the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

wave transformation and wave driven flow across a steep coral reef observations of waves setup and wave driven mean flows were made on a steep coral forereef and its associated lagoonal system on the north shore of moorea french polynesia despite the steep and complex geometry of the forereef and wave amplitudes that are nearly equal to the mean water depth linear wave theory showed very good agreement with data measurements across the reef illustrate the importance of including both wave transport owing tostokes drift as well as the eulerianmean transportwhen computing the fluxes over the reef finally the observed setup closely follows the theoretical relationship derived from classic radiation stress theory although the two parameters that appear in the model one reflecting wave breaking the other the effective depth over the reef crest must be chosen to match theory to data

numerical modeling of low frequency wave dynamics over a fringing coral reef abstract low frequency infragravity wave dynamics on a fringing coral reef were investigated using the numerical model xbeach roelvink et al 2009 first the skill of the model was evaluated in one and two dimensions based on its predictions of short waves 0 04 0 2 hz infragravity waves 0 004 0 04 hz and water level measurements tidal and wave setup obtained during a 2009 field study at ningaloo reef in western australia the model calibration was sensitive to friction coefficients for short waves and current infragravity bed friction which were assumed independent in this model study although the one dimensional cross shore model captured the gradients in the dominant hydrodynamic processes at the site a high current ig bed friction coefficient was required this resulted in an overestimation and a phase lag between the observed and predicted wave setup signal in the two dimensional model a lower more realistic current infragravity wave friction coefficient was required to achieve optimum performance due to the presence of significant reef and lagoon mean flows in the model which led to reduced setup across the reef the infragravity waves were found to propagate from the surf zone across the reef in a dominantly cross shore direction towards the shore but with substantial frictional damping the infragravity waves were strongly modulated also over the reef by tidal depth variations primarily due to the variability in frictional dissipation rates when the total water depth over the reef varied two mean wave driven circulation cells were observed in the study area with cross shore flow becoming more alongshore dominated before exiting the system via the two channels in the reef the results reveal that short waves dominated bottom stresses on the forereef and near the reef crest however inside the lagoon infragravity waves become increasingly dominant accounting up to 50 of the combined bottom stresses

forcing of resonant modes on a fringing reef during tropical storm man yi 1 open basin resonant modes have been observed at tidal frequencies on coastal shelves but their excitation on coral reef platforms has only been suggested the topography of and water depth over most fringing reefs correspond to resonant periods that are the order of tens of minutes and fall outside of the energetic part of the wave spectrum during tropical storm man yi low frequency near resonant oscillations dominated the variance of the sea surface elevation at the shoreline of ipan reef guam the excitation of the resonant modes resulted both from a large increase in water level over the reef due to wave setup which increased the resonant frequencies and the occurrence of wave group forcing with time scales commensurate with these increased resonant frequencies

infragravity wave dynamics in a barred coastal region a numerical study this paper presents a comprehensive numerical study into the infragravity wave dynamics at a field site characterized by a gently sloping barred beach the nonhydrostatic wave flow model swash was used to simulate the local wavefield for a range of wave conditions including mild and storm conditions the extensive spatial coverage of the model allowed us to analyze the infragravity wave dynamics at spatial scales not often covered before overall the model predicted a wavefield that was representative of the natural conditions supporting the model application to analyze the wave dynamics the infragravity wave field was typically dominated by leaky waves except near the outer bar where bar trapped edge waves were observed relative contributions of bar trapped waves peaked during mild conditions when they explained up to 50 of the infragravity variance near the outer bar the infragravity wave growth was partly explained by nonlinear energy transfers from short waves this growth was strongest for mild conditions and decreased for more energetic conditions when short waves were breaking at the outer bar further shoreward infragravity waves lost most of their energy due to a combination of nonlinear transfers bottom friction and infragravity wave breaking nonlinear transfers were only effective near the inner bar whereas near the shoreline where losses were strongest the dissipation was caused by the combined effect of bottom friction and breaking this study demonstrated the model s potential to study wave dynamics at field scales not easily covered by in situ observations

paleosol stable isotope evidence for early hominid occupation of east asian temperate environments hominids left africa and occupied mainland asia by 1 8 myr ago about 1 15 myr agohomo erectusand an associatedstegodon ailuropodafauna migrated from subtropical china across the qinling mountains into the temperate loess plateau this migration may be an evolutionary milestone in human adaptability because it may represent the first occupation of a nontropical environment loess paleosol stable isotope ratios from the last interglacial glacial cycle provide comparative data for reconstructing the hominid paleoenvironments the climate during gongwangling hominid occupation about 1 15 myr ago was influenced by both siberian mongolian winter and indian summer monsoon systems characterized as a cold cool dry winter and warm mild semihumid summer and fall the gongwangling hominids preyed mainly on warm climate adapted animals such asstegodon ailuropodafauna suggesting a warm season occupation the stable isotope ratios also indicate that the chenjiawo hominids occupied an environment similar to that of the gongwangling about 650 000 yr ago the associated fauna with a mixture of forest and steppe warm and cold cool climate adapted animal assemblage s suggests a permanent occupation by this time thus the reliable earliest and permanent occupation of temperate environments may have occurred 150 000 yr earlier in eastern asia rather than in europe

elevated and variable values of 13c in speleothems in a british cave system 13c isotope variations in speleothems have been investigated for samples from the british isles where plants which use the hatch slack or c4 photosynthetic pathway are not present the range of 13c expected in speleothem carbonate formed in isotopic equilibrium with soil co2 derived from the overlying c3 vegetation should thus fall in the range 12 to 6 forty one actively growing speleothem samples from low discharge sites were analysed from stump cross caverns yorkshire england ten percent have 13c greater than 6 in addition a large range of 13c was observed 8 06 1 38 a 1 variability of 17 with adjacent samples having 13c differing by a maximum of 4 74 similar findings were obtained from a review of analyses of late quaternary speleothem samples from the british isles with 75 of flowstone samples and 57 of high flow stalagmite samples exhibiting elevated 13c three possible processes are proposed as possible causes of elevated 13c in speleothems firstly fractionation may occur between the stalactite and stalagmite due to evaporation or degassing secondly degassing of the groundwaters may have occurred within the aquifer before reaching the cave void allowing release of some co2 from the water whilst remaining saturated in calcium finally the elevated 13c may be due to short water residence times in the soil such that equilibrium between soil water and soil co2 is not reached evidence presented here demonstrates that any one of these mechanisms may be important in the karst areas of the british isles caution is needed before interpreting the 13c signal within speleothems in terms of palaeovegetation

observations of wave transformation over a fringing coral reef and the importance of low frequency waves and offshore water levels to runup overwash and coastal flooding many low lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events to quantify wave dynamics and wave driven water levels on fringing coral reefs a 5 month deployment of wave gauges and a current meter was conducted across two shore normal transects on roi namur island in the republic of the marshall islands these observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef the larger event coincided with a peak spring tide leading to energetic highly skewed infragravity 0 04 0 004 hz and very low frequency 0 004 0 001 hz waves at the shoreline which reached heights of 1 0 and 0 7 m respectively water surface elevations combined with wave runup reached 3 7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach resulting in flooding of inland areas this overwash occurred during a 3 h time window that coincided with high tide and maximum low frequency reef flat wave heights the relatively low relief characteristics of this narrow reef flat may further drive shoreline amplification of low frequency waves due to resonance modes these results 1 demonstrate how the coupling of high offshore water levels with low frequency reef flat wave energetics can lead to large impacts along fringing reef lined shorelines such as island overwash and 2 lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events negatively impacting coastal resources and infrastructure

swash oscillations on a natural beach run up swash oscillations were measured on a gently sloping beach face for a variety of incident wave conditions run up energy spectra at wind wave frequencies show an 3 dependence and energy levels that are independent of incident wave height this suggests saturation in contrast run up energy at surf beat periods increase approximately linearly with increasing incident wave energy thus in the inner surf zone where wave breaking limits the energy at wind wave frequencies the principal manifestation of large incident wind waves is energetic surf beat

stable carbon isotope budget of co2 in a wet modern soil as inferred from fe co3 oh in pedogenic goethite possible role of calcite dissolution abstract 13c values of the fe co3 oh component in pedogenic goethites from a young soil developed on the eocene weches formation in east texas increase from approximately 13 or 14 at depths of 31 64 cm to values around 6 to 4 at depths greater than 122 cm this spatial distribution of 13c values suggests that dissolution of precursor fossiliferous marine calcite still present at deeper levels in the soil has contributed significantly to the isotopic budget of co2 in this soil a local isotopic material balance was calculated for the soil co2 at each sample depth using a calcite 13c value of 1 an organic matter 13c value of 25 and the measured 13c value of the fe co3 oh component in each sample although there is presently no calcite in the upper 120 cm of the profile the calculated apparent contribution of co2 from a calcite source ranges from 16 to 45 at these shallow depths below 120 cm dissolution of calcite appears to contribute more than 50 of the co2 in the soil gas similar results might be expected in other wet goethite bearing soils that contain relict calcite and thus have not achieved the highly leached characteristics of laterites such as those in the amazon basin models of the soil co2 budget in such systems may need to consider both oxidation of organic matter and dissolution of carbonate minerals as in situ sources of carbon isotope variation in co2 the variation with depth of the 13c values of the fe co3 oh component suggests an ongoing process of goethite dissolution and reprecipitation in the active aerobic soil zone if so the extremely low solubility of goethite in oxidizing environments suggests that this dissolution process is probably biologically mediated dissolution and reprecipitation of goethite in an aerobic soil would favor the recording of steady state soil co2 13c patterns preservation of such information in ancient soils would probably depend upon burial and consequent removal from the biologically active soil zone

infragravity wave generation on shore platforms bound long wave versus breakpoint forcing abstract shore platforms are ubiquitous morphological features along rocky coastlines and display a spectrum of forms from gently sloping to sub horizontal with a low tide cliff they generally front eroding coastal cliffs and play an important natural coastal protection role by dissipating wave energy especially during energetic wave conditions sea swell wave energy dissipates during wave breaking but the transfer of incident wave energy to lower frequencies resulting in infragravity waves can enable significant amounts of wave energy to persist up to the shoreline this residual wave motion at the shoreline can carry out geomorphic work for example by directly impacting the cliff face but also for removing cliff toe debris there are two main mechanisms for generating infragravity wave motion group bound long waves and breakpoint forcing and it is not known which of these mechanisms operate on shore platforms here we show using field data collected at a sloping platform in england and a sub horizontal platform in new zealand and supported by numerical modelling that the group bound long wave mechanism is most important on sloping platforms whereas breakpoint forcing dominates on sub horizontal platforms our results also suggest that the infragravity wave motion on the sloping platform is somewhat more energetic than that on the sub horizontal platform implying that the latter type of platform may provide better protection to coastal cliffs however site specific factors especially platform elevation with respect to tidal level and platform gradient play a key role in wave transformation processes on shore platforms and more field data and modelling efforts are required to enhance our understanding of these processes especially collected under extreme wave conditions hs 5 m

the importance of explicitly modelling sea swell waves for runup on reef lined coasts abstract the importance of explicitly modelling sea swell waves for runup was examined using a 2d xbeach short wave averaged surfbeat xb sb and a wave resolving non hydrostatic xb nh model of roi namur island on kwajalein atoll in the republic of marshall islands field observations on water levels wave heights and wave runup were used to drive and evaluate both models which were subsequently used to determine the effect of sea level rise and extreme wave conditions on wave runup and its components results show that specifically modelling the sea swell component using xb nh provides a better approximation of the observed runup than xb sb which only models the time variation of the sea swell wave height despite good model performance of both models on reef flat water levels and wave heights xb sb has a bias of 0 108 0 057 m and scatter index of 0 083 0 639 whereas xb nh has bias of 0 132 0 055 m and 0 122 0 490 respectively however both models under predict runup peaks the difference between xb sb and xb nh increases for more extreme wave events and higher sea levels as xb nh resolves individual waves and therefore captures ss wave motions in runup however for even larger forcing conditions with offshore wave heights of 6 m the island is flooded in both xb sb and xb nh computations regardless the sea swell wave energy contribution in such cases xb sb would be adequate to model flooding depths and extents on the island while requiring 4 5 times less computational effort

the dynamics of infragravity wave transformation over a fringing reef a 3 week field study was conducted to investigate the dynamics of low frequency infragravity wave motions over a fringing reef at ningaloo reef western australia short period wave motions 0 04 0 2 hz were observed to dissipate on the reef crest beyond which infragravity wave motions 0 004 0 04 hz gradually dominated toward the lagoon however both the short waves and the infragravity waves were relatively small both 0 3 m on the reef flat owing to the shallow water depth 2 m the results revealed that the surf zone generation of free infragravity wave motions on the steep 1 20 fore reef slope was dominated by breakpoint forcing as opposed to shoaling bound waves which was also supported by detailed numerical simulations of the generation process this is consistent with theory suggesting the efficiency of the breakpoint forcing mechanism should be high in this steep slope regime shoreward propagating infragravity waves traveled across the reef but were damped by bottom friction dissipation however this was at a rate much smaller than experienced by the residual short waves with these rates of frictional dissipation also strongly dependent on the water depth over the reef the infragravity wave heights increased at higher water levels and hence were strongly modulated by the tide due to the strong dissipation of infragravity waves over this wide and shallow reef that is hydraulically rough any seaward propagating infragravity waves that reflected at the shoreline were small leading to the dominance of progressive shoreward propagating infragravity wave motions throughout the reef and lagoon

do stable isotope data from calcrete record late pleistocene monsoonal climate variation in the thar desert of india late pleistocene terrestrial climate records in india may be preserved in oxygen and carbon stable isotopes in pedogenic calcrete petrography shows that calcrete nodules in quaternary sediments of the thar desert in rajasthan are pedogenic with little evidence for postpedogenic alteration the calcrete occurs in four laterally persistent and one nonpersistent eolian units separated by colluvial gravel thermoluminescence and infrared and green light stimulated luminescence of host quartz and feldspar grains gave age brackets for persistent eolian units i iv of ca 70 000 60 000 ca 60 000 55 000 ca 55 000 43 000 and ca 43 000 25 000 yr respectively the youngest eolian unit v is 10 000 yr old and contains no calcrete stable oxygen isotope compositions of calcretes in most of eolian unit i in the upper part of eolian unit iv and in the nonpersistent eolian unit range between 4 6 and 2 1 pdb these values up to 4 4 greater than values from eolian units ii and iii are interpreted as representing nonmonsoonal18o enriched normal continental waters during climatic phases when the monsoon weakened or failed conversely 25 000 60 000 yr old calcretes eolian units ii and iii probably formed under monsoonal conditions the two periods of weakened monsoon are consistent with other paleoclimatic data from india and may represent widespread aridity on the indian subcontinent during isotope stages 2 and 4 the total variation in 13c is 1 7 0 0 1 7 and 13c covaries positively and linearly with 18o 13c values are highest when 18o values indicate the most arid climatic conditions this is best explained by expansion of c4grasses at the expense of c3plants at low latitudes during glacial periods when atmosphericpco2was lowered c4dominance was overridingly influenced by global change in atmosphericpco2despite the lowered summer rainfall

modeling wave processes over fringing reefs with an excavation pit abstract the excavation of reef flat sand and aggregate for engineering projects is a common practice on atoll islands with attendant coastal management and hazard mitigation issues to assess the impact of reef flat excavation pits on wave transformation a numerical study is carried out based on one dimensional weakly dispersive highly nonlinear boussinesq equations model simulations are compared to field observations made at majuro atoll republic of the marshall islands ford et al 2013a at a 75 m wide fringing reef flat with a 17 m wide 4 m deep excavation pit and at an adjacent unmodified reef flat with a calibrated empirical breaking model and uniform friction coefficient the numerical model is shown to satisfactorily reproduce the observed sea and swell ss and infragravity ig frequency band wave heights for a moderate amplitude wave event by removing the lateral morphological differences of the field experiment the model shows that an excavation pit reduces increases shoreline ig ss wave heights compared to numerical tests without the pit in qualitative agreement with ford et al 2013a an eof analysis demonstrates that the reduction in ig wave heights is associated with modifications of the and wavelength ig standing modes across the reef caused by the pit model tests are used to evaluate the effects of cross reef pit location and width on wave transformation shoreline wave heights are least affected by a pit located near the reef crest and both ss and ig wave heights increase as the pit location moves shoreward shoreline wave heights are an increasing function of pit width as the increase in ss wave height exceeds the decrease in ig wave height produced by the pit the effects of incident wave height and spectral bandwidth are also examined for the reef with and without pit it is found that both shoreline ss and ig wave heights increase with the increasing incident wave height for both profiles the numerical model results also demonstrate that the shoreline response is sensitive to the bandwidth of the incident wave spectrum and larger ig shoreline wave heights are excited for narrower spectral bandwidths until wave reflection limits the forcing

late holocene climate in the lower narmada valley gujarat western india inferred using sedimentary carbon and oxygen isotope ratios we report the late holocene climate and vegetation of the lower narmada valley gujarat western india as inferred from the stable carbon and oxygen isotopic composition 13c and 18o of sediment

does δ13ccarb of the chinese loess indicate past c3 c4 abundance a review of research on stable carbon isotopes of the chinese loess current research on stable carbon isotopes of the chinese loess is reviewed the stable carbon isotopic composition of soil organic matter som 13corg of paleosols formed during interglacials is more positive than that within loess accumulated during glacials spatially it becomes progressively more negative from the eastern chinese loess plateau clp to the western however stable carbon isotopic composition of pedogenic carbonates 13ccarb from the same sequence produces an opposing trend both temporally and spatially and variation differs from expectations under conditions of equilibrium this indicates that 13ccarb in the chinese loess cannot be used to reconstruct the relative proportion of c3 c4 plants in past ecological communities furthermore use of 13ccarb to reconstruct the expansion of c4 plants in older tertiary red clay deposits is considered unreliable we believe 13ccarb may act as an indirect indicator of vegetation density following on changes in moisture supply controlled by the intensity of the asian summer monsoon but conclude that full understanding of the paleoclimatic significance of 13ccarb in the chinese loess and underlying tertiary red clay requires better understanding of modern isotopic processes

observations and predictions of run up for a significant range of offshore wave conditions and foreshore slopes run up observations are compared to semiempirical formulations and predictions of an existing numerical model based on the depth averaged one dimensional nonlinear shallow water equations with bore like breaking wave dissipation and quadratic bottom friction the numerical model is initialized with time series of sea surface elevation and cross shore velocity observed in 80 cm mean water depth approximately 50 m offshore of the mean shoreline on a gently sloping beach and in 175 cm water depth 100 m offshore of the shoreline on a steep concave beach run up was measured with a stack of resistance wires at elevations 5 10 15 20 and 25 cm above and parallel to the beach face at sea swell frequencies nominally 0 05 f 0 18 hz run up energy is limited by surf zone dissipation of shoreward propagating waves so that increasing the offshore wave height above a threshold value does not substantially increase the predicted or observed sea swell run up excursions e g run up is saturated existing semiempirical saturation formulations are most consistent with the observations and numerical model predictions of run up excursions nearest the bed in contrast at infragravity frequencies 0 004 f 0 05 hz where surf zone dissipation is relatively weak and reflection from the beach face is strong e g saturation formulas are not applicable the run up excursions increase approximately linearly with increasing offshore wave height the numerical model also accurately predicts that the tongue like shape of the run up results in sensitivity of run up measurements to wire elevation for instance run up excursions and mean vertical superelevation above the offshore still water level increase with decreasing wire elevation and continuous thinning of the run up tongue during the wave uprush can result in large phase differences between run up excursions measured at different wire elevations numerical model simulations suggest that run up measured more than a few centimeters above the bed cannot be used to infer even the sign of the fluid velocities in the run up tongue

mixed geothermal and shallow meteoric origin of opal and calcite beds in pliocene lower pleistocene axial fluvial strata southern rio grande rift rincon hills new mexico u s a abstract exposed in upper pliocene fluvial strata in the eastern rincon hills and adjacent jornada del muerto basin southern rio grande rift new mexico usa are five laterally continuous beds 0 2 to 1 0 m thick of opal ct which straddle the east rincon hills normal fault four of these opal beds change basinward over 1 km or less to white friable lithofeldspathic sand with opal glaebules and then to microcrystalline calcite the opal and calcite generally replaced fine sand at shallow depths although two beds locally precipitated from standing water 87sr 86sr values 0 71301 to 0 71724 of the opal beds are consistent with precipitation from an advecting high temperature geothermal fluid that flowed through bedrock and or from a high temperature geothermal fluid derived from a deep crustal source carbon and oxygen isotopic values 13cpdb 7 1 to 0 6 18opdb 9 1 to 5 6 of the calcite beds lie between and overlap those of paleozoic carbonate and pliocene paleosol calcite suggesting precipitation from a mixture of a high temperature geothermal fluid that interacted with paleozoic carbonates and shallow meteoric groundwater for which paleosol calcite is a proxy the geothermal fluids are interpreted to have upwelled along the east rincon hills fault flowed laterally at or just below the surface and precipitated opal in response to rapid cooling and evaporation downflow precipitation of opal glaebules occurred as a result of decreasing silica concentrations and perhaps by mixing with shallow meteoric groundwater from which calcite precipitated probably by co2 degassing

morphology and stable and radiogenic isotope composition of pedogenic carbonates in late quaternary relict soils new mexico u s a an integrated record of pedogenic overprinting abstract this petrographic and stable 13c and 18o and radiogenic 14c isotope study of pedogenic carbonates from late quaternary soils in the rio grande rift region of new mexico documents that carbonate formation in semiarid to arid soils aridisols occurs principally by overprinting and can result in a complex petrographic and isotopic record with increasing duration of exposure 7 to 900 ky of the four studied profiles pedogenic carbonates exhibit 1 an increase in the degree of intraprofile 13c and 18o heterogeneity 2 increased development of down profile 13c and 18o trends 3 an increase in the degree of intermorphologic and intramorphologic stable isotope variation commonly in samples distributed laterally within narrow depth intervals and 4 development of covariation between 13c and 18o values radiocarbon ages of the carbonates permit assessment of the degree of isotope heterogeneity in contemporaneous carbonates and recognition of temporal isotopic trends the range of exposure times recorded by the studied soils are analogous to those associated with the formation of fossil soils this makes the studied soils ideal for evaluating the origin of stable isotope heterogeneity in paleosol carbonates and the implications of those heterogeneities for the use of stable isotopes as paleoenvironmental proxies specific implications of this study include the following 1 pedogenic carbonates that form by overprinting are a cumulative record of the soil conditions present during their accumulation thus isotope analysis of overprinted carbonates can result in time averaging of changing climatic paleoenvironmental and paleoecologic conditions 2 carbonates may record only a fraction of the duration of development of their host profile 3 there is a high level of uncertainty associated with using the sequence of morphologic development of carbonate as a function of time or maturity in paleosols 4 an exponential decrease in carbonate 13c values with depth in a paleosol does not imply that the carbonates are contemporaneous or accumulated under invariant soil conditions 5 shifts in soil and paleoclimatic conditions may be recorded by the 13c and 18o values of carbonates distributed within narrow depth intervals of a given soil in addition to those distributed down profile or even from within individual carbonate samples

transition from arid to hyper arid environment in the southern levant deserts as recorded by early pleistocene cummulic aridisols abstract the time at which deserts established their current arid or hyper arid conditions remains a fundamental question regarding the history of earth cosmogenic isotope exposure ages of desert pavement and welded calcic gypsic salic reg soils that developed on relatively flat alluvial surfaces 2 ma ago in the negev desert indicate long geomorphic stability under extremely dry conditions over a short interval during their initial stage of development between 1 2 ma these cumulative soils are characterized by calcic soils reaching maximum stage iii of carbonate morphology this interval is the only period when calcic soil horizons formed on stable abandoned alluvial surfaces in the southern negev desert since 1 ma pedogenesis changed toward more arid soil environment and the formation of gypsic salic soil horizons that were later followed by dust accumulation the dichotomy of only moderately developed calcic soil stages ii iii during a relatively long time interval 105 106 years indicates an arid environment that does not support continuous development but only occasional calcic soil formation the very low 18o and relatively high 13c values of these early pedogenic carbonates support soil formation under arid climatic conditions such an environment was probably characterized by rare and relatively longer duration rainstorms which occasionally allowed deeper infiltration of rainwater and longer retention of soil moisture this in turn enabled the growth of sparse vegetation that enhanced deposition of pedogenic carbonate at 1 ma these rare events of slightly wetter conditions ceased and less atmospheric moisture reached the southern negev desert leading to deposition of soluble salts and dust deposited in the soils the combination of long term hyperaridity scarcity of vegetation and lack of bioturbation salts cementation dust accumulation and tight desert pavement cover has protected the surfaces from erosion forming one of the most remarkably stable landscapes on earth a landscape that essentially has not eroded but accumulated salt and dust for more than 106 yr

two dimensional modelling of wave dynamics and wave forces on fringing coral reefs abstract two dimensional numerical modelling of swell wave dynamics on idealized fringing reefs is performed using swan covering a wide range of bathymetries climate forcing conditions and water depths over the reefs the results illustrate the impact of reef geometry and bathymetry coral species and sea level rise on key hydrodynamic parameters on the reef and on forces on corals the modelling demonstrates that one dimensional models underestimate the wave action on the reef flat wide short reefs and narrow long reefs have similar wave heights at the centre of the reef flat for a given reef length the wave height first decreases with increasing reef width then increases to a local maximum when reef width is approximately equal to the reef length and then decreases for further increases in width this pattern is a result of combined dissipation and refraction processes which combine to lead to different zones of cross reef wave transformation provided that a reef retains its hydrodynamic functions in breaking and refracting the waves sea level rise enhances the wave heights and wave orbital velocities on the reef flat if vertical coral growth does not keep pace with sea level rise loss of the hydrodynamic functions of the reef may occur on deeper reefs and result in a reduction of near bed velocities with sea level rise hydrodynamic forces on corals vary by coral species and slr changes the magnitude of the forces on different species in different ways which may lead to less favourable conditions for certain coral species for long period swell the intermediate size corals are drag dominated and behave similarly to branching corals whereas for short period swell their behavior is similar to that of the inertia dominated massive corals for intermediate corals different responses to slr may therefore be expected for different overall regional wave climates over time this process may contribute to changes in the structural complexity of reefs the influence of sea level rise on the forces on corals on the reef flat is different under swell and cyclonic wind conditions since wind influences wave period in the latter case

late quaternary environmental changes in the upper las vegas valley nevada abstract five stratigraphic units and five soils of late pleistocene to holocene age crop out in dissected badlands on corn creek flat 30 km northwest of las vegas nevada and at tule springs nearer to las vegas the record is dominantly fluvial but contains evidence of several moister marsh forming periods the oldest unit b dates perhaps to the middle wisconsin and the more widespread unit d falls between 30 000 and 15 000 yr b p unit d therefore correlates with pluvial maximum lacustrine deposits elsewhere in the great basin standing water was not of sufficient depth or extent during either period to form lake strandlines between 14 000 and 7200 yr b p unit e standing surface water gradually decreased a trend also apparent in great basin pluvial lake chronologies during the same period groundwater carbonate cementation and burrowing by cicadas cicadae accompany the moist phase units after 7200 yr b p increased wind action decreased biotic activity and at least 25 m of water table lowering accompanied widespread erosion of older fine grained deposits based on pack rat midden and pollen evidence this coincides with major vegetation changes in the valley from sagebrush dominated steppe to lower mohave desertscrub

observations of wave energy fluxes and swash motions on a low sloping dissipative beach 1 field observations of swash and ocean waves show that runup saturation at infragravity frequencies 0 025 0 035 hz infragravity waves where typically less than 5 of the linear energy flux was reflected from the beach and where similar to the sea swell band the swash energy was independent of offshore wave energy the infragravity frequency range of saturation was determined by the tide with saturation extending to lower frequencies at low tide when the local beach face slope over the concave shaped profile was gentler runup was strongly dominated by infragravity frequencies which accounted on average for 96 of the runup variance and its energy levels were entirely consistent with strong infragravity wave dissipation observed in the surfzone particularly when including the nonlinear contributions to the wave energy fluxes the infragravity wave dissipation was strongly associated with breaking of sea swell waves which abruptly decreased nonlinear transfers to infragravity frequencies and made infragravity dissipation prevail over forcing within the breaking region our observations show evidence of nonlinear interactions involving infragravity and high frequency harmonic waves and suggest that these harmonics could play a role in the wave energy balance near the shoreline on low sloping dissipative beaches

the influence of coral reefs and climate change on wave driven flooding of tropical coastlines a numerical model xbeach calibrated and validated on field data collected at roi namur island on kwajalein atoll in the republic of marshall islands was used to examine the effects of different coral reef characteristics on potential coastal hazards caused by wave driven flooding and how these effects may be altered by projected climate change the results presented herein suggest that coasts fronted by relatively narrow reefs with steep fore reef slopes 1 10 and steeper and deeper smoother reef flats are expected to experience the highest wave runup wave runup increases for higher water levels sea level rise higher waves and lower bed roughness coral degradation which are all expected effects of climate change rising sea levels and climate change will therefore have a significant negative impact on the ability of coral reefs to mitigate the effects of coastal hazards in the future

modeling of nonlinear wave propagation over fringing reefs abstract the applicability of existing nonlinear triad spectral models for steep slopes 0 1 0 2 characteristic of reef environments was investigated using both deterministic phase resolving and stochastic phased averaged formulations model performance was tested using laboratory observations of unidirectional wave transformation over steep and smooth bathymetry profiles the models developed for mild slopes were implemented with minimal modifications the inclusion of breaking parametrizations and linear steep slope corrections required by laboratory data the deterministic model produced typically more accurate predictions than the stochastic one but the phase averaged formulation proved fast enough to allow for an inverse modeling search for the optimal breaking parametrization the effects of the additional assumptions of the stochastic approach resulted in a slower than observed evolution of the infragravity band despite the challenge posed by the fast wave evolution and energetic breaking characteristic to the steep reef slopes both formulations performed overall well and should be considered as good provisional candidates for use in numerical investigation of wave current interaction processes on steep reefs

spectral wave dissipation over a barrier reef 1 a 2 week field experiment was conducted to measure surface wave dissipation on a barrier reef at kaneohe bay oahu hawaii wave heights and velocities were measured at several locations on the fore reef and the reef flat which were used to estimate rates of dissipation by wave breaking and bottom friction dissipation on the reef flat was found to be dominated by friction at rates that are significantly larger than those typically observed at sandy beach sites this is attributed to the rough surface generated by the reef organisms which makes the reef highly efficient at dissipating energy by bottom friction results were compared to a spectral wave friction model which showed that the variation in frictional dissipation among the different frequency components could be described using a single hydraulic roughness length scale surveys of the bottom roughness conducted on the reef flat showed that this hydraulic roughness length was comparable to the physical roughness measured at this site on the fore reef dissipation was due to the combined effect of frictional dissipation and wave breaking however in this region the magnitude of dissipation by bottom friction was comparable to wave breaking despite the existence of a well defined surf zone there under typical wave conditions the bulk of the total wave energy incident on kaneohe bay is dissipated by bottom friction not wave breaking as is often assumed for sandy beach sites and other coral reefs

the role of rare rainstorms in the formation of calcic soil horizons on alluvial surfaces in extreme deserts abstract soils in similar geomorphic settings in hyperarid deserts 1 should have similar characteristics because a negative moisture balance controls their development however reg soils in the hyperarid southern negev and namib deserts are distinctly different soils developed on stable alluvial surfaces with only direct input of rainfall and dust depend heavily on rainfall characteristics annual rainfall amount can be similar 15 30 mm but storm duration can drastically alter reg soil properties in deserts the cooler fall winter and dry hot summers of the southern negev desert with a predominance brief 1 day rainstorms result in gypsic saline soils without any calcic soil horizon although the namib desert receives only 50 60 of the southern negev annual rainfall its rainstorm duration is commonly 2 4 days this improves leaching of the top soil under even lower annual rainfall amount and results in weeks long grass cover the long term cumulative effect of these rare rain grass relationships produces a calcic gypsic saline soil the development of these different kinds of desert soils highlights the importance of daily to seasonal rainfall characteristics in influencing soil moisture regime in deserts and has important implications for the use of key desert soil properties as proxies in paleoclimatology

plio pleistocene climate change and timing of peninsular ranges uplift in southern california evidence from paleosols and stable isotopes in the fish creek vallecito basin article i nfo abundant plio pleistocene paleosols in the fish creek vallecito basin record the effects of late neogene global climate change on inland southern california analysis of 82 paleosol horizons ranging in age from 3 9 to 0 7 ma reveals two primary populations vertic paleosols with abundant mud cracks and calcic paleosols with pronounced calcite accumulation zones vertic paleosols are dominant in older deposits but disappear from the stratigraphic record by 2 8 ma after which point calcic paleosols are nearly the only paleosol type present pedogenic carbonate nodules from 47 horizons were analyzed for oxygen and carbon isotopic compositions in late pliocene time carbonate 13 c values become depleted from an average of 5 1 between 3 9 and 3 5 ma to 7 3 vpdb between 2 75 and 2 25 ma recording an increase in c3 plants at the expense of c4 grasses this finding suggests that summer precipitation decreased in the study area from 3 8 to 2 5 ma possibly due to a weakening of the summer monsoon the absence of vertic paleosols in post 2 8 ma deposits supports this hypothesis the increase in abundance of calcic paleosols through time suggests a long term increase in aridity a gradual enrichment of about 2 in 18 o values from 3 9 to 0 7 ma also likely resulted from increased aridification and evaporative enrichment of soil water our findings suggest that global cooling in late pliocene time resulted in increased aridity in southern california due to decreased monsoonal activity and the end of persistent el nino conditions in the pacific ocean the observed enrichment in

isotopic evidence for temporal variation in proportion of seasonal precipitation since the last glacial time in the inland pacific northwest of the usa abstract large scale atmospheric circulation patterns determine the quantity and seasonality of precipitation the major source of water in most terrestrial ecosystems oxygen isotope 18o dynamics of the present day hydrologic system in the palouse region of the northwestern u s a indicate a seasonal correlation between the 18o values of precipitation and temperature but no seasonal trends of 18o records in soil water and shallow groundwater their isotope values are close to those of winter precipitation because the palouse receives 75 of its precipitation during winter palouse loess deposits contain late pleistocene pedogenic carbonate having ca 2 to 3 higher 18o values and up to 5 higher carbon isotope 13c values than holocene and modern carbonates the late pleistocene 18o values are best explained by a decrease in isotopically light winter precipitation relative to the modern winter dominated infiltration the 13c values are attributed to a proportional increase of atmospheric co2 in soil co2 due to a decrease in soil respiration rate and 13c discrimination in plants under much drier paleoclimate conditions than today the regional climate difference was likely related to anticyclonic circulation over the pleistocene laurentide and ice sheet

pedogenic phreatic carbonates on a middle devonian givetian terrigenous alluvial deltaic plain gilwood member watt mountain formation northcentral alberta canada in the muskeg trough of northcentral alberta the gilwood member contains widespread carbonate deposits that formed within terrigenous mudstone and sandstone hosts stratigraphic depositional and petrographic relationships indicate that these carbonates represent calcretes and dolocretes calcretes observed best with cathodoluminescence display microcrystalline alpha fabrics circumgranular cracks root networks displacive growth fabrics elongate channel voids and rare coloform growths with flower spar similarly dolocretes have microcrystalline alpha fabrics brecciation gradational contacts with host mudstones extensive layered nodular horizons and are associated with anhydrite and pyrite 13c values range between 7 to 1 and 6 to 3 for calcretes and dolocretes respectively oxygen isotopes are more variable and differ with host lithologies 18o of calcretes ranges between 11 to 8 for sandstones and 8 to 3 for mudstones whereas 18o of dolocretes ranges between 3 to 1 for marine mudstones and 6 to 2 for pedogenic mudstones regional mapping indicates that calcretes thicken towards the deepest parts of the muskeg trough widespread dolocretes extend beyond the eastern and western limits of muskeg trough and are useful marker intervals for regional correlations dolocretes of restricted lateral extent are found within gleyed palaeosol mudstones next to calcretized channel sandstones calcrete isotopic values are interpreted as indicative of carbonate precipitation from waters with meteoric water input however the higher 18o values in dolocretes are indicative of a contribution from an isotopically heavier source such as seawater stratigraphically calcretes are most common along the western and northern edges of muskeg trough thus calcrete accumulation was further controlled by meteoric water in flow from the highland to the west and sluggish groundwater flow in muskeg trough in contrast regionally widespread dolocrete horizons appear to have formed from mixing of fresh waters derived from the highland to the west and seawaters introduced from the east regionally restricted dolocretes which are found next to channel sandstones formed from groundwater out flow from the permeable channel sandstones which resulted in calcretization in channel proximal mudstones and dolomitization in channel distal mudstones

relationship between climate and vegetation and the stable carbon isotope chemistry of soils in the eastern mojave desert nevada abstract the relationship between the stable c isotope composition of the soil environment and modern climate and vegetation was determined empirically along a present day climatic transect in the eastern mojave desert the 13c of the soil co2 and carbonates decreased with increasing elevation and plant density even though plant assemblages at all elevations were isotopically similar several factors including differences in the ratios of pedogenic of limestone calcite and differences in past vegetation were considered as explanations of this trend however it appears that in the sparsely vegetated mojave desert the 13c of pedogenic carbonate is controlled by differences in plant density and biological activity this relationship may provide a tool for assessing past vegetational densities as long as the vegetation is isotopically homogeneous

nonhydrostatic and surfbeat model predictions of extreme wave run up in fringing reef environments abstract the accurate prediction of extreme wave run up is important for effective coastal engineering design and coastal hazard management while run up processes on open sandy coasts have been reasonably well studied very few studies have focused on understanding and predicting wave run up at coral reef fronted coastlines this paper applies the short wave resolving nonhydrostatic xb nh and short wave averaged surfbeat xb sb modes of the xbeach numerical model to validate run up using data from two 1d alongshore uniform fringing reef profiles without roughness elements with two objectives i to provide insight into the physical processes governing run up in such environments and ii to evaluate the performance of both modes in accurately predicting run up over a wide range of conditions xbeach was calibrated by optimizing the maximum wave steepness parameter maxbrsteep in xb nh and the dissipation coefficient alpha in xb sb using the first dataset and then applied to the second dataset for validation xb nh and xb sb predictions of extreme wave run up rmax and r2 and its components infragravity and sea swell band swash sig and sss and shoreline setup were compared to observations xb nh more accurately simulated wave transformation but under predicted shoreline setup due to its exclusion of parameterized wave roller dynamics xb sb under predicted sea swell band swash but overestimated shoreline setup due to an over prediction of wave heights on the reef flat run up swash spectra were dominated by infragravity motions allowing the short wave but not wave group averaged model xb sb to perform comparably well to its more complete short wave resolving xb nh counterpart despite their respective limitations both modes were able to accurately predict rmax and r2

the vesicular layer and carbonate collars of desert soils and pavements formation age and relation to climate change abstract the vesicular fine grained a horizon av is the widespread ubiquitous surficial horizon of desert soils in diverse landforms and parent materials of varying ages now known to form mostly through accumulation of eolian dust recent studies show that dust accumulation and concomitant soil development are genetically linked to stone pavement formation changes in the magnitude of eolian activity and effective leaching related to quaternary climatic changes are also hypothesized to have influenced the evolution of the av horizon numerical modeling geochronologic and field laboratory studies elucidate the nature of pedogenic processes controlling compositional evolution of av how the changing av horizon increasingly influences soil infiltration and carbonate translocation and accumulation and the control that clasts of the evolving pavement exert on pedogenic processes results of a model that determines soil bulk chemical composition based on mixing of estimated proportions of externally derived eolian material and parent materials imply that the evolution of the soil bulk composition is strongly influenced by av horizon formation the early development of a weakly to moderately developed av horizon directly over gravelly parent material in late and middle holocene soils moderately influences soil infiltration but significant leaching of very soluble materials and some carbonate in dust are permitted in older pleistocene soils however the texturally more mature av and underlying cumulic nongravelly horizons more strongly limit the rate and depth of leaching and soil bulk composition therefore more closely approximates a simple mixture of dust and parent material other aspects of av horizon development and its relations to the pavement are evaluated through studies of pavement clasts with coatings of soil carbonate referred to as carbonate collars development of a numerical model that integrates soil hydrology a co2 production diffusion model calcite kinetics and thermodynamic considerations composition and thermal characteristics of pavement clasts and the textural and structural properties of the surface horizon provides the basis for testing a hypothesis of collar formation model results combined with results of 13c and 18o analyses of collar carbonate demonstrate how precipitation of calcite on pavement clasts and within the av is favored at a depth much shallower than that indicated by the classic carbonate depth climate relationship of jenny and leonard jenny h j leonard c d 1935 functional relationships between soil properties and rainfall soil science 38 363 381 and arkley arkley r j 1963 calculations of carbonate and water movement in soil from climatic data soil science 96 239 248 or simulated by numerical models of carbonate accumulation simultaneous development of thick carbonate collars and the av horizon requires the sustained pavement clast av horizon coupling for at least centuries to possibly millennia new thermoluminescence ages also indicate that much of the av horizon formed in the holocene and that it is certainly much younger than the older pleistocene pavements this supports the previously proposed hypothesis that increased dust flux during the pleistocene to holocene transition triggered and or greatly accelerated av horizon development an understanding of the genesis of collars provides not just an understanding of how carbonate can accumulate in surface environments but it also provides important clues into processes of pavement evolution and preservation of av horizons during long glacial periods the av horizon is not merely an insignificant surficial zone of recent dust accretion instead its development profoundly influences the genesis of desert soils and pavements

wave setup over a fringing reef with large bottom roughness abstractthe effect of bottom roughness on setup dynamics was investigated using high resolution observations across a laboratory fringing reef profile with roughness elements scaled to mimic the frictional wave dissipation of a coral reef results with roughness were compared with smooth bottom runs across 16 offshore wave and still water level conditions the time averaged and depth integrated force balance was evaluated from observations collected at 17 locations along the flume and consisted of cross shore pressure and radiation stress gradients whose sum was balanced by quadratic mean bottom stresses the introduction of roughness had two primary effects first for runs with roughness frictional wave dissipation occurred on the reef slope offshore of the breakpoint reducing wave heights prior to wave breaking second offshore directed mean bottom stresses were generated by the interaction of the combined wave current velocity field with the roughness elements these two mechanisms acted counter to

edge wave trapping and amplification on barred beaches theoretical predictions show that edge waves may be trapped on bars providing a possible mechanism for bar growth simple solutions to the linear shallow water equations reveal that bar trapping is controlled by the depth of the water over the bar hbar and the geometry of the inshore trough relative to the bar for specific geometries amplification over the bar approaches an order of magnitude or more as the phase speed approaches where amplification is defined as the surface displacement over the bar relative to the surface displacement at the shoreline the amplification increases with the cross shore length scales of the profiles the amplification is somewhat frequency dependent generating stronger currents at the location of the bar in specific frequency ranges previous work showed that particular edge wave modes have the correct length scales to generate beach features such as bars and beach cusps but field observations notably shoreline run up data frequently show no evidence of edge wave energy being concentrated at the appropriate frequencies however for bar trapped modes edge wave energy is concentrated at the location of the bar therefore this edge wave energy will not necessarily be evident in shoreline measurements strong correlation exists between the energy distribution of the longshore component of the orbital velocity observed in data collected at superduck october 11 1986 and the distribution expected for a white edge wave spectrum at the shoreline this suggests that bar trapped edge waves exist in particular at incident wave frequencies

adcp observations of edge waves off oahu in the wake of the november 2006 kuril islands tsunami received 13 september 2007 revised 5 october 2007 accepted 8 november 2007 published 15 december 2007 1 during the 2006 kuril islands tsunami edge waves propagating along oahu s south shore were observed via depth averaged adcp velocity and pressure data acquired in real time by a coastal observatory at 12 m depth and 400 m offshore time varying rotary component velocity spectra obtained via wavelet analysis agree with the phase lag observed between pressure and each cartesian velocity component in indicating the directions of rotation and travel of progressive edge waves furthermore the theoretical ratios between power in the free surface elevation and in each velocity component of edge waves agree with those observed and a nonlinear shallow water model shows edge waves of various modes propagating along the shore near our observation location importantly the maximum surge in sea level occurred at a time when edge waves of all constituent frequencies were superposed citation bricker j d s munger c pequignet j r wells g pawlak and k f cheung 2007 adcp observations of edge waves off oahu in the wake of the november 2006 kuril islands tsunami geophys res lett 34 l23617 doi 10 1029 2007gl032015

numerical experiments on low frequency fluctuations on a submerged coastal reef abstract low frequency fluctuations on a reef coast are studied through a numerical model based on nonlinear conservation equations of mass and momentum the model is used to investigate the long wave generation and propagation phenomena under both breaking and non breaking incident short wave groups the effects of incident wave characteristics and reef topography on the long wave phenomena are discussed the results show that the long wave elevations on reef coasts are substantial which explains the large water level fluctuations observed at certain occasions

wave setup over a pacific island fringing reef 1 measurements obtained across a shore attached fringing reef on the southeast coast of the island of guam are examined to determine the relationship between incident waves and wave driven setup during storm and nonstorm conditions wave setup on the reef flat correlates well r 0 95 and scales near the shore as approximately 35 of the incident root mean square wave height in 8 m water depth waves generated by tropical storm man yi result in a 1 3 m setup during the peak of the storm predictions based on traditional setup theory steady state inviscid cross shore momentum and depth limited wave breaking and an idealized model of localized wave breaking at the fore reef are in agreement with the observations the reef flat setup is used to estimate a similarity parameter at breaking that is in agreement with observations from a steeply sloping sandy beach a weak 10 increase in setup is observed across the reef flat during wave events the inclusion of bottom stress in the cross shore momentum balance may account for a portion of this signal but this assessment is inconclusive as the reef flat currents in some cases are in the wrong direction to account for the increase an independent check of fringing reef setup dynamics is carried out for measurements at the neighboring island of saipan with good agreement

morphology and isotope heterogeneity of late quaternary pedogenic carbonates implications for paleosol carbonates as paleoenvironmental proxies abstract stable isotope values and radiocarbon ages were determined for pedogenic carbonate microsamples from relict soils and palaeosols from the rio grande rift region of new mexico carbonate nodules and clusters were sampled from fluvial and piedmont soils and palaeosols with widely varying exposure durations 7 900 ky pedogenic carbonates from individual soils exhibited irregular relationships between age and depth ranging in radiocarbon age by 13 ky at individual depths 18 o values and to a lesser extent 13 c values likewise had wide ranges within soils however comparing the stable isotope values of carbonates with similar radiocarbon ages within and between soils revealed consistent trends in stable isotope values over time 18 o values of pedogenic carbonates tended to decrease with decreasing age 25 17 radiocarbon ka and increased with decreasing age 13 c values with either depth or age although the oldest palaeosol piedmont carbonates radiocarbon ages of 24 5 19 2 ka are 1 more negative than the younger piedmont palaeosol carbonates pedogenic carbonates in the relict fluvial soil which has by far the longest exposure period showed the greatest range in 13 c values comparing the 13 c values of samples of similar radiocarbon age from the relict fluvial soil indicates a transition from a mixed c 3 c 4 ecosystem at 11 ka to an effectively pure c 3 ecosystem at 9 ka followed by a return to mixed vegetation by 5 ka thus although c 4 vegetation persisted in southern new mexico through the last glaciation drought resistant c 3 vegetation became dominant at 9 ka prior to significant strengthening of the summer monsoon this study illustrates that the stable isotope values of carbonate nodules and clusters from relict soils and or slowly buried palaeosols can be used for palaeoenvironmental reconstructions in the context of a detailed chronologic framework

the distribution and discrimination of shallow authigenic carbonate in the pliocene pleistocene palomas basin southern rio grande rift nine types of authigenic carbonate are present in the pliocene pleistocene alluvial fan and axial fluvial sediment of the palomas half graben in the southern rio grande rift pedogenic and other vadose carbonate includes 1 pedogenic carbonate of stage ii and stage iii morphology underlying bw and bt horizons 2 mudstones in which the carbonate nodules may be pedogenic or the result of shallow groundwater invasion of the vadose zone 3 pedogenic calcic nodules and tubules in eolian sand and 4 gully bed cement of proximal fan conglomerates formed by infiltration and evaporation of surface runoff shallow groundwater carbonate exists as 5 thin 30 50 cm massive beds with an upper fringe of nodules and tubules precipitated at the water table and in the capillary fringe 6 thick 1 5 3 m massive beds deposited by lateral flow of groundwater or at springs and 7 thin 30 cm calcified root mats associated with near surface water saturated sediment or springs phreatic spar cements 8 occupy the interstices of conglomerates and sandstones and locally exist as 9 oriented concretions groundwater carbonates are best developed near the toes of the large hanging wall derived alluvial fans whereas phreatic cement preferentially exists in footwall derived alluvial fan conglomerates pedogenic carbonate is distinguished from groundwater carbonate by the association with other diagnostic paleosol horizons a predominantly vertical arrangement of root traces peds desiccation cracks and calcic tubules and by gradational contacts the 13 c and 18 o values are similar among pedogenic and shallow groundwater carbonate although locally nodules in eolian sand and gully bed cement have higher 18 o values perhaps due to the effects of evaporation some phreatic cements may be distinguished from pedogenic and shallow groundwater carbonate by lower values of 13 c and 18 o authigenic carbonate in footwall derived alluvial fan sediment has consistently higher values of 13 c than that in hanging wall derived sediment which may reflect differences in vegetative type and or density on either side of the basin

morphology and genesis of carbonate soils on the kyle canyon fan nevada u s a the physical and chemical properties of soils formed in an arid climate on calcareous alluvium of the kyle canyon alluvial fan southern nevada were studied in order to infer the rates and relative importance of various soil forming processes these studies included field and microscopic observations and analyses of thin sections major oxides extractable iron and clay minerals the results are interpreted to reflect five major pedogenic processes 1 the calcic horizons and calcretes of kyle canyon soils form by precipitation of caco3 derived from eolian dust and alluvium as clast coats matrix cement and massive layers 2 the a and uppermost b horizons are essentially dust derived for they contain large amounts of detrital material not present in the alluvial parent material and their major oxide content is similar to that of modern dust 3 clay particles are translocated from a into b horizons 4 iron bearing minerals in the near surface b horizons are slowly oxidized 5 carbonate and aluminosilicate grains are both displaced and replaced by pedogenic caco3 the silica released by replacement of aluminosilicates may be locally precipitated as amorphous or opaline silica and or incorporated into newly formed palygorskite and sepiolite rates of soil development at kyle canyon are approximate due to uncertainties in age estimates some soil field properties change at rates that are similar to rates for soils formed in rhyolitic parent material near mercury nevada the rate of accumulation of caco3 3 5 g m 2 yr 1 at kyle canyon is an order of magnitude faster than that near mercury but is comparable to rates calculated for soils in southern new mexico and utah

impact of coral reef mining pits on nearshore hydrodynamics and wave runup during extreme wave events small island developing states are among the most vulnerable areas to the impact of natural hazards and climate change flooding due to storm surges and extreme waves coastal erosion and salinization of freshwater lenses are already a serious threat and could lead to irreversible consequences in the coming decades reef flat mining is one of the most common practices to source the required material for the implementation of coastal protection measures but concerns remain that partial removal of the protective reef could increase wave loading on the islands however the available data and knowledge on the effects of these mining pits are currently very limited this study provides new insights on the effects that pits may have on nearshore hydrodynamics and wave runup results are based on a large numerical data set of fringing reefs derived using the validated xbeach nonhydrostatic process based model model results indicate that excavation pits cause a decrease in infragravity wave energy around the fundamental mode of the reef which is partly caused by reduced wave transmission additionally changes in sea and swell wave energy are attributed to reduced transmission a decrease in wave dissipation and triad wave wave interaction furthermore in 13 of all modeled cases an increase in wave runup is observed mainly due to more sea and swell wave energy reaching the shoreline this probability is lowest for narrow pits relative to the reef flat width or pits located further from shore

an isotopic study of paleosol carbonates from olduvai gorge the isotopic composition of paleosol carbonates from olduvai gorge can be used to give estimates of the paleoclimatic history of east africa during the plio pleistocene oxygen isotopes are indicative of major changes in the isotopic composition of meteoric water while carbon isotopes are indicative of major changes in the fraction of biomass using the hatch slack c4 photosynthetic pathway three major periods of climatic change in this terrestrial setting occurred at about 1 67 1 3 and 0 6 myr these involved major changes in flora as well as major changes in the isotopic composition of meteoric water overall the climate has become warmer and more arid over the past 2 2 myr

ecological background to plio pleistocene hominin occupation in north africa the vertebrate faunas from ain boucherit ain hanech and el kherba and paleosol stable carbon isotope studies from el kherba algeria in contrast to well studied paleoenvironments of plio pleistocene hominin sites in east africa little is known about the ecology of the earliest north african human occupation sites the recent studies at ain hanech and el kherba in northeastern algeria have broadened the range of plio pleistocene hominin ecology to include the earliest known archaeological sites documented in north africa ain hanech and el kherba are significant for yielding savanna like faunas associated with oldowan stone tools dated back to approximately 1 8 million years ago this paper focuses on reconstructing the ecology of ain hanech and el kherba based on excavated faunas and stable carbon isotope of pedogenic carbonates from el kherba stratigraphic profile the results point out to an overall open paleolandscape and a c3 predominantly paleovegetation both woody and grasses in addition the stable carbon isotopic evidence shows a clear environmental change through time at el kherba which likely impacted hominin foraging activities in level a

observations of surf beat forcing and dissipation 1 we used a simple energy balance equation and estimates of the cross shore energy flux carried by progressive surf beat to calculate the rate of net surf beat forcing or dissipation on a beach near duck north carolina far inside the surf zone surf beat dissipation exceeded forcing outside the surf zone surf beat forcing exceeded dissipation when incident waves were large surf beat dissipation inside the surf zone and forcing just outside the surf zone were both very strong the surf beat energy dissipated in the surf zone in a single beat period was of the same order as the total amount of surf beat energy stored in the surf zone during storms shoreward propagation of surf beat maintained surf beat energy in the surf zone net surf beat dissipation in the surf zone scaled as predicted by a simple bottom stress parameterization the inferred dissipation factor for surf beat was 0 08 within the range of wave dissipation factors usually observed in the field and 27 80 times larger than drag coefficients appropriate for the mean longshore current the observed rapid forcing rapid dissipation and shoreward propagation of surf beat are not simulated by existing models of surf beat dynamics

differential response of vegetation to postglacial climate in the lower salmon river canyon idaho late pleistocene to holocene terrestrial climate and vegetation records in the lower salmon river canyon of idaho are interpreted from the stable isotopic composition of soil carbonates and from aeolian sedimentation frequencies carbonate and sediment samples from six sections were processed and analyzed with the resulting isotopic and grainsize data organized in relation to a normalized time series developed from an associated radiocarbon chronology this record is interpreted in regards to changes in aridity temperature and wind speed during the late quaternary and is further compared with regional paleoenvironmental records lowered n 18 o and n 13 c concentrations before 20 000 yr bp are interpreted as reflecting late wisconsinan cold conditions after 18 000 yr bp climatic conditions show warmer periods punctuated by sharp returns to colder temperatures and increased c3 flora by 12 000 yr bp higher resolution data show very unstable climatic conditions across the pleistocene holocene boundary reflected in wide variations in n 18 o and n 13 c and aeolian sand deposition during the period between 12 000 and 9000 yr bp the lower salmon river canyon is thought to have experienced marked seasonality with summers and winters respectively warmer and colder than today this climatic scenario was accompanied by an initial instability in canyon vegetation following the establishment of a low energy floodplain in the canyon after 10 000 yr bp a pattern of c3 dominant riparian flora appears during the middle holocene climatic and vegetative variability is much reduced from the preceding period after 4000 yr bp soil carbonate isotopes reflect a trend toward cooler climate conditions and more mesic vegetation populations 2002 elsevier science b v all rights reserved

deglacial paleoclimate in the southwestern united states an abrupt 18 6 ka cold event and evidence for a north atlantic forcing of termination i we present a new u series dated speleothem record pc 1 from the great basin that documents deglacial climate variability between ca 20 1 and 15 6 ka our data show an abrupt 18 6 ka cold event preceding heinrich event 1 that is consistent with expansion of the laurentide ice sheet during the binge phase of ice growth this event coincided with dessication of pluvial lake mojave suggesting cold and dry conditions in the southern great basin at this time pc 1 d 18 o values before and during heinrich event 1 are similar but an increase in stalagmite growth rates suggests wetter conditions that coincided with deposition of spring deposits in southern nevada the time interval of our record is consistent with the timing of pluvial conditions in the great basin as evident from a comparison to regional wetness proxies our new speleothem record recovered from the recharge area for devils hole does not show a d 18 o increase coincident with the abrupt increase in devils hole d 18 o at c 18 ka challenging the view

westerly jet stream controlled climate change mode since the last glacial maximum in the northern qinghai tibet plateau abstract climate change from the northern qinghai tibet plateau qtp is affected by the combined effects of the asian summer monsoon and the westerlies however changes in monsoon vapor transport and the westerly jet stream as well as their effect to climate change mode there are not clear at different time scales here we present composite research using paleoclimate reconstructions and ensemble simulations since the last glacial maximum lgm on the basis of an eolian sedimentary sequence in the northern qtp results from 317 surface sediment samples show that pedogenic carbonate 18 o is affected both by precipitation and temperature and organic carbon isotope 13 corg reflects the vegetation growth status in areas where precipitation is greater than 290 mm proxies from the sedimentary sequence and the paleoclimate modeling intercomparison project 3 pmip3 simulations show a close relationship between climate change mode in the northern qtp and the westerly jet stream whose movement is triggered by warm or cold conditions in the high latitude regions that is when the climate is in cold glacial period the westerly jet stream strengthens and moves southward and the mountains become wetter this climate change mode can be validated by records from mountains of north america and africa according to the cmip5 simulations the westerly jet stream will strengthen in the future and climate in the northern qtp and the high altitude region of the mid latitudes will become wetter with global warming

volatile emissions from the crater and flank of oldoinyo lengai volcano tanzania as a comparison to airborne infrared ir flux measurements ground based sampling of fumarole and soil gases was used to characterize the quiescent degassing of co2 from oldoinyo lengai volcano aerial and ground based measurements are in good agreement 75 of the aerially measured co2 flux at lengai 0 05 0 06 1012 mol yr 1 or 6000 7200 tonnes co2 d 1 can be attributed to seven large crater vents in contrast to etna and vulcano island where 15 50 of the total co2 flux emanates diffusely through the volcanic flanks diffuse emissions were measured only within 500 m of the crater rim at lengai contributing 2 of the total flux the lack of extensive flank emissions may reflect the dimensions of the magma chamber and or the lack of a shallow fluid flow system thermodynamic restoration of fumarole analyses shows that gases are the most co2 rich and h2o poor reported for any volcano containing 64 74 co2 24 34 h2o 0 88 1 0 h2 0 1 0 4 co and 0 1 h2s hcl hf and ch4 volatile emissions of s cl and f at oldoiyno lengai are estimated as 4 5 1 5 and 1 0 107 mol yr 1 respectively accuracy of the airborne technique was also assessed by measuring the c emission rate from a coal burning power plant co2 fluxes were measured within 10 near the plant however poor resolution at increased distances caused an underestimation of the flux by a factor of 2 the relatively large co2 fluxes measured for alkaline volcanoes such as oldoinyo lengai or etna may indicate that midplate volcanoes represent a large yet relatively unknown natural source of co2

the destruction of paleoclimatic isotopic signals in pleistocene carbonate soil nodules of western australia stable carbon and oxygen isotopic analyses were conducted on small 10 mm spherical pleistocene carbonate soil nodules from 53 different levels in a 9 15 m soil auger collected in northern western australia the 13c and 18o values range from 4 to 0 and 9 to 6 pee dee belemnite standard respectively comparison of these values to the 13c values of coexisting soil organic matter som reveals marked differences between the two records the som values record an enrichment of 16 through the section whereas the carbonate values record only a 4 variability application of a diffusion production model to the data indicates isotopic disequilibrium between the two carbon records one possible interpretation of the apparent isotopic disequilibrium is that the nodules formed at depths of 1 cm but this interpretation is not supported by field observations an alternative is that the soil organic matter currently in the profile was emplaced after nodule formation such a scenario would have to have occurred numerous times during the late pleistocene as the nodules grew below different soil zones through time a third explanation is that diagenetic alteration of the carbonates in the presence of dissolved inorganic groundwater carbon has occurred this interpretation is consistent with the widely fluctuating regional groundwater table it is also supported by petrographic fabrics and heterogeneous cathodoluminescence patterns indicative of initial pedogenic development of the nodules and then at least one dissolution event multiple precipitation events prolonged nodule growth by displacive spars and microspars cementation and recrystallization of some micrite the results illustrate potential problems for 1 the use of some pedogenic carbonate isotopic records as proxies for environmental change and 2 the use of altered 18o values and unaltered 13c values as screening tools for the presence or absence of diagenesis the results highlight the necessity of understanding regional environmental conditions and diagenetic histories prior to using pedogenic carbonates in paleoreconstructions

evidence of past environmental conditions during the evolution of a calcretised wadi system in southern jordan using stable isotopes abstract a stratigraphically and temporally ordered sequence of channel calcretes preserved along the wadi dana southern jordan records the quaternary evolution of the formation and infilling of rock cut channels and their subsequent incision in a tectonically subsiding basin it is currently unknown under what palaeoenvironmental conditions these non pedogenic calcretes formed stable isotope analyses have been used to investigate whether any past topographical hydrological vegetational diagenetic and or temporal signatures can be identified from the channel calcretes the results of this research indicate that channel calcrete development is influenced by altitudinal variation affecting vegetation and hydrology within the landscape as well as location within individual wadi channels which has an affect on diagenetic processes the lack of calcretisation of a terrace that is between 1 and 1 5 m above the modern wadi floor supports the idea that the environment is currently too arid for calcrete to develop thus the presence of older wadi dana channel duricrusts suggests wetter conditions when they formed the 18o data of the calcrete implies cooler conditions than today as there is little evidence of a strong evaporative effect any temporal control is limited and mainly a function of stratigraphic position with some numeric dating

paleoclimate and paleovegetation of lower narmada basin gujarat western india inferred from stable carbon and oxygen isotopes abstract surface sediment samples depth 0 160 cm and a paleosol depth 10 15 m both part of a sediment profile exposed in a cliff section of narmada river western india were analyzed for stable isotopes 13 c and 18 o three organic carbon samples from top 160 cm and two paleosol samples from top and bottom of the paleosol were dated by the radiocarbon method 13 c of both soil carbonates and soil organic carbon fall in the range of mixed c3 and c4 vegetation except for the paleosol which shows differences attributable to the contribution of bedrock carbonate during calcite formation the vegetation was dominantly c3 in the late pleistocene from 15 10 ka bp which shifted to mixed c3 c4 during the holocene enhanced monsoon was observed at 12 5 and 1 6 ka bp the presence of c4 grasses in the late holocene is detectable the present day vegetation is dominantly c3 type 13 c 25 4 probably due to anthropogenic activity where grasslands c4 have been replaced by c3 vegetation recently last 50 years the enhanced atmospheric co 2 concentration in recent times could be a probable agent for the current dominance of c3 vegetation

field study of wave attenuation on an offshore coral reef a major field experiment was conducted which obtained measurements of the attenuation and transformation of short gravity waves as they cross the windward edge of an offshore coral reef water level data were collected for over 3000 individual time series during a wide range of environmental conditions at the innermost measurement site which is located on the horizontal reef flat after the completion of wave breaking the upper bound of significant and maximum wave heights is limited to less than 40 and 60 of the reef flat water depth respectively as with significant wave height both the shape and energy level of the reef flat spectra are strongly affected by changes in reef flat water depth for higher tide levels the spectra on the reef flat closely mimic the corresponding incident spectra however the attenuation is greater for both lower frequencies and higher energy portions of the spectra this causes the reef flat spectra to be broader than those measured windward of the reef at lower water levels considerable energy losses due to wave breaking and bottom friction occur most of the energy loss comes from the vicinity of the spectral peak and energy shifts to harmonics of the peak of the spectrum can be seen

stable isotope chemistry of fossil bone as a new paleoclimate indicator abstract during fossilization bone is thought to recrystallize and alter chemically on timescales of kyr to a few tens of kyr i e similar to the timescale for formation of soils therefore c and o isotope compositions of bone apatite should correlate with trends in soil water composition and aridity and serve as paleoclimate indicators this hypothesis was tested by analyzing c and o isotope compositions of the co 3 component of fossil bone apatite from mid oligocene through late pleistocene units in oregon and western idaho including the john day 19 4 30 0 ma mascall 15 2 15 8 ma and rattlesnake 7 2 7 8 ma formations whose paleosol sequences have been studied in detail and the juntura 10 11 ma hagerman 3 2 ma and fossil lake 18 o values provide a baseline of meteoric water compositions stable isotope compositions of bone co 3 do change in response to broad climatic trends but show poor correlation with compositions of corresponding paleosol co 3 at specific horizons instead compositional deviations between bone and paleosol co 3 correlate with compositional deviations with the next higher paleosol this suggests that the timescale for fossilization exceeds one paleosol cycle based on stratigraphic evidence and simple alteration models fossilization timescales are estimated at 20 50 kyr indicating that bone co 3 will prove most useful for sequences spanning 100 kyr c isotopes show negative and strong positive deviations during wet and dry climates respectively and short term trends correspond well with changes in aridity within the mascall and rattlesnake formations as inferred from paleosols a proposed correction to 18 o values based on 13 c anomalies implies a small 1 5 increase in meteoric water 18 o during the late oligocene global warming event consistent with a minimum temperature increase of 4 c a strong inferred decrease in 18 o of 4 5 after 7 ma closely parallels compositional changes in tooth enamel and reflects a doubling in the height of the cascade range

energy transfer between wind waves and low frequency oscillations on a fringing reef ipan guam field observations from a guam fringing reef are used to examine the cross reef energy exchange between high frequency sea and swell ss and low frequency infragravity ig and far infragravity fig waves energetic ss waves significant wave heights 2 4 m break at the outer reef leading to weak 1 m conditions on the shallow reef flat as ss waves shoal on the reef face before breaking ig and fig energy fluxes both increase through nonlinear energy transfer from the ss waves in contrast through the surf zone the ig energy flux decreases whereas fig flux increases the decrease in ig energy flux through the surf zone is attributed to breaking ss waves working against the incident bound ig wave energy which dominates breakpoint forced ig waves yielding a net flux decrease in contrast fig energy flux increases through the surf zone consistent with breakpoint forcing and the absence of an energetic bound fig component on the reef face ig and fig energy fluxes decay on the shallow reef flat due primarily to frictional dissipation with tidal modulations attributed to nonlinear conversion and friction forcing at fig frequencies may lead to a normal mode response on the reef with comparable incoming and outgoing fig energy fluxes at the outer reef flat depending on water level over the reef flat and the degree of frictional dissipation

wave transformation and shoreline water level on funafuti atoll tuvalu the influence of sea swell ss waves infragravity ig waves and wave setup on maximum runup rmax is investigated across different tidal stages on fatato island funafuti atoll tuvalu field results illustrate that ss waves are tidally modulated at the shoreline with comparatively greater wave attenuation and setup occurring at low tide versus high tide a shoreward increase in ig wave height is observed across the 100 m wide reef flat at all tidal elevations with no tidal modulation of ig wave height at the reef flat or island shoreline a 1 d shock capturing green naghdi solver is used to replicate the field deployment and analyze rmax model outputs for ss wave height ig wave height and setup at the shoreline match field results with model skill 0 96 model outputs for rmax are used to identify the temporal window when geomorphic activity can occur on the beach face during periods of moderate swell energy waves can impact the beach face at spring low tide due to a combination of wave setup and strong ig wave activity under mean wave conditions the combined influence of setup ig waves and ss waves results in interaction with island sediment at midtide at high tide ss and ig waves directly impact the beach face overall wave activity is present on the beach face for 71 of the study period a significantly longer duration than is calculated using mean water level and topographic data

standing infragravity waves over an alongshore irregular rocky bathymetry rocky reef coastlines typically feature highly variable and often abrupt cross shore and alongshore changes in bathymetry the effects of this irregular rocky bathymetry on the dynamics of infragravity waves are largely unknown most models of infragravity wave dynamics have been developed and validated on smooth alongshore uniform bathymetries which may break down over these highly variable bathymetries a 2 week field experiment was conducted on a rocky reef fringed beach to investigate how the variable bathymetry affects the spatial and temporal variability of infragravity waves the height of short sea swell waves decreased over the shallow reef due to breaking whereas the height of infragravity waves increased toward the shoreline both during a storm event hm0 2 3 m and under moderate wave conditions hm0 1 0 1 8 m the infragravity waves formed a persistent cross shore standing wave pattern along the entire shoreline despite the irregular bathymetry in addition the alongshore components of infragravity waves refracted by the presence of the nearshore reef were observed to propagate in opposite directions up and down the coast resulting in a local alongshore standing wave pattern thus the presence of highly variable nearshore bathymetry which commonly occurs along rocky reef coastlines may produce both cross shore and alongshore standing wave patterns

the offshore boundary condition in surf zone modeling abstract numerical models predicting surfzone waves and shoreline runup in field situations are often initialized with shoreward propagating sea swell and infragravity waves at an offshore boundary in 10 30 m water depth we develop an offshore boundary condition based on fourier analysis of observations with co located current and pressure sensors that accounts for reflection and includes nonlinear phase coupling the performance of additional boundary conditions derived with limited or no infragravity observations are explored with the wave resolving nonlinear model swash 1d in some cases errors in the reduced boundary conditions applied in 11 m depth propagate shoreward whereas in other cases errors are localized near the offshore boundary boundary conditions that can be implemented without infragravity observations e g bound waves do not accurately simulate infragravity waves across the surfzone and could corrupt predictions of morphologic change however the bulk properties of infragravity waves in the inner surfzone and runup are predicted to be largely independent of ig offshore boundary conditions and dominated by ig generation and dissipation

latest pleistocene to holocene loess in the central great plains optically stimulated luminescence dating and multi proxy analysis of the enders loess section nebraska usa abstract loess deposits of the central great plains usa and their intercalated soils provide a detailed record of climatically driven changes within the aeolian system during the pleistocene holocene transition and the holocene here we present a detailed optically stimulated luminescence osl chronology as well as multi proxy analysis obtained for the first time on the enders section located in southwestern nebraska central great plains the section records multiple episodes of rapid loess deposition alternating with soil formation rapid accumulation of late pleistocene peoria loess was replaced around 13 14 ka by formation of the brady soil until 9 5 0 6 ka the holocene bignell loess then buried the brady soil and accumulated episodically throughout the holocene the loess paleosol stratigraphy since the late pleistocene at the enders site is very similar to that at other sites in western nebraska and the newly developed osl chronology based on three grain size classes adds new confidence to earlier dating the high resolution grain size profile from enders shares many features with similar data from the previously studied wauneta site including three peaks of fine grained material just above and within the brady soil likely representing response to millennial scale climatic changes during the pleistocene holocene transition this study demonstrates the potential for developing high resolution well dated paleoclimatic records from the loess of the central great plains contrasts between great plains and eurasian loess records reflect differences in the late pleistocene to holocene climatic evolution and other factors influencing the loess system

kuwaiti dolocrete petrology geochemistry and groundwater origin abstract near surface sediments in southern kuwait show extensive development of duricrusts the host materials are siliciclastic sandstones of the post eocene kuwait group inland the duricrusts are dominantly pedogenic calcrete with some silcrete and gypcrete whereas within 10 20 km of the coast dolomite is the dominant duricrust mineral both these dolocretes and the inland calcretes display a similar maturation sequence in which carbonate rich nodules develop and coalesce carbonate progressively replacing and displacing detrital grains the dolomite of the dolocretes forms mosaics of crystals typically 10 70 m in size varying from simple rhombs to spherulites an intermediate morphology named artichoke dolomite from its appearance in sem is particularly abundant authigenic palygorskite is associated with the dolomite dissolution of cores or zones within dolomite crystals has occurred calcite is present as sparry crystals always post dating dolomite and is the expected precipitate from present day soil and groundwaters chemical analyses of dolomite show highly negative values of 13 c to 10 7 pdb and 18 o varying from 0 6 to 3 3 pdb the oxygen isotope values are interpreted as reflecting evaporation of a marine based fluid manganese values of around 1000 ppm show that this fluid was reducing strontium data show variability reflecting mineral fluid reactions the general absence of metastable carbonates and presence of zoning in dolomite crystals suggests that meteoric dilution of seawater also occurred given that the duricrusts lack biogenic features the light carbon isotope values are taken to indicate oxidation of seeping hydrocarbons the dolocretes are interpreted as groundwater precipitates near the water table of a brackish water body formed at a time of higher relative sea level than today

water level effects on breaking wave setup for pacific island fringing reefs the effects of water level variations on breaking wave setup over fringing reefs are assessed using field measurements obtained at three study sites in the republic of the marshall islands and the mariana islands in the western tropical pacific ocean at each site reef flat setup varies over the tidal range with weaker setup at high tide and stronger setup at low tide for a given incident wave height the observed water level dependence is interpreted in the context of radiation stress gradients specified by an idealized point break model generalized for nonnormally incident waves the tidally varying setup is due in part to depth limited wave heights on the reef flat as anticipated from previous reef studies but also to tidally dependent breaking on the reef face the tidal dependence of the breaking is interpreted in the context of the point break model in terms of a tidally varying wave height to water depth ratio at breaking implications for predictions of wave driven setup at reef fringed island shorelines are discussed

soils at the hyperarid margin the isotopic composition of soil carbonate from the atacama desert northern chile we evaluate the impact of exceptionally sparse plant cover 0 20 and rainfall 2 114 mm yr on the stable carbon and oxygen composition of soil carbonate along elevation transects in what is among the driest places on the planet the atacama desert in northern chile d 13 c and d 18 o values of carbonates from the atacama are the highest of any desert in the world d 13 c vpdb values from soil carbonate range from 8 2 at the wettest sites to 7 9 at the driest we measured plant composition and modeled respiration rates required to form these carbonate isotopic values using a modified version of the soil diffusion model of cerling 1984 earth planet sci lett 71 229 240 in which we assumed an exponential form of the soil co2 production function and relatively shallow 20 30 cm average production depths overall we find that respiration rates are the main predictor of the d 13 c value of soil carbonate in the atacama whereas the fraction c3 to c4 biomass at individual sites has a subordinate influence the high average d 13 c value 4 1 of carbonate from the driest study sites indicates it formed perhaps abiotically in the presence of pure atmospheric co2 d 18 o vpdb values from soil carbonate range from 5 9 at the wettest sites to 7 3 at the driest and show much less regular variation with elevation change than d 13 c values d 18 o values for soil carbonate predicted from local temperature and d 18 o values of rainfall values suggest that extreme 80 in some cases soil dewatering by evaporation occurs at most sites prior to carbonate formation the effects of evaporation compromise the use of d 18 o values from ancient soil carbonate to

calcretes related to phreatophytic vegetation from the middle triassic otter sandstone of south west england carbonate cementation in the triassic otter sandstone of budleigh salterton sw england occurs in two distinct forms large vertical concentrically zoned cyclinders and thin subhorizontal sheets the former represent rhizocretions of the tap roots of phreatophytic plants which colonized bars and abandoned channels on a large braidplain the sheets represent cementation around ancient water tables the precipitation of the rhizocretions took place at least in part during the life of the plants and 13c and 18o values support the view that evapo transpiration induced carbonate precipitation palaeosol profiles are rare in the otter sandstone reflecting the geomorphological instability of the braidplain surfaces in contrast rhizocretionary and sheet calcretes which formed several metres below the active depositional surface are abundant because they had a high preservation potential

infragravity waves on fringing reefs in the tropical pacific dynamic setup cross shore pressure and current observations from four fringing reefs of lengths ranging from 135 to 420 m reveal energetic low frequency 0 001 0 05 hz motions the spatial structure and temporal amplitudes of an empirical orthogonal function analysis of the pressure measurements suggest the dominant low frequency variability is modal incoming and outgoing linear flux estimates also support partially standing modes on the reef flat during energetic events a cross covariance analysis suggests that breakpoint forcing excites these partially standing modes similar to previous findings at other steep reefs the dynamics of symonds et al 1982 with damping are applied to a step reef with forcing obtained by extending a point break model of vetter et al 2010 for breaking wave setup to the low frequency band using the shoaled envelope of the incident free surface elevation a one parameter linear analytical model for the reef flat free surface elevation is presented which describes between 75 and 97 of the variance of the observed low frequency shoreline significant wave height for all reefs considered over a range of conditions the linear model contains a single dimensionless parameter that is the ratio of the inertial to dissipative time scales and the observations from this study exhibit more low frequency variability when the dissipative time scale is greater than the inertial time scale for the steep reefs considered

from a black to a gray box a mass balance interpretation of pedogenesis we utilize chemical elements as tracers in a mass balance analysis that provides functional relationships among soil chemical composition bulk density and volume change in relation to parent material these analytical functions are based on the principle of conservation of mass and include a term quantifying mass flux into out of the soil and between horizons we apply the technique to the oldest member of a chronosequence developed on marine terraces in northern california it is an alfisol that evolved from beach sand to its present state nearly one third of its weight is composed of secondary clay minerals in about 240 ky aside from large increases in organic carbon desilication is the dominant factor in soil evolution 29 50 83 g cm 2 si was leached from the beach sand during pedogenesis the rate of desilication is roughly 2 1 t km 2 yr 1 0 21 g cm 2 ky 1 an order of magnitude slower than that implied by the si denudation rate calculated for the mattole river watershed weathering of primary minerals and synthesis of secondary minerals is relatively well advanced suggesting that the rate of desilication may be declining the local beach is composed of quartz and sodic plagioclase with smaller amounts of chlorite mica and kaolinite the soil has substantially different mineralogy sand is dominated by quartz and clay is dominated by kaolinite halloysite chloritic intergrades and gibbsite bases are also leached though the total mass was much less 57 2 55 g cm 2 of na in the beach sand was lost as plagioclase weathered by focusing on elemental and mineralogical gains and losses we emphasize the essential connection between the pedologic environment and the external hydrochemical environment

wave run up on a high energy dissipative beach 1 because of highly dissipative conditions and strong alongshore gradients in foreshore beach morphology wave run up data collected along the central oregon coast during february 1996 stand in contrast to run up data currently available in the literature during a single data run lasting approximately 90 min the significant vertical run up elevation varied by a factor of 2 along the 1 6 km study site ranging from 26 to 61 of the offshore significant wave height and was found to be linearly dependent on the local foreshore beach slope that varied by a factor of 5 run up motions on this high energy dissipative beach were dominated by infragravity low frequency energy with peak periods of approximately 230 s incident band energy levels were 2 5 to 3 orders of magnitude lower than the low frequency spectral peaks and typically 96 of the run up variance was in the infragravity band a broad region of the run up spectra exhibited an f 4 roll off typical of saturation extending to frequencies lower than observed in previous studies the run up spectra were dependent on beach slope with spectra for steeper foreshore slopes shifted toward higher frequencies than spectra for shallower foreshore slopes at infragravity frequencies run up motions were coherent over alongshore length scales in excess of 1 km significantly greater than decorrelation length scales on moderate to reflective beaches

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

paleoclimatic implications of pedogenic carbonates in holocene soils of the gangetic plains india abstract this study attempts to reconstruct the holocene climatic history of the indo gangetic plains based on micromorphological characteristics and stable isotope composition of calcretes in a soil chronoassociation between the ramganga and rapti rivers the calcrete from the b2 horizon of older soils qgh4 qgh5 6500 13 500 year bp consists of septaric and irregularly shaped nodules of dense micrite and diffused needles associated with the illuvial clay pedofeatures fabric of the calcretes of older soils show inclusion of soil constituents and precipitation of carbonates in between weathered layers of micas formation of this calcrete took place during the pedogenesis in an arid to semi arid climate that also influenced vegetation and c4 type biomass such as chenopodium and typha angustata spread in the area a change to warm and humid phase at 6500 year bp led to dissolution and reprecipitation of the calcretes this led to the formation of blocky crystals and needles of calcite in voids and coarsening of the fabric in the lower horizons the vegetation pattern also changed to woodland with anogeissus and tecomella spp the younger soils bp show secondary carbonate accumulation associated mainly along the voids in lower parts of the profiles these are relatively coarse textured with little or no inclusion of soil constituents this coarse grained calcrete results from capillary rise from a fluctuating water table in a sub humid climate similar to present carbon and oxygen isotope data suggest that the formation of pedogenic carbonate in old soils qgh4 and qgh5 by evapotranspiration during arid to semi arid climate in the upper horizons the carbonates are depleted in 13c as their formation was influenced by the sparse vegetation and low soil respiration rate in the lower horizons the carbonates show enrichment of 13c due its extensive dissolution reprecipitation during the humid climate the younger soils showed the enrichment of 13c in their calcretes and support their formation from fluctuating shallow groundwater table the oxygen isotope values similar to that of meteoric water of the area indicate calcrete precipitation in equilibrium with the soil water

observations of runup and energy flux on a low slope beach with high energy long period ocean swell the transformation of surface gravity waves from 11 m depth to runup was observed on the low sloped 1 80 agate beach oregon with a cross shore transect of current meters pressure sensors and a scanning lidar offshore wave heights h0 ranged from calm 0 5 m to energetic 7 m runup measured with pressure sensors and a scanning lidar increases linearly with h0l0 1 2 with l0 the deep water wavelength of the spectral peak runup saturation in which runup oscillations plateau despite further increases in h0l0 1 2 is not observed infragravity wave shoaling and nonlinear energy exchanges with short waves are included in an infragravity wave energy balance this balance closes for high infragravity frequencies 0 025 0 04 hz but not lower frequencies 0 003 0 025 hz possibly owing to unmodeled infragravity energy losses of wave breaking and or bottom friction dissipative processes limit but do not entirely damp increases in runup excursions in response to increased incident wave forcing

late quaternary weathering erosion and deposition in nahal yael israel an impact of climatic change on an arid watershed in their seminal paper in 1979 bull and schick proposed a conceptual model for the geomorphic response to pleistocene to holocene climate change based on the hyperarid nahal yael watershed in the southern negev desert in this model the change from semiarid late pleistocene to hyperarid early holocene climates reduced vegetation cover increased the yield of sediment from slopes and accelerated aggradation of terraces and alluvial fans the model is now over 30 yr old and during this time chronologic paleoenvironmental and hydrogeomorphic research has advanced here we reevaluate the model using data acquired in nahal yael over the 30yr since the original model was proposed recent studies indicate that the late pleistocene climate was hyperarid and a transition from semiarid to hyperarid climates did not occur the revised chronology reveals a major 35 20 ka episode of accelerated late pleistocene sediment production on slopes with lower rates probably already at ca 50ka due to increased frequency of wetting drying cycles caused by frequent extreme storms and floods between 35 and 27 ka without lag time these sediments were transported and aggraded in depositional landscape components fluvial terraces and alluvial fans this intensified sediment production and delivery phase is unrelated to the pleistocene holocene transition the depositional landforms were rapidly incised between 20 and 18 ka since and or soon after this last glacial maximum lgm incision most material leaving the basin originated from sediments stored in depositional landforms and was not produced from bedrock using these new data we propose a revision to the bull and schick model in this hyperarid environment our revision suggests that the model should include the frequent storms and floods responsible for a late pleistocene pulse of intense weathering due to numerous cycles of wetting and drying on slopes and coeval sediment transport to fluvial terraces and alluvial fans we also discuss the common use and pitfalls of using the bull and schick conceptual model to explain observations in diverse arid environments usually without sufficient data on basin specific stratigraphic chronologic paleoenvironmental and paleoclimatic information

response of a modern cave system to large seasonal precipitation variability abstract speleothems are capable of providing information on the response of middle and low latitude terrestrial environments to global climate change during the pleistocene and holocene multiproxy speleothem studies however have demonstrated that complex interactions can occur in cave settings between processes that are directly and indirectly related to climate change thorough and extended monitoring of modern cave environments is necessary in order to fully understand how each cave responds to these processes on seasonal and interannual timescales and how environmental signals are preserved in speleothem carbonate regular environmental monitoring began at black chasm cavern in the sierra nevada foothills california during the winter of 2006 2007 monthly measurements of cave air temperature humidity and p co 2 in black chasm demonstrate that the cave is ventilated in the winter months when cold dense surface air sinks into the cave cave drip water flow nearly ceases during the late summer and autumn increases substantially during the winter and spring and responds within hours to storm events during the height of the rainy season rainwater and drip water 18 o and 2 h are controlled by variations in surface air temperature and moisture source while rainfall source influences rainwater isotopes through individual storm events it has less influence on drip water isotopic composition due to mixing of recharge waters delivered by different rainfall events in the epikarst variations in drip water chemistry 13 c mg ca and sr ca indicate that the greatest level of calcite precipitation upflow from the drip water collection site prior calcite precipitation occurs during the autumn october november when drip rates are slow and cave air p co 2 is low the least prior calcite precipitation occurs during the summer july august when drip rates are slow but cave air p co 2 is at a maximum while p co 2 is a primary control on prior calcite precipitation during all seasons the predominant influence of drip rate variability on prior calcite precipitation is evident when considering only those seasons winter spring and autumn characterized by low cave air p co 2 thus drip rate variability and in turn rainfall amount should provide the primary control on trace element variations ultimately captured in speleothem calcite the isotopic and chemical variability observed in black chasm drip waters supports previous interpretations of speleothem paleoclimate proxy records from a nearby cave where such monitoring is not feasible observations of the modern cave environment at black chasm provide a reference point for the interpretation of stalagmite proxy records from similar seasonal mediterranean climates

numerical modeling of infragravity wave response during delilah 1 the nearshore circulation model shorecirc is applied to simulate the infragravity wave conditions at two intervals during the 1990 delilah campaign at duck n c the model has been extended to solve the energy equation for random short waves on the timescale of the wave groups which acts as a wave driver for the long wave model to simulate the wave conditions an algorithm has been derived which synthesizes a directional offshore wavefield from measured data including the bound directional low frequency components the model data comparison shows that the mean short wave transformation and mean longshore current are predicted well the structure of the infragravity spectrum as measured in the nearshore array is correctly represented albeit that the energy levels are underpredicted in most locations the 2 d frequency longshore wavenumber spectra show that the infragravity wave energy consists mostly of edge waves and that the computations qualitatively resemble the measurements it is shown that for 1 day bar trapped edge waves are present the model is also used to show that the influence of the longshore variability is small for this particular beach and that the directional spreading in the offshore wave field is critical in predicting the nearshore infragravity wave conditions correctly edge waves which propagate against the current are generated by the directionally broad short wave forcing and to a lesser extent by back scattering the nonlinear terms are relatively unimportant for the prediction of the infragravity wave climate the cross shore gradient of the onshore directed radiation stress is the most important of the forcing terms

δ18o and δ13c records from a cenozoic sedimentary sequence in the lanzhou basin northwestern china implications for palaeoenvironmental and palaeoecological changes abstract in northwestern china carbonate 18 o variation has been closely associated with evaporation and precipitation whereas the variation of carbonate 13 c generally reflects patterns of palaeovegetation located within the transitional zone between the chinese loess plateau and the tibetan plateau the lanzhou basin has developed a continuous sequence of cenozoic sediments which have been subjected to detailed sedimentological and high resolution magnetostratigraphic analyses in the present study pedogenic carbonate o and c isotopic analyses were obtained throughout the entire cenozoic sequence the 18 o record exhibits a general positive trend with several abrupt changes a dramatic positive shift in the 18 o record at 33 ma indicates the initiation of the aridification process within the basin which was likely associated with the late eocene westward retreat of the tethys sea and global cooling two significant positive shifts in the 18 o record at 22 ma and 3 5 ma are synchronous with major increases in aeolian dust deposition on the chinese loess plateau and in the north pacific ocean suggesting the intensified aridity of the asian interior which is likely related to the stepwise uplift of the tibetan plateau via the blocking of water vapour pathways the 13 c values exhibit a weak positive trend with a remarkable shift at 3 5 ma this trend is likely related to a decrease in vegetation density in response to the ongoing cenozoic aridification whereas the shift at 3 5 ma may reflect the large scale expansion of c 4 plants

abiotic versus biotic controls on the development of the fairmont hot springs carbonate deposit british columbia canada the relict fairmont hot springs deposit formed largely of carbonates covers an area of 0ae 5k m 2 and is up to 16 m thick the triangle shaped discharge apron which broadens down valley is divided into a proximal part with beds dipping at 10 and a distal part with beds dipping at 10 to 15 the deposit is formed of the 1 basal macrophyte 2 lower carbonate 3 middle clastic 4 upper carbonate and 5 upper clastic sequences two charcoal samples embedded in the lower carbonate sequence yielded dates of 8690 90 and 8270 70 cal yr bp indicating that much of the deposit formed post glacially during the early to mid holocene deposit aggradation ceased in the mid to late holocene when the fairmont creek valley was incised the lower and upper carbonate sequences which are the thickest sequences are composed of nearly equal parts of travertine abiotic and tufa biotic with feather dendrite travertine radiating dendrite travertine and stromatolite tufa dominating competition between calcite precipitation rates and biotic growth rates controlled the distribution of tufa and travertine across the discharge apron calcite and biotic growth rates were controlled largely by flow velocity across the apron which in turn was controlled by topography and regular fluctuations in spring water discharge volume during times of high spring discharge slow sheet flow over the proximal part of the apron promoted stromatolite growth whereas fast turbulent flow on the distal part of the apron induced rapid feather dendrite formation during times of low spring discharge quiescent shallow evaporative pools conducive to radiating dendrite formation formed on the proximal part of the apron whereas slow flow on the distal part promoted stromatolite growth facies with high calcite supersaturation experienced rapid abiotic dendrite growth that precluded most biotic growth