dating of pore waters with 129 i relevance for the origin of marine gas hydrates pore waters associated with gas hydrates at blake ridge in the atlantic ocean were dated by measuring their iodine 129 iodine ratios samples collected from sediments with ages between 1 8 and 6 million years ago consistently yield ages around 55 million years ago these ages together with the strong iodine enrichment observed in the pore waters suggest that the origin of iodine is related to organic material of early tertiary age which probably is also the source of the methane in the gas hydrates at this location

halogen systematics in the mallik 5l 38 gas hydrate production research well northwest territories canada implications for the origin of gas hydrates under terrestrial permafrost conditions abstract the authors report here halogen concentrations in pore waters and sediments collected from the mallik 5l 38 gas hydrate production research well a permafrost location in the mackenzie delta northwest territories canada iodine and br are commonly enriched in waters associated with ch4 reflecting the close association between these halogens and source organic materials pore waters collected from the mallik well show i enrichment by one order of magnitude above that of seawater particularly in sandy layers below the gas hydrate stability zone ghsz although cl and br concentrations increase with depth similar to the i profile they remain below seawater values the increase in i concentrations observed below the ghsz suggests that i rich fluids responsible for the accumulation of ch4 in gas hydrates are preferentially transported through the sandy permeable layers below the ghsz the br and i concentrations and i br ratios in mallik are considerably lower than those in marine gas hydrate locations demonstrating a terrestrial nature for the organic materials responsible for the ch4 at the mallik site halogen systematics in mallik suggest that they are the result of mixing between seawater freshwater and an i rich source fluid the comparison between i br ratios in pore waters and sediments speaks against the origin of the source fluids within the host formations of gas hydrates a finding compatible with the results from a limited set of 129i i ratios determined in pore waters which gives a minimum age of 29 ma for the source material i e at the lower end of the age range of the host formations the likely scenario for the gas hydrate formation in mallik is the derivation of ch4 together with i from the terrestrial source materials in formations other than the host layers through sandy permeable layers into the present gas hydrate zones

recycling of iodine in fore arc areas evidence from the iodine brines in chiba japan the distribution of iodine in the earth s crust is dominated by its accumulation in marine sediments if fluxes between terrestrial and marine compartments are considered however a significant imbalance exists between known sources and sinks of iodine we present here evidence from the fore arc area near chiba japan the world s largest brine iodine producing area that iodine is mobilized from marine sediments during the early stages of subduction based on detailed chemical analyses of 22 brines and 129i dating of 13 of these samples collected from the kazusa formation we show that iodine in these fluids is derived from organic rich marine sediments with a minimum age of 50 myr geochemical characteristics of the brines and the age of the iodine indicate that the iodine enrichment is caused by mobilization from subducting marine sediments and not by derivation from the host formation age 1 2 myr the direct return of iodine from marine sediments into the oceans during the subduction of oceanic plates could provide the missing link in the iodine cycle and be an important pathway also in the marine cycle of carbon

the effects of variability in bank material properties on riverbank stability goodwin creek mississippi abstract bank retreat is an important area of research within fluvial geomorphology and is a land management problem of global significance the yazoo river basin in mississippi is one example of a system which is experiencing excessive erosion and bank instability the properties of bank materials are important in controlling the stability of stream banks and past studies have found that these properties are often variable spatially through an investigation of bank material properties on a stretch of goodwin creek in the yazoo basin mississippi this study focuses on i how and why effective bank material properties vary through different scales ii how this variation impacts on the outputs from a bank stability model and iii how best to appropriately represent this variability within a bank stability model the study demonstrates the importance that the variability of effective bank material properties has on bank stability at both the micro scale within a site and at the meso scale between sites in a reach this variability was shown to have important implications for the usage of the bank stability and toe erosion model bstem a deterministic bank stability model that currently uses a single value to describe each bank material property as a result a probabilistic representation of effective bank material strength parameters is recommended as a potential solution for any bank stability model that wishes to account for the important influence of the inherent variability of soil properties

halogen and 129i systematics in gas hydrate fields at the northern cascadia margin iodp expedition 311 insights from numerical modeling we measured halogen concentrations and i 129 i ratios in five drilling sites of integrated ocean drilling program expedition 311 offshore vancouver island canada in order to identify potential sources of fluids and methane in gas hydrate fields iodine is dominated by organic decomposition and transports with fluids in reducing environments and the presence of the cosmogenic radioisotope i 129 t 1 2 15 7 ma allows the age determination of organic sources for iodine here we report halogen concentrations in 135 pore water samples i concentrations in 48 sediment samples and i 129 i ratios measured in a subset of 20 pore water samples most i 129 i ratios fall into a range around 500 x 10 15 corresponding to a minimum age of 25 ma and the lowest ratio of 188 x 10 15 t min 47 ma was observed at 208 m below sea floor mbsf in site 1326 these ages are considerably older than that of the local sediments in the gas hydrate fields and that of the subducting sediments on the juan de fuca plate indicating that old accreted sediments in the accretionary wedge contribute a significant amount of iodide and by association of methane to the gas hydrate occurrences a geochemical transport reaction model was applied to simulate the advection of deeply sourced fluids and the release of iodide bromide and ammonia in the host sediments due to organic matter degradation the model was first tested with data from two well studied areas ocean drilling program site 1230 peru margin and site 1245 hydrate ridge the model results for the expedition 311 sites indicate that the in situ release of young iodine is relatively minor in comparison to the contribution of migrating fluids carrying large amounts of old iodine from deep sources the comparison between the sites demonstrates that the total organic content has a strong effect on the rate of in situ iodine release and that lateral flows along fractures can have a significant influence on pore water chemistry especially at the cascadia margin the iodine results indicate that mobilization and transport of methane from sources in the upper plate of active margins is an important process which can also play a substantial role in the formation of gas hydrate fields

relations among subduction parameters clues to the dynamics of the subduction process are found in the many measurable parameters of modern subduction zones based on a critical appraisal of the geophysical and geological literature 26 parameters are estimated for each of 39 modern subduction zones to isolate causal relationships among these parameters multivariate analysis is applied to this data set this analysis yields empirical quantitative relations that predict strain regime and strike slip faulting in the overriding plate maximum earthquake magnitude benioff zone length slab dip arc trench gap and maximum trench depth excellent correlation is found between length of the benioff zone and the product of convergence rate and age of the downgoing slab this relationship is consistent with the conductive heating model of molnar et al 1979 if the model is modified in one respect the rate of heating of the slab is not constant it is substantially slower during passage of the slab beneath the accretionary prism and overriding plate the structural style in the overriding plate is determined by its stress state though the stress state of overriding plates cannot be quantified one can classify each individual subduction zone into one of seven semiquantitative strain classes that form a continuum from strongly extensional class 1 back arc spreading to strongly compressional class 7 active folding and thrusting this analysis indicates that strain class is probably determined by a linear combination of convergence rate slab age and shallow slab dip interplate coupling controlled by convergence rate and slab age is an important control on strain regime and the primary control on earthquake magnitude arc parallel strike slip faulting is a common feature of convergent margins forming a forearc sliver between the strike slip fault and trench optimum conditions for the development of forearc slivers are oblique convergence a compressional environment and a continental overriding plate the primary factor controlling presence of strike slip faulting is coupling strongly oblique convergence is not required the rate of strike slip faulting is affected by both convergence obliquity and convergence rate maximum trench depth is a response to flexure of the underthrusting plate the amount of flexural deflection at the trench depends on the vertical component of slab pull force which is very sensitive to slab age and shallow slab dip shallow slab dip conforms to the cross sectional shape of the overriding plate which is controlled by width of the accretionary prism and duration of subduction deep slab dip is affected by the mantle trajectory established at shallow depth but may be modified by mantle flow much of the structural complexity of convergent margins is probably attributable to terrane juxtaposition associated with temporal changes in both forearc strike slip faulting and strain regime empirical equations relating subduction parameters can provide both a focus for future theoretical studies and a conceptual and kinematic link between plate tectonics and the geology of subduction zones

thermodynamic and pore water halogen constraints on gas hydrate distribution at odp site 997 blake ridge abstract marine sediment sequences with ch4 hydrate are characterized by an atypical depth profile in dissolved cl squeezed from pore space a shallow subsurface cl maximum overlies a lengthy and pronounced cl minimum this pore water cl profile represents a combination of multiple processes including glacial interglacial variations in ocean salinity advection and diffusion of ions that are excluded during gas hydrate formation at depth and release of fresh water from dissociation of hydrate during core recovery in situ quantities of gas hydrate can be determined from a measured pore water cl profile provided the in situ pore water signature prior to core recovery can be separated ocean drilling program odp site 997 was drilled into a large ch4 hydrate reservoir on the blake ridge in the western atlantic ocean previously we have constructed a high resolution pore water cl profile at this location here we present a coupled chloride hydrate numerical model to explain basic trends in the cl profile and to isolate in situ cl concentrations the model is based on thermodynamic and ecological considerations and uses established equations for describing chemical behavior in marine sediment pore water systems the model incorporates four key concepts 1 most gas hydrate is formed immediately below the so42 reduction zone 2 fluid dissolved ions and gas advect upward through the sediment column 3 ch4 hydrate dissociates at the base of hydrate stability conditions and 4 seawater salinity fluctuates during glacial interglacial cycles of the late pliocene and quaternary rates of upward advection in the model are sufficient to account for measured br and i concentrations as well as ch4 oxidation at the base of the so42 reduction zone in situ pore water cl inferred from the model is similar to that determined by limited direct sampling in situ ch4 hydrate amounts inferred from the model an average of about 4 of porosity are broadly consistent with those determined by direct gas sampling and indirect geophysical techniques the model also predicts production of substantial quantities of free ch4 gas bubbles 2 5 of porosity at a depth immediately below the lowest accumulation of ch4 hydrate in the sediment column our explanation for the pore water cl profile at site 997 is important because it provides a theoretical mechanism for understanding the distribution of interstitial water cl gas hydrate and free gas in a marine sediment column

hydrological and sedimentary controls over fluvial thermal erosion the lena river central yakutia abstract water regime and sedimentary features of the middle lena river reach near yakutsk central yakutia were studied to assess their control over fluvial thermal erosion the lena river floodplain in the studied reach has complex structure and embodies multiple levels varying in height and origin two key sites corresponding to high and medium floodplain levels were surveyed in 2008 to describe major sedimentary units and properties of bank material three units are present in both profiles corresponding to topsoil overbank cohesive and channel fill noncohesive deposits thermoerosional activity is mostly confined to a basal layer of frozen channel fill deposits and in general occurs within a certain water level interval magnitude frequency analysis of water level data from tabaga gauging station shows that a single interval can be deemed responsible for the initiation of thermal action and development of thermoerosional notches this interval corresponds to the discharges between 21 000 and 31 000 m 3 s 1 observed normally during spring meltwater peak and summer floods competence of fluvial thermal erosion depends on the height of floodplain level being eroded as it acts preferentially in high floodplain banks in medium floodplain banks thermal erosion during spring flood is constrained by insufficient bank height and erosion is essentially mechanical during summer flood season bank retreat rate is argued to be positively linked with bank height under periglacial conditions

a terrain based site conditions map of california with implications for the contiguous united states abstract we present an approach based on geomorphometry to predict material properties and characterize site conditions using the v s 30 parameter time averaged shear wave velocity to a depth of 30 m our framework consists of an automated terrain classification scheme based on taxonomic criteria slope gradient local convexity and surface texture that systematically identifies 16 terrain types from 1 km spatial resolution 30 arcsec shuttle radar topography mission digital elevation models srtmdems using 853 v s 30 values from california we apply a simulation based statistical method to determine the mean v s 30 for each terrain type in california we then compare the v s 30 values with models based on individual proxies such as mapped surface geology and topographic slope and show that our systematic terrain based approach consistently performs better than semiempirical estimates based on individual proxies to further evaluate our model we apply our california based estimates to terrains of the contiguous united states comparisons of our estimates with 325 v s 30 measurements outside of california as well as estimates based on the topographic slope model indicate our method to be statistically robust and more accurate our approach thus provides an objective and robust method for extending estimates of v s 30 for regions where in situ measurements are sparse or not readily available

iodine ages of pore waters at hydrate ridge odp leg 204 cascadia margin implications for sources of methane in gas hydrates hydrate ridge off the coast of oregon usa is a prime example for gas hydrate occurrences in active margin settings it is part of the cascadia margin and was the focus of ocean drilling program odp leg 204 which successfully recovered fluids from nine sites from the southern part of the ridge iodide concentrations in pore fluids associated with gas hydrates are strongly enhanced by factors up to 5000 compared to seawater which allows the use of this biophilic element as tracer for organic source regions we applied the cosmogenic isotope 129 i t 1 2 15 7 ma system to determine the age of the organic source formation responsible for the iodide enrichment in all sites at odp leg 204 129 i i ratios were found to decrease with depth to values around 250 10 15 corresponding to minimum ages of 40 ma but in several sites maxima in the 129 i i ratios point to the local addition of young iodide the results indicate that a large amount of iodide was derived from deep accreted sediments of eocene age and that additional source regions provide iodide of late miocene age the presence of old iodide in the pore waters suggests that fluid pathways are open to allow transport over large distances into the gas hydrate fields the strong correlation between iodide and methane in hydrate fields coupled with the similarity in transport parameters in aqueous solutions suggests that a large fraction of methane in gas hydrates also has old sources and is transported into the present locations from source regions of eocene age

rates of soil development from four soil chronosequences in the southern great basin abstract four soil chronosequences in the southern great basin were examined in order to study and quantify soil development during the quaternary soils of all four areas are developed in gravelly alluvial fans in semiarid climates with 8 to 40 cm mean annual precipitation lithologies of alluvium are granite gneiss at silver lake granite and basalt at cima volcanic field limestone at kyle canyon and siliceous volcanic rocks at fortymile wash ages of the soils are approximated from several radiometric and experimental techniques and rates are assessed using a conservative mathematical approach average rates for holocene soils at silver lake are about 10 times higher than for pleistocene soils at kyle canyon and fortymile wash based on limited age control holocene soils in all four areas appear to develop at similar rates and pleistocene soils at kyle canyon and fortymile wash may differ by only a factor of 2 to 4 over time spans of several millennia a preferred model for the age curves is not linear but may be exponential or parabolic in which rates decrease with increasing age these preliminary results imply that the geographical variation in rates within the southern great basin mojave region may be much less significant than temporal variation in rates of soil development the reasons for temporal variation in rates and processes of soil development are complexly linked to climatic change and related changes in water and dust erosional history and internally driven chemical and physical processes

a blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

10be distribution in soils from merced river terraces california abstract the distribution and residence time of cosmogenic 10 be in clay rich soil horizons is fundamental to understanding and modelling the migration of 10 be on terrestrial sediments and in groundwater solutions we have analyzed seven profiles of clay rich soils developed from terrace sediments of the merced river california the terraces and soils of increasing age are used to compare the 10 be inventory with a simple model of accumulation decay and erosion the data show that the distribution of 10 be varies with soil horizon clay content that the residence time of 10 be in these horizons exceeds 10 5 years and that to a rough approximation the inventory of 10 be in a thoroughly sampled soil profile fits the equation n q em 1 e where q is delivery rate e is erosion rate m is the concentration of 10 be in the eroding surface layer is the decay constant and t is the age of the depositional unit from which the soil has developed the general applicability of this model is uncertain and warrants further testing in well calibrated terrace sequences

old iodine in fluids venting along the central american convergent margin focused fluid expulsion at cold vents is a common feature of subduction zones serving as an important backflux of water and volatile elements to the oceanic reservoir the strong enrichment of iodine in fluids collected from mounds along the central american convergent margin allowed the determination of 129i i ratios for age calculations in order to determine potential source formations in this active erosional margin the majority of the determined iodine ages are between 40 and 20 ma because these ages are older than the age of host sediments and underthrust sediments on the oceanic plate 18 ma a major contribution of iodine must come from old organic rich sources in the upper plate both the iodine concentrations and ages determined for the mounds in this study are similar to reported values for hydrate fields at accretionary margins indicating that iodine and associated organic carbon cycling at both erosional and accretionary margins may occur on similar time scales

comparison of stable isotopes ratios of 36cl cl and 129i 127i in brine and deep groundwater from the pacific coastal region and the eastern margin of the japan sea abstract fifty three samples including brines associated with oil and natural gas reservoirs and groundwater samples from deep boreholes were collected from the pacific and japan sea coastal regions in japan the 129 i 127 i and 36 cl cl ratios and stable isotopes d and 18 o are compared to investigate differences related to the geotectonic settings of the two regions the d and 18 o data indicate that brine and groundwater from the pacific coastal region reflect mixing of meteoric water with connate seawater in the pores of sedimentary rocks on the other hand brine and groundwater from the japan sea coastal region have been hydrothermally altered in particular brines associated with petroleum accumulations at niigata and akita showed the same isotopic characteristics as fluids found in the kuroko deposits of the green tuff region in northeastern japan there is little difference in the 36 cl cl ratios in brine and groundwater from the pacific and japan sea coasts most brine and some deep groundwater except those from the pleistocene kazusa group have already reached the average secular equilibrium ratio of 9 9 2 7 10 15 for their mudstone and sandstone reservoirs there was no correlation between the 36 cl cl ratios and differences in geotectonic setting between the pacific and the japan sea coast the molar i br ratio suggests that the i in all of water samples was of biogenic origin the average 129 i 127 i ratio was 290 130 10 15 to 294 105 10 15 in both regions showing no relationship to the different geotectonic settings the uncontaminated brine and groundwater samples are likely to have retained the original 129 i 127 i ratios of marine i released from the old organic matter stored in sedimentary rock

129i and 36cl in dilute hydrocarbon waters marine cosmogenic in situ and anthropogenic sources abstract the long lived halogen radioisotopes 129 i and 36 cl provide valuable information regarding the source of fluids in hydrocarbon systems and in localized areas where infiltration of younger meteoric water has occurred despite the utility of these two isotopes in providing time signatures for fluid end members considerable uncertainty remains regarding the interpretation of intermediate age waters in hydrologic systems these waters are likely the result of the combination of two or more halogen sources at some time in the past each with its own characteristic concentration and isotopic composition in order to unravel the evolution of these intermediate age waters the effect that infiltration of meteoric water has on the isotopic composition of older formation waters is modeled also evaluated is the effect that the timing of dilution has on 129 i and 36 cl signatures observed in the present specifically the hypothesis that halogen isotopic signatures imparted by the mixing of brine and meteoric waters early in the development of a sedimentary basin are quantitatively different from those imparted by the mixing of old brines with recent meteoric waters the modeled results are compared to previously published isotopic data from production wells in the fruitland formation coalbed methane system portions of the basin preserve enough of the original brine source to retain 129 i i ratios roughly recording the age of deposition of organic matter 73 76 ma even where some degree of dilution by meteoric water has occurred however the 129 i signatures of waters that presently contain less than 10 of the original formation water component indicate that mixing has occurred within the past 10 ma consistent with recently published 4 he data both 36 cl concentrations and 36 cl cl ratios show that waters containing more than 10 formation water are all in secular equilibrium with the host formation coals in contrast waters with less than 1 of the original formation water s cl content all have 36 cl cl ratios which are greater than secular equilibrium values indicating the migration of meteoric water into the coal formation more recently than 2 ma although 36 cl signatures in the fruitland formation are not significantly affected by anthropogenic input 129 i i ratios in a subset of samples that retain less than 1 of the initial formation water component suggest input of anthropogenic 129 i during the past 50 a

genetic interpretations of elemental and chemical differences in a soil chronosequence california abstract soils developed on fluvial terraces in central california have similar parent materials climatic settings vegetation cover and slopes but range in age from 40 000 to 3 000 000 years the soils have chemical compositions that change systematically with increasing age such chemical differentiation is most likely the result of long term weathering and mineralogical transformations that occurred since deposition of terrace fills and stabilization of the geomorphic surfaces the changes in composition with time closely mimic other studies on mineral weathering in which alkali and alkali earth elements are lost more rapidly than transitional elements the relative rates of element loss were determined by changes in element ratios over time net losses and gains of elements in different size fractions were monitored by their concentrations relative to zr the most stable constituent both sand and finer size fractions have lost considerable amounts of ca mg na and k aluminum appears to have been lost from the sand fraction and gained in the fine fraction over a 3 million year time span although there is no evidence for losses of fe and ti from sands there is a net influx of fe and ti into finer fractions probably gained from undetectable yet significant weathering of sand grains etching of sand grains clay mineralogy and microprobe analyses also indicate that the soils have undergone these chemical transformations during their formation mineralogical analyses also mimic other studies on mineral weathering in which the pyroxenes weather more rapidly than hornblende which weathers more rapidly than sphene or zircon

tracing crustal fluids applications of natural 129i and 36cl the two cosmogenic isotopes 129i and 36cl have half lives and geochemical characteristics that make their application of interest in the tracing of crustal fluids oil field brines and geothermal fluids the focus of this review is to compare 129i data from volcanic fluids with those from mud volcanoes and gas hydrate locations associated with the same subduction zone in order to demonstrate that fundamentally different hydrologic systems are present in active margins whereas 129i i ratios in volcanic fluids are site dependent and show a relation to the ages of subducting marine sediments ratios in fore arc fluids are similar in all sites investigated and are independent of the ages of the host sediments and the age of the subducting slab volcanic fluids contain iodine transported in sediments from the trench to the main volcanic zone whereas iodine in fore arc fluids is derived from organic material stored in the upper plates of subduction zones

halogen concentrations in pore waters and sediments of the nankai trough japan implications for the origin of gas hydrates abstract presented here are halogen concentrations cl br and i in pore waters and sediments from three deep cores in gas hydrate fields of the nankai trough area the three cores were drilled between 1999 and 2004 in different geologic regions of the northeastern nankai trough hydrate zone iodine concentrations in all three cores increase rapidly with depth from seawater concentrations 0 00043 mmol l to values of up to 0 45 mmol l the chemical form of i was identified as i in accordance with the anaerobic conditions in marine sediments below the so 4 reduction depth the increase in i is accompanied by a parallel although lesser increase in br concentrations while cl concentrations are close to seawater values throughout most of the profiles large concentration fluctuations of the three halogens in pore waters were found close to the lower boundary of the hydrate stability zone related to processes of formation and dissociation of hydrates in this zone generally low concentrations of i and br in sediments and the lack of correlation between sediment and pore water profiles speak against derivation of i and br from local sediments and suggest transport of halogen rich fluids into the gas hydrate fields differences in the concentration profiles between the three cores indicate that modes of transportation shifted from an essentially vertical pattern in a sedimentary basin location to more horizontal patterns in accretionary ridge settings because of the close association between organic material and i and the similarity of transport behavior for i and ch 4 the results suggest that the ch 4 in the gas hydrates also was transported by aqueous fluids from older sediments into the present layers

sources of solutes and heat in low enthalpy mineral waters and their relation to tectonic setting new zealand abstract approximately 90 of the low enthalpy spring systems in new zealand are distributed along the present day convergence of the pacific and australian plates which varies from subduction to oblique plate collision forearc subducted waters rising in the hikurangi accretionary prism consist of pore waters containing labile organic material water of hydration from clays and seawater these subducted waters are traceable in the north island axial ranges and the northern marlborough fault system in the south island albeit modified by temperature mixing with surface and heated meteoric waters and protracted interaction with the rock the signature of subducted marine sediments in the hikurangi trench is retained in the chemical and isotopic compositions of the taupo volcanic zone magmatic arc type waters the concentrations of b ba br ca cl i k li mg na rb and sr solutes found in high concentrations in forearc subducted waters increase from northeast to southwest towards the incipient subduction zone in the puysegur trench southwest of south island most thermal mineral waters in the south island are expelled along the alpine fault zone where plate collision results to rapid uplift of the southern alps elevated geothermal gradients and fault shearing of rocks in the alpine fault zone variations in temperatures 175 30 c and mineral water compositions are affected by elevation hydrological gradient intensity of tectonic activity permeability fluid volume and rate of throughput and rates of uplift as the main trace of the alpine fault zone is approached concentrations of cl and other solutes generally increase suggesting increasing contributions from ascending cl rich metamorphic waters outside the active convergent zone low enthalpy springs discharge diagenetically modified ancient forearc waters na cl sedimentary formation waters and heated seawater na hco 3 cl waters and na hco 3 deep circulating heated meteoric waters the total surface heat flow in the north island low enthalpy mineral waters is more than 10 higher than in the south island with projected subsurface temperatures as high as 250 c this is because of the widespread occurrence of shallow magmatic and mantle sources associated with pliocene to holocene volcanism and back arc continental rifting the sources of heat and solutes in low enthalpy mineral waters outside the taupo volcanic zone and ngawha are decoupled except for rapidly ascending hot pore waters in the hikurangi accretionary prism and low temperature serpentinization ca cl waters in fiordland

soil geomorphology present dilemmas and future challenges abstract understanding the manner in which landscapes change is still a major challenge for geomorphologists recent work has shown quite convincingly that landscape evolution occurs during relatively short periods of intense adjustment followed by longer periods of stability the challenge is to determine the way in which such change occurs and the factors which control the changes this paper by using a number of specific examples from a variety of environments suggests that many of these issues may be resolved by adopting an integrative approach involving soil information as well as geomorphological concepts

strong climate and tectonic control on plagioclase weathering in granitic terrain abstract investigations to understand linkages among climate erosion and weathering are central to quantifying landscape evolution we approach these linkages through synthesis of regolith data for granitic terrain compiled with respect to climate geochemistry and denudation rates for low sloping upland profiles focusing on na as a proxy for plagioclase weathering we quantified regolith na depletion na mass loss and the relative partitioning of denudation to physical and chemical contributions the depth and magnitude of regolith na depletion increased continuously with increasing water availability except for locations with mean annual temperature

pedogenic correlation of lateritic river terraces in central taiwan abstract the pakua chushan and touliu terraces are three groups of lateritic river terraces resulting from different fluvial systems in central taiwan their geomorphic features do not enable regional correlations to be made in this study an alternative scheme based on the quantification of a pedogenic development is proposed for this correlation four soil pedons from the chushan and touliu terraces are classified as ultisols cs 1 cs 2 and tl 1 and an inceptsol tl 4 following the soil taxonomy an additional six soil pedons including an oxisol pk 1 ultisols pk 2 3 4 and 5 and an inceptsol pk 6 from the pakua terraces were included from a previous study tsai h huang w s hseu z y chen z s 2006 a river terrace soil chronosequence of the pakua tableland in taiwan soil science 171 167 179 the weighted mean profile development indices wpdi for the pedons suggest a chronological order of i pk 1 ii pk 2 iii pk 3 iv pk 4 cs 1 and tl 1 v pk 5 and cs 2 vi pk 6 and vii tl 4 the correlation suggests the chushan and touliu terraces correspond to the same surface of an anticline separated by the chinshui river surface deformation reflects the growth of the underlying structure in which uplift folding occurred in the hinge zone and tilted to the east along the fold limb as a result of the southern extension of the pakua anticline however the different geometries on both the surface and subsurface from southern pakua anticline indicate a mechanism of fault bend folding for touliu hill

trinidad mud volcanoes where do the expelled fluids come from abstract in order to establish the origin of fluids expelled from mud volcanoes in trinidad we analyzed their major element trace element and isotopic h o sr compositions the mineralogical chemical and sr isotope compositions of associated expelled muds were also determined on the basis of their chemical and sr isotope compositions the fluids were divided into two groups those southwest and northeast of a major right lateral wrench fault the los bajos fault that both controls the chemical quality of the fluids and acts as a drain strontium isotopes were derived via mixing between a radiogenic source 0 71135 and a nonradiogenic source 0 70671 for both southwest and northeast groups however the nonradiogenic source possibly feeding the northeast group showed a lower sr concentration than that of the southwest group h and o isotope data show that the fluids became enriched in 18 o through interaction with wall rocks the fluids were originally oceanic but their properties were subsequently modified by diagenesis as evidenced by chemical data and mixing between fluids issued from two deep seated reservoirs and surface aquifer end members the gas phase expelled with the mud and the fluid through the mud volcanoes is composed mainly of methane with minor carbon dioxide the amount of expelled gas seems the same in samples from both sides of the los bajos fault the almost unique methane content of the gas phase and the large positive 18 o shifts of the reservoir end member as well as b li and ba contents reveal that the fluids from the deep seated reservoirs inherited their chemical compositions at high temperature fluid rock interactions estimates of equilibrium temperatures of the two deep seated reservoirs suggest that to acquire the estimated higher temperature 150 c the mud volcanoes must have been fed partly by a reservoir located at a depth of more than 3 km this depth corresponds to previous geologic information which located the deep seated reservoir in miocene sediments at such a comparable depth the mixing of the original fluids with a less deep seated reservoir and meteoric waters on the ascending path suggests the presence of a recharge mechanism and contributes to the dynamics of the expulsion itself

response of alluvial fan systems to the late pleistocene to holocene climatic transition contrasts between the margins of pluvial lakes lahontan and mojave nevada and california usa abstract dated shorelines of late pleistocene pluvial lakes lahontan great basin desert northwest nevada and mojave mojave desert eastern california provide timelines for the assessment of alluvial fan sedimentation at the lake margins during the late pleistocene to early holocene two sets of alluvial fan systems have been mapped the stillwater fans feeding lake lahontan and the zzyzx fans feeding lake mojave their contrasting morphologies suggest different responses of the two fan systems to late pleistocene to early holocene climatic change at the time the stillwater fan systems underwent minimal sedimentation with the catchment hillslopes apparently stable the zzyzx fans experienced major changes in water and sediment supply from the catchment hillslopes there was a major phase of hillslope debris flow activity followed by fanhead trenching and distal fan progradation both areas were wetter and colder in the late pleistocene than they are today but during the transition to the holocene the zzyzx area was more likely to experience intense rains associated with the monsoonal penetration of warm moist tropical air into the southwest vegetation reconstructions for the late pleistocene to the early holocene suggest that catchment hillslopes in the mojave supported a desert shrub vegetation but those in the stillwaters supported juniper woodland and grasses at low elevations and pine at higher elevations contrasts in hillslope vegetation cover together with storm activity may account for the different responses of the alluvial fans to climatic change during the pleistocene to holocene climatic transition after the falls in lake levels of lakes lahontan and mojave in the early holocene both areas underwent aridification resulting in reductions in hillslope vegetation cover increased storm runoff led to fanhead trenching and distal progradation of the alluvial fans variations in fan style at that time may relate primarily to base level conditions resulting from different gradients on the exposed lake shores

saprolite formation beneath coastal plain sediments near washington d c crystalline rocks buried beneath atlantic coastal plain sediments in the washington d c area commonly have weathering profiles that resemble exposed saprolite of the piedmont cuts along the washington metropolitan area transit authority wmata route in northern virginia show a bedrock weathering profile beneath cretaceous and younger sediments three lines of evidence indicate that this buried weathering profile saprolite has formed in the subsurface and is post miocene in age the thickness of the profile ranging from 2 to 15 m is thinner beneath clays and thicker beneath sands apparently a function of the permeability of the overlying material the buried profile shows no evidence of soil formation at its upper surface and therefore no evidence of ever having been sub aerially exposed consolidation tests on the cohesive clayey silts in the samples of the weathering profile indicate mechanical equilibrium with the present overburden whereas consolidation tests on superjacent cretaceous clays indicate over consolidation resulting from a thicker pre upper miocene overburden the post miocene age for the subsurface saprolite profile shows that not all saprolite beneath cretaceous sediment is pre cretaceous in age these observations have important implications for the interpretation of age of the exposed piedmont saprolite

soils of the indo gangetic plains a pedogenic response to landscape stability climatic variability and anthropogenic activity during the holocene abstract bound by the himalaya in the north and the craton in the south the indo gangetic plains igp is one of the largest fluvial plains of the world the igp is monotonously flat with a spread of surface soils in hot arid conditions of rajasthan in west to per humid conditions in west bengal the soil geomorphology of the igp detailed during the last few decades is useful in determining the interrelationship among the pedogenesis the climate and the landscape evolution during the holocene these studies demonstrate that the igp soils developed on five geomorphic surfaces with varying degree of development soils occurring on older geomorphic surfaces 2 5 ka are polygenetic with a distinct record of climatic changes and neotectonics the present synthesis is based on recent developments in pedology achieved through macro and micromorphology clay mineralogy pedogenic calcrete and polygenetic pedogenic features of the igp soils a critical evaluation of the igp soils has helped to comprehend the subtle nuances of the pedogenic processes that were also influenced by anthropogenic activities and cultivation over this vast agricultural tract during the holocene we provide state of the art information on the pedology polygenesis and soil degradation natural and anthropogenic over the last 10 ka the review has potential as a reference for critical assessment of the pedosphere for health and quality in different parts of the world in addition it facilitates developing a suitable management practices for the food security in the 21st century

holocene soil chronofunctions southern alps new zealand abstract field and laboratory data for two soil chronosequences from the high country of the south island of new zealand suggest rapid soil formation rates the areas studied are the ben ohau range and the mt cook area where mean annual precipitation is about 1 and 4 m respectively most soil ages are estimated from the thicknesses of rock weathering rinds soil chronofunctions are derived for indices that depict field profile and color development and a modified index of profile anisotropy for laboratory data out of a possible 21 chronofunctions 16 are statistically significant at the 0 05 level and 8 are from each area most 13 of the chronofunctions best fit a power model and the remaining ones are split between linear 2 and exponential 1 models although problems exist in the purity of the chronosequences because other soil forming factors are not constant duration of pedogenesis seems to be the most significant factor in explaining the trends despite the large differences in mean annual precipitation between the two areas many of the derived curves for property vs time are quite similar

pore fluid chemistry from the second gas hydrate drilling expedition in the ulleung basin ubgh2 source mechanisms and consequences of fluid freshening in the central part of the ulleung basin east sea during the second gas hydrate drilling expedition in the ulleung basin ubgh2 pore fluids were collected from sites that sampled sediments from the continental slope to the basin center and included locations within and outside seismic identified chimney like features at five non chimney sites established during the ubgh2 discrete excursions to low cl concentrations within the gas hydrate occurrence zone ghoz are associated with water enriched in d and 18o as expected from gas hydrate dissociation during core recovery estimates of gas hydrate saturation values sh based on cl and d values are in good agreement and show that when gas hydrate occurs in discrete horizons or within strata bound fractures throughout the ghoz it occupies 5 65 of the pore space fluids recovered from three sites characterized by seismic inferred chimneys show massive hydrate accumulation near the seafloor accompanied by the formation of shallow cl rich brines with d and 18o values lower than seawater chemical and isotopic data from fluids sampled at all drilled sites reveal significant fluid freshening below the gas hydrate stability zone ghsz the distribution of cl k and d indicate that the observed freshening is predominantly caused by clay mineral dehydration illitization previously reported heat flow values in the center of the basin indicate that the sediments deeper than 800 mbsf meter below seafloor are warm enough to expect clay diagenesis with the onset of smectite to illite transformation source fluid temperatures 70 c are confirmed through the use of na li and mg2 li geothermometry based on these observations we propose the following scenario for the evolution of formation fluids in the ulleung basin where high formation temperatures and rapid sedimentation at the basin center led to sediment compaction and clay dehydration reactions that result in fluid overpressures and associated fracturing of the formation sediment fractures and fluid possible gas migration in the chimney features imaged in seismic records are consistent with our postulated upward transport of fluids from 800 m depth though the ghsz and to the seafloor

the use of element clay ratios assessing gains and losses of iron manganese and phosphorus in soils of sedimentary rocks on a landscape scale abstract quantitative statements about soil development on a landscape level of scale are difficult to work out especially in soils of stratified sediments this article presents an easily applicable method to infer gains and losses of fe mn and p in soilscapes developed on sedimentary rocks for this an element clay ratio was introduced the amounts of pedogenic cbd fe mn and total p in kg were calculated on a pedon basis i e for the volume under 1 m 2 down to the c horizon or any arbitrary depth in soils without a c horizon and divided by the amounts of clay in the same volume p ratio a comparison with the element clay ratio of the mixture of parent material s c ratio allows semi quantitative statements about elemental gains and losses due to solutional processes if only transformation processes are working p ratios should equal the c ratios in the case of fe and mn i e remaining constant with time any depletion or relative or absolute accumulation of the elements can be inferred from values which differ from this trend in the case of phosphorus the p ratios should decrease with time compared to the c ratios relative and absolute gains should result in minor differences between p and c ratios or p ratios exceeding c ratios the results of mass balance calculations on 27 pedons of southwestern germany with a broad amplitude of parameters fe mn p clay redoximorphism as well as the results of chronosequences of different climates parent materials and durations of soil development fits very well with the results of the ratio method developed by using the ratio method areas of depletion and accumulation can be identified in catenary studies as well as linkages between soils inferred e g interpedon translocations deductions of influences of man are possible too the assumptions and restrictions of the method were discussed in detail

late miocene climate and life on land in oregon within a context of neogene global change abstract clarendonian 12 ma fossil soils plants molluscs fish and mammals of eastern oregon allow reconstruction of late miocene paleogeography paleoclimate and paleoecology on land between the global thermal maximum of the middle miocene 16 ma and global cooling and drying of the late miocene 7 ma six different pedotypes of paleosols recognized near unity and juntura allow reinterpretation of local mammalian paleoecology fossil beavers dominated gleyed entisols of riparian forest abundant camels and common hipparionine horses dominated alfisols of wooded grassland and grassy woodland diatomites overlying mammal bearing beds have bullhead catfish ictalurus ameiurus vespertinus as well as fossil leaves dominated by live oak quercus pollardiana fossil plants and soils of unity and juntura are most like those of grassy live oak woodland and savanna on the western slopes of the sierra nevada in northern california today fossil plants and soils indicate mean annual temperature of 12 9 7 7 17 7 c and mean annual precipitation of 879 604 1098 mm miocene paleoclimatic changes in eastern oregon show no relationship to changes in oxygen isotopic composition of marine foraminifera usually taken as an index of global paleoclimatic change mismatch between land and sea paleoclimatic records is most likely an artefact of global ice volume perturbation of oxygen isotopic values instead miocene paleoclimatic change in eastern oregon parallels changes in carbon isotopic composition of marine foraminifera presumably through fluctuations in greenhouse gases

determination of source ages and migration patterns of brines from the u s gulf coast basin using 129i abstract the long lived cosmogenic and fissiogenic isotope 129i has been applied to the study of source ages and migration patterns of oil field brines from the u s gulf coast basin 129 i i ratios were measured in sixty samples of saline formation water from depths of 660 4503 m in several oil fields in southeast texas south central louisiana and offshore louisiana comparisons between measured ratios and the decay curve for surface hydrospheric 129i result in minimum source ages much older than present host formation ages indicating vertical migration of brine from older deeper sources conservative corrections for a fissiogenic component due to spontaneous fission of 238u in the subsurface result in the following median source ages iberia field 55 ma port barre field 53 ma and eugene island blocks 316 and 330 55 ma pointing to wilcox group shales as source formations mesozoic sources cannot be ruled out due to the uncertainties in estimating the fissiogenic component some of the ratios measured in texas gulf coast brines show evidence of a greater fissiogenic component which indicates that the brines have resided in formations with locally high u concentrations

soil polygenesis as a function of quaternary climate change northern great basin usa abstract the quaternary environmental history of the northern great basin is characterized by a combination of lower temperature and higher moisture than present using water balance analysis of soils sampled along a climatic gradient we demonstrate that long term average effective moisture was about 2 4 cm yr 1 greater than present although this long term average represents most of quaternary time there are important short term excursions from these values during full glacial and interglacial times full glacial conditions are characterized by effective moisture about 7 9 cm yr 1 greater than present interglacial times similar to present conditions are characterized by dry lake basins that provide major increases in eolian activity these climatic extremes drive pedogenic processes that leave polygenetic imprints on soils of pleistocene age soils that are now dominated by opaline silica carbonate and smectite contain evidence of earlier more acidic chemical environments conducive to dissolution of primary carbonate and formation of kaolinite during interglacial time more eolian activity and less effective moisture combine to decrease the depth of leaching increase base cations and modify the soil chemical environment in relict paleosols in a soil of bull lake age 150 ky bp desert loess accumulation created a 25 increase in water holding capacity and decreased the depth of water penetration by 65 cm climatic drying at the end of the pleistocene decreased leaching depth by about 150 cm

bromine and iodine in peru margin sediments and pore fluids implications for fluid origins at the peruvian convergent margin two distinct pore fluid regimes are recognized from differences in their cl concentrations the slope pore fluids are characterized by low cl concentrations but elevated br and i concentrations due to biogenic production the shelf pore fluids exhibit elevated cl and br concentrations due to diffusive mixing with an evaporitic brine in the slope pore fluids the br i and nh4 concentrations are elevated following bacterial decomposition of organic matter but the i concentrations are in excess of those expected based on mass balance calculations using nh4 and br concentrations the slope sediment organic matter which is enriched in iodine from oxidationreduction processes at the oxygenated sediment water interface is responsible for this enrichment the increases in dissolved i and the i enrichments relative to nh4 and br correlate well with sedimentation rates because of differential trapping following regeneration the pore fluid i br ratios suggest that membrane ion fiitration is not a major cause of the decreases in cl concentrations other possible sources for low cl water including meteoric water clathrate dissociation and or mineral dehydration reactions imply that the diluting component of the slope low cl fluids has flowed at least 1 km through the sediment the low bottom water oxygenation in the shelf is responsible for the low if any enrichment of iodine in the shelf sediments fluctuations in bottom water oxygen concentrations in the past however may be responsible for the observed variations in the sediment ibr ratios comparison of na cl and br cl molar ratios in the pore fluids shows that the shelf high cl fluid formed from mixing with a brine that formed from seawater concentrated by twelve to nineteen times and probably was modified by halite dissolution this dense brine located below the sediment sections drilled appears to have flowed a distance 500 km through the sediment

use of cosmogenic 129i to constrain numerical models of fluid flow in marine sediments application to the blake ridge hydrate province 1 concentrations of cosmogenic iodine 129i in the pore fluid of marine sediments often indicate that the pore fluid is much older than the host sediment even when vertical flow due to sediment compaction is taken into account old pore fluid has been used in previous studies to argue for pervasive upward fluid flow and a deep methane source for hydrate deposits alternatively old pore fluid age may reflect more complex flow patterns we use a two dimensional numerical transport model to account for the effects of topography and fractures on pore fluid pathlines when sediment permeability is anisotropic we find that fluid focusing can cause significant lateral migration as well as regions where downward flow reverses direction and returns toward the seafloor longer pathlines can produce pore fluid ages much older than that expected with a one dimensional compaction model for steady state models with geometry representative of blake ridge usa a well studied hydrate province we find pore fluid ages beneath regions of topography and within fractured zones that are up to 70 ma old our results suggest that the measurements of 129i 127i reflect a mixture of new and old pore fluid however old pore fluid need not originate at great depths methane within pore fluids can travel laterally several kilometers implying an extensive source region around the deposit this type of focusing should aid hydrate formation beneath topographic highs

40ar 39ar geochronology constraints on late miocene weathering rates in minas gerais brazil ar 40 ar 39 incremental heating ages for twenty one grains of cryptomelane collected at 0 42 45 and 60 in depths in the cachoeira mine weathering profile minas gerais permit calculating long term 10 ma time scale weathering rate saprolitization rate in se brazil pure well crystallized cryptomelane grains with high k contents 3 5 wt yield reliable geochronological results the ar 40 ar 39 plateau ages obtained decrease from the top to the bottom of the profile 12 7 0 1 to 7 6 0 1 ma at surface 7 6 0 2 to 6 1 0 2 ma at 42 m and 7 1 0 2 to 5 9 0 1 ma at 45 in 6 6 0 1 to 5 2 0 1 ma at 60 in yielding a weathering front propagation rate of 8 9 1 1 m m y from the geochronological results and the mineral transformations implicit by the current mineralogy in the weathering profiles it is possible to calculate the saprolitization rate for the cachoeira mine lithologies and for adjacent weathering profiles developed on granodiorites and scbists the measured weathering front propagation rate yields a saprolitization rate of 24 9 3 1 t km 2 yr this average long term 10 ma saprolitization rate is consistent with mass balance calculations results for present saprolitization rates in weathering watersheds these results are also consistent with longterm saprolitization rates estimated by combining cosmogenic isotope denudation rates with mass balance calculations c 2005 elsevier b v all rights reserved

soil geomorphology the linkage of pedology and surficial processes geologists have made significant contributions to the discipline of pedology however until recently direct contributions came largely prior to 1935 as exemplified by those of powell and shaler during the late 19th century tandarich et al 1987 during much of the twentieth century geology and pedology have generally evolved along nearly separate pathways re integration of the two disciplines began slowly in the late 1950s and early to middle 1960s through the research and publications of ruhe 1956 1960 1964 richmond 1962 and morrison 1964 1965 1967 richmond s and morrison s research has provided much of the basis for the use of soils in the study of the stratigraphy of quaternary deposits in the western u s a birkeland 1984 the soil stratigraphic unit the geosol is a key component of the methodology developed by morrison geosols are presumed to have formed only during soil forming intervals interglacial or interstadial periods when climatic conditions were deemed optimal for rapid soil development recognition of soil stratigraphic units as geosols automatically conferred climatic as well as stratigraphic significance to buried soils this approach may have great utility in regions at higher latitudes that were characterized by extremes of climatic fluctuation during the qua ternary catt 1986 with little or no soil development during cold climate intervals a rather different approach involving the use of soils has been adopted by geoscientists conducting geomorphological research during the mid to late 1960s studies by researchers such as balster daniels hawley gile parsons and yaalon focussed on the nature of the relationships linking soils and landscape elements in many respects the philisophical approach to soil geomorphic research emphasized in the studies of these scientists strongly reflected the intellectual impact of jenny 1941 on the science of pedology this philosophy also strongly influenced the research of birkeland and following publication of birkeland s important textbook pedology weathering and geomorphological research 1974 a dramatic increase in the use of pedology in the geosciences occurred as researchers focussed on the study of landscape evolution in our view this emerging marriage of pedology and studies of surficial processes provides a critical framework for both the study of soil genesis and the study of evolution of and or stability of landscape elements

a quantitative comparison of soil development in four climatic regimes abstract a new quantitative soil development index based on field data has been applied to chronosequences formed under different climatic regimes the four soil chronosequences developed primarily on sandy deposits have some numeric age control and are located in xeric inland merced calif xeric coastal ventura calif aridic las cruces n mex and udic susquehanna valley pa soil moisture regimes to quantify field properties points are assigned for developmental increases in soil properties in comparison to the parent material currently ten soil field properties are quantified and normalized for each horizon in a given chronosequence including two new properties for carbonate rich soils in addition to the eight properties previously defined when individual properties or the combined indexes are plotted as a function of numeric age rates of soil development can be compared in different climates the results demonstrate that 1 the soil development index can be applied to very different soil types 2 many field properties develop systematically in different climatic regimes 3 certain properties appear to have similar rates of development in different climates and 4 the profile index that combines different field properties increases significantly with age and appears to develop at similar rates in different climates the soil development index can serve as a preliminary guide to soil age where other age control is lacking and can be used to correlate deposits of different geographical and climatic regions

controls on the 129i i ratio of deep seated marine interstitial fluids old organic versus fissiogenic 129 iodine iodine and its radioisotope 129i have been successfully used to trace the origin of pore waters in submarine fluid escape structures because of their close association with organic material in deeply buried sediments we report here halogen concentrations and 129i i ratios for fluids of five mud volcanoes sampled along an e w transect across the gulf of cadiz in the ne atlantic ocean concentrations of iodide and bromide increase consistently seaward accompanied by a decrease in 129i i ratios from 6490 10 15 to 663 10 15 the exceptionally high 129i i ratios at the near shore locations reflect the presence of fissiogenic 129i produced in situ by spontaneous fission of 238u within terrigenous sediments and released into pore water during clay mineral diagenetic processes the observed 129i i and halogen trends together with similar changes in 87sr 86sr ratios indicate a progressive seaward transition from inorganic terrigenous to organic marine fluid sources comparison of our results with literature data for varying geological settings reveals a general relationship between fissiogenic 129i radiogenic 87sr and the lithology or provenance of rocks and sediments respectively while 129i i ratios in continental rock hosted aquifers and terrigenous sedimentary systems are dominated by in situ production of fissiogenic 129i iodine isotopes in oceanic settings or volcanogenic marine sediments reflect the release of old iodine from deeply buried organic matter the gulf of cadiz represents the full transition between these continental and oceanic 129i i and 87sr 86sr end members this is the first systematic investigation of fissiogenic 129i production in marine sedimentary environments

soil chronosequence development in dunes on the southeast african coastal plain maputaland south africa abstract dunes have accreted on the southeast african coastal plain in coast parallel patterns of degraded whaleback ridges sand megaridges and extended parabolic dunes since the pliocene in the maputaland dune field relative dating is complicated by soil degradation erosion and vegetation cover this project assessed alternative relative and numeric dating techniques that can be used to differentiate dune systems and eolian sand bodies soil profile characteristics were used to calculate soil development indices sdi for soil horizons sampled from hand augered holes and rare exposures infrared stimulated luminescence irsl dating of representative dunes and sand units helped define the pedogenesis achieved since deposition the quartzose dune sands have weathered to form very deep soil profiles enhanced sdi values for horizons or sampled intervals down the profile reflect ph decrease advanced rubification or distinct mottling clay increase and harder consistency with depth the youngest holocene profiles exhibit decreasing horizon index values with depth below the a horizon whereas late pleistocene profiles display sdi values increasing with depth within the upper 3 m of the profile within some mid to late pleistocene eolian sands greater profile horizonation and catena complexity manifests as complex soil profiles or distinctly mottled clay enriched horizons at depths of 2 5 m below the surface the sdi profiles from specific dune systems or stratigraphic units cluster well and effectively characterize soil development in dune sand units of different ages depositional age plotted against sampled horizon index values makes it possible to determine generalized rates of soil profile development and to compare pedogenic processes on the high rainfall coastal barrier dunes to those found in the drier interior sampled horizon index values distinguish buried soil profiles and highlight possible localized surficial reworking

glacial sequence near mccall idaho weathering rinds soil development morphology and other relative age criteria abstract the sequence of glacial deposits near mccall idaho previously assigned to the pinedale and bull lake glaciations contains deposits of four different ages these ages are defined by multiple relative age criteria including weathering rinds soil development surface rock weathering morainal morphology and loess stratigraphy the thickness of weathering rinds on basaltic clasts is statistically representative and reproducible and can be used to estimate numerical ages following in order of decreasing relation to age are soil development surface rock weathering and moraine morphology the glacial deposits near mccall appear to correspond to times of high worldwide ice volume indicated by the marine oxygen isotope record pilgrim cove and mccall deposits both assigned to the pinedale glaciation are late wisconsin in age perhaps 14 000 and 20 000 years respectively they represent a rare case in which deposits of pinedale age can be separated by relative age data timber ridge deposits assigned to the bull lake glaciation have subdued but well preserved morainal morphology relative age data indicate that they are pre wisconsin in age probably about 140 000 150 000 years old although we cannot exclude an older age williams creek deposits are clearly distinct from and intermediate in age between mccall and timber ridge deposits weathering rinds and the inferred ages of the other deposits suggest an early wisconsin age for williams creek deposits

a quantitative soil stratigraphic approach to the correlation and dating of post glacial river terraces in glen feshie western cairngorms little is known about holocene river terrace development in upland scottish valleys interpretation of many of the terrace sequences previously suggested to have been formed by meltwaters either from the last scottish ice sheet or the loch lomond advance has generally been based on morphological data in this paper an alternative approach to the traditional height based method of terrace correlation and dating is presented using data from glen feshie western cairngorms terrace fragments are numerically classified and objectively grouped using quantitative soil stratigraphic data principal components analysis is used to both quantify pedological data and separate temporal trends in the data from variance due to local site factors the scores on the temporal component are used to derive soil stratigraphic units developed on the surficial sediments of the glen feshie terraces by grouping soil sites using a hierarchical clustering technique this provides evidence for at least five soil stratigraphic units developed on the fluvial surfaces various methods of absolute dating control permits association of these surfaces with five phases of terrace development these are placed tentatively at 13 000 10 000 3600 1000 and 80 radiocarbon years b p suggesting at least three phases of valley floor incision in glen feshie during the late holocene

soilscape of west central taiwan its pedogenesis and geomorphic implications abstract five different soil types including entisol inceptisol alfisol ultisol and oxisol are distributed across west central taiwan these soils cover the surfaces of three geological terrains namely the pleistocene anticline the holocene coastal plain and the modern alluvial fan these soils developed from the similar parent materials facilitating the analysis of soil diversity and the processes of pedogenesis the soil chronosequence of entisol inceptisol endoaquept reddish inceptisol dystrudept ultisol oxisol with increasing age is suggested for the progressive pathway of soil development the degree of pedogenesis was quantified using a weighted profile development index wpdi which indicates that the soils from the tropics develop faster than those in temperate and or mediterranean climates but was not as fast as those documented in the published literature moreover the distribution of soils during pedogenesis conformed to the order of landform formation soil genesis and the way in which the different soils evolve illustrate the paleo environments of the fluvial system in the area

pedogenesis of a chronosequence in the sacramento valley california u s a i application of a soil development index abstract a quantitative soil development index based on field morphologic data has been applied to a chronosequence of six soils at honcut creek in central california the soils range from 600 yr to 1 6 m y in age and exist in a xeric thermic soil climatic regime plots of the development of individual properties versus the log of soil age are generally linear of the eight soil properties used in the index clay films texture plus wet consistence structure and rubification color hue and chroma are most highly correlated with soil age correlation coefficients for linenar regression of 0 96 0 87 dry consistence moist consistence melanization color value and ph lowering are not as highly correlated with soil age correlation coefficients of 0 68 0 55 although correlation coefficients for all eight soil properties are significant at 0 01 or 0 05 level depth functions of a horizon index that incorporates all eight soil properties chart the development of the a horizons in holocene soils and the development of the cambic and then argillic horizons in older soils total depth of soil development increases from about 60 cm in holocene soils to more than 5 m in the oldest soils lithologic discontinuities and stratification are brought out in the horizon index because of their effects on soil development soils on the alluvial terraces of honcut creek have developed systematically over the 1 6 m y age span of the chronosequence correlation coefficients for regressions of the profile index versus the log of soil age are 0 97 significant at 0 01 level the coefficient of variation of replicate profiles decreases with increasing soil age the soil development index substantiates the geologic and pedologic correlations made during geologic mapping and soil survey of the area although differences among soils in parent material and topographic factors complicate the age trends

age and speciation of iodine in groundwater and mudstones of the horonobe area hokkaido japan implications for the origin and migration of iodine during basin evolution abstract this paper reports the concentration speciation and isotope ratio 129i 127i of iodine from both groundwater and host rocks in the horonobe area northern hokkaido japan to clarify the origin and migration of iodine in sedimentary rocks cretaceous to quaternary sedimentary rocks deposited nearly horizontally in tenpoku basin and in the horonobe area were uplifted above sea level during active tectonics to form folds and faults in the quaternary samples were collected from the pliocene koetoi and late miocene wakkanai formations fms which include diatomaceous and siliceous mudstones the iodine concentration in groundwater up to 270 mol l is significantly higher than that of seawater with the iodine enrichment factor relative to seawater reaching 800 1500 the iodine concentration in the rocks decreases from the koetoi to wakkanai fms suggesting that iodine was released into the water from the rocks of deeper formations the iodine concentration in the rocks is sufficiently high for forming iodine rich groundwater as found in this area x ray absorption near edge structure xanes analysis shows that iodine exists as organic iodine and iodide i in host rocks whereas it exists mainly as i in groundwater the isotope ratio is nearly constant for iodine in the groundwater at 0 11 0 23 10 12 and it is higher for iodine in rocks at 0 29 1 1 10 12 giving iodine ages of 42 60 ma and 7 38 ma respectively some iodine in groundwater must have originated from paleogene and even late cretaceous fms which are also considered as possible sources of oil and gas in view of the old iodine ages of the groundwater the iodine ages of the rocks are older than the depositional ages implying that the rocks adsorbed some iodine from groundwater which was sourced from greater depths the iodine concentration in groundwater decreases with decreasing chlorine concentration due to mixing of iodine rich connate water and meteoric water a likely scenario is that iodine rich brine formed during the long term basin evolution from the cretaceous to quaternary and that this brine was diluted by mixing with meteoric water during uplifting and denudation of the area

halogens and noble gases in sedimentary formation waters and zn pb deposits a case study from the lennard shelf australia abstract halogen ratios br cl and i cl and concentrations provide important information about how sedimentary formation waters acquire their salinity but the possible influence of organic br derived from sedimentary wall rocks is rarely quantified here it is demonstrated that br cl versus i cl mixing diagrams can be used to deconvolve organic br contributions that organic matter has a limited range of br i ratios and that organic br is a more significant component in zn pb deposit ore fluids than previously recognised the significance of these findings is illustrated for the lennard shelf zn pb deposits of western australia fluid inclusions related to lennard shelf zn pb mineralisation have variable salinity and hydrocarbon contents the halogen data from these fluid inclusions require mixing of three fluid end members 1 an evaporated seawater bittern brine 30 wt nacl equiv with greater than seawater br cl ratio 2 a lower salinity pore fluid 5 wt nacl equiv with moderately elevated br cl and i cl and 3 fluids with br cl ratios of 5 times seawater and extremely elevated i cl ratios of 11 500 times seawater the first two fluids have 40 ar 36 ar of 300 400 and greater than air saturated water 36 ar concentrations that are typical of fluid inclusions related to zn pb mineralisation the third organic rich fluid has the highest 40 ar 36 ar ratio of up to 1500 and a depleted 36 ar concentration mineralisation is interpreted to have resulted from mixing of zn rich evaporitic brines and h 2 s present in hydrocarbons it is suggested that aqueous fluids acquired organic br and i from hydrocarbons and that hydrocarbons exsolving from the aqueous fluid removed noble gases from solution interaction of variably saline brines and hydrocarbons could account for the variable br cl and i cl composition and 36 ar concentrations recorded by lennard shelf fluid inclusions the distinct 40 ar 36 ar signature of the fluid with the highest i cl ratio suggests the hydrocarbons and brines were sourced independently from different parts of the sedimentary basin these data indicate the complementary nature of halogen and noble gas analysis and provide new constraints on important mixing processes during sediment hosted zn pb mineralisation

morphological and chemical characteristics of soil catenas on pinedale and bull lake moraine slopes in the salmon river mountains idaho abstract morphological and chemical properties of soils developed on moraines of granitic composition and forested with lodgepole pine in bear valley idaho change significantly with age and slope position soil development on pinedale and bull lake moraine slopes of similar curvature and steepness was assessed at the summits shoulders backslopes and footslopes of both catenas and at the toeslope of the bull lake catena many soil properties show trends in development with both age and slope position these properties include clay content clay film development color plagioclase weathering and dithionite citrate extractable iron fed the degree of development of all these properties is greater on the bull lake catena relative to that on the pinedale catena this trend reflects increased soil development with age on both catenas development of soil properties is commonly highest at the footslope or toeslope sites and minimum at the backslope site downslope changes are attributed to both colluviation and pedogenic processes including sorting of sediments during downslope transport greater accumulation of eolian materials transported to downslope sites by surface processes and greater in situ weathering of mineral grains at the footslope and toeslope sites

soil development on stable landforms and implications for landscape studies abstract soil development parameters include a wide variety of morphological chemical and mineralogical parameters but some of the best indicators of time and surface stability are derived from field morphology over long time spans the most common time function for soil development is exponential or logarithmic in which rates decrease with increasing age over shorter time spans in semi arid and moister climates holocene and pleistocene soil development functions appear as linear segments with holocene rates about 10 to 50 times those of pleistocene rates in contrast to significant temporal variation in rates geographical variation in rates within a the southern great basin and b the east central valley of california is on the order of 2 or 3 times when comparing soil development indices of the semi arid great basin to those of moister central california holocene rates are similar but pleistocene rates are more than 10 times slower in the great basin in a range of climatic settings the reasons for declining rates over time are several and are complexly related to erosional history fluxes in water and dust related to climatic changes rates of primary mineral dissolution and intrinsic soil processes

needle ice processes and sediment mobilization on river banks the river ilston west glamorgan uk abstract this paper examines the role of needle ice processes in the bank erosion system of a site on the river ilston west glamorgan south wales uk bank retreat rates were monitored with erosion pins over a 2 25 year period concurrent detailed data were also obtained on river flow levels and ambient air and stream temperatures unique data on river bank thermal regimes are presented along with rare information on the morphological properties and sediment yield characteristics of needle ice growths needle ice occurred even with mild freezing temperatures if sufficient bank moisture was present with average growth rates of approximately 1 mm h 1 bank material incorporation and mobilization within needle ice was significant sediment yields of up to 4 02 kg m 2 of bank face were observed and represented between 32 and 43 of total bank erosion recorded most sediment was incorporated within needle ice when growth became stressed because of overrapid cooling and or limited moisture supplies which supports the models of outcalt and fukuda four mechanisms of direct needle ice sediment transport on river banks were identified direct particle fall sediment laden rivulets sliding failures and toppling failures however the indirect preparatory role of needle ice and frost disturbance of bank surfaces is also emphasized and the enhanced fluvial erosion which takes place when bank materials have first been conditioned by frost related processes is noted both indirect and direct effects are expressed in a simple conceptual model and a number of the important system linkages examined combinations of needle ice action and subsequent fluid entrainment of weakened bank material appear to be the dominant mechanism for bank erosion here pronounced and persistent erosional notches in the lower parts of the bank profile were observed showing that in winter even single low magnitude flow events can effect significant channel width adjustment here

iodine 129 chronological study of brines from an ordovician paleokarst reservoir in the lunnan oilfield tarim basin abstract previous studies have shown that brines in an ordovician paleokarst reservoir of the lunnan oilfield in the tarim basin china are the product of mixing of paleo evaporated seawater in the east with paleometeoric waters in the west in order to put time constraints on the brine and related hydrocarbons in this field 10 brine samples were collected for which the iodine concentrations and 129 i i ratios were measured and discussed the iodine concentration 3 70 31 2 mg l and the 129 i i ratio 189 897 10 15 show that the iodine in the paleoseawater and meteoric water mw had different origins and 129 i characteristics the paleoseawater has a high iodine content 31 mg l indicating that iodine was introduced into the reservoir along with thermally generated hydrocarbons possibly in the cretaceous from the caohu sag in the eastern area based on consideration of all possible origins of iodine and 129 i in the brines it is suggested that the meteoric water maintained its initial iodine content 0 01 mg l and 129 i i ratio 1500 10 15 whereas the iodine enriched paloseawater ipsw exhibited a secular 129 i equilibrium n sq 39 atom l as a result of fissiogenic 129 i input in the reservoir over a long period of time the model of brine evolution developed on that basis confirmed that meteoric water entered the reservoir in the miocene at about 10 ma and partially mixed with the iodine enriched paleoseawater the movement of meteoric water was facilitated by faults created during the himalayan orogeny then became more dense after dissolving paleogene halite and infiltrated into the reservoir at high pressure the iodine and 129 i concentration in the brine contains information about the path and history of the fluid in the reservoir this may be useful in oil exploration since the movement of water was to some extent related to hydrocarbon migration

iodine dating of pore waters associated with gas hydrates in the nankai area japan the nankai hydrate field japan is an example of gas hydrate deposits associated with an active subduction zone in order to determine the origin of gas hydrates in this area 129i i ratios together with halogen concentrations were measured in a set of pore water samples collected from two boreholes in the nankai hydrate field iodine concentrations are between 100 and 230 m i e strongly enriched compared to seawater while cl concentrations were found to be close to that of seawater except for one sample 129i i ratios are between 180 and 520 10 15 giving minimum ages between 24 and 48 ma because these ages are considerably older than present host sediments 2 ma and subducting marine sediments 21 ma in this area iodine and by association methane in the gas hydrates must have been derived from source formations located in the continental side of the subduction zone the results do not support derivation of gas hydrates from present host sediments or currently subducting sediments but could be related to release and long time recycling of fluids from marine formations of early tertiary age

determination of natural and anthropogenic 129i in marine sediments sup 129 i concentrations in two sediment cores from the continental slope near cape hatteras were determined with tandem accelerator mass spectrometry tams the natural sup 129 i sup 127 i ratios in these cores are approximately 10 sup 12 the input of anthropogenic sup 129 i has increased this ratio to values close to 10 sup 10 at the surfacee of the sediments the observed natural level of sup 129 i is about two orders to magnitude above the current detection limit with tams which opens up to possibility for applications of sup 129 i in the marine system such as dating of sediments and crude oils and tracing of slow water movement in sediments

soil evolution over the quaternary period in a mediterranean climate se spain palaeosols in the granada basin se spain have been studied in two different situations surface soils on geomorphically stable surfaces since the early pleistocene with younger pedogenic overprinting and buried soils on unstable surfaces from the middle late pleistocene on which successive erosional depositional episodes have alternated with pedogenic episodes for each soil clay and iron accumulation indices the fet alt sit ratio clay mineralogy and micromorphological features were used to estimate the degree of soil development from the early to the early late pleistocene the main pedogenic processes were the leaching of carbonates weathering illuviation and rubification which resulted in bt horizons with red colours clay texture clay coatings and kaolinite neoformation the degree of weathering and the development of these bt horizons varied over time and the soils that formed on the surfaces from the early pleistocene show strongest weathering and development however after their formation there were periods in which they were partially truncated and recalcified resulting in polygenetic soils the different degrees of development of the buried soils during the last 474 000 years indicate that the wettest warm period was stage 7 and the driest stage 5 stages 9 and 11 must have had climates with intermediate wetness since the clay accumulation and iron oxide accumulation indices the differences in fet alt sit ratio between bt and c horizons the extent of kaolinite neoformation and the micromorphological features of the soils formed during stage 7 are all similar to the surface soils that formed on early pleistocene deposits these features cannot be used to date surfaces older than 242 000 bp by contrast the soils that formed during stage 7 and later periods show different extents of development and thus can be used for the approximate dating of landforms d 2002 elsevier science b v all rights reserved

origin of hydrocarbons in the green tuff region of japan 129i results from oil field brines and hot springs in the akita and niigata basins abstract the akita and niigata basins are part of the green tuff region of honshu japan which hosts major occurrences of oil and gas and of hydrothermal sulfide sulfate kuroko deposits the green tuff formation is associated with the opening of the japan sea which occurred in the early miocene and was accompanied by large scale volcanic activities we measured halogen concentrations and 129i i ratios in oil and gas field brines and hot springs in order to determine the origin of iodine and indirectly of hydrocarbons in this area and their association with geological processes during the formation of the japanese island arc based on the concentration of iodine these samples fall into three categories type a i 190 m type b 150 m i 90 m and type c i

variations in 129i 127i ratios in recent marine sediments evidence for a fossil organic component abstract the value of the pre bomb 129 i 127 i ratio in the hydrosphere is important for the use of this isotope system for dating and tracing purposes in order to determine this value and to examine spatial variability 129 i 127 i ratios were measured in 25 sediment samples from five cores taken at geographically distinct coastal areas the results indicate a pre anthropogenic 129 i 127 i ratio of 1500 10 15 in good agreement with values derived from previous sediment and groundwater studies results from shallow sediments show that the layer of bioturbation is dominated by the addition of anthropogenic 129 i the good agreement between results for this layer from different cores supports the understanding that marine iodine is isotopically homogeneous and associated with organic material which is actively remineralized at the sediment water interface lower ratios down to 354 10 15 corresponding to an age of 32 5 ma and larger variations than expected were found in sections of the cores below the layer of bioturbation these observations can be explained by the presence of refractory fossil organic material transported by rivers to the sediments from uplifted continental shales the results suggest that marine iodine is present in two forms a labile component which is isotopically homogeneous and a refractory component which is associated with kerogen or other fossil organic compounds whose 129 i 127 i ratio reflects the age of these compounds 129 i 127 i ratios can be used to identify and date fossil organic material in recent sediments the presence of which can alter the assumptions underlying models of the global carbon cycle

origin and age of pore waters in an actively venting gas hydrate field near sado island japan sea interpretation of halogen and 129i distributions abstract a gas hydrate field with highly active venting of methane was recently found near sado island in the eastern japan sea piston cores were collected from active venting sites and nearby locations in the umitaka spur joetsu knoll area during two cruises in 2004 ut04 and 2005 ky05 08 we report here halogen concentrations and 129 i i ratios in pore waters associated with gas hydrates from these expeditions the strongly biophilic behavior of i and to a lesser degree of br together with the presence of the long lived iodine radioisotope 129 i allow evaluation of potential source materials for methane in gas hydrate systems depth profiles of all three halogens particularly the very rapid downward increases of br and i concentrations strongly suggest input of deep fluids enriched in br and i but the profiles also display the effects of gas hydrate formation and dissociation although the 129 i i ratios are modified by 129 i from seawater and sediments at shallow depth likely ratios of the deep fluids are estimated to be between 400 10 15 and 600 10 15 equivalent to a late oligocene to early miocene age ages in the active methane venting sites typically are closer to the old end of this range than those in the reference sites this age range suggests that the methane associated with venting and gas hydrate formation in this area is derived from organic materials accumulated during the initial opening of the japan sea the umitaka spur joetsu knoll gas hydrate field demonstrates the movement of deep fluids associated with the release of significant amounts of methane from the seafloor processes which might be important components of mass transfer and carbon cycle in the shallow geosphere

deep sea bottom simulating reflectors calibration of the base of the hydrate stability field as used for heat flow estimates ocean drilling program and deep sea drilling project downhole data from three areas the southwestern japan nankai margin the continental slope off peru and the blake bahama outer ridge provide temperature calibrations for bottom simulating reflectors bsr that mark the base of a clathrate hydrate stability field the inferred temperatures at bsrs provide an important reference for the mapping of geothermal gradient and heat flow from subduction zone accretionary sedimentary wedges the borehole results provide information on which stability field is applicable for the bsrs and thus calibrate the heat flow estimates while an ideal calibration has not been possible the bsr temperatures at the three sites in the temperature range 25 27 c have been estimated with uncertainties of 0 7 to 2 0 c the temperatures correspond closely to the laboratory dissociation temperatures for pure water pure methane hydrate at equivalent pressures no laboratory data are available for seawater salinity and methane at equivalent pressures but extrapolation from lower pressures gives temperatures 1 2 c lower which is just significantly different the data also could be explained by the stability curve for seawater salinity and methane with about 7 co2 or with a small amount of higher hydrocarbons but most hydrate samples that have been recovered by deep sea drilling have contained almost pure methane the uncertainties in the temperature at the bsr should contribute no more than 5 error in heat flow estimates from bsr depths if the pure water methane stability field is used

a predictive numerical model for potential mapping of the gas hydrate stability zone in the gulf of cadiz this paper presents a computational model for mapping the regional 3d distribution in which seafloor gas hydrates would be stable that is carried out in a geographical information system gis environment the construction of the model is comprised of three primary steps namely 1 the construction of surfaces for the various variables based on available 3d data seafloor temperature geothermal gradient and depth pressure 2 the calculation of the gas function equilibrium functions for the various hydrocarbon compositions reported from hydrate and sediment samples and 3 the calculation of the thickness of the hydrate stability zone the solution is based on a transcendental function which is solved iteratively in a gis environment the model has been applied in the northernmost continental slope of the gulf of cadiz an area where an abundant supply for hydrate formation such as extensive hydrocarbon seeps diapirs and fault structures is combined with deep undercurrents and a complex seafloor morphology in the gulf of cadiz the model depicts the distribution of the base of the gas hydrate stability zone for both biogenic and thermogenic gas compositions and explains the geometry and distribution of geological structures derived from gas venting in the tasyo field gulf of cadiz and the generation of bsr levels on the upper continental slope

tectonic geomorphology of the san andreas fault zone in the southern indio hills coachella valley california geomorphic investigation of the san andreas fault zone in the indio hills indicates many tectonically produced landforms including beheaded streams right lateral deflected and offset streams sags shutter ridges pressure ridges and fault scarps near biskra palms an alluvial fan pediment complex has an apparent cumulative offset of about 0 7 km along the mission creek fault zone north branch san andreas fault many of the tectonic landforms as well as the fracture pattern that has developed during the pleistocene are explainable by simple shear or uplift associated with a small left bend in the main trace of the mission creek fault the ratio of vertical to horizontal displacement in the vicinity of the bend is about 0 04 exposed in pushawalla canyon 5 km northwest of the alluvial fan pediment complex are 1 a sequence of stream terraces 2 folded plio pleistocene fanglomerates and 3 an example of stream capture following a right lateral deflection or offset of several hundred metres a left step of the mission creek fault in pushawalla canyon is a probably cause of folds and sporadic uplift that produced the stream terraces possible cause of recent stream capture are 1 juxtaposition of pushawalla canyon with a relict canyon moving northwestward along the mission creek fault or 2 right lateral deflection or offset of pushawalla canyon along the fault with simultaneous headward erosion of a shorter steep stream flowing toward the coachella valley estimation of a slip rate and identification of paleoseismicity for the san andreas fault in the indio hills is difficult however degree of topographic dissection formation and preservation of desert pavement and relative soil profile development suggest that the age of the offset fan may be as old as 70 000 yr but that most likely it is on the order of 20 000 to 30 000 yr these age estimates for the offset fan indicate a minimum slip rate for the san andreas fault of 10 to 35 mm yr with about 23 to 35 mm yr the most likely the pattern of observed offset drainages is complex but suggests that during the past few thousand years creep events or moderately large earthquakes have periodically produced several metres of right lateral displacement

natural iodine 129 as an environmental tracer abstract iodine 129 t 1 2 16 my is a naturally occurring tracer which can be used to study hydrologic and geologic processes on time scales up to 100 my the pre bomb atmospheric ratio 129 i i should have been constant in time and space and is the starting value in ground water recharge subsequent ratio changes in ground water should be determined by isotope contributions from three sources recharge water iodine leached from the formation and in situ uranium fission the mathematical expression of these time dependent processes forms the basis for dating and tracing applications the expected behavior of natural 129i in ground water is compared to results from field studies ground water samples from the great artesian basin australia provide an estimate of the atmospheric equilibrium ratio 6 10 13 down gradient changes in water up to 1 my old suggest that subsurface production can be significant the usefulness of 129i as an indicator of brine source and age is verified in brines collected in and around louisiana salt domes the method leads to ages of 7 and 9 my for two brine pockets trapped within jurassic salt and 32 to 40 my for oil field brines in miocene sands adjacent to the domes the results demonstrate the capability of tandem accelerator mass spectrometry to measure as few as 107 atoms of 129i in 10 mg i with 10 precision although such atom sensitivity can be achieved otherwise the accelerator technique is necessary to measure naturally low pre 1945 cosmogenic isotope ratios

holocene and late pleistocene slip rates on the san andreas fault in yucaipa california using displaced alluvial fan deposits and soil chronology we derived slip rates on the san andreas fault from displacement of alluvial fans and from approximate dating of the fans by the degree of soil development distinctive red purple sedimentary rocks of the miocene potato sandstone exposed on yucaipa ridge in the san bernardino mountains were transported down wilson creek and shed across the modern trace of the san andreas fault soils developed in alluvial fan deposits contain red purple clasts of the potato sandstone and are progressively more developed toward the north west as a result of fault displacement we used soil development to estimate the ages of these alluvial fans and underlying deposits using dated soils from cajon pass and from the central valley of california we estimated ages of wilson creek deposits using a statistical method of maximum likelihood these methods also utilize monte carlo simulations of larger data populations and account for soil variability uncertainty of calibration dates and the limited number of soils described and sampled resulting age estimates have considerable as much as 80 uncertainty resulting largely from quality of calibration dates slip rates for three time intervals were obtained by restoring the medial axis of each displaced fan to wilson creek maximum slip rates were also obtained by restoring the westernmost extent of each fan to wilson creek best estimate rates averaged to the present for 0 to 14 000 yr are 14 to 25 mm yr for 0 to 30 000 yr 22 to 34 mm yr and for 0 to 65 000 or 90 000 yr 12 to 16 mm yr maximum rates averaged to present for 0 to 14 000 yr are as high as 65 mm yr older rates are as high as 80 mm yr when holocene rates are accounted for actual or incremental slip rates for the interval 30 000 to 65 000 or 90 000 yr b p are probably 6 to 13 mm yr these data tentatively suggest that slip rates on the modern trace have increased during the late quaternary uncertainties in slip and age data however allow for rates to have been nearly constant or even decreasing toward the present

progressive and regressive pedogenesis and complex soil evolution abstract the simultaneous operation of regressive and progressive pedogenetic pathways raises the possibility that soil evolution may exhibit patterns far richer and more complex than increasing development over time this possibility is explored via a numerical model incorporating the relative rates of progressive and regressive pedogenesis and feedbacks between these rates and the degree of soil development this model may exhibit deterministic chaos and sensitive dependence on initial conditions with realistic parameter values variations in profile development in a region of the north carolina coastal plain where soil forming factors are relatively constant is consistent with deterministic chaos chaotic soil evolution suggests that soil development may reflect the interplay between progressive and regressive soil forming processes in addition to or instead of the age of a surface or deposit the former may produce a state of development which is unique to a particular time sensitively dependent on the unknown initial conditions and not simply related to age soils and their genetic signatures as indicators of relative ages and quaternary environments may need to be reinterpreted in this light

cryogenic disturbance and pedogenic lag effects as determined by the profile developmental index the styggedalsbreen glacier chronosequence norway abstract a chronosequence with a terminal moraine dating to the mid eighteenth century is found at the norwegian glacier styggedalsbreen patches of sorted polygonal ground nets with varying degrees of activity occur along the chronosequence with activity decreasing with distance from the ice margin soil development was studied along the chronosequence in three differently aged terrain units 1 recently deglaciated i e 20 30 yr 2 deglaciated ca a d 1930 and 3 deglaciated between a d 1836 and 1867 within each similarly aged terrain unit pedogenesis was investigated in regards to three different categories of decreasing disturbance regimes 1 polygon centers 2 polygon borders and 3 relatively stable nonpolygonal ground physical soil properties along with the use of a soil development index i e pdi show significant differences in pedogenic development between the three different categories of disturbance within similarly aged terrain units the relatively stable nonpolygonal soils have thicker horizons and so higher pdi values as compared to the soils of sorted polygons suggesting that soil properties show the intensity of disturbance significant variations of pdi values were also observed with distance from the ice margin within decades of deglaciation and subsequent pedogenic development surficial a horizons obtained the highest index values over that of bw and c horizons suggesting developmental history is most represented in surficial horizons on very recently developed soils these findings suggest that soil indices are useful geochronological tools on young landscapes and can be used to explore the pedogenic heterogeneity found across the landscape resulting from disturbance processes

late miocene advent of tall grassland paleosols in oregon abstract paleosols in the late miocene rattlesnake formation reveal three successive paleoclimatic regimens that can be dated using cumulative paleosol development prior to the radiometrically dated rattlesnake ash flow tuff 7 05 ma the basal rattlesnake formation ca 7 5 7 3 ma has a suite of weakly calcareous paleosols indicating subhumid paleoclimate 800 1000 mm mean annual precipitation or map and seasonal waterlogging a shift at ca 7 3 ma to semi arid paleoclimate map 500 850 is indicated by paleosols with calcic horizons at depths of 105 85 cm a second shift at ca 7 2 ma ushered in an assemblage of soils with shallow 36 53 cm calcic horizons indicating semi arid conditions map 200 600 mm not much different from today along with the climatic shifts documented by the paleosols there also are substantial changes in alluvial architecture and paleotopography the lower rattlesnake formation ca 7 5 7 2 ma was deposited by a stream flowing northeast in an ancestral john day valley the upper part of the formation ca 7 2 7 1 ma was deposited within large alluvial fans shed from the growing anticline of picture gorge basalt to the north stepwise changes in former vegetation can also be interpreted from paleosols the basal rattlesnake formation 7 5 7 3 ma has a suite of paleosols with root traces clay skins and manganese nodules like those of riparian woodland and seasonally waterlogged riparian meadow the succeeding paleoclimatic sequence 7 3 7 2 ma includes the earliest known mollic paleosols with deep 50 cm calcareous nodules interpreted as former soils of tall grassland also found are manganese stained paleosols of seasonally waterlogged meadows and weakly developed paleosols of early successional riparian vegetation a later paleoclimatic sequence 7 2 7 1 ma includes desert shrubland paleosols as well as paleosols of early successional riparian vegetation fossil bones and teeth found in many paleosols indicate coeval changes in mammalian faunas the major shift from woodland to grassland at ca 7 3 ma introduced into this area tall grassland ecosystems including large cursorial horses and pronghorns aridification continued with the shift to shrubland ca 7 2 ma early hemphillian which corresponds to continent wide mass extinction of most remaining browsing mammals from the clarendonian chronofauna

129i and 36cl concentrations in waters of the eastern clear lake area california residence times and source ages of hydrothermal fluids abstract the clear lake area of northern california is the location of hot spring activity some of which is associated with the formation of au and hg deposits we measured 129 i i and 36 cl cl ratios in nine warm springs formation springs six cold springs with elevated levels of cl and i mineral springs and five springs of recent meteoric origin dating of the i in the formation waters indicated that sources of i in these waters are formations with minimum ages between 60 and 80 ma this age range is in good agreement with the ages of the franciscan complex and the great valley sequence the dominant formations in this area because the mineral waters are essentially formation waters diluted with meteoric water i in these waters is of the same origin residence times of the waters were calculated based on the build up of129i and 36cl as a consequence of the presence of u and th in the crust the residence time of the formation waters in the great valley sequence the location for most of these springs was probably not longer than 84 000 yr the concentrations found for 36cl and 129i in the mineral waters indicate that these waters have residence times of similar magnitude in formations such as the franciscan complex or the clear lake volcanics which have slightly higher levels of u and th than the great valley sequence