spatial variability of soil properties at different scales within three terraces of the henares river spain abstract this paper applies statistical and geostatistical procedures to a soil chronosequence on the terraces of the henares river ne madrid to analyse the spatial distribution of several soil properties and use the contribution of geostatistics to establishing a landscape evolution model of the area particle size distribution ph calcium carbonate and organic carbon were analysed statistical procedures focus on analysing differences between terraces geostatistical procedures identify short and medium range variations within individual terraces at different scales standard transitive variogram models describe the properties of the younger terrace whereas the linear intransitive model fits the majority of variograms of the older terrace the analysis confirms and quantifies the decrease in variability of soil properties from young to old deposits showing thus an increment of soil homogenisation with time ageing of the terraces causes the variables to show nontransitive variogram models with unbounded variances within the observation range

the convenient fiction of steady state soil thickness abstract steady state regolith or soil thickness ssst whereby surface removals are approximately balanced by production of new soil by bedrock weathering is a common assumption in most models of hillslope and landscape evolution ssst is also a fundamental assumption in the use of cosmogenic radionuclides crn to estimate erosion and weathering rates the steady state concept is based on feedbacks between soil thickness and weathering at the base of the regolith such that sometimes after an optimal or threshold thickness is achieved thicker soils lead to lower weathering rates and vice versa ssst is thus only applicable to soils formed chiefly from weathering of the underlying bedrock where sufficient time has elapsed for regolith accumulation and where effects of processes other than weathering and surface removals on thickness are negligible even within this domain the widespread occurrence of deep weathering profiles regolith stripping and inherited regolith features makes ssst problematic as a conceptual model for pedogenesis or weathering profile development the ratio of soil thickness to total weathering profile thickness is proposed as a simple index of steady state steady state profiles formed on weathered bedrock should exhibit ratios close to unity data from the cumberland plateau region of eastern kentucky show that soil weathering profile ratios in shallow 20 m and generally significantly greater than soil thicknesses in the region suggesting ratios convenient fiction facilitating the use of some models and tools the potential pitfalls arise from the possibility that the utility of ssst as a convenient fiction in some contexts may be mistaken for a realistic representation of the dynamics of pedogenesis and weathering profile evolution

relative age relationships of debris flow deposits in the southern blue ridge north carolina abstract periods of increased landscape instability in the southern blue ridge were assessed with relative ages of three sequences of debris flow deposits the sequences consist of a series of lobate deposits that are expressed as step like landforms on the floors of host valleys data were collected at three sites from soil pits on the toe and apex of debris flow deposits relative ages were obtained by qualitatively and statistically examining data on clast weathering soil color clay content and iron species consistent results among the indicators of relative age demonstrate that they have utility in warm to temperate humid environments at each site the topographically highest debris flow deposits are slightly older than those at lower elevations one deposit at each of the three sites has a relative age that is very similar to that of one deposit at the other sites this similarity in age indicates that an external factor such as extreme precipitation accounts for the formation of debris flows at approximately the same time in the geological past one of the sites however also has deposits that are clearly younger than the deposits at the other sites which indicates that intrinsic factors also affect the formation of debris flows in the region

the frequency and distribution of recent landslides in three montane tropical regions of puerto rico landslides are common in steep mountainous areas of puerto rico where mean annual rainfall and the frequency of intense storms are high each year landslides cause extensive damage to property and occasionally result in loss of life average population density is high 422 people km2 and is increasing this increase in population density is accompanied by growing stress on the natural environment and physical infrastructure as a result human populations are more vulnerable to landslide hazards the blanco cibuco and coamo study areas range in surface area from 276 to 350 km2 and represent the climatologic geographic and geologic conditions that typify puerto rico maps of recent landslides developed from 1 20 000 scale aerial photographs in combination with a computerized geographic information system were used to evaluate the frequency and distribution of shallow landslides in these areas several types of landslides were documented rainfall triggered debris flows shallow soil slips and slumps were most abundant hillslopes in the study area that have been anthropogenically modified exceed 12 in gradient are greater than 300 m in elevation and face the east northeast are most prone to landsliding a set of simplified matrices representing geographic conditions in the three study areas was developed and provides a basis for the estimation of the spatial controls on the frequency of landslides in puerto rico this approach is an example of an analysis of the frequency of landslides that is computationally simple and therefore may be easily transferable to other settings

very long period oscillations of mount erebus volcano as the signal decays vlp scalar moments up to 5 10 11 n m exceed sp moments by an order of magnitude or more suggesting distinct though genetically related sp and vlp source mechanisms we conclude that vlp signals arise from excitation of a quasi linear resonator that is intimately associated with the conduit system and is excited by gravity and inertial forces associated with gas slug ascent eruption and magma recharge vlp signal stability across hundreds of eruptions spanning 5 years the persistence of the lava lake and the rapid posteruptive lava lake recovery indicate a stable near summit magma reservoir and vlp source process index terms 4544 oceanography physical internal and inertial waves 7280 seismology volcano seismology 8419 8414 volcanology eruption mechanisms 8419 volcanology eruption monitoring 7280 keywords strombolian very long period volcano seismology

a soil chronosequence study of the reno valley italy insights into the relative role of climate versus anthropogenic forcing on hillslope processes during the mid holocene abstract relatively few soil chronosequences with good age control exist for late pleistocene and holocene deposits in the mediterranean region of europe yet surface soils and their young buried counterparts can provide meaningful information about the timing and processes of landscape response to external forcing such as climate or anthropogenic change here we present the results of a study that examines a well dated chronosequence of nineteen soil exposures in surficial deposits ranging in age from hundreds of years to hundreds of thousands of years located in the reno river valley near bologna italy the soil forming climate of the reno valley sits on a threshold between that which facilitates the accumulation of caco 3 and that which facilitates the translocation and formation of clay minerals and iron oxides once formed secondary iron oxides are relatively immobile in oxidizing conditions in the soil profile and therefore consistently record age trends with feo fed ratios decreasing predictably with soil age for all soils in the chronosequence the morphology of secondary carbonate accumulation and its depth of leaching also vary predictably with soil age but only for soils younger than about 12 000 years in these young soils horizons that contain secondary carbonate progress from relatively shallow stage i bk horizons in late holocene aged soils to deeper stage iii bk horizons in latest pleistocene aged soils in soils older than approximately 12 000 cal ybp however carbonate dissolution during wetter climates and the addition of colluvium and or dust to terrace surfaces become important factors in the preservation of carbonate in the profile and carbonate content is not predictable by age alone without significant depositional additions these older soils become decalcified pedogenic carbonate precipitated during drier climates is susceptible to dissolution during wetter periods as evidenced by discontinuous carbonate coatings on grains in some soils therefore overall measurable pedogenic carbonate content is spatially and temporally variable as a function of input of fresh carbonate and locally controlled soil moisture conditions particle size does not decrease predictably with soil age for reno valley soils and appears to be strongly influenced by parent material variability in younger soils and by dust additions in older soils our detailed examination of soil stratigraphy in the reno valley revealed evidence of significant aggradation of colluvium and tributary fans in the middle holocene between 6000 and 4000 ybp this aggradation pre dates bronze age agricultural expansion and appears to be instead attributable to the climate conditions of the middle holocene that have been documented elsewhere in italy for this time period this study demonstrates that late pleistocene and holocene surface soils in the mediterranean region of europe can effectively help elucidate rates and processes of landscape evolution

geochemical modeling of nonsteady state magma chambers a case study from an ultrafast spreading ridge east pacific rise 17 19 s we propose a numerical method for modeling the geochemical evolution of nonsteady state changing volume magma chambers using analyses of erupted lavas the method allows estimation of the ratio between concentrations of an incompatible element in the erupted and incoming liquids e1 the relations between e1 the dimensionless magma flux through the reservoir and time are shown graphically we apply this model to the behavior of magma chambers underlying three segments of the east pacific rise between 17 00 s and 18 40 s with different axial morphology the geochemical data vary according to the axial morphology of the segments the lavas sampled along a dome shaped axis display more restricted compositional variations than the lavas from the axial caldera of collapsed segments these geochemical features thought to reflect variable magma chamber states are consistent with a cyclical model of a successively inflating and deflating magma chamber the results of our modeling imply that 1 the inflation could be about twice as long as deflation and 2 the magmatic volume expelled from the reservoir during deflation is at least three times larger than the volume expelled during inflation

divergent evolution and the spatial structure of soil landscape variability abstract the spatial structure of soil variability at the landscape scale was examined on adjacent geomorphic surfaces dating from 80 to 200 ka in eastern north carolina the purpose was to determine whether there is evidence at broader scales distances of 102 104 m for the divergent evolution observed in the field at very detailed scales distances of 100 102 m the state probability function spf which measures spatial dependence for categorical environmental data along a transect was applied to soil series mapped at a 1 24 000 scale the older talbot terrace and younger pamlico terrace surfaces showed distinctly different patterns of spatial variability the range of spatial dependence was shorter on the older surface about 200 vs 300 m and the spf was higher at any given distance indicating more variability the spf for the pamlico surface also indicates a periodicity related to fluvial dissection of the landscape which is not readily detectable on the talbot transect despite its greater degree of dissection the results confirm earlier field studies which suggest that pedogenesis is marked by divergence whereby differences in initial conditions or local perturbations persist and increase to produce a more variable soil cover

response of eolian geomorphic systems to minor climate change examples from the southern californian deserts abstract eolian processes and landforms are sensitive to changes in atmospheric parameters and surface conditions that affect sediment supply and mobility the response of eolian geomorphic systems to minor climate change can be examined through process response models based on a combination of relations between short term changes in climatic variables and eolian activity and the geologic and geomorphic record of holocene eolian activity at both time scales eolian activity in southern californian deserts is strongly controlled by variations in precipitation wind energy is not a limiting factor in this region formation of eolian deposits is a product of climatic changes that increase sediment supply from fluvial and lacustrine sources and may therefore be closely tied to periods of channel cutting and geomorphic instability during intervening periods eolian deposits migrate away from sediment source areas and are reworked modified and degraded remobilization of existing dormant dunes is a product of reduced vegetation cover and soil moisture in periods of drier climates the major control on these processes is decadal to annual changes in rainfall that determine vegetation cover and soil moisture content

characterizing the heterogeneity of karst critical zone and its hydrological function an integrated approach spatial heterogeneity in the subsurface of karst environments is high as evidenced by the multi phase porosity of carbonate rocks and complex landform features that result in marked variability of hydrological processes in space and time this includes complex exchange of various flows e g fast conduit flows and slow fracture flows in different locations here we integrate various state of the art methods to understand the structure and function of this poorly constrained critical zone environment geophysical hydrometric and tracer tools are used to characterize the hydrological functions of the cockpit karst critical zone in the small catchment of chenqi guizhou province china geophysical surveys using electrical resistivity tomography ert inferred the spatial heterogeneity of permeability in the epikarst and underlying aquifer water tables in depression wells in valley bottom areas as well as discharge from springs on steeper hillslopes and at the catchment outlet showed different hydrodynamic responses to storm event rainwater recharge and hillslope flows tracer studies using water temperatures and stable water isotopes d and 18o could be used alongside insights into aquifer permeability from ert surveys to explain site and depth dependent variability in the groundwater response in terms of the degree to which new water from storm rainfall recharges and mixes with old pre event water in karst aquifers this integrated approach reveals spatial structure in the karst critical zone and provides a conceptual framework of hydrological functions across spatial and temporal scales

comparing conservative and nonconservative tracers in karst and using them to estimate flow path geometry summary a controlled recharge event was conducted with multiple tracers in a karst aquifer in southeastern minnesota a pool adjacent to a sinkhole was filled with approximately 13 000 l of water after tracers were added and thoroughly mixed the pool was emptied into the sinkhole data were collected at freiheit spring approximately 95 m north of the sinkhole to monitor spring responses flow peaked first at the spring and suspended sediment peaked next then nearly identical uranine chloride and d peaks occurred temperature was the last of the tracers to peak the initial increase in flow at the spring recorded the time at which the water reached a submerged conduit sending a pressure pulse to the spring at approximately the speed of sound in open water the initial increase in uranine chloride and d at the spring recorded the arrival of the recharge water the initial change in temperature and its peak occurred later than the same features in the uranine chloride and d breakthrough curves as water flowed along this flow path water exchanged heat with the aquifer producing a lagged damped thermal peak at the spring the combination of hydraulic response and conservative and nonconservative tracers illustrates unique pressure advective and nonconservative processes geometrical properties of the flow system may be estimated using these tracers by summing discharge between the time of the initial increase in stage produced by a pressure pulse in a fully phreatic flow path and the time of the chloride peak the conduit volume is estimated as 47 10 m3 heat transport simulations were used to reproduce the modified thermal signal and simulations with planar flow paths and hydraulic diameters of 7 and 8 cm produced the best fits to the observed temperature breakthrough curve these volume and hydraulic diameter estimates together predict a bedding plane flow path that is 3 5 cm high by 9 m wide or 4 cm high by 8 m wide the different tracers provide complementary information and the combination of parameters provides useful constraints on flow path geometry

a strand plain soil development sequence in northern michigan usa abstract a practical problem limiting the theoretical application of a soil chronosequence study lies in the difficulty of identifying an appropriate geomorphic age sequence with more than a few surfaces a sequence of approximately 75 strand plain beach ridges located along the northern shore of lake michigan usa overcomes this problem and was used to explore rates of soil development in the initial stages of podzolization well drained pedons were sampled on 24 of the ridges with an age range of 10 to 5200 years chronofunctions were developed using statistical regression techniques for most forms of extractable fe and al both linear and log linear functions adequately describe the changes in property with surface age dithionite citrate extractable fe content however shows little correlation with surface age high r 2 values 0 7 for chronofunctions representing most extractable sesquioxide forms suggest that b horizon sesquioxide content increases with surface age as expected for soils undergoing podzolization visual inspection of chronofunction data suggests that scatter increases on surfaces older than 3000 years possibly because soil spatial variability increases with surface age theory suggests that the log linear form of chronofunctions may be preferable to the linear form for these pedons in general equation slopes are steeper for chronofunctions representing only the initial 1650 years of soil development than for those representing the entire 5200 year sequence suggesting that initially rapid pedogenesis slows over time most chronofunctions for ph and weighted profile organic c are not statistically significant possibly because the temporal resolution of the chronosequence is too coarse to detect valid trends for properties that rapidly approach a steady state

carbon dioxide and dissolution rate dynamics within a karst underflow overflow system savoy experimental watershed arkansas usa abstract within numerical models of karst development geochemical and hydrological boundary conditions are typically assumed to be constant however rates of calcite dissolution in natural karst systems can vary substantially in time in particular variation in carbon dioxide co2 concentrations has been shown to produce time variability in dissolution rates in karst streams but controls on co2 variation within karst systems are relatively poorly quantified here we analyze hourly in situ measurements of dissolved co2 discharge and specific conductance at a pair of karst underflow overflow springs and examine potential drivers of variability in co2 and dissolution rates the springs display strong seasonal variability in co2 and saturation state as well as moderate variation during storm events though both springs have elevated co2 concentrations in the summer season the overflow spring experiences a substantial decrease in dissolved co2 below a critical discharge threshold we hypothesize that this decrease results from ventilation within the overflow portion of the system as segments of the flow path transition from full pipe to open channel flow the overflow spring experiences substantially lower average dissolution rates than the underflow spring despite larger discharge and chemical variability during high flow events at the overflow spring though open systems are frequently presumed to have higher dissolution rates because of their ability to replenish co2 that is consumed in the dissolution process these data suggest that dissolution rates within the closed portion of the system may in some cases be higher due to the inability of closed flow paths to ventilate excess co2 to the atmosphere such conditions are likely to occur in conduits where co2 concentrations are elevated above atmospheric levels and average flow through times are short compared to the time scale over which water reaches equilibrium with respect to calcite

the evolution of the shiwanghe river valley in response to the yellow river incision in the hukou area shaanxi china abstract tributary response to mainstream incision is an important landscape evolution process the objective of this study is to examine tributary valley evolution in response to mainstream incision the shiwanghe river a tributary of the yellow river in the hukou area was chosen for a case study the terraces and knickpoints of the shiwanghe river were investigated and correlated to those of the mainstream optically stimulated luminescence osl was applied to date fluvial terraces longitudinal profiles of river and terraces were used to analyze valley evolution the terrace sequence of the shiwanghe river near their confluence is almost identical to the yellow river terraces at the hukou area this suggests that terrace formations of the tributary and the mainstream are synchronous and influenced by similar factors but the formation age of the same tributary terrace varies from downstream to the upper reaches of the river valley for such terraces their formation should be controlled by knickpoint migration a sudden drop in base level caused by the yellow river incision would trigger the formation of a knickpoint in the tributary a new terrace would be formed as the knickpoint propagated upstream throughout the tributary valley due to the different erodibility of bedrock a set of interbedded sandstone and shale the major knickpoint would disassemble into a cluster of small ones during its propagation the age of terrace formation with various valley segments depends on knickpoint migration rate and distance from the confluence vertical incision of the yellow river results in knickpoint recession of its tributaries the migration rate of knickpoints was affected by climate lithologic variation and to some extent structural control

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

thermal energy storage in an unconfined aquifer 1 field injection experiment a thermal injection and storage experiment was conducted to investigate the feasibility of storing thermal energy in shallow unconfined aquifers near the water table heated water was injected into a shallow aquifer and plume temperatures were monitored over a 141 day period by means of a dense array of bundle type piezometers the highly detailed data which provide the three dimensional temperature distribution within the aquifer give good insight into the physical processes of aquifer thermal energy storage and provide an excellent basis for the verification of simulation models the experimental data also allow the physical processes of heat advection dispersion retardation buoyancy and boundary heat loss to be quantified in a companion paper a three dimensional density dependent groundwater flow and thermal transport model is developed and validated using the results of the thermal injection experiment

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

interpretations and common challenges of aeolian records from north american dune fields abstract geomorphic and chronologic data for dune fields are evaluated for three contrasting areas of north america 1 the prairie parkland and boreal ecozones of the northern great plains in canada 2 the central great plains of the usa and 3 the deserts of southwestern usa and northern mexico luminescence and radiocarbon ages for periods of dune accumulation and stability are compared with palaeoenvironment proxies to provide an assessment of the boundary conditions of dune system response to changes in sediment supply availability and mobility dune fields in the northern great plains were formed from sediment originating from glaciofluvial or glaciolacustrine sediments deposited during deglaciation 16 11 ka subsequent aeolian deposition occurred in parkland and prairie dune fields as a result of mid holocene 8 5 ka and late holocene despite spatial and temporal gaps in chronometric data as a result of sampling biases the record from north american dune fields indicates the strong influence of sediment supply on dune construction with changes in sediment availability as a result of drought episodes resulting in dune field reactivation and reworking of pre existing sediment

time dimension in the geochemical approach and hazard estimates of a volcanic area the isle of ischia case italy abstract the volcano tectonics and magmatic evolution of the isle of ischia one of the active volcanoes of the naples area has been reconstructed in order to estimate the volcanic hazards in the region taking advantage of previous chronological and petrochemical studies five successive volcanic phases and the magmatic processes characterizing each of them have been identified moreover the high resolution k ar time scale and the trace element sr isotope and mineral chemistry distributions enable an evaluation of both the duration and the trends of these processes each phenomenon is related to a specific volcano tectonic setting including negative or positive calderic movements the most recent phase is clearly related to the mt epomeo horst uplift 780 m in the last 33 000 years this last phase corresponds to scattered eruptions distributed at the periphery of the horst the geochemical features of historical eruptions suggest an evolution of the system toward a more basic bulk composition it does not give rise to a high eruptive hazard on the contrary the morphological disequilibrium due to the rapid uplift of m epomeo horst generates the hazard of screes and mudflows this hazard is increased by seismic crises like in the casamicciola disaster in 1883

petrology of basalts from the central indian ridge lat 25 23 s long 70 04 e estimates of frequencies and fractional volumes of magma injections in a two layered reservoir abstract mineralogy melt inclusions in crystals and reverse zoning in minerals of oceanic basalts can be used to get an insight into the functioning of a magma chamber beneath a spreading zone dredged basalts from the central indian ridge cir 21 km from the rodriguez triple junction rtj exhibit two groups of olivine and plagioclase of different composition the first group is composed of forsteritic olivine fo 90 and very anorthitic plagioclase an 89 90 resorbed megacrysts containing numerous melt inclusions those observed in the core of the plagioclase megacrysts are the most primitive their compositions have been considered as the parental magma composition mg number 0 77 low tio 2 0 31 wt and low na 2 o 1 2 1 4 wt these magmas have a density about 2 70 g cm 3 and viscosity close to 100 poises at 1250 c liquidus temperature in the diagramfeo mgo vs tio 2 mgo 100 the zigzag evolution of the melt inclusions from core to rim of these plagioclase megacrysts has been interpreted as the result of three cycles of injection of parental liquid mixing and olivine crystallization the second group of minerals is essentially composed of more evolved olivine fo 86 88 and plagioclase an 67 72 euhedral mesocrysts some olivines are reverse zoned 3 steps they crystallized from hybrid liquids resulting from three successive mixings between batches rising from the base of the magma chamber and an evolved magma at the top of the reservoir time between the mixings can be calculated from the diffusion profiles of ni in the reverse zoned olivines these three mixings have been achieved within 4 days a two layer model for the magmatic reservoir is proposed to account for the mineralogy the melt inclusions and glassy matrix compositions of those basalts an estimation of the total volume of the chamber has been made knowing the volume of extruded magmas at zero age the chamber would have a radius of 400 500 m relative volume of lower layer where the first group of minerals crystallized and the upper layer where the second group of minerals formed is around 1 3

primitive melt replenishment and crystal mush disaggregation in the weeks preceding the 2005 2006 eruption 9 50 n epr abstract the 2005 2006 eruption at 9 50 n east pacific rise provides an exceptional opportunity to investigate the magma plumbing system beneath a well studied ridge system the eruption was preceded by two years of increasingly intense seismicity and occurred from the same location as a previous and well characterized eruption in 1991 1992 here we use the crystal cargo of samples from this eruption to investigate magma reservoir processes in the lead up to the eruption as well as their temporal relationship to the seismicity that preceded it compositional zoning in some plagioclase crystals indicates primitive melt replenishment occurred roughly six weeks or less before the eruption this replenishing event is seen only in the crystals from the central region of the eruption 9 50 9 52 n this is also the area where the most primitive lava compositions are observed and together these observations support models of replenishment being spatially focused the short time between the input of a more primitive melt and eruption onto the seafloor suggests replenishment likely contributed to triggering the eruption rare resorbed plagioclase crystals and glomerocrysts of plagioclase and olivine some of which have rims far from equilibrium with their host melt suggest that disaggregation of a crystal mush occurred within a few days prior to eruption interstitial melt from within this mush zone must have been mixed back into the erupted lava a form of in situ crystallization thus the erupted magmas evolved in a replenished tapped magma reservoir in which at least a part of the crystallization occurred in situ

a geochemical approach to model periodically replenished magma chambers does oscillatory supply account for the magmatic evolution of epr 17 19 s abstract we propose a new approach to model the geochemical evolution of continuously replenished and tapped steady state magma chambers we use a sinusoidal function to model cyclic magma supply the temporal evolution of a reservoir is described using differential equations in which the amount of refilling magma does not depend on the size of the chamber these equations can be used to calculate incompatible trace element concentrations and magma quantities we examine the geochemical consequences of episodic injections noises and wall rock assimilation we also explore possible variations in crystallization rate to show its potential the theoretical treatment has been applied to the epr 17 19 s a site with a strong magma budget which has been the subject of several geological geophysical studies the practical application requires geological parameters to be constrained as well as the extreme values of the lava concentration range a first step specifies the incompatible trace element composition of the replenishing melt which corresponds in the epr case to a magnesian liquid mgo 9 5 wt it is then possible to determine other parameters such as cycle period 750 years magma residence time 300 years and reservoir size from 4 1 to 8 6 km3 per 20 km segment lastly variations in crystallization rate do not significantly alter the results

truncation and accretion of soil profiles on coastal plain croplands implications for sediment redistribution soil stratigraphy and morphology in a small agricultural watershed on the coastal plain at clayroot north carolina indicate long term decadal scale patterns of the redistribution of sediment the most dramatic truncation of the soil profile occurs on convex upper slopes and suggests tillage and aeolian erosion as the major processes of soil loss thicker soils immediately downslope from convexities are consistent with redistribution by tillage but significant aeolian soil loss also occurs from some fields thinner apparently truncated soils were also associated with relatively steeper lower slope areas where contemporary rilling was observed the presence of thicker cumulic soils at toeslopes where small fans are observed at rill termini and about a half meter of alluvium in drainage ditches indicates that water erosion is also quite prominent distinctive soil stratigraphy is found in areas of aeolian deposition where podzolization in sandy surface deposits has created compound soil profiles on convex slopes tillage and wind erosion result in net soil loss with the former dominating on wetter soils and when plowing occurs and aeolian processes dominating on drier hilltops and when no till or minimum tillage practices are followed soils are thicker immediately downslope from convexities with thinner soils and rill erosion on lower slopes thickened soils and colluvial deposition in the form of thin fan deposits occur at toeslopes and in depressions the borders of fields often have thicker soils because of aeolian deposition water wind and tillage processes are all significant in soil redistribution at the clayroot site with relative importance in space and time controlled by topography soil properties seasonal moisture and vegetative cover and tillage practices

open system crystallization and mixing in two layer magma chambers abstract a modeling technique is presented for describing trace element behavior in tholeiitic magmas evolving by either perfect or imperfect fractional crystallization and magma mixing in periodically replenished two layer reservoirs in which eruption events occur at various times the models are based on density versus mafic index calibrations and can be used to examine two replenishment situations 1 dense picritic liquid ponds at the base of the magma chamber or 2 light liquid rises buoyantly through the resident magma and collects at the top of the reservoir input parameters are bulk solid liquid distribution coefficients d and enrichment depletion factors e i e the ratios between concentrations of trace elements in the erupted and incoming liquids respectively the results show graphically the relations between the weight fractions of incoming liquid w the crystallized magma x 1 and x 2 and the erupted magma y t these models can be used to distinguish imperfect fractional crystallization from rayleigh s law dependent fractionation they are applied to mid ocean ridge basalts morb dredged from galapagos spreading center gsc at 85 w and to rocks from the newark island layered intrusion nili the most likely mechanism to explain the gsc morb variations is imperfect fractional crystallization by contrast the nili variations appear to have been chiefly controlled by perfect fractional crystallization the y t versus w relations for these two situations are very different indications are that at galapagos the erupted magma amounts to less than 5 wt of the reservoir whereas at nili half of the mass of the initial replenishing magma was erupted during a cycle

roof assimilation at fast spreading ridges an investigation combining geophysical geochemical and field evidence 1 the role of assimilation at the roof of the axial magma chamber amc at fast spreading mid ocean ridges is investigated using field geophysical and geochemical data field observations from ophiolites indicate that roof assimilation is a common process but provide little constraint on the amount of material assimilated arguments based on geophysical data that include the subsidence of the layer 2a 2b boundary across the width of the amc and the depth of large axial summit troughs require at least 50 100 m of assimilation however significant variations in the depth of the amc on the east pacific rise epr over short along axis distances suggest up to 500 m fluctuations in the depth of the amc may be common on short timescales geochemical modeling of the over enrichment of chlorine in epr basalts suggests that 20 of the oceanic crust may go through a cycle of crystallization alteration then assimilation this is far more than can be accounted for by roof subsidence and suggests that fluctuations in the level of the roof must account for the majority of the assimilation assimilation most likely occurs on a number of different timescales ranging from decadal due to perturbations in the thermal regime related to diking to longer period fluctuations controlled by magma supply from the mantle large scale roof assimilation has implications for the accretion of the lower crust due to heat losses associated with assimilation and for the interpretation of the geochemistry of the oceanic crust

flow characterization through heat transfer evidence in a carbonate fractured medium first approach water temperature records at the outlet of a fractured carbonate system during an annual cycle show two types of variation slow variations over a small range resulting from the thermal equilibrium between water and rock in the aquifer and more rapid variations over a wider range transmitted more quickly due to the inflow of water through fractures or karstic pipes starting at the outlet we present first a model of thermal exchange for flow in a conduit then a model of thermal exchange in a porous medium between the surface and the reservoir the comparison with the data recorded at guichy nievre france allows us to establish the fact that on this site the vertical flow between the surface and the reservoir is rapid through a fracture network as is the case for the flow at the outlet

inherited vs acquired complexity in east texas weathering profiles complexity in weathering profiles may reflect variability in the parent material and or complex feedback relationships within regolith weathering systems because regolith formation modifies or destroys the parent material it is difficult to determine the extent to which variability in the weathering profile is inherited as opposed to created by the weathering processes the state probability function spf designed to model the spatial pattern of transitions in system states is applied to complex weathering profiles formed in glauconitic materials in east texas to address this issue the weathering profile is remarkably complex with units ranging from unweathered parent material to highly modified weathering products similar to those found in the bt horizons of the overlying rhodic paleudalf there is a very general vertical sequence with more weathered material near the top and less weathered material near the bottom however the pattern is quite irregular highly weathered units are found everywhere except at the base of the study section and much less developed units are found throughout though the spf indicates a high degree of spatial complexity the value never approaches or exceeds that which would be expected in a random vertical sequence of weathering horizons variation inherited from the parent material would produce spf values greater than that for a random sequence the complex patterns in the east texas regolith are thus attributable primarily to feedbacks within the weathering system and indicate that the complexity is dominantly acquired whatever anisotropy there may have been in the parent material has been magnified and overprinted by complex interactions within the weathering system

combined tracer tests in the karst aquifer of the artesian mineral springs of stuttgart germany chlorinated solvents have been detected at low concentrations in some of the mineral and medicinal springs spas of stuttgart since 1984 these springs discharge from a confined karst aquifer in order to investigate both the properties of the aquifer and the mechanisms of contaminant transport two multi tracer tests were carried out in 1998 and 1999 both fluorescent tracers naphthionate eosin pyranine and particle tracers clubmoss spores microspheres were used all available wells and springs were sampled for at least 12 months in these experiments naphthionate produced the best results maximum flow velocities were established to be within the range of 53 and 230 m day the breakthrough curves demonstrated a heterogeneous aquifer the results identified flow to the springs from the west and south west it was possible to prove an assumed boundary between the northern zone of low mineralised water and the southern zone of highly mineralised water

simple transport models for karst systems abstract tracer tests are useful field methods with a wide range of applications in karst aquifers the measured tracer breakthrough curve at a karst spring allows the estimation of the important transport properties of the karst system the breakthrough curve is typically characterized by a long tailing and a low tracer recovery that is not captured by the classical one dimensional advection dispersion model partitioning models are often used and require a large number of parameters in the present work simplified transport models are proposed to simulate the typical karst breakthrough curve the model setup consists of a karst conduit that is interacting laterally with the surrounding matrix the solute transport in both the conduit and matrix are governed by the one dimensional advection dispersion equation and the resulting mathematical model consists of a coupled system of differential equations the laplace transform method is used to derive the transport models for various flow and boundary conditions the models are in terms of four physically meaningful parameters that represent the advection and dispersion properties of the flow in the conduit and matrix algebraic relationships to estimate the model parameters are also derived in terms of the key features of the breakthrough curves the main advantage of the proposed models are their simple formulation and ability to capture the long tailing of the breakthrough curve in terms of just a few parameters application of the models to two real karst aquifers demonstrate their effectiveness in simulating the observed breakthrough curves and estimating the key transport parameters

combining hydrodynamics hydrochemistry and environmental isotopes to understand the hydrogeological functioning of evaporite karst springs an example from southern spain abstract this work adopts a multicriteria approach combining diverse karst hydrogeology techniques to investigate the functioning of evaporite karst systems which are normally less studied due to the poor quality of their water resources the applicability of using several methods was also verified in view of previous experience at a pilot site within southern spain the natural responses of the main discharge point of the system of study lower anzur spring were controlled by continuous monitoring of the discharge rate water temperature and electrical conductivity water samples were collected for chemical analysis and for the determination of intrinsic fluorescence water stable isotopes 18o 2h and tritium 3h concentrations physico chemical data were statistically examined applying principal component analysis pca and trend analysis tests mann kendall and sen s slope the system shows a clear karstic functioning highly dependent on concentrated recharge and influenced by a limited drainage capacity of the conduit network the piston flow effects at the beginning of floods indicate a contribution to the drainage of deep ascending flows through the saturated zone subsequent drops in temperature and mineralization values in the water drained by the spring as well as a recent infiltration deduced from the signature of intrinsic fluorescence and stable isotopes point to a good hydrogeological connection from the recharge areas to the spring later restoration of the initial values of mineralization in a much shorter time than those of temperature reveals a faster geochemical evolution of the recently infiltrated groundwater which may be a distinctive trait of evaporite karst aquifers lastly the high solute content of the spring water in depletion conditions with ascending trends of mineralization and temperature observed during several dry years as a consequence of lower recharge contribution together with the tritium activity of selected samples suggest the existence of an old component partly responsible for the spring base flow thus groundwater would be linked to gravity driven regional flows but also to recent conduit flows all the results obtained led us to devise a hydrogeological conceptual model to precisely reflect the functioning of the studied system the results presented here demonstrate the advantages of using diverse techniques when investigating evaporite karst aquifers

complex trace element effects of mixing fractional crystallization composite processes applications to the alaer granite pluton altay mountains xinjiang northwestern china abstract complex patterns of intersection of linear with power function curvilinear data point arrays are observed on ratio ratio correlation plots of trace elements in the alaer palaeozoic granite pluton altay mts xinjiang northwestern china data points in the linear array are relatively lower in sio 2 content and differentiation index d i and they become progressively decreased rightwards along the array in abundances of zr and hf which could be better explained by mixing between zircon rich restite and the granite melt data points in curvilinear arrays are higher in sio 2 content and d i value and therefore have presumably suffered more extensive fractional crystallization the complex patterns cannot be resolved with the classical models two models for the complex trace element effects of mixing fractional crystallization are developed in the paper with which the patterns can be resolved in all models we begin with a linear data array formed by simple two component mixing and then superpose fractional crystallization trends to generate a family of curves model 1 d 1 d 3 d 2 d 3 or d 1 d 3 d 2 d 3 in the general situation fractional crystallization curves assume a cluster of concave up or convex up power function curves which intersect the initial mixing line sloping positively special cases 1 3 d 1 d 2 d 3 or d 1 d 2 d 3 or d 2 d 1 d 3 the fractional crystallization curve is transformed into a straight line special case 4 d 1 d 2 d 3 the fractional crystallization line coincides with the initial mixing line model 2 d 1 d 3 d 2 or d 1 d 3 d 2 fractional crystallization curves assume the form of hyperbolic curves which intersect the initial mixing line sloping negatively in all of the two models the iso fraction lines are uniformly steeper d 1 d 2 or more gentle d 1 d 2 than the initial mixing line iso fraction lines increase d 1 d 2 or decrease d 1 d 2 progressively in slope with the decrease of residual liquid mass fraction f through modelling of the data point arrays on ratio ratio correlation plots of trace elements one can discern and distinguish between simple mixing pure fractional crystallization and mixing fractional crystallization composite processes initial compositions of the magma and the mixing modes can also be constrained through modelling the functional form concavity or convexity and the power index of the fractional crystallization curves the relative incompatibility of trace elements can be estimated semi quantitatively and the incompatibility sequence can be established it is demonstrated through modelling that the alaer granite pluton experienced mixing fractional crystallization composite processes the mixing mode is probably described by the restite model the incompatibility sequence of the 7 concerned trace elements is d th d la d y d nb d ta d hf d zr this incompatibility sequence may be applicable to the anatectic granites

the effects of magma replenishment processes on 238u 230th disequilibrium short lived isotope data are increasingly used to investigate magma chamber residence times arc lavas have excellent potential as tracers of magma evolution because their magmas are often out of u series isotope equilibrium and some arc magmas have yielded surprisingly old pre eruption u series ages from mineral separates a model is presented to examine the behaviour of u th isotopes for a range of conditions between closed system and steady state magmatic systems magmas can be maintained out of secular equilibrium for long periods of time by periodic mixing events with new magma batches the latter results in oscillations in 230th 232th consistent with the relatively constant values observed in lavas of different ages from some centres the effects of periodic reinjection of magma and mixing of old and young crystals on u series mineral isochrons are also considered mixtures of crystals produced by either replenished or closed system processes can readily result in linear arrays in many cases it may be valid to interpret these as minimum average residence times for the crystals whereas the liquid residence times calculated from u series data for periodically replenished systems are maximum values

a one dimensional heat transport model for conduit flow in karst aquifers summary a one dimensional heat transport model for conduit flow in karst aquifers is presented as an alternative to two or three dimensional distributed parameter models which are data intensive and require knowledge of conduit locations this model can be applied for cases where water temperature in a well or spring receives all or part of its water from a phreatic conduit heat transport in the conduit is simulated by using a physically based heat transport equation that accounts for inflow of diffuse flow from smaller openings and fissures in the surrounding aquifer during periods of low recharge additional diffuse flow that is within the zone of influence of the well or spring but has not interacted with the conduit is accounted for with a binary mixing equation to proportion these different water sources the estimation of this proportion through inverse modeling is useful for the assessment of contaminant vulnerability and well head or spring protection the model was applied to 7 months of continuous temperature data for a sinking stream that recharges a conduit and a pumped well open to the madison aquifer in western south dakota the simulated conduit flow fraction to the well ranged from 2 to 31 of total flow and simulated conduit velocity ranged from 44 to 353 m d

petrogenesis of the flood basalts forming the northern kerguelen archipelago implications for the kerguelen plume the thick 20 km crust of the kerguelen archipelago formed as the tectonic setting of the kerguelen plume changed from an oceanic ridge centered location at 43 ma to its present location beneath the antarctic plate the uppermost crust is dominantly flood basalt with a thickness of up to 10 km inverse isochron 40ar 39ar ages for upper and lower lavas in a 630 m section of basalt flows from mont bureau are 30 4 and 29 0 ma re os isotopic systematics are consistent with this age most of the lavas in two stratigraphic sections mont bureau and mont rabouillere from the northern part of the archipelago have sr nd and pb isotopic characteristics similar to the youngest upper miocene to pleistocene lavas erupted in the southeast part of the archipelago i e initial 87sr 86sr 0 7050 143nd 144nd 10 mgo alkalic lavas in the southeast province of the archipelago in these northern sections it is confined to transitional lavas with

effects of partial and full pipe flow on hydrochemographs of logsdon river mammoth cave kentucky usa summary logsdon river within kentucky s mammoth cave system drains the 25 km2 cave city groundwater basin temperature specific conductance stage and velocity were measured at the river s downstream end within the cave with 2 min resolution for one year beginning on may 5 1995 new interpretation of these data show relationships to the conduit s geometry and fluid transport behavior the 37 observed storm hydrographs chemographs are classified into two groups open channel flow and pipe flow conduit filled in the 16 pipe flow events logsdon river exceeded the capacity of its conduit raising the water table above the conduit ceiling with some storm water thus temporarily stored within the aquifer adjacent to the conduit pipe flow events were characterized by depression of specific conductance spc before peak discharge a peak in spc at peak discharge and a second depression in spc after peak discharge the first spc minimum represents the maximum concentration of passing storm water and the second is interpreted as the result of recent storm water draining back into the conduit having been temporarily stored in the aquifer adjacent to the conduit mean velocity decreases in the transition from partial to full pipe flow due to increased head loss at full pipe flow compared to nearly full pipe flow each of the open channel flow cases shows a depression in spc either coincident with or after peak discharge while the hydrochemographs of pipe flow are mainly controlled by the aquifer conduit network geometry in open channel cases they are mainly controlled by external recharge conditions including behavior of sinking streams

simplified physically based models for free surface flow in karst systems abstract most karst aquifers are characterized as a dual flow system comprised of a highly conductive conduit network embedded in a low porosity matrix the conduits are hydraulically connected to the matrix and behave either as a drain or a source depending on the recharge conditions simplified physically based models are herein employed to simulate the spring outflow for such aquifer systems the processes consist of a free surface flow in the conduit that is interacting laterally with a laminar groundwater flow in the surrounding matrix the conduit is subject to a concentrated recharge at its upstream end while the groundwater aquifer is subject to a diffuse recharge over its contributing surface area the flow system is described by a coupled system of partial differential equations the conduit flow is approximated by the kinematic wave equation and the groundwater flow by the linearized boussinesq equation the governing equations are solved using the laplace transform method after an appropriate linearization of the nonlinear coefficient the derived spring discharge models are a function of three dimensionless parameters the time lag parameter the lumped conduit parameter and the aquifer parameter the simulation results highlight the contrast between pressure driven and gravity driven flows and the importance of the conduit matrix interaction on the response of the karst system application of the models on real karst aquifers demonstrates their effectiveness in simulating the observed spring hydrograph using lumped physical parameters of the karst system

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

quantitative tracing of the maligne karst system alberta canada abstract early dye tracing studies on the large maligne karst aquifer in the canadian rocky mountains gave indeterminate results and low tracer recoveries in contrast a recent series of tests using high precision field fluorometry gave well defined breakthrough curves and far higher but variable recovery low recovery in one test may be accounted for by hydraulic switching or interaction with an alluvial aquifer which buries the principal conduit outlets a 16 km long karst conduit averaging between 90 and 170m 2 in cross sectional area drains the principal sinking lake to a group of karst springs a 14 km tributary conduit linking a high karst valley to the major conduit both drains and feeds the karst lake although during winter it has flows transitional between laminar and turbulent regimes a strong nonlinear relation between travel time and discharge suggests a partly vadose system that is little influenced by unsteady flow static and maximum dynamic conduit storage were estimated to be 1 95 and 0 76 10 6 m 3 respectively

mechanisms of heat exchange between water and rock in karst conduits 1 previous studies motivated by understanding water quality have explored the mechanisms for heat transport and heat exchange in surface streams in karst aquifers temperature signals play an additional important role since they carry information about internal aquifer structures models for heat transport in karst conduits have previously been developed however these models make different sometimes contradictory assumptions additionally previous models of heat transport in karst conduits have not been validated using field data from conduits with known geometries here we use analytical solutions of heat transfer to examine the relative importance of heat exchange mechanisms and the validity of the assumptions made by previous models the relative importance of convection conduction and radiation is a function of time using a characteristic timescale we show that models neglecting rock conduction produce spurious results in realistic cases in contrast to the behavior of surface streams where conduction is often negligible conduction through the rock surrounding a conduit determines heat flux at timescales of weeks and longer in open channel conduits radiative heat flux can be significant in contrast convective heat exchange through the conduit air is often negligible using the rules derived from our analytical analysis we develop a numerical model for heat transport in a karst conduit our model compares favorably to thermal responses observed in two different karst settings a cave stream fed via autogenic recharge during a snowmelt event and an allogenically recharged cave stream that experiences continuous temperature fluctuations on many timescales

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

paleosols in clastic sedimentary rocks their geologic applications interest in pre quaternary paleosols has increased over the past decade in large part because they have proved to be beneficial in solving diverse geological problems the majority of paleosols are described from continental deposits most commonly from alluvial strata criteria for recognizing these paleosols have been extensively described however classifying them has proved more complicated pre quaternary paleosols are generally classified according to one or more modern soil classification systems although one new classification has been proposed exclusively for paleosols to avoid problems using the modern soil classifications in addition to taxonomic classification paleosols can be categorized according to the interplay among deposition erosion and the rate of pedogenesis when they formed paleosols can be solitary if they formed during a period of landscape stability following the development of an unconformity such paleosols are commonly thick and extremely well developed more commonly paleosols are vertically stacked or multistory because they formed in sedimentary systems undergoing net aggradation if erosion was insignificant and sedimentation was rapid and unsteady compound paleosols generally formed if the rate of pedogenesis exceeded the rate of deposition composite paleosols developed thick cumulative paleosols indicate that erosion was insignificant and that sedimentation was relatively steady both autogenic and allogenic processes can influence depositional and erosion patterns and thus affect the kinds of soils that form consequently paleosols can help to interpret the history of sediment deposition and the autogenic and allogenic processes that influenced a sedimentary basin paleosols are also helpful in stratigraphic studies including sequence stratigraphic analyses they are used for stratigraphic correlations at the local and basinal scale and some workers have calculated sediment accumulation rates based on the degree of paleosol development in addition to their stratigraphic applications paleosols can be used to interpret landscapes of the past by analyzing paleosol landscape associations at different spatial scales ranging from local to basin wide in scope at the local scale lateral changes in paleosol properties are largely the result of variations in grain size and topography at the scale of the sedimentary basin paleosols in different locations differ because of basinal variations in topography grain size climate and subsidence rate paleosols are used to reconstruct ancient climates even to estimate ancient mean annual precipitation map and mean annual temperature mat ancient climatic conditions can be interpreted from modern soil analogs or by identifying particular pedogenic properties that modern studies show to have climatic significance stable carbon and oxygen isotopes are also used to interpret ancient climate and some effort has been made to estimate mat from isotopic composition on the basis of

river response to quaternary subsidence due to evaporite solution gallego river ebro basin spain abstract the stream terrace evolution of the gallego river during the quaternary was controlled by both climatic change and subsidence quaternary terrace deposits overlying tertiary clay and limestone are between 2 and 5 m thick whereas above evaporite formations the alluvial deposits may be as much as 110 m thick chronologically the first period of alluvial thickening involved the stream terraces t2 105 m above the present thalweg t3 95 m and t4 85 m which have been dated by paleomagnetic reversals as matuyama pre 780 000 the second subsidence period affected the deposits of the stream terrace t9 30 dated as brunhes post 780 000 in both thickening periods the subsidence was due to solution of the underlying evaporite formations halite and gypsum presumably during intervals of high water flow in the proposed model the valley subsidence was balanced by stream aggradation maintaining the river equilibrium profile the subsidence recorded in the alluvial deposits shows a complex spatial and temporal evolutionary pattern and total subsidence was assumed to be equal to the alluvial thickening for each subsidence period reaching up to 165 and 25 m respectively

vertisol genesis in a humid climate of the coastal plain of texas u s a numerous genetic studies of vertisols have been conducted using qualitative and semi quantitative methods across a broad range of climates however no detailed investigations exist on vertisols formed in humid climates using multiple pedogenic techniques on both a microlow ml and microhigh mh hence we sampled and characterized a ml and mh from a lake charles pedon mean annual rainfall 1090 mm mean annual temperature 20 c in the late pleistocene coastal plain beaumont formation of east texas according to the official series description the lake charles classifies as a fine smectitic hyperthermic typic hapludert with mollic and calcic diagnostic horizons coupled with field morphology and characterization data micromorphology and constituent mass balance interpretations were used to reconstruct the major pathway of pedogenesis in response to greater water recharge the ml contains darker colors more organic carbon greater depth of carbonate leaching and lower ph the proportion of oxalate extractable iron increases toward the surface and is in greater abundance in the ml than mh in contrast dithionite extractable iron increases with depth and has similar quantities in both the ml and mh the parent material and lower profiles contain asepic microfabric dominated by micaceous rich coarse clay and silt the asepic zone deep contains an abundance of soft carbonate masses and iron manganese segregations that appear to be forming contemporaneously with the presence of argillans substantiating clay translocation during the early history of soil formation sepic microfabric dominates the upper profiles of both the ml and mh in part from the transformation of biotite to smectite which is more pronounced in the microlow because of more intense weathering hard carbonate nodules and iron manganese concretions are abundant in the upper sepic zone and contain skelsepic microfabric suggesting that they are no longer growing dilation was the dominant strain force during pedogenesis from volume expansion in response to crack infills and shrink swell processes mass flux calculations indicate that total clay gains occurred in both the ml and mh during pedogenesis late pleistocene vertisols appear to approach steady state when forming in humid climates the soil mechanics model best explains the observed depth distribution of properties including slickensides with pedoturbation playing a secondary role in the genesis of these humid climate vertisols

geomorphological and sedimentological features in quaternary fluvial systems affected by solution induced subsidence ebro basin ne spain abstract the quaternary evolution and the morpho sedimentary features of some of the most important rivers in spain ebro and tagus rivers among others have been controlled by subsidence due to alluvial karstification of the evaporitic bedrock the subsidence mechanism may range from catastrophic collapse to slow sagging of the alluvium by passive bending in the ebro basin the mechanisms and processes involved in karstic subsidence were studied through the analysis of present day closed depressions as well as through old subsidence depressions palaeocollapses and solution induced basins and associated deformations recorded in the quaternary alluvial sediments the gallego ebro river system is presented as a case study of channel adjustments and geomorphic and sedimentary evolution of fluvial systems in dissolution induced subsidence areas in this fluvial system evaporite dissolution during particular quaternary time intervals namely early and middle pleistocene have lead to the development of a solution induced basin approximately 30 km long by 8 km wide filled by quaternary deposits with a total thickness in excess of 190 m the main river response to balance the subsidence in the alluvial plain was aggradation in the central reach of the subsiding area and degradation both in the upstream reach and in the valley sides where alluvial fans and covered pediments may prograde over the fluvial sediments the main sinking areas are recognized in the sedimentary record by anomalous thickenings in the alluvial deposits and fine grained sediments deposited in backswamp and ponded areas

regime and trace element evolution of open magma chambers o hara and co workers1 2 have recently summarized some of the evidence accumulated for open system cyclic magmatic systems and provided useful geochemical equations for the replenishment eruption cycles of an ideal magma reservoir i show here that o hara s theory fits the situation where the volcanic eruption taps the more differentiated magma before the mixing stage an alternative ideal model is discussed which is applicable to the more common process of hybrid magma eruption in mid ocean ridge basalts this new model may explain why large variations in incompatible elements coexist with moderate depletion of compatible elements