially important consideration when using 18o in natural carbonates as a proxy for terrestrial and ocean temperature

geochemistry and stable isotopic composition of tufa waters and precipitates from the interlake region manitoba canada constraints on groundwater origin calcitization and tufa formation abstract new major trace and isotopic geochemical results from a regional study of springs discharging from the major carbonate rock aquifer in the interlake region of manitoba canada are used to understand water rock reactions timing of recharge discharge tufa formation processes and as baseline data spring waters are fresh with total dissolved solids tds concentrations ranging from 150 to 880 mg l waters discharging in the northern part of the study area have lower tds are dominantly ca mg hco3 waters with low so4 concentrations

seasonal variation in water chemistry and depositional processes in a tufa bearing stream in sw japan based on 5 years of monthly observations abstract annually laminated freshwater carbonate tufa is a potential source of high resolution terrestrial paleoclimate data in order to understand the processes and characteristics of climate information recorded in tufa the chemical components of carbonate rich water its flow rate and soil pco2 were recorded monthly during a 5 year period december 1997 to december 2002 at shimokuraida niimi city okayama prefecture sw japan water issues from a limestone cave there flows along a 450 m long stream and deposits tufa that commonly exhibits distinct annual laminations among observed properties the co2 partial pressures in the soil and the spring water show the clearest seasonal patterns which are similarly high in summer autumn and low in winter spring the spring water pco2 partly reflects soil pco2 but is controlled by another temperature dependent process natural ventilation between the subsurface and the atmosphere the concentration of dissolved caco3 does not mirror the seasonal pattern of spring water pco2 but is largely influenced by rainfall dilution the development of annual laminations results from seasonal changes in the depositional rate of caco3 which was faster from summer to autumn and slower from winter to spring this seasonal pattern is initially controlled by relatively regular changes in water temperature and flow rate both of which correlated positively with the calcite precipitation rate high calcite precipitation in summer autumn formed a densely calcified texture whereas a precipitation low rate winter spring formed a porous texture changes in the concentrations of minor dissolved components mg2 na k cl no3 so42 and sio2 exhibited no seasonal pattern because the amplitude of the mg ca change is very high at shimokuraida the mg ca ratio of tufa calcite does not reflect paleotemperatures while mg ca ratio of water does not correspond to rainfall intensity too

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

mg ca ratios in freshwater microbial carbonates thermodynamic kinetic and vital effects the ratio of magnesium to calcium mg ca in carbonate minerals in an abiotic setting is conventionally assumed to be predominantly controlled by mg ca solution and a temperature dependant partition coefficient this temperature dependence suggests that both marine e g foraminiferal calcite and corals and freshwater e g speleothems and surface freshwater deposits tufas carbonate deposits may be important archives of palaeotemperature data however there is considerable uncertainty in all these settings in surface freshwater deposits this uncertainty is focussed on the influence of microbial biofilms biogenic or vital effects may arise from microbial metabolic activity and or the presence of extracellular polymeric substances eps this study addresses this key question for the first time via a series of unique through flow microcosm and agitated flask experiments where freshwater calcite was precipitated under controlled conditions these experiments reveal there is no strong relationship between mg ca calcite and temperature so the assumption of thermodynamic fractionation is not viable however there is a pronounced influence on mg ca calcite from precipitation rate so that rapidly forming precipitates develop with very low magnesium content indicating kinetic control on fractionation calcite precipitation rate in these experiments where the solution is only moderately supersaturated is controlled by biofilm growth rate but occurs even when light is excluded indicating that photosynthetic influences are not critical our results thus suggest the apparent kinetic fractionation arises from the electrochemical activity of eps molecules and are therefore likely to occur wherever these molecules occur including stromatolites soil and lake carbonates and via colloidal eps speleothems

oxygen isotopes in meteoric calcite cements as indicators of continental paleoclimate because meteoric water 18 o values decrease with decreasing ambient temperature and increasing latitude 18 o values of meteoric calcite cement should exhibit a similar relation with paleolatitude and be an indicator of continental paleotemperatures to test this we compiled isotopic and paleolatitude data for 20 meteoric cements and nine speleothems ranging in age from devonian to modern and in paleolatitude from 3 5 to 83 mean 18 o values for meteoric cements and speleothems both show the same negative correlation with paleolatitude the 18 o vs latitude trend for these carbonates is almost identical to that predicted for modern inland environments but differs from the trend for coastal environments this suggests that the ground water controlling the ultimate composition of meteoric cement is derived predominantly from inland recharge if it is assumed that the modern meteoric water 18 o vs temperature relation is valid for the past and that insignificant evaporation occurred prior to carbonate precipitation then coastal and inland paleotemperatures can be calculated from the 18 o values of meteoric calcite 18 o mcl and seawater 18 o sw by using the equations t coastal 13 3 32 6 0 231 0 0613 18 o mcl 18 o sw and t inland 17 8 16 2 0 572 0 1233 18 o mcl 18 o sw where t is temperature in c calcite precipitated from coastal meteoric water at temperatures between 0 and 25 c will exhibit a narrow range in 18 o 6 to 4 where 18 o sw 0 the 18 o of calcite precipitated from inland meteoric water will be sensitive to paleotemperature ranging from 14 to 5 where 18 o sw 0 for temperatures of 0 to 25 c

use of 13c to trace origin and cycling of inorganic carbon in the rhone river system dissolved inorganic carbon dic and particulate inorganic carbon pic were sampled at 20 sites on the rhone and its main tributaries from switzerland to the mediterranean in march september and july flood event 1996 flux estimation and dic and pic values are used to trace watershed inputs and fluvial processes affecting the inorganic carbon budget dic concentration and values vary between 1 mm at 5 near the rhone s source and 3 mm at 10 near its mouth with tributaries draining lowland carbonate dominated areas at 3 8 mm and 11 there is an inverse relationship between river dic concentration and dic the headwaters are characterized by high dic values and low dic indicating a minor input of respired co2 dic should be mainly produced through the reaction of carbonate with atmospheric co2 or organic sulfuric acids in lowland carbonate dominated areas values of 11 are consistent with production of dic by weathering of limestone c 1 with co2 derived from the oxidation of organic matter 21 5 the evolution of the rhone s dic concentration and appear to be largely determined by mixing between the rhone and its main tributaries the co2 fluxes and dic mass balance calculated for the different segments of the rhone point to a net but very limited input of fluvial respired co2 from the oxidation of organic c 5 the pic represents a small but quite variable fraction of the inorganic carbon 3 except on alpine catchments and during floods in these cases it can be up to 10 of the dic concentration and export the carbon and oxygen isotopic composition of pic from the rhone during a flood and from alpine tributaries falls within the range of limestones 2 6 relatively light pic isotopic composition indicate mixing of sedimentary rocks and carbonate precipitated in situ data for the rhone system are typical of watersheds presenting high chemical weathering rates for hco3 and alpine lowland conditions

use of a landscape simulator in the validation of the siberia catchment evolution model declining equilibrium landforms this paper presents a study to test the ability of the current generation of landscape evolution models to correctly predict landscape form from measured erosion processes landscapes generated by the siberia landscape evolution model were compared to experimental model landscapes in declining equilibrium the model simulations were compared using geomorphologically and hydrologically significant parameters comparisons of the simulated landscapes with the experimental landscapes were carried out using the hypsometric curve width function cumulative area distribution and area slope relationship these comparisons demonstrate that siberia can correctly simulate the experimental model landscape at declining equilibrium the simulation showed sensitivity to the spatial distribution of the rainfall particularly with respect to hypsometry using the correct measured distribution of rainfall was necessary rather than using a spatially uniform rainfall distribution the results also highlighted the importance of digital terrain map dtm error in deriving geomorphic statistics the observed landform had a consistently larger width function than the simulation only when the simulations were corrupted with elevation errors with statistical properties of the errors in the experimental landscape dtm as measured by photogrammetry did the observed and simulated width functions match

geomorphological theory of the hydrological response the geomorphological theory of the hydrological response originated by rodriguez iturbe and valdes is reviewed with reference to the general framework of the formulation of transport processes by travel time distributions this review by no means exhaustive of the publications on this subject collects in a reasonably organic manner some relevant theoretical developments and a few significant applications

effects of vertical resolution and map scale of digital elevation models on geomorphological parameters used in hydrology the advent of digital elevation models dems has made it possible to objectively extract calculate and store geomorphological parameters for hydrological modelling at several scales for a grid based dem the threshold area used to extract the channel network is analogous to the scale of the map produced in addition to the map scale the effects of the vertical resolution of the dem on some frequently used geomorphological parameters in hydrology are examined using high resolution dems of two natural and two artificial catchments the vertical resolution was varied between 1 cm and 1 m the most common vertical resolution of dems at a fixed map scale the mean absolute percentage error in the geomorphological parameters caused by a decrease in vertical resolution is within the range 0 5 for the medium sized catchments and 0 10 for the small catchments studied although it is true that a change in vertical resolution may cause a change in the individual pixel slope area and topographic index area slope particularly in low relief terrain their cumulative distributions do not show any significant change with the vertical resolution the shape of the normalized width function is not very sensitive to the vertical resolution and the map scale for small catchments order change may occur at different map scales for the different vertical resolution dems of the same catchment causing a significant change in order related parameters such as horton ratios it is suggested that the vertical resolution of the dem of a catchment be considered satisfactory for most hydrological applications if the ratio of the average drop per pixel and vertical resolution is greater than unity this ratio criterion could be used to define the minimum pixel area for reliable channel network definition for any given vertical resolution the minimum pixel area places a lower bound on the horizontal resolution with which a channel network can be extracted from a dem these results could potentially be used to assess the adequacy for hydrological purposes of existing and proposed digital elevation databases

new insights into biological influence on the geochemistry of freshwater carbonate deposits abstract ambient temperature freshwater carbonates tufas have outstanding potential as palaeoclimate archives however it has proven difficult to constrain the behaviour of the geochemical parameters on which important proxy systems rely current thinking on the development of trace element ratios in tufa rests upon an assumption of precipitation driven by degassing of co2 with the final precipitate being in equilibrium with ambient river water this study provides evidence that although supersaturation is largely regulated by degassing precipitation in sterile flowing systems does not occur throughout the air water interface but only at lines of intersection between this interface and a solid surface precipitation at the bottom as is normal in river sites is not found to occur however when benthic microbial communities biofilms are present extensive precipitation does occur within them in preference and or addition to that at the air water interface precipitation is therefore not purely a consequence of degassing and some microbiological influence is necessary to generate precipitates analogous to nature we further investigate whether these biofilms alter the behaviour of trace elements within tufa systems in addition to modulating the sites and mechanisms of precipitation via a series of experiments biofilms are shown to accumulate large inventories of calcium and other dissolved ions ba sr and mg and we demonstrate that this process is chemoselective in favour of ions with low charge densities these observations have consequences for interpretation of trace element records from tufas based on an assumption of equilibrium with river water and also for other carbonate deposits associated with biofilm activity travertines marine stromatolites lacustrine and soil carbonates speleothems conversely our study provides new insight into the reasons for discrepancy of tufa mg ca ratios from expectation and thus provides encouragement for the potential of mg ca palaeothermometry in freshwater carbonate systems

gully position characteristics and geomorphic thresholds in an undisturbed catchment in northern australia gullying is a significant process in the long term dynamics and evolution of both natural and rehabilitated i e post mining landscapes from a landscape management perspective it is important that we understand gully initiation and development as it is well recognized that catchment disturbance can result in the development of gullies that can be very difficult to rehabilitate this study examines gully position using geomorphic statistics relating to features such as depth width and length in a catchment undisturbed by european activity in the northern territory australia the results demonstrate that gullying occurs throughout the catchment and that a slope area threshold does not exist and that gully position broadly follows the catchment area slope relationship simple relationships relating catchment area and slope to gully depth width and length provide poor results despite these relationships having been found to apply for ephemeral gullies in cropland the results suggest that gully initiation thresholds are low as a result of an enhanced fire regime a threshold model for gully position that uses catchment area and slope to switch between gully and hillslope was evaluated and found broadly to capture gully position copyright 2006 john wiley sons ltd

temperature dependence of oxygen and clumped isotope fractionation in carbonates a study of travertines and tufas in the 6 95 c temperature range conventional carbonate water oxygen isotope thermometry and the more recently developed clumped isotope thermometer have been widely used for the reconstruction of paleotemperatures from a variety of carbonate materials in spite of a large number of studies however there are still large uncertainties in both 18o and 47 based temperature calibrations for this reason there is a need to better understand the controls on isotope fractionation especially on natural carbonates in this study we analyzed oxygen carbon and clumped isotopes of a unique set of modern calcitic and aragonitic travertines tufa and cave deposits from natural springs and wells together these samples cover a temperature range from 6 to 95 c travertine samples were collected close to the vents of the springs and from pools and tufa samples were collected from karstic creeks and a cave the majority of our vent and pool travertines and tufa samples show a carbonate water oxygen isotope fractionation comparable to the one of tremaine et al 2011 with some samples showing higher fractionations no significant difference between the calcite water and aragonite water oxygen isotope fractionation could be observed the 47 data from the travertines show a strong relationship with temperature and define the regression 47 0 044 0 005 106 t2 0 205 0 047 the ph of the parent solution mineralogy and precipitation rate do not appear to significantly affect the 47 signature of carbonates compared to the temperature effect and the analytical error the tufa samples and three biogenic calcites show an excellent fit with the travertine calibration indicating that this regression can be used for other carbonates as well this work extends the calibration range of the clumped isotope thermometer to travertine and tufa deposits in the temperature range from 6 c to 95 c

modelling geomorphic response to environmental change in an upland catchment in the uk s upland catchments river terraces and alluvial features indicate a history of periodic aggradation and degradation linked to holocene changes in land use primarily deforestation and climate change altering flood frequency and magnitude although both factors are important calculating their individual effects is complicated by the likelihood of their concurrent alteration to investigate the relative impacts of land use and climate change a cellular model is applied to the upland catchments of cam gill beck above starbotton north yorkshire this is divided into 1 million 2 m by 2 m grid cells to which a range of process laws are applied these include approximate expressions for mass movement rates soil creep the influence of vegetation and hillslope hydrology as well as fluvial erosion and deposition in ten grain size fractions this provides a good representation of valley floor geometry while retaining a fully dynamic interaction with the surrounding valley sides previous applications of this model have shown the detailed formation of bars and berms as well as examples of braiding avulsion and channel range running on a silicon graphics origin 2000 computer an ensemble of simulations were completed bracketing a wide range of environmental scenarios involving changes in flood frequency magnitude and vegetation cover over time scales ranging from 10 to 100 years these showed that decreasing tree cover and increasing rainfall magnitude individually produced similar 25 to 100 increases in sediment discharge whereas in combination they generated a 1300 rise furthermore channels formed by the model in response to increased rainfall magnitudes are located where relic channels are found in cam gill beck implying that these are the products of previous periods of high rainfall magnitudes copyright 2000 john wiley sons ltd

climatic change recorded by stable isotopes and trace elements in a british holocene tufa combined stable isotope d18o and d13c and trace element mg sr geochemistry from bulk tufa calcite and ostracod shell calcite from an early holocene british tufa reveal clear records of holocene palaeoclimatic change variation in d18o is caused principally by change in the isotopic composition of holocene rainfall recharge itself caused mainly by change in air temperature the d13c variability through much of the deposit reflects increasing influence of soil zone co2 owing to progressive woodland soil development bulk tufa mg ca and sr ca are controlled by their concentrations in the spring water importantly mg ca ratios are not related to d18o values and thus show no temperature dependence first order sympathetic relationships between d13c values and mg ca and sr ca are controlled by aquifer processes residence times co2 degassing and calcite dissolution reprecipitation and probably record intensity of palaeorainfall recharge effects stable isotope records from ostracod shells show evidence of vital effects relative to bulk tufa data the ostracod isotopic records are markedly spiky because the ostracods record snapshots of relatively short duration years whereas the bulk tufa samples record averages of longer time periods probably decades the d18o record appears to show early holocene warming a thermal maximum at ca 8900 cal yr bp and the global 8200 yr bp cold event combined d13c mg ca and sr ca data suggest that early holocene warming was accompanied by decreasing rainfall intensity the mg ca data suggest that the 8200 yr bp cold event was also dry warmer and wetter conditions were re established after the 8200 yr bp cold event until the top of the preserved tufa sequence at ca 7100 cal yr bp

landscape evolution valley excavation and terrace development following abrupt postglacial base level fall many high latitude fluvial systems are adjusting to base level changes since the last glaciation channels that experienced base level fall may still be incising often through glacial diamictons tills these tills can be quite competent behaving more like weak bedrock than unconsolidated sediment and erode at a fast pace thus providing a unique opportunity to test models of channel incision and knickpoint migration in transient systems here we integrate light detection and ranging lidar topography strath terrace chronology and numerical modeling to determine knickpoint migration and incision history of the le sueur river in central minnesota usa results indicate that the le sueur river is best modeled as a detachment limited channel with downstream coarsening related to lag clasts from tills playing a critical factor in longitudinal profile development the le sueur river meanders as it incises so we coupled the best fit incision model to a meander model to determine valley excavation history the excavation history was used to determine a natural background erosion rate prior to land use changes associated with settlement and agricultural expansion in the mid 1800s we compared background fine sediment silt and clay erosion rates with historic decadal average annual suspended loads results show that modern fine sediment contributions from sources associated with valley excavation are three times higher than modeled presettlement loads recent changes in hydrology associated with land use and climate change have increased flows in rivers leading to higher sediment loads not just from field erosion but from increased bank and bluff erosion in the deeply incised valleys

a physical explanation for an observed area slope elevation relationship for catchments with declining relief a general relationship between the contributing area slope and mean elevation of catchments with relief declining after a tectonic uplift event is presented this relationship is based on the continuity equation for runoff and erosion processes in the catchment the key hypothesis underlying this relationship is that as a catchment declines the nondimensionalized catchment approaches a constant form this hypothesis is verified for computer simulated catchments the area slope elevation relationship covers several cases catchments declining toward a peneplain catchments declining from a high slope dynamic equilibrium resulting from a high rate of tectonic uplift to a low slope one resulting from a lower rate of tectonic uplift and catchments declining from an elevated initial condition as for example in the decline of a mine spoil heap a previously published relationship between slope and area for catchments in dynamic equilibrium and based on runoff and erosion physics is shown to be a special case of this general relationship the new area slope elevation relationship is compared with data from simulated catchments and a field catchment it is thus shown that for declining catchments the area slope elevation relationship is a good predictor of catchment form for catchments with declining relief it is argued that the slope area elevation relationship is sufficient with the planiform drainage pattern to completely define the elevation properties of the catchment such as for instance the hypsometric curve

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

results from a new model of river basin evolution this paper briefly describes a model of the erosional development of catchments and their channel networks the model differentiates between the dominant transport processes in hillslope and channels the development of channels and hillslopes occurs in an integrated manner as a function of physically observable mechanisms the growth of a river basin is qualitatively described the model concepts are used to study the basin during periods of growth transient periods as well as during dynamic equilibrium this leads to hypotheses about the relationship between slopes relief tectonic uplift erodability runoff and catchment area it is shown that the model leads to very reasonable and desirable behaviour of hillslopes during retreat and degradation

interglacial growth of tufa in croatia tufa samples from the krka river area in croatia were dated by 14c and 230th 234u methods the study area is situated in the karst region of the southern dinarides 14c ages of 40 tufa samples collected at the waterfalls coincide with the early holocene interglaciation up to 6000 14c yr b p comparison of conventional 14c dates of holocene tufa and those of speleothems in the dinaric karst shows that speleothem formation started several thousand years earlier than tufa growth samples of old tufa deposits from the krka river 17 and plitvice lakes 12 area and speleothem samples from caves in dinaric karst 5 yield 34 230th 234u dates most of which cluster around interglacial marine 18o stage 5 21 eight of 13 older dates belong to interglacial stages 7 and 9 only 5 dates fall within stage 6 and 8 glaciations 230th 234u dates of speleothems and tufa samples from central europe have indicated that these were formed preferentially during warm and humid interglacial and interstadial periods and it appears that this is true of southern croatia as well stable isotope 13c 18o analyses of 40 tufa samples from the krka river area were compared with stable isotope analyses of tufa from the plitvice lakes area the 13c values for both locations are similar and range from 10 to 6 indicating similar conditions of tufa formation a systematic difference between the 18o values of tufa in these two areas reflects the regional distribution of the oxygen composition of precipitation

revisiting the hypsometric curve as an indicator of form and process in transport limited catchment hypsometry has historically been used as an indicator of geomorphic form of catchments and landforms yet there has been little work aimed at relating hypsometry to landform process and scale this paper uses the siberia catchment evolution model to explore linkages between catchment process and hypsometry siberia generates results that are qualitatively and quantitatively similar to observed hypsometric curves for physically realistic parameters however we show that not only does the hypsometry reflect landscape runoff and erosion process but it is strongly dependent on channel network and catchment geometry we show that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve though little on the hypsometric integral for landforms dominated by fluvial sediment transport the classic strahler mature hypsometric curve is only generated for catchments with roughly equal width and length narrow catchments show a hypsometric curve more similar to strahler s monadnock form for landscapes dominated by diffusive transport the simulated hypsometric curve is concave down everywhere this being consistent with curves reported for some example catchments in france because the transition between diffusive dominance to fluvial is scale dependent with larger catchments exhibiting greater fluvial dominance then the hypsometric curve is a scale dependent descriptor of landforms experimental results for simulated landforms from a small scale rainfall erosion simulator are reported it is shown that siberia yields satisfactory fits to the data confirming its ability to predict the form of the hypsometric curve from a simple model of geomorphic processes 1998 john wiley sons ltd

a physical explanation of an observed link area slope relationship an observed log log linear relationship between channel slope and contributing area is explained by the erosional physics that lead to catchment form it is postulated that tectonic uplift is in balance with the fluvial erosion down wasting that dominates catchment erosion and it is shown that this relationship results in the observed log log linear relationship at dynamic equilibrium in addition it has been observed that there are deviations from this log log linear relationship near the catchment divide with observed slopes being lower than those predicted from the relationship this is explained by noting that for small areas fluvial erosion effects are dominated by soil creep and rain splash modeled by diffusive physics the area at which this deviation from log log linearity occurs is that point on the hillslope at which diffusive physics like soil creep and rain splash begin to dominate fluvial erosion these predictions are confirmed by numerical simulations using a catchment evolution model

the impact of different gridding methods on catchment geomorphology and soil erosion over long timescales using a landscape evolution model many digital elevation models are gridded from irregularly spaced data this study examines differences in catchment geomorphology and hydrology as a result of kriging and delaunay triangulation gridding methods both methods have been widely used as tools for placing irregularly spaced data onto a regular grid in the past numerical modelling has been performed with little assessment of model input variability and the variability produced by different gridding methods has not been fully assessed given the importance of the impact of digital elevation model error and potential impact on model output little work has been done to understand the impact of this type of potential error examination of the different catchment realizations demonstrates that when using kriging point or block or delaunay triangulation there are subtle differences in catchment area and elevation as well as networking properties subtle differences also exist in hillslope profile nevertheless when comparing catchment descriptors such as the hypsometric curve area slope relationship and cumulative area distribution there is little hydrological and geomorphological difference between these catchments further when these digital elevation models are used as landscape input in a long term landscape evolution model i e siberia there is little geomorphological difference or hydrological difference between the two digital elevation models after a 50 000 year modelled period consequently either method is appropriate for the study catchment these findings provide confidence in the conversion of irregularly spaced data onto a regular grid using kriging or delaunay triangulation and that either method can be used copyright 2006 john wiley sons ltd

stable isotope variations in modern tropical speleothems evaluating equilibrium vs kinetic isotope effects applications of speleothem calcite geochemistry in climate change studies require the evaluation of the accuracy and sensitivity of speleothem proxies to correctly infer paleoclimatic information the present study of harrison s cave barbados uses the analysis of the modern climatology and groundwater system to evaluate controls on the c and o isotopic composition of modern speleothems this new approach directly compares the 18 o and 13 c values of modern speleothems with the values for their corresponding drip waters in order to assess the degree to which isotopic equilibrium is achieved during calcite precipitation if modern speleothems can be demonstrated to precipitate in isotopic equilibrium then ancient speleothems suitable for paleoclimatic studies from the same cave environment may also have been precipitated in isotopic equilib rium if modern speleothems are precipitated out of isotopic equilibrium then the magnitude and direction of the c and o isotopic offsets may allow specific kinetic and or equilibrium isotopic fractionation mechanisms to be identified carbon isotope values for the majority of modern speleothem samples from harrison s cave fall within the range of equilibrium values predicted from the combined use of 1 calcite water fractionation factors from the literature 2 measured temperatures and 3 measured 13 c values of the dissolved inorganic carbon of drip waters calcite samples range from 0 8 higher to 1 1 lower than predicted values the 13 c depletions are likely caused by kinetically driven departures in the fractionation between hco3 aq and caco3 from equilibrium conditions caused by rapid calcite growth 13 c enrichments can be accounted for by rayleigh distillation of the hco3 aq reservoir during degassing of 13 c depleted co2 modern speleothems from harrison s cave are not in o isotopic equilibrium with their corresponding drip waters and are 0 2 to 2 3 enriched in 18 o relative to equilibrium values 18 o variations in modern calcite are likely controlled by kinetically driven changes in the fractionation between hco3 aq and caco3 from equilibrium conditions to nonequilibrium conditions consistent with rapid calcite growth in contrast to 13 c 18 o values of modern calcite may not be affected by rayleigh distillation during degassing because co2 hydration and hydroxylation reactions will buffer the o isotopic composition of the hco3 aq reservoir if the effects of rayleigh distillation manifest themselves in the o isotopic system they will result in 18 o enrichment in the hco3

c and o stable isotope variability in recent freshwater carbonates river krka croatia three types of recent carbonate precipitates from the river krka croatia were analysed 1 bulk tufa from four main cascades in a 34 km long section of the river flow through the krka national park 2 a laminar stromatolite like incrustation formed in the tunnel of a hydroelectric power plant close to the lowest cascade and 3 recent precipitates collected on artificial substrates during winter spring and summer periods stable isotope compositions of carbon d 13 c and oxygen d 18 o in the carbonate and organic carbon d 13 corg were determined and compared with d 18 o of water and d 13 c of dissolved inorganic carbon dic the source of dic which provides c for tufa precipitation was determined from the slope of the line dic dic0 1 vs d 13 c dic dic dic0 sayles curry 1988 the d 13 c value of added dic was 13ae6 corresponding to the dissolution of co2 with d 13 c between 19ae5 and 23ae0 vienna pee dee belemnite vpdb the observed difference between the measured and calculated equilibrium temperature of precipitation of bulk tufa barriers indicates that the higher the water temperature the larger the error in the estimated temperature of precipitation this implies that the climatic signals may be valid only in tufas precipitated at lower and relatively stable temperatures the laminar crust comprising a continuous record of the last 40 years of precipitation shows a consistent trend of increasing d 13 c and decreasing d 18 o the lack of covariation between d 13 c and d 18 o indicates that precipitation of calcite was not kinetically controlled for either of the elements d 13 c and d 18 o of precipitates collected on different artificial substrates show that surface characteristics both of substrates and colonizing biota play an important role in c and o isotope fractionation during carbonate precipitation

climatic significance of seasonal trace element and stable isotope variations in a modern freshwater tufa abstract we present a continuous 14 yr long 1985 to 1999 high resolution record of trace element mg sr ba u and stable isotope 13c 18o variations in a modern freshwater tufa from northwestern queensland australia by utilizing the temperature dependence of the 18o signal an accurate chronology was developed for the sampled profile which allowed a comparison of the chemical records with hydrological and meteorological observations as a consequence it was possible to constrain the relevant geochemical processes relating climate variables such as temperature and precipitation to their chemical proxies in the tufa record temperatures calculated from the mg concentrations of the tufa samples provide close approximations of average annual water temperature variations furthermore we demonstrate that temporal changes in mg ca water can be estimated using an empirically derived equation relating mg ca water to the sr ba ratio measured in the tufa samples by means of this relationship it is theoretically possible to determine the mg ca ratio of paleowaters and hence to derive reliable estimates of former water temperatures from the mg concentrations of fossil tufas from the study area sympathetic variations in sr ba and 13c along the sampled profile record changes in water chemistry which are most probably caused by variable amounts of calcite precipitation within the vadose zone of the karst aquifer this process is thought to be markedly subdued whenever the amount of wet season precipitation exceeds a given threshold accordingly distinct minima in sr ba and 13c are interpreted to reflect years with above average rainfall the pronounced seasonal and annual variability of the u concentration along the profile is thought to primarily record changes in the u flux from the soil to the water table we suggest that during intensive rain events u is transported to the phreatic zone by complexing organic colloids giving rise to conspicuous u maxima in the tufa after above average wet seasons this study demonstrates the potential of freshwater tufas to provide valuable information on seasonal temperature and rainfall variations if tufa deposits turn out to be reasonably resistant to secondary processes combined investigation of speleothems and tufas from the same area could become a promising approach in future research while speleothems offer continuous records of long term paleoenvironmental changes tufas could provide high resolution time windows into selected periods of the past

metastability of liquid water on mars abstract a simple model of local heat transport on mars demonstrates that transient melting of ice may occur in depressions and gullies nearly anywhere on the planet where thin ice is illuminated by normal incidence insolation an experiment has been performed to confirm the model of evaporation rate at low pressure reduction of radiative cooling due to gully geometry is shown to be important since appropriate meteorological topographic and optical conditions may occur on slopes nearly anywhere on the planet hydrological features such as gullies would likely form only where such ice might accumulate notably in sheltered locations at high latitudes it is suggested that cold trapping of winter condensation could concentrate a sufficient amount of ice to allow seasonal melting in gullies

the production of digital elevation models for experimental model landscapes automated digital photogrammetry was used to produce digital elevation models of experimental model landscapes under controlled laboratory conditions as part of a series of rainfall erosion experiments looking at the evolution of landforms in response to erosion the method allowed the elevations of the experimental landscapes to be studied in great detail on a regular grid digital terrain map with relatively very little effort digital photogrammetry produced elevation data at a resolution of 6 mm with a standard deviation of 2 0 mm over an experimental catchment relief of approximately 200 mm this resolution is considerably better than that achievable by conventional manual photogrammetry the density of grid points was sufficiently high that small scale details such as knickpoints developing in channels were represented the method can facilitate the study of both experimental and natural landscapes in great detail copyright 2001 john wiley sons ltd

contrasts in variations of the carbon and oxygen isotopic composition of travertines formed in pools and a ramp stream at huanglong ravine china implications for paleoclimatic interpretations abstract water samples and modern endogenic thermogene travertine calcite deposited on plexiglass substrates in travertine pools and a ramp stream were collected along the huanglong ravine sichuan sw china at regular 10 day intervals from early may to early november in 2010 including both wet and dry conditions temporal and spatial variations in the 13 c and 18 o values of the modern travertine were examined to understand their potential for paleoclimatic and paleoenvironmental interpretations it was found that 13 c and 18 o of travertine formed in the ramp stream were low in the warm rainy season and high in the cold dry season their positive correlation was mainly due to dilution and rainfall seasonal effects on 13 c and 18 o values respectively i e low 13 c values were caused by dilution by overland flow with depleted 13 c values and reduced co 2 degassing in the warm rainy season while low 18 o values of travertine were because of low 18 o values of water induced by seasonal variation in oxygen isotopic ratios of rainwater meanwhile kinetic effect on oxygen isotopic fractionation during ramp travertine deposition existed and reduced this positive correlation in contrast the 13 c and 18 o values of the pool travertines displayed a converse behavior which was caused mainly by the temperature effect low 18 o values and high 13 c values in the warm rainy season were correlated chiefly with the higher water temperatures therefore the 13 c and 18 o values of the travertine may be used for paleo rainfall or paleotemperature reconstruction respectively this study demonstrates that endogenic travertine like epigenic meteogene tufa may be a suitable candidate for high resolution paleoclimatic and paleoenvironmental reconstructions however since travertines deposited under differing hydrodynamic conditions e g pools with still water contrasted to fast flow streams have different climatic responses it is necessary to check the depositional facies of fossil travertine samples before they can be used for palaeoclimate temperature and or rainfall reconstruction