on the in situ aqueous alteration of soils on mars abstract early 3 gy wetter climate conditions on mars have been proposed and it is thus likely that pedogenic processes have occurred there at some point in the past soil and rock chemistry of the martian landing sites were evaluated to test the hypothesis that in situ aqueous alteration and downward movement of solutes have been among the processes that have transformed these portions of the mars regolith a geochemical mass balance shows that martian soils at three landing sites have lost significant quantities of major rock forming elements and have gained elements that are likely present as soluble ions the loss of elements is interpreted to have occurred during an earlier stage s of weathering that may have been accompanied by the downward transport of weathering products and the salts are interpreted to be emplaced later in a drier mars history chemical differences exist among the sites indicating regional differences in soil composition shallow soil profile excavations at gusev crater are consistent with late stage downward migration of salts implying the presence of small amounts of liquid water even in relatively recent martian history while the mechanisms for chemical weathering and salt additions on mars remain unclear the soil chemistry appears to record a decline in leaching efficiency a deep sedimentary exposure at endurance crater contains complex depth profiles of so4 cl and br trends generally consistent with downward aqueous transport accompanied by drying while no model for the origin of martian soils can be fully constrained with the currently available data a pedogenic origin is consistent with observed martian geology and geochemistry and provides a testable hypothesis that can be evaluated with present and future data from the mars surface

the oceanic crust in 3d paleomagnetic reconstruction in the troodos ophiolite gabbro the troodos complex cyprus provides an opportunity to study the structural configuration along a fossil intersection of a spreading axis and a transform fault we complement studies at troodos that have reconstructed the brittle deformation of the upper crust by new paleomagnetic data from the gabbro suite the gabbro suite is exposed at the extinct spreading axis continuing the solea graben toward the intersection with the fossil arakapas oceanic transform this is a unique exposure of deep crustal rocks formed at both an inside corner and an outside corner of a ridge transform intersection remanence directions from gabbros 23 sites were used as indicators for rigid body rotation the spatial distribution of rotation axes allow recognition of three regions to which deformation is partitioned 1 a western region outside corner that experienced primarily tilt about horizontal axis 2 a central region with minor rotation and 3 an eastern area inside corner where vertical axis rotations are dominant the absence of significant rotation in the 6 km wide central domain together with its location between the inside and the outside corner uncover the root of a fossil axial volcanic zone a zone sufficiently hot so the upper crust can decouple from the substrate clockwise rotation in the gabbro increases from the axial zone eastward similar to that in the overlying dikes indicating coupling of the lower crust with the brittle upper oceanic crust the transition from the decoupled layers of sheeted dikes and gabbro in the axial zone to the dikes gabbro coupling in the inside corner is in keeping with deepening of the brittle ductile transition from the dike gabbro boundary into the lower crust away from the axial zone our conclusions are consistent with one of the previous reconstructions in which the solea spreading axis was orthogonal to the arakapas trunsform fault and with recent studies of the present day lower oceanic crust however the newly inferred surface trace of the solea spreading axis is further to the east probably reflecting the tilt of axial upper crust rotated blocks c 2006 elsevier b v all rights reserved

an isotopic study of soils in chronological sequences of alluvial deposits providence mountains california the carbon sup 14 c and sup 13 c and oxygen isotopic composition of pedogenic carbonate was determined for two soil chronosequences on limestone and granitic alluvium in the providence mountains area in the mojave desert california the measured sup 14 c ages of pedogenic carbonate coating on clasts were interpreted in the light of a diffusion reaction model developed in our recent studies model ages of soil formation calculated from the measured sup 14 c ages of pedogenic carbonate are in correct relative order as determined by geomorphic evidence and are also consistent with model ages from the measured sup 14 c ages of soil organic matter sup 14 c model ages suggest that the order geomorphic surfaces we studied are of late pleistocene age ca 47 17 ka and the younger surfaces formed during the holocene ca 11 4 ka these age estimates of the geomorphic surfaces are older than the previously assigned ages based on a combination of soil development geomorphic relationships and several infrared stimulated luminescence dates but they are within a few thousand years of these other age estimates stable carbon isotopic composition of the soil carbonate indicates either a slight increase in c sub 4 or cam crassulacean acid metabolism plants or a decrease inmore plant density in this area during the holocene both the carbon and oxygen isotopic composition of soil carbonates suggests that the climate in the eastern mojave desert has in general become warmer and drier during the holocene 57 refs 9 figs 5 tabs less

pedogenic carbonate formation recrystallization versus migration process rates and periods assessed by 14c labeling 1 under arid to semihumid climatic conditions dissolution of primary carbonate and recrystallization with carbon c from soil co2 leads to accumulation of significant amounts of pedogenic secondary carbonate most soils of arid and semiarid regions contain a carbonate accumulation horizon the depth of which is related to climatic conditions and properties of parent material it remains unclear whether this carbonate migrates from the upper horizons before or after recrystallization with soil co2 the aim of this study was to determine recrystallization rates during initial pedogenesis and to estimate the accumulation depth of secondary carbonate based on c isotopic exchange during secondary carbonate formation in an experiment with alternating moisture conditions maize grown on 1 m high loess filled columns was pulse labeled in14co2 atmosphere every 3 weeks after 6 months portions of secondary recrystallized caco3 were determined in 5 cm segments based on 14c respired in the rhizosphere and subsequently incorporated into newly formed secondary carbonate more than 80 of recrystallized carbonate ca14co3 was leached from the uppermost 15 cm of the loess column and more than 70 of total secondary carbonate were accumulated in a depth between 15 and 50 cm based on the recrystallization rate calculated for the uppermost 15 cm of the loess column 1 77 0 26 10 5 day 1 between 300 and more than 1 700 years are necessary for complete decalcification of the upper 15 cm our modeled data are consistent with formation of calcic horizons under relatively humid conditions

flow directions in dikes from anisotropy of magnetic susceptibility data the bootstrap way one of the first applications of anisotropy of magnetic susceptibility ams was an attempt to determine flow directions from mafic dikes khan 1962 since the seminal work of knight and walker 1988 defining the expected behavior of ams in response to magma flow there has been increasing interest in using ams for this purpose here we present a quantitative method for interpretation of ams data from dikes using a parametric bootstrap first dikes must be sampled with at least five and preferrably more samples from within 10 cm of the dike margin the distributions of the eigenvalues and eigenvectors of the ams tensor are delineated by calculating eigenparameters of many bootstrapped paradata sets we generate paradata sets by first selecting a sample at random then calculating a replacement set of data by drawing tensor elements from normal distributions with the mean and standard deviation of the entire site the bounds containing 95 of the eigenparameters of the bootstrapped data serve as confidence limits for the parameter of interest classification of dikes proceeds as follows sites whose maximum and intermediate eigenvalues could not be distinguished are deemed uninterpretable in addition sites with principal eigenvectors with angles 45 away from the dike margin inverse or with markedly different directions on either side of the dike scissored are excluded the remaining dikes are classified as having unique flow direction information if the principal eigenvectors from at least one side are distinct from the dike plane based on the distribution of the bootstrapped principal eigenvectors if neither side has principal eigenvectors distinct from the dike plane the dikes are classified as having lineation information only a study comprising 251 dikes from the troodos ophiolite has 151 sites with directional data 38 sites with lineations only 7 inverse sites 5 scissored sites and 55 sites not fitting into any other category the flow directions interpreted from the data were generally southerly toward a fossil transform zone

the origins of shallow water carbonate lithofacies thickness distributions one dimensional forward modelling of relative sea level and production rate control the observation that shallow marine carbonate strata often have exponential lithofacies thickness distributions is one of the most fundamental results in carbonate stratigraphy in recent years because it is an observation that can be tested for its repeatability in various outcrop and subsurface examples and also because it raises the question of what sedimentary processes and climatic and oceanographic settings might lead to formation of a particular lithofacies thickness distribution this observation in turn links to the significant issue of how carbonate strata record climatic and oceanographic change through geological time this study applies a simple one dimensional numerical stratigraphic forward model of carbonate platform strata dougal to study how relative sea level oscillations could control lithofacies distribution dougal records platform top carbonate accumulation influenced by water depth dependent sediment production in euphotic oligophotic and aphotic production profiles with a lag depth controlling onset of production results from five single model runs highlight the issue of non stationary behaviour where statistical properties of the strata change with elevation up the section and show that exponential lithofacies thickness distributions can be generated from an entirely deterministic model results of multiple model runs 27 200 in total spanning a range of production and accommodation creation rates demonstrate that the three main controls on carbonate lithofacies distribution in this one dimensional model are i complex variations in the rate of creation of accommodation here due to high frequency glacio eustatic oscillations ii rate of sediment production dominated in these model runs by euphotic production rates and iii operation of autocyclic oscillations in deposition driven by a lag depth effect and formed during certain high frequency rising limbs on the glacio eustatic curve in these multiple model runs only ca 13 of the total runs created exponential distributions compared with 28 in the documented outcrop examples suggesting that other processes not included in this model play an important role more work is required to determine what these processes might be obvious candidates would be the various sedimentary processes that occur in three dimensions on platform tops such as sediment transport and variations in rate and type of sediment production related to biological variability and other process that occur in other different depositional settings for example sediment transport on slopes

pedogenic carbonates forms and formation processes abstract soils comprise the largest terrestrial carbon c pool containing both organic and inorganic c soil inorganic carbon sic was frequently disregarded because 1 it is partly heritage from soil parent material 2 it undergoes slow formation processes and 3 has very slow exchange with atmospheric co2 the global importance of sic however is reflected by the fact that sic links the long term geological c cycle with the fast biotic c cycle and this linkage is ongoing in soils furthermore the importance of sic is at least as high as that of soil organic carbon soc especially in semiarid and arid climates where sic comprises the largest c pool considering the origin formation processes and morphology carbonates in soils are categorized into three groups geogenic carbonates gc biogenic carbonates bc and pedogenic carbonates pc in this review we summarize the available data and theories on forms and formation processes of pc and relate them to environmental factors after describing the general formation principles of pc we present the specific forms and formation processes for pc features and the possibilities to use them to reconstruct soil forming factors and processes the following pc are described in detail earthworm biospheroliths rhizoliths and calcified roots hypocoatings nodules clast coatings calcretes and laminar caps the second part of the review focuses on the isotopic composition of pc 13c 14c and 18o as well as clumped 13c and 18o isotopes known as 47 the isotopic signature of pc enables reconstructing the formation environment the dominating vegetation 13c temperature 18o and 47 and the age of pc formation 14c the uncertainties in reconstructional and dating studies due to pc recrystallization after formation are discussed and simple approaches to consider recrystallization are summarized finally we suggest the most important future research directions on pc including the anthropogenic effects of fertilization and soil management in conclusion pc are an important part of sic that reflect the time periods and formation processes in soils a mechanistic understanding of pc formation is a prerequisite to predict terrestrial c stocks and changes in the global c cycle and to link the long term geological with short term biological c cycles

multiple tectonic rotations and transform tectonism in an intraoceanic suture zone sw cyprus abstract new palaeomagnetic data from the late cretaceous neotethyan troodos ophiolite and related units in sw cyprus provide compelling evidence that transform tectonism is recorded outside the main outcrop of the fossil southern troodos transform fault zone sttfz high level intrusive and extrusive sequences were sampled along the sw margin of the troodos massif and in ophiolitic slivers preserved along arcuate fault lineaments further to the south and west these units show cross cutting relationships with corresponding differences in remanent magnetisation directions characteristic of syn magmatic rotation in an active transform setting net tectonic rotation analyses allow decomposition of the total rotation at these sites into early and late components early transform related rotations are consistently clockwise in agreement with all other studies of rotations associated with the sttfz further to the east late rotations and the net rotations derived at localities where cross cutting relationships were not present are regarded as composite in origin the composite rotation axes closely relate to the orientation of observed regional structures in these circumstances additional constraints are used to attempt geologically viable interpretations the overall distribution of transform related rotations steeply and shallowly plunging rotation axes and spreading axis related rotations sub horizontal rotation axes is comparable with that along the sttfz and adjacent parts of the troodos massif this is most readily explained by simple along strike extension of the primary spreading axis and transform fabrics into sw cyprus with minor late disruption by high angle dextral shear zones and neotectonic graben systems

the anatomy of a mississippian visean carbonate platform interior uk depositional cycles glacioeustasy and facies mosaics abstract late visean platform interior carbonate strata of northern england and wales have traditionally been interpreted to comprise shallowing up cyclothems the upper boundaries of which are marked by unconformities that record subaerial exposure events these strata were deposited during what is understood to be a greenhouse to icehouse transition and the cyclothems are assumed to reflect glacioeustatic sea level oscillations associated with this climatic change importantly these interpretations reflect a qualitative model which assumes that facies respond in a simple way to water depth variations and so migrate and stack in a predictable pattern as eustatic sea level fluctuates exposure surfaces and most facies are however laterally discontinuous across the platform tops quantitative statistical analysis and simple 1d stratigraphic forward modelling suggest that the observed vertical facies stacking patterns on the derbyshire and north wales platforms are not cyclical the most ordered arrangement of facies that could be interpreted as ideal cycles in each section are variable within and across the platforms this observational and analytical evidence suggests that instead of a simple dominant external glacioeustatic forcing on sedimentation a model commonly proposed for the late visean carbonate strata of northern england and wales strata were deposited as a facies mosaic under variable hydrodynamic conditions influenced by autogenic processes as well as local environmental fluctuations in salinity and temperature and perhaps in conjunction with glacioeustasy and syn rift tectonic processes which occurred from metre scale to kilometre scale as suggested by the ideal cycles

correlation and dating of quaternary alluvial fan surfaces using scarp diffusion great interest has recently been focused on dating and interpreting alluvial fan surfaces as a complement to the radiometric methods often used for surface exposure dating this paper illustrates a rapid method for correlating and dating fan surfaces using the cross sectional shape of gullies incised into fan surfaces the method applies a linear hillslope diffusion model to invert for the diffusivity age t m2 using an elevation profile or gradient slope profile gullies near the distal end of fan surfaces are assumed to form quickly following fan entrenchment scarps adjacent to these gullies provide a measure of age the method is illustrated on fan surfaces with ages of approximately 10 ka to 1 2 ma in the arid southwestern united states two areas of focus are death valley california and the ajo mountains piedmont arizona gully profile morphology is measured in two ways by photometrically derived gradient slope profiles and by ground surveyed elevation profiles the t values determined using ground surveyed profiles are more consistent than those determined using photo derived t values however the mean t values of both methods are comparable the photometric method provides an efficient way to quantitatively and objectively correlate and relatively date alluvial fan surfaces the t values for each surface are determined to approximately 30 50 accuracy

the mamonia complex sw cyprus revisited remnant of late triassic intra oceanic volcanism along the tethyan southwestern passive margin upper triassic volcanic and sedimentary rocks of the mamonia complex in southwestern cyprus are exposed in erosional windows through the post cretaceous cover where the mamonia complex is tectonically imbricated with the troodos and akamas ophiolitic suites most of these upper triassic volcanic rocks have been considered to represent remnants of triassic oceanic crust and its associated seamounts new nd and pb isotopic data show that the whole mamonia volcanic suite exhibits features of oceanic island basalts oib four rock types have been distinguished on the basis of the petrology and chemistry of the rocks volcanism began with the eruption of depleted olivine tholeiites type 1 and oceanic island tholeiites type 2 associated with deep basin siliceous and or calcareous sediments the tholeiites were followed by highly phyric alkali basalts type 3 interbedded with pelagic halobia bearing limestones or white reefal limestones strongly lree enriched trachytes type 4 were emplaced during the final stage of volcanic activity nd and pb isotopic ratios suggest that tholeiites and mildly alkali basalts derived from partial melting of heterogeneous enriched mantle sources fractional crystallization alone cannot account for the derivation of trachytes from alkaline basalts the trachytes could have been derived from the partial melting at depth of mafic material which shares with the alkali basalts similar trace element and isotopic compositions this is corroborated by the rather similar isotopic compositions of the alkali basalts and trachytes the correlations observed between incompatible elements nb th and varepsilon nd and pb isotopic initial ratios suggest that the mamonia suite was derived from the mixing of a depleted mantle dmm and an enriched component of high 238u 204pb himu type models using both nd and pb isotopic initial ratios suggest that the depleted tholeiites type 1 derived from a dmm source contaminated by an enriched mantle type 2 component em2 and that the oceanic tholeiites type 2 alkali basalts type 3 and trachytes type 4 were derived from the mixing of the enriched mantle source of the depleted tholeiites with a himu component none of the mamonia volcanic rocks show evidence of crustal contamination the upper triassic within plate volcanism likely erupted in a small southerly neotethyan basin located north of the eratosthenes seamount and likely floored by oceanic crust

preservation of forcing signals in shallow water carbonate sediments abstract no consensus has been reached on whether the metre scale cycles that commonly occur in peritidal carbonates are predominately a product of external relative sea level variations allocycles or an intrinsic property of carbonate production generated via the interaction of non linear processes autocycles for any forcing signal such as eustatic sea level change to be detectable in stratigraphy its effects must be preserved here a deterministic three dimensional geological process model is used to explore how such cycles are preserved in the geological record in the presence of autocyclic processes each simulation produced cycle thickness distributions that are statistically indistinguishable from a theoretical poisson process regardless of whether auto or allo cycles dominated spectral analysis of depositional time series constructed from idealised geological sections showed that all detectable signals occurred within the milankovitch forcing frequency bands even when no milankovitch forcing was present thus it is deduced that from any geological section alone external forcing signals are detectable but are not distinguishable from autocyclically produced signals interestingly there is no correlation between the percentage of sediment preserved and the accuracy with which signals are detectable in the preserved sediment in some model realisations even with preservation as low as 40 the correct forcing signal can be detected accurately while conversely sections with preservation as high as 90 can have poor signal preservation the reverse can also be true in other models it is therefore concluded that distinguishing allocyclic and autocyclic forcing in shallow marine or peritidal carbonate successions is likely to be extremely difficult except in cases of extraordinary sedimentary preservation and dating accuracy

suitability of biogenic carbonate of lithospermum fruits for 14c dating lithospermum boraginaceae belongs to a small group of plant taxa that accumulate biogenic carbonate in their fruits in this genus carbonate incrustations form in the cells of the epidermis and sclerenchyma of the pericarp fossil lithospermum fruits nutlets with well preserved calcified tissues commonly occur in quaternary sediments and cultural layers we tested the suitability of biogenic carbonate of lithospermum fruits for radiocarbon dating using a total of 15 ams measurement results from four modern and 11 fossil samples the 14 c data from modern samples suggest that lithospermum utilises only atmospheric carbon to synthesise calcite in the nutlets in general the ages determined through 14 c dating of fossil fruitscorresponded well with the absolute age intervals for archaeological sites over the last 5000 yr biogenic carbonate of lithospermum fruits like that of celtis represents a new source of chronological information for late quaternary studies 2006 university of washington all rights reserved

dike surface lineations as magma flow indicators within the sheeted dike complex of the troodos ophiolite cyprus mesoscopic flow lineations and anisotropy of magnetic susceptibility ams have been measured for dikes within the cretaceous age troodos ophiolite with the goal of comparing the direction of initial magma flow through dike conduits immediately following crack propagation with that of flow of subsequent magma emplaced during later stages of dike growth dike margin indicators of flow include cusp axes and elongate vesicles found high in the ophiolite pseudostratigraphy and ridge and groove structures termed hot slickenlines found throughout the complex a unique flow direction is determined where elongate vesicles near dike margins display imbrication with respect to the margin significant changes in vesicle elongation directions across dikes likely indicate either changes in magma flow direction after dike propagation or back flow of magma during the waning stages of intrusion surface lineations generally lie subparallel to the direction of flow inferred from ams determinations on cores within 5 cm of dike margins surface lineations also lie subparallel to the long axis e1 of the orientation ellipsoid defined by long axes of groundmass plagioclase phenocrysts measured in sections from ams cores correlation of surface lineations with interior indicators of flow ams plagioclase trachytic texture indicate that the surface features are good proxies for grain scale magma flow directions during dike propagation in troodos dikes orientations of surface flow features in the dikes of the troodos ophiolite indicate an approximately equal mix of subhorizontal to near vertical magma flow contradicting the paradigm of primarily vertical flow of magma beneath continuous axial magma chambers at oceanic spreading centers our data are consistent with a model of magma emplacement both vertically and horizontally away from isolated magma chambers beneath axial volcanoes spaced along a ridge crest

methanogenesis in eocene arctic soils inferred from δ13c of tree fossil carbonates we report on the carbon and oxygen stable isotope composition of fossil tree material collected at the white mountain locality of the buchanan lake formation on axel heiberg island in the high arctic of canada the fossils are middle eocene in age and have been permineralized with carbonate microscopic examination of fossils revealed them to be the remains of metasequoia stems composed of secondary carbonate calcite and original wood intermingled at the cellular level because the specimens show little compression crushing or tissue degradation we believe that carbonate permineralization occurred soon after burial and therefore provides insight into eocene carbon cycling at the locality the carbon isotope signature of the carbonate suggests that methanogenesis resulted in a 13 c enriched co2 pool that equilibrated with soil water and gave rise to unusually 13 c enriched caco3 tree fossil carbonate exhibited strikingly high d 13 c values 4 0 to 7 4x compared to published phanerozoic pedogenic carbonate d 13 c values these d 13 c values in conjunction with fractionation factors a previously determined for carbonate precipitation and methanogenic pathways indicate an eocene soil co2 pool containing 80 95 co2 produced as a by product of acetate fermentation methanogenesis because methane in the atmosphere is a powerful greenhouse gas we suggest that methane emissions from axel heiberg soils contributed to the relatively warm arctic climate during the middle eocene d 2004 elsevier b v all rights reserved

fossil ridge transform intersection in the troodos ophiolite new perspectives from rock magnetism in the gabbro suite and fracture mechanics analysis 1 the missing link in the comprehensive view of the ridge transform intersection rti frozen in troodos is that portion of the extinct spreading axis between the solea graben and the fossil arakapas transform directional indicators of magma flow verified by paleomagnetic tests along with tectonic indicators permit tracing the extinct spreading axis through the gabbro suite at the continuation of the solea graben axis these indicators of axial deformation include measurements of the anisotropy of magnetic susceptibility ams and petrofabric determinations in the gabbro dikes major normal faults and fabric of mantle rocks the inferred axis is curved as it approaches the fossil transform the sense of curvature is in agreement with dextral slip along the fossil transform assuming curvature has resulted from transform induced shear stresses fracture mechanics analysis predicts the control on the axis shape by the ratio between driving stresses of spreading sh and resistance for sliding along the fossil transform t accordingly the curved shape of the spreading axis frozen in troodos indicates t sh 0 1 0 2 whereas for straight axis and orthogonal rti the analysis predicts t sh 0 01 these results suggest that the fossil curvature reflects a strong transform relative to curvature free rtis a strong arakapas transform is also in agreement with previous evidence of diffused deformation north of the transform such as block rotation and sigmoidal structure of dikes and faults

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

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

radiocarbon dating reveals the timing of formation and development of pedogenic calcium carbonate concretions in central sudan during the holocene abstract calcic soil horizons are common in arid and semi arid lands and represent the result of the progressive accumulation of calcium carbonate in the soil profile over time this process leads to the occurrence of several pedogenic phases of calcium carbonate dissolution precipitation for this reason timing the formation and development of calcic horizons through radiometric dating is not straightforward as time averaging effects due to the superimposition of the same process over time occur on this basis this study aims to define the timing and dynamics of formation and development of pedogenic calcium carbonate concretions from semi arid central sudan highlighting the relevance of a multi disciplinary approach and the effectiveness of radiocarbon dating coupled to an accurate sampling strategy applied to pedogenic carbonates calcic soil horizons bk were sampled during the archaeological excavation of site 16 d 4 at al khiday central sudan and studied by optical cathodoluminescence and scanning electron microscopy as well as by chemical physical and stable isotopes c and o analyses micromorphological analyses reveal the occurrence of distinctive calcitic pedofeatures here described as calcitic cemented nodules and calcitic rich matrix radiocarbon ages obtained for these pedofeatures mostly refer to the early holocene for calcitic cemented nodules 11 5 9 9 and 9 6 cal ka and to the middle holocene for powdery calcitic rich matrix 7 9 7 7 6 3 and 6 1 cal ka samples additionally 13c and 18o values indicate major shifts of environmental conditions from the early to the middle holocene in agreement with the available information from detailed palaeoenvironmental studies carried out in the region in particular early holocene pedogenic calcitic features can be related to short arid phases during general wetter climate conditions whereas those formed in the middle holocene can be related to short humid phases results show that bk horizons were characterized by alternate periods of calcite accumulation precipitation and dissolution and periods of quiescence or extremely slow growth rates thus the formation and development of bk horizons have been a long lasting process significantly influenced by climatic fluctuations this study represents a further step in the comprehension of the development of calcium carbonate concretions and at a wider perspective calcrete the paper also contributes to the definition of a reliable method to radiometrically date the formation of calcic pedofeatures on a broader perspective this work may offer a significant tool for archaeometric studies where the interaction between secondary calcite and archaeological material is significant e g radiocarbon dating of bioapatite in bones and palaeoenvironmental studies in arid lands where bk horizon development is a function of past rainfall

evolution of the lower gangetic plain landforms and soils in west bengal india abstract three major landforms uplands old fluvial deltaic plains and young fluvial plains are identified from the lower gangetic plains of west bengal india on the basis of remote sensing and field studies morphologic quantitative and thermoluminescence studies of soils of the study area have been conducted two types of uplands are recognised upland in the west overlain by red soils autochthonous and allochthonous types and upland in the north barind tract characterised by three topographic levels aspects of the autochthonous upland red soils lower to middle pleistocene age show the ferrugination ferrisol phase of development soils of the old fluvial deltaic plains 6 3 ka and lower level of the barind tract have argillic horizons and exhibit the fersiallitisation phase of development development of ferrugination and fersiallitisation phases was favored due to the pre weathered nature of the parent material soils of the old fluvial deltaic plains barind tract lower level and young fluvial plains show effects of hydromorphism due to waterlogging in the form of segregations of fe mn oxides gleying and chloritisation probably due to ferrolysis in the upper horizons of some of these soils neotectonics seems to have affected development of landforms and soils significantly due to reactivation of some basement faults in the western region some tectonic blocks subsided causing transgression during the early pleistocene and at ca 7 ka subsequent uplift of these blocks caused regressions and development of soils on the exposed landscapes episodic uplift of the barind tract in the northern region may have given rise to three topographic levels some faults confine the courses of the damodar ganga and bhagirathi rivers

genesis age and archaeological significance of a pedosediment in the depression around tell mozan syria abstract a pedosedimentological profile from the ditch surrounding the lower town of the bronze age site of mozan is investigated for its soil and sedimentological characteristics and has been dated in order to gain information on the use of the ditch and on the landscape development surrounding the settlement the depression did not contain large amounts of water flowing or stagnant and probably was used for agricultural purposes accumulation that in part includes anthropogenically derived redeposited and bioturbated debris started at around 2800 cal bc or later and was especially intensive at some time between 2800 and 1000 cal bc deposition may have been caused by intensive agricultural use of the landscape during the urban explosion of the early bronze age or in the early middle bronze age

growth rates of pedogenic carbonate coatings on coarse clasts abstract growth rates of pedogenic carbonate coatings on clasts can be used as a simple quantitative index of soil and sediment age as well as a chronological framework for palaeoecological reconstructions they are also probably connected with general intensity of formation of bk horizons in soils previously data on coating growth rates were restricted ecologically and geographically to desert regions of north america this paper presents growth rates of holocene pedogenic carbonate coatings on clasts within an extended range of environments calculated on the basis of archaeological and radiocarbon dating the rates in this study are higher than in earlier reports carbonate coatings can thicken with rates up to 1 mm 1000 years or higher in semi arid and semi humid climates at least five factors are likely to control growth rates 1 climate 2 lithology of carbonate parent material 3 depth under the soil surface 4 clast size 5 bulk density and composition of cutans favorable factors for comparatively rapid coating thickening seems to be climatic conditions ranging from semi arid to semi humid high carbonate content of parent material and large size of clasts there is also an optimal depth of carbonate coating growth in a soil profile little information on bulk density and composition of cutans is available but they appear to play an important role as one of the factors governing growth rates of pedogenic carbonate coatings on clasts

stable carbon and oxygen isotopes in quaternary soil carbonates as indicators of ecogeomorphic changes in the northern chihuahuan desert usa stable carbon and oxygen isotopes in soil carbonates provide an additional technique for investigating quaternary ecogeomorphic changes in arid and semiarid regions this study presents 13c and 18o values in surface and buried soils in a basin and range region of southern new mexico and west texas three landform categories were investigated for their isotopic content 1 middle piedmont slopes 2 a lower piedmont slope and adjacent playa depressions and 3 an intermontane basin floor soils of the middle piedmont slopes had greatest 13c variability ranging from 0 6 in buried soils to 11 1 pdb in surface soils soils of the basin floor had greatest variability in 18o values ranging from 0 6 to 7 6 pdb fossil pollen patterns roughly paralleled 13c shifts with cheno am pollen exhibiting greatest changes both isotope and pollen data across stratigraphic discontinuities suggest that a conversion from c4 grasses to c3 desert shrubs accompanied holocene erosion

pedogenic carbonate cutans on clasts in soils as a record of history of grassland ecosystems pedogenic carbonate cutans coatings pendants rinds on coarse clasts are common in stony soils of arid and semiarid regions dominated by open vegetation this paper gives an overview of the potential of the carbonate cutans for paleograssland research using data from literature and personal observations carbonate coatings are stratified into distinct microlamina which can provide a record of local environmental changes lamina made of a rather pure calcium carbonate with better formed and parallel oriented crystals seem to be indicative of relatively dry phases that were less favorable for biological activity a high content of admixtures poorer formed and randomly oriented calcite crystals presumably mark wetter periods characterized by climatic amelioration at a most general level n 13 c of the cutan carbonate can provide information on the type of photosynthesis of local vegetation whereas n 18 o in carbonate material of the coatings correlates with oxygen isotopic composition of precipitation water at the site and is sensitive to fluctuations in temperature to obtain chronological evidence on cutan formation the 14 c and th u methods can be applied with certain limitations additionally cutan growth rates can be used to evaluate the age of these features fl 2002 elsevier science b v all rights reserved

paleoseismological investigation of the oblique normal ekkara ground rupture zone accompanying the m 6 7 7 0 earthquake on 30 april 1954 in thessaly greece archaeological and geochronological constraints on ground rupture recurrence 1 observations in trenches excavated across the ekkara rupture zone erz the longest of the sporadic ground ruptures that accompanied the m 6 7 7 0 earthquake of 30 april 1954 on the domokos fault zone dfz identify a left lateral oblique normal fault with a slip vector aligned with the regional extension direction verifying the tectonic origin of the erz the paleoseismological interpretation of stratigraphic soil stratigraphic and tectonic features is discussed with emphasis on the issues related to strongly oblique fault kinematics two pre 1954 events of ground rupture are recognized e1 and e2 and an event of ground cracking only e1a shortly after e1 event e2 was accompanied by larger displacement than e1 and 1954 but this does not necessarily imply a stronger earthquake archaeological dating of transported ceramic sherds constrains e1 between 6750 and 4450 b p more likely 6450 5750 b p luminescence dating of colluvial deposits and 14c dating of pedogenic carbonates stone coatings place e2 at 17 500 2500 b p preferred age in the hazard wise most conservative interpretation recent recurrence intervals of erz activations exceed 3195 years the sporadic nature of the 1954 ruptures precludes certainty on whether the erz has recorded every past activation of the dfz unless data are also collected from other dfz rupture zones minimum limiting estimates of 0 3 0 5 mm yr slip rate are derived for the erz and the true slip rate is not expected to exceed 1 mm yr slip rate estimates for the erz may be minima for the dfz slip rate however because coseismic deformation in the past may have been distributed to more than one rupture zones at the surface

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

application of a soil water balance model to evaluate the influence of holocene climate change on calcic soils mojave desert california u s a abstract we used a process based soil water balance model to simulate the downward flux of soil water under varied conditions of climate vegetation and soil texture to determine the potential impact of episodic periods of wetter pluvial climate during the holocene on calcic soils in the mojave desert that have a bimodal distribution of carbonate daily weather data associated with a relatively wet climate years with extreme increases in annual rainfall 33 cm yr and dry climate historic average annual rainfall 15 cm yr was used to simulate the affects of pleistocene and holocene climate change on soil water balance linkages among atmospheric circulation patterns regional increases in precipitation and historic flooding in the mojave desert california suggest that historic wet years provide an analog for wetter climates that occurred during the last glacial period latest pleistocene and episodically during holocene periods of pluvial activity modeling results indicate that soil water balance for dry and wet years strongly corresponds with the upper and lower zones of carbonate accumulation respectively soil water only reached the lower zone of carbonate during a wet year when extreme increases in winter spring storm activity resulted in a significant increase in precipitation and the downward flux of soil water the linkage between increases in frontal storm activity and pluvial events suggests that the shallow zone of the bimodal distribution of carbonate is a result of periods of significant decreases in winter and spring rainfall and not primarily due to increases in holocene temperature or the development of clay rich horizons calculation of carbonate solubility and accumulation rates suggests that the bimodal distribution of carbonates in soils may have also been impacted by episodic periods of extreme increases in precipitation associated with perennial lakes during the holocene results suggests that much of the carbonate in the upper 75 cm of pleistocene soils may have accumulated during the late holocene rather than throughout the entire holocene

radiocarbon dating of thin pedogenic carbonate laminae from holocene archaeological sites radiocarbon dating has been previously suggested to be applicable to pedogenic carbonate however until now the validity of radiocarbon dates from pedogenic carbonate remained poorly understood because of the relatively low resolution of chronological controls in this study we compared the radiocarbon dates a total of 21 of thin 0 2 0 3 mm in thickness laminae of pedogenic carbonate coatings on clasts from holocene archaeological sites in the eastern mediterranean and south siberia with independently estimated age ranges for these sites we obtained a high correlation between the oldest laminae of coatings with the site ages the 14 c ages of pedogenic carbonate were systematically younger by c 0 3 1 6 ka mean c 0 75 ka compared with archaeological sites this finding suggests that pedogenic carbonate despite potential complicating factors can be dated more accurately with 14 c than has been generally appreciated

a comparison of mineralogical techniques and potassium adsorption isotherm analysis for relative dating and correlation of late quaternary soil chronosequences abstract the utility of potassium adsorption isotherm analysis kia for relative dating and correlation of soil chronosequences was assessed by a comparison with some widely used mineralogical techniques the soils studied near detroit michigan are brown 10yr calcareous entisols developed in holocene 4 ka floodplain sediments and inceptisols and alfisols with redder 7 5yr 5yr cambic and argillic b horizons formed on late pleistocene 14 5 12 4 ka fluvial terraces fluvial paleochannels and paleoshorelines beach ridges of proglacial lakes the soils show a positive linear correlation between soil age and clay content depth of carbonate leaching and fe oxide accumulation in contrast the duration of soil formation is too short for variations in heavy mineral frequencies to discriminate soil age reliably scanning electron microscopy shows that chemical weathering stage is indicated by progressive etching and pitting of calcite apatite and amphibole with increasing soil age k isotherms are linear or slightly curvilinear indicating that ion exchange is dominant over specific adsorption a statistically significant linear correlation between k distribution constant and soil age attributed to progressive weathering of mica suggests that kia is useful for relative dating of genetically related soils once a well dated chronosequence is established kia produces results comparable to or better than mineralogical techniques however soil morphology and a clay redness index are more effective than mineralogical and chemical techniques for interchronosequence correlation

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

evidence for holocene environmental changes in the northern fertile crescent provided by pedogenic carbonate coatings abstract holocene environmental changes in the northern fertile crescent remain poorly understood because of the scarcity of local proxy records in the region in this study we investigated pedogenic soil formed carbonate coatings on stones at the pre pottery neolithic site gobekli tepe as an indicator of local early mid holocene environmental changes the 14c ages and stable isotopic composition of carbon and oxygen in thin 0 2 0 3 mm thick pedogenic carbonate lamina indicate two main periods of coating formation the early holocene ca 10000 6000 cal yr bp and the mid holocene ca 6000 4000 cal yr bp during the first period there was an inverse relationship between 13c and 18o curves a decrease in 13c values coincide with an increase in 18o values for this period a trend towards higher temperatures is suggested in the mid holocene the mean rate of coating growth was 2 3 times higher than in the early holocene both 13c and 18o reached their maximum values during this time and the direction of changes of the 13c and 18o curves became similar the combination of data suggests that this period was the most humid in the holocene and on average warmer than the early holocene at ca 4000 cal yr bp secondary accumulation of carbonate ceased presumably reflecting a shift to a more arid climate

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

modern soil system constraints on reconstructing deep time atmospheric co2 abstract paleosol carbonate based estimates of paleo atmospheric co 2 play a prominent role in constraining radiative forcing and climate sensitivity in the deep time large uncertainty in paleo co 2 estimates made using the paleosol carbonate co 2 barometer however arises primarily from their sensitivity to soil respired co 2 s z this parameter is poorly constrained due to a paucity of soil co 2 measurements during carbonate formation in modern soils and a lack of widely applicable proxies of paleo soil co 2 here the 13 c values of carbonate and soil organic matter som pairs from 130 holocene soils are applied to a two component co 2 mixing equation to define soil order specific ranges of soil co 2 applicable for constraining s z in their corresponding paleosol analogs equilibrium carbonate som pairs characterized by 13 c carb som values of 12 2 15 8 define a mean effective fractionation of 14 1 and overall inferred total soil co 2 contents during calcite formation of s z during calcite formation is 1500 2000 ppmv range of 500 2500 ppmv overall higher values 2000 5000 ppmv are indicated by the subset of these soils characterized by higher moisture content and productivity near atmospheric levels 400 200 ppmv of estimated s z are indicated by immature soils recording their low soil productivity vertisols define the largest range in total soil co 2 25 000 ppmv reflecting their seasonally driven dynamic hydrochemistry a s z range of 1000 10 000 ppmv is suggested for paleo vertisols for which calcite precipitation can be constrained to have occurred in an open system with two component co 2 mixing with a best estimate of 2000 ppmv 1000 ppmv appropriate for paleo vertisols for which evidence of protracted water saturation is lacking mollisol pairs define a best estimate of s z of 2500 ppmv range of 600 4000 ppmv for late cretaceous and cenozoic analogs non equilibrium pairs with 13 c values 16 make up 51 of the dataset lending support to the hypothesis that pedogenic carbonate precipitation occurs during periods of low productivity in a soil atmosphere with a large component of atmospheric co 2 predictable scaling between estimated soil co 2 and the difference in 13 c between measured pedogenic carbonate and that predicted to have formed from soil respired co 2 inferred from measured som can be used to further constrain appropriate ranges of s z for reconstruction of paleo atmospheric p co 2 soil co 2 estimates are poorly correlated to mean annual precipitation likely reflecting that for carbonate bearing soils where moisture limits co 2 production total soil co 2 is most strongly influenced by actual evapotranspiration

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

pedogenic carbonates in texas stable isotope distributions and their implications for reconstructing region wide paleoenvironments abstract pedogenic carbonates are ubiquitous in paleosols through geologic history and have been widely used to speculate on paleoclimatic conditions during their formation they are widespread and well developed in large areas of texas a majority are of late quaternary age and have formed across a range of climatic conditions on various types of substrates to evaluate the usefulness of pedogenic carbonates as environmental indicators this study investigates regional scale trends in stable isotope compositions of pedogenic carbonates across approximately 900 km of texas the 13c values of 49 pedogenic carbonate profiles 182 analyses on various host strata e g limestone igneous rocks range from 10 6 to 0 7 v pdb most 13c values are evenly distributed between 9 and 1 and the 18o values range from 9 1 to 0 2 v pdb mainly between 6 and 2 there is no correlation between carbon and oxygen isotopic values r2 0 0002 pedogenic carbonates in the texas gulf coastal plains southern high plains and west texas exhibit higher 13c values than those in south and central texas which corresponds to the spatial change in vegetation between c4 dominated and c3 dominated plants the marked increase in 13c values of the pedogenic carbonates from the tertiary strata into the overlying quaternary strata confirms the invasion of a c4 biomass into the southern high plains since the early pliocene from east to west the 18o values of late quaternary pedogenic carbonates decrease gradually a trend that mimics the spatial variation of 18o values of modern meteoric water primarily due to the increased distance from the gulf of mexico source of most of the meteoric water in contrast to the regional trends the stable isotope values of some pedogenic carbonates developed on marine limestone and calcareous alluvium in central texas and south texas have isotopic signatures inherited from the host strata in addition some of the 13c values of pedogenic carbonate nodules in the gulf coastal plains have been affected by saline groundwater soil carbonates formed in the shallow parts of the profile such as petrocalcic horizons may have also been influenced by the atmospheric co2 nevertheless climatic trends are readily apparent in the isotopic data thus demonstrating their potential value in region wide paleoclimatic analyses

palaeoclimatic indicators in soils buried under archaeological monuments in the eurasian steppe a review the russian experience of the local reconstruction of the eurasian steppe climate during the last 5000 years based on geoarchaeological approaches is reviewed examples of traditional palaeoclimatic reconstructions in russia based on organic matter highly soluble salts and gypsum content and location of salts and gypsum horizons in the profile of buried soils are given pedogenic carbonate as a palaeoclimatic indicator is considered the possibilities of the quantitative reconstruction of the palaeoprecipitation based on magnetic properties of buried soils are observed the innovative approach of palaeoclimatic reconstruction based on soil microbiology methods is reviewed the problem of temporary transformation of palaeoclimatic indicators in buried soils is shown a methodology for the interpretation of palaeoclimatic indicators of buried soils for a local palaeoclimatic reconstruction is given

reply to comment on tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism by g j borradaile and k lucas

carbon isotopic subsets of soil carbonate a particle size comparison of limestone and igneous parent materials abstract the c isotopic analysis of pedogenic carbonate is an important method for investigating paleoclimatic conditions and carbon sequestration however a calcic soil sample may contain multiple types of carbonate especially in soils formed in limestone parent material to evaluate isotopic values of the different soil carbonate types stable c isotopic analysis was applied to an array of particle size classes in bulk soil that was collected from soils formed in limestone parent material and neighboring soils formed in igneous parent material a pronounced trend of decreasing 13 c with progressively decreasing soil particle size was revealed in soils of both parent materials ranging from about 2 to 6 for limestone soils and 1 to 5 for igneous soils thin section microscopy and radiocarbon dating also indicated multiple subsets of calcium carbonate types in soils thin section analysis disclosed the presence of limestone detritus calcitans aggregates of carbonate crystals and calcified root hairs radiocarbon dating revealed different 13 c values of carbonate crystals of different ages ranging from about 2620 to 40 290 years for limestone soils and 1660 to 5830 years for igneous soils these results indicate 1 limestone particles in soil may contribute to a complex mixture of 13 c values that is absent from soils formed in igneous parent material and 2 it is necessary to recognize that isotopic values of bulk soil represent a mixture of different 13 c values from different size fractions and ages in both limestone and igneous soils

relict soil evidence for profound quaternary aridification of the atacama desert chile abstract a relict soil on a late tertiary early quaternary gravelly alluvial fan in the southern atacama desert was studied to determine if evidence of quaternary climate change was evident in the profile stratigraphic relations of soil morphological features indicated that the initial phase of soil development was extensive chemical weathering with the loss of si na etc and the formation of secondary clay this was then followed by a prolonged period of carbonate accumulation that has discontinuously impregnated the earlier formed argillic horizons the carbonate accumulation occurred both as fine grained accumulations that engulfed and expanded the gravelly soil matrix and as carbonate that formed dense and continuous coatings on gravel bottoms overlying the carbonate is a holocene calcareous sand unit stable c and o isotope profiles of the disseminated carbonate show that this material appears to have formed under conditions of low to modest plant cover and significant soil water evaporation very similar to soils presently found at higher latitudes and altitudes in modern argentina seven transects of the carbonate laminations on the gravels at 10 m scale reveal that all show a nearly 4 increase in 13 c values with time over distances of approximately 150 mm and variable 18 o values the shift in c isotope values which is unlikely to be due to significant changes in c3 vs c4 vegetation reflects a profound and prolonged aridification with a corresponding lowering of plant density and soil respiration the precise beginning of the aridification is unknown due to a lack of carbonate dating methods amenable to the time frame involved when all changes are considered this remarkable soil indicates that local rainfall declined from somewhere between 500 to 1000 mm y 1 in the late tertiary early quaternary to the present climate of about 25 mm y 1 future work will focus on developing more precise geochronological controls but this initial study reveals the enormous potential that carbonate bearing relict soils have for understanding climate change

post speleogenetic biogenic modification of gomantong caves sabah borneo article i nfo the gomantong cave system of eastern sabah malaysia is well known as an important site for harvesting edible bird nests and more recently as a tourist attraction although the biology of the gomantong system has been repeatedly studied very little attention has been given to the geomorphology here we report on the impact of geobiological modification in the development of the modern aspect of the cave an important but little recognized feature of tropical caves basic modeling of the metabolic outputs from bats and birds co2 h2o heat reveals that post speleogenetic biogenic corrosion can erode bedrock by between 3 0 mm ka 1 m 300 ka and 4 6 mm ka 1 m 200 ka modeling at high densities of bats yields rates of corrosion of 34 mm ka or 1 m 30 ka sub aerial corrosion creates a previously undescribed speleological feature the apse flute which is semicircular in cross section and 80 cm wide it is vertical regardless of rock properties developing in parallel but apparently completely independently and often unbroken from roof to floor they end at a blind hemi spherical top with no extraneous water source half dome ceiling conch pockets are remnants of previous apse fluting sub cutaneous corrosion creates the floor level guano notch formed by organic acid dissolution of bedrock in contact with guano speleogenetic assessment suggests that as much as 70 95 of the total volume of the modern cave may have been opened by direct subaerial biogenic dissolution and biogenically induced collapse and by sub cutaneous removal of limestone over a timescale of 1 2 ma 2011 elsevier b v all rights reserved

late quaternary stratigraphy and luminescence geochronology of the northeastern mojave desert abstract the chronology of the holocene and late pleistocene deposits of the northeastern mojave desert have been largely obtained using radiocarbon ages our study refines and extends this framework using optically stimulated luminescence osl to date deposits from valjean valley silurian lake playa red pass and california valley of particular interest are eolian fine silts incorporated in ground water discharge gwd deposits bracketed at 185 140 and 20 50 ka alluvial fan deposits proved amenable for osl by dating both eolian sand lenses and reworked eolian sand in a matrix of gravel that occurs within the fan stratigraphy lacustrine sand in spits and bars also yielded acceptable osl ages these osl ages fill gaps in the geochronology of desert deposits which can provide data relevant to understanding the responses of several depositional systems to regional changes in climate this study identifies the most promising deposits for future luminescence dating and suggests that for several regions of the mojave desert sediments from previously undated landforms can be more accurately placed within correct geologic map units

climate controls on spatial and temporal variations in the formation of pedogenic carbonate in the western great basin of north america pedogenic carbonate is common in arid and semiarid soils and though its stable c and o isotope composition has been shown to reflect local environmental conditions questions remain about the quantitative nature of this relationship and the implications for paleoclimate applications to further address these questions a climosequence of four holocene soils in fish lake valley nevada western united states was instrumented and examined over the course of more than a year the annual precipitation along the transect ranges from 80 mm yr 1 to 220 mm yr 1 results show that the c and o stable isotope compositions of soil co 2 h 2 o and carbonate change systematically with elevation and climate however there was considerable temporal variability in the conditions that affected carbonate isotope values at the lowest elevation co 2 13 c and h 2 o 18 o values were similar to that in equilibrium with carbonate nearly year round at the midelevation sites spring through summer co 2 13 c and h 2 o 18 o values appeared to most closely match the 13 c and 18 o values of pedogenic carbonate at the highest elevation the c and o isotopes of carbonate did not reflect the soil co 2 13 c and h 2 o 18 o values measured during the period of study but they did appear to reflect soil respiration rates during the late spring the transect shows that arid soil carbonate 13 c values strongly reflect variations in soil respiration rates and the resulting concentrations of soil co 2 these results also indicate that depth profile sampling may be required to adequately constrain respiration rates which affect the interpreted atmospheric co 2 concentrations

dating fluvial terraces by 230th u on pedogenic carbonate wind river basin wyoming abstract reliable and precise ages of quaternary pedogenic carbonate can be obtained with 230th u dating by thermal ionization mass spectrometry applied to carefully selected milligram size samples datable carbonate can form within a few thousand years of surface stabilization allowing ages of quaternary deposits and surfaces to be closely estimated pedogenic carbonate clast rinds from gravels of glacio fluvial terraces in the wind river basin have median concentrations of 14 ppm u and 0 07 ppm 232th with median 230th 232th 270 making them well suited for 230th u dating horizons as thin as 0 5 mm were sampled from polished slabs to reduce averaging of long 105 yr and sometimes visibly discontinuous depositional histories dense translucent samples with finite 230th u ages preserve within rind stratigraphic order in all cases ages for terraces wr4 167 000 6 400 yr and wr2 55 000 8600 yr indicate a mean incision rate of 0 26 0 05 m per thousand years for the wind river over the past glacial cycle slower than inferred from cosmogenic nuclide dating terrace wr3 which formed penecontemporaneously with the final maximum glacial advance of the penultimate rocky mountain bull lake glaciation has an age of 150 000 8300 yr indicating that it is broadly synchronous with the penultimate global ice volume maximum

early to middle miocene climate in the atacama desert of northern chile abstract the cenozoic paleoclimate of the atacama desert is not well known we examined 14 early to mid miocene paleosols exposed in the el tesoro mine near calama chile the paleosols developed on an aggrading alluvial fan system and lie above the mineralized gravel horizons that host a copper ore body soil forming conditions that oscillated between chemical weathering and clay production humid analogous to modern alfisols to environments favoring the accumulation of pedogenic carbonate arid to semi arid analogous to modern aridisols are indicated in contrast the region is presently hyperarid and soils accumulate sulfates chlorides and nitrates while total chemical analyses clearly show the accumulation of ca by the carbonate rich paleosols none of the soils exhibit significant losses of elements by leaching the 18 o values of the carbonates range from 8 79 to 3 16 vpdb the o isotope data when combined with published data from the region reveal a significant divergence in the o isotope composition of precipitation in the eastern and western margins of the andean plateau since the early miocene suggesting that simple interpretations of declining 18 o values of carbonate with increasing elevation may not be appropriate these paleosols clearly indicate that wetter conditions prevailed in what is now the atacama desert during the early to mid miocene

potential for14c dating of biogenic carbonate in hackberry celtis endocarps abstract hackberry endocarp celtissp contains significant amounts up to 70 wt of biogenic carbonate that is nearly pure aragonite caco3 because of their high mineral content hackberry endocarps are found abundantly in tertiary and quaternary sediments and are very common in many north american archaeological sites we analyzed the14c content of different components of modern hackberries including the biogenic carbonate in hackberry endocarps collected at known times over the past century the14c content of the endocarp carbonate accurately records the14c content of the atmosphere 14c dates of fossil endocarp carbonates compared favorably with dates obtained by other means at archaeological and geological sites ranging in age from the late pleistocene through the early holocene we therefore suggest that hackberry endocarp is a suitable substrate for14c dating provided that its morphological and mineralogical integrity is preserved

ams detection of inverse fabrics without aarm in ophiolite dikes inverse fabric contributions from single domain sd magnetite complicate interpretation of magmatic flow from anisotropy of magnetic susceptibility ams in the s troodos ophiolite dike swarm flow directions and magma chamber dimensions may only be inferred correctly if magnetic fabrics correspond to the orientation distribution od of minerals magnetite shape fabrics were isolated by anisotropy of anhysteretic remanence aarm but ams ambiguously merges magnetite and silicate fabrics however with the retrospective benefit of aarm in this area we recommend avoiding sd complications by excluding magnetite rich samples for which the bulk low field susceptibility 27 500 si magma flow was steeply upwards to the sw proximal to an axial magma chamber

palaeomagnetic insights into the evolution of neotethyan oceanic crust in the eastern mediterranean abstract a synopsis of palaeomagnetic data from three late cretaceous eastern mediter ranean tethyan ophiolites troodos hatay and baer bassit and their sedimentary coversequences is presented these data provide valuable insights into the role of regional andlocal scale tectonic rotations in the geodynamic evolution of neotethyan oceanic crust thegeologically earliest phases of tectonic rotation are documented in the troodos ophiolite where rotations around both subvertical and subhorizontal axes are readily related to thedevelopment of the spreading fabrics and structures during crustal genesis subsequent c 74 anticlockwise intra oceanic rotation of a troodos microplate has been quantified throughanalysis of the in situ sedimentary cover of the troodos ophiolite results indicate that bulkanticlockwise rotation began soon after the cessation of spreading and ended by the end ofthe eocene with c 50 60 of microplate rotation being over by the maastrichtian the timeat which ophiolite thrust sheets were emplaced onto the arabian continental margin to theeast of troodos recent results from the emplaced structurally dismembered baer bassitophiolite indicate extreme anticlockwise rotations of ophiolitic thrust sheets varying on akilometre scale new data from the post emplacement sedimentary cover confirm that onlya small component of these rotations is due to post emplacement tectonism baer bassitrepresents the leading edge of the emplaced ophiolitic sheet new data from the morecoherent section preserved in the hatay ophiolite to the north demonstrate significantanticlockwise rotation this is equivalent to the rotation of the most northerly part of thebaer bassit units to the south and is of the same sense and magnitude as the pre maastrichtian phase of microplate rotation documented in the troodos this suggests acommon intra oceanic origin for the majority of the troodos and hatay rotations and asignificant component of the more variable rotations observed in baer bassit overall therefore the data support a model involving 1 intra oceanic rotation of a coherent regionof crust within the southern neotethyan basin this rotated unit is more areally extensivethan has previously been inferred from consideration of data from the troodos ophiolitealone 2 emplacement of part of the rotated unit onto the arabian platform 3 subsequentlocalized post emplacement modification related to the development of the current plateconfiguration

facies sequences on a carbonate ramp the carboniferous limestone of south wales during early carboniferous times a major sea level rise led to the development of an extensive carbonate ramp over what is now south wales differential subsidence and sea level changes resulted in distinctive facies sequences in the ramp succession and a model is offered which recognizes three distinct geomorpho tectonic settings inner mid and outer ramp the inner ramp zone occurs in the more landward part of the province and was an area undergoing little or no subsidence the sequence is dominated by oolitic grainstones and peritidal limestones representing shoal and back shoal environments the peritidal units are transgressive deposits consisting of stacked asymmetrical shallowing up cycles the sequence contains many subaerial breaks and tectonic uplift resulted in base level changes and fluvial incision the mid ramp zone sequence is intermediate in thickness between the inner and outer ramp successions and consists mainly of bioclastic limestones deposited below fairweather wave base sedimentation periodically exceeded sea level rise and subsidence and regressive progradational oolitic sand bodies developed the thickest of which are stacked units with up to four individual sand bodies storm processes were of major importance in this setting the outer ramp zone is represented by a thick sequence of muddy bioclastic limestones deposited below storm wave base and major waulsortian reef mounds also developed none of the shallowing phases seen in the other ramp zones can be detected in this sequence subsidence and eustatic sea level rise seem to have been the major controls on deposition but the recognition of eustatic sea level falls is difficult the detailed facies model for ramp carbonates presented here may be applicable elsewhere in the geological record

actualistic ophiolite provenance the cyprus case abstract the island of cyprus represents an excellent site to assess quantitatively petrologic clastic response to actively obducting oceanic sources in order to define an actualistic reference for ophiolite provenance in terms of framework composition and heavy mineral suites an improved methodology an extension of the classic ternary qfl logic to include a wider spectrum of key indexes and ratios provides an accurate synthesis of modal data and allows differentiation of three main petrographic provinces and at least seven subprovinces diagnostic signatures of detritus from various levels of an oceanic lithospheric source and criteria for distinguishing provenance from suprasubduction versus mid oceanic ophiolites are also outlined modern sands derived from the troodos ophiolite contain variable proportions of largely pelagic carbonate to chert boninite to basalt diabase to metabasite plagiogranite to gabbroic and cumulate grains supplied from progressively deeper seated levels of the multilay

a significant middle pleistocene tephra deposit preserved in the caves of mulu borneo article i nfo article history received 23 may 2011 available online xxxx a distinctive white sediment in the caves of mulu sarawak borneo is a well preserved tephra representing a fluvially transported surface air fall deposit re deposited inside the caves we show that the tephra is not the younger toba tephra formerly considered as most likely the shards are rod shaped with elongate tubular vesicles the largest grains 170 m in length of rhyolitic composition and 87 sr 86 sr ratio of 0 70426 0 00001 u th dating of associated calcites suggest that the tephra was deposited before 125 4 ka and probably before 156 2 ka grain size and distance from closest potential source suggests an eruption of vei 7 prevailing winds grain size thickness of deposit location of potential sources and sr isotopic ratio limit the source to the philippines comparisons with the literature give the best match geochemically with layer 1822 from ku et al 2009a dated by ocean core stratigraphy to 189 ka this tephra represents a rare terrestrial repository indicating a very substantial plinian ultra plinian eruption that covered the mulu region of borneo with ash a region that rarely receives tephra from even the largest known eruptions in the vicinity it likely will be a valuable chronostratigraphic marker for sedimentary palaeontological and archaeological studies

gold mineralization associated with low temperature off axis fluid activity in the troodos ophiolite cyprus silicification of umbers in the troodos ophiolite complex in cyprus provides evidence for low temperature hydrothermal activity occurring late in the process of ocean crust formation after the crust had moved away from the oceanic spreading centre umbers which are mn fe rich sediments precipitate some distance away from oceanic spreading axes the movement of the fluids partially silicifying the umbers must post date umber formation and therefore also occurs off axis these fluids may form part of low temperature hydrothermal circulation similar to those identified by off axis heat anomalies in the modern oceans in cyprus the silicified umbers often are located away from volcanogenic massive sulphide vms deposits and are aligned along sea floor faults they are characterized by quartz veins as well as pervasive silicification recent analyses have revealed unexpectedly anomalous 1 5 ppm concentrations of au in these silicified umbers gold mineralization is known to occur in ophiolite complexes as part of the metal concentrations in vms deposits these deposits are thought to be formed by ancient hydrothermal circulation similar to that associated with black smokers observed at modern mid ocean ridges the research presented in this paper provides evidence for a second phase of au mineralization in cyprus caused by low temperature silicifying fluids resulting from oceanic hydrothermal activity which occurred away from the spreading centre the mineralizing fluids which silicified the umbers may have been more widespread impregnating other lithologies and may have overprinted the first phase of au mineralization in some vms deposits after they had become inactive and had been moved away from the spreading centre the mineralizing fluids passing through these vms may have used the same structural pathways as the original base metal rich hydrothermal solutions which formed the vms

on the sense of slip of the southern troodos transform fault zone cyprus it is generally accepted that the 5 10 km wide zone of wrench faulting preserved in the arakapas valley and limassol forest areas of cyprus along the southern margin of the troodos ophiolite is part of a fossil oceanic transform fault system however despite detailed study of this the southern troodos transform fault zone and neighboring part of the main troodos massif no consensus has been reached as to its sense of motion some have postulated sinistral slip some dextral whereas others have suggested that it slipped both ways and reversed its sense of motion by ridge jumping to resolve this issue and better determine the spreading history of the troodos ophiolite we present new field observations from the transform tectonized area and reexamine existing evidence for the sense of slip of the transform although we find evidence for both sinistral and dextral shear along the fault zone while in an oceanic environment the overwhelming indications are for dextral slip genuine sinistral slip indicators are restricted to a few mylonitic shear zones of limited extent which can be related to local geometrical complexities associated with intrusion of gabbroic plutons into the transform zone there is no need to invoke wholesale reversals of slip along the transform fault nor therefore the radical reorganizations of the troodos spreading system that have previously been proposed

propagating rift tectonics of a caledonian marginal basin multi stage seafloor spreading history of the solund stavfjord ophiolite in western norway abstract the late ordovician solund stavfjord ophiolite in western norway represents a remnant of the iapetus oceanic lithosphere that developed in a caledonian marginal basin the ophiolite contains three structural domains that display distinctively different crustal architecture that reflects the mode and nature of magmatic and tectonic processes operated during the multi stage seafloor spreading evolution of this marginal basin domain i includes from top to bottom an extensive extrusive sequence a transition zone consisting of dike swarms with screens of pillow breccias a sheeted dike complex and plutonic rocks composed mainly of isotropic gabbro and microgabbro extrusive rocks include pillow lavas pillow breccias and massive sheet flows and are locally sheared and mineralized containing epidosites sulfide sulfate deposits fe oxides and anhydrite veins reminiscent of hydrothermal alteration zones on the seafloor along modern mid ocean ridges a fossil lava lake in the northern part of the ophiolite consists of a 65 m thick volcanic sequence composed of a number of separate massive lava units interlayered with pillow lavas and pillow breccia horizons the ne trending sheeted dike complex contains multiple intrusions of metabasaltic dikes with one and two sided chilled margins and displays a network of both dike parallel normal and dike perpendicular oblique slip faults of oceanic origin the dike gabbro boundary is mutually intrusive and represents the root zone of the sheeted dike complex the internal architecture and rock types of domain i are analogous to those of intermediate spreading oceanic crust at modern mid ocean ridge environments the ophiolitic units in domain ii include mainly sheeted dikes and plutonic rocks with a general nw structural grain and are commonly faulted against each other although primary intrusive relations between the sheeted dikes and the gabbros are locally well preserved the exposures of this domain occur only in the northern and southern parts of the ophiolite complex and are separated by the ene trending domain iii in which isotropic to pegmatitic gabbros and dike swarms are plastically deformed along ene striking sinistral shear zones these shear zones which locally include fault slivers of serpentinite intrusions are crosscut by n20 e striking undeformed basaltic dike swarms that contain xenoliths of gabbroic material the nw trending sheeted dike complex in the northern part of domain ii curves into an ene orientation approaching domain iii in the south the anomalous nature of deformed crust in domain iii is interpreted to have developed within an oceanic fracture zone or transform fault boundary ree chemistry of representative extrusive and dike rocks from all three domains indicates n to e morb affinities of their magmas with high th ta ratios that are characteristic of subduction zone environments the magmatic evolution of domain i encompasses closed system fractional crystallization of high mg basaltic magmas in small ephemeral chambers which gradually interconnected to form large chambers in which mixing of primary magmas with more evolved and fractionated magma caused resetting of magma compositions through time the compositional range from high mg basalts to ferrobasalts within domain i is reminiscent of modern propagating rift basalts we interpret the ne trending domain i as a remnant of an intermediate spread rift system that propagated northeastwards in present coordinate system into a pre existing oceanic crust which was developed along the nw trending doomed rift domain ii in the marginal basin the n20 e dikes laterally intruding into the anomalous oceanic crust in domain iii represent the tip of the rift propagator the inferred propagating rift tectonics of the solund stavfjord ophiolite is similar to the evolutionary history of the modern lau back arc basin in the sw pacific and suggests a complex magmatic evolution of the caledonian marginal basin via multi stage seafloor spreading tectonics

effect of co2 concentration on the initial recrystallization rate of pedogenic carbonate revealed by 14c and 13c labeling abstract in calcareous parent material pedogenic carbonate formation mostly involves dissolution and recrystallization of lithogenic carbonates with co 2 of soil air leading to a complete exchange of lithogenic carbon with soil derived carbon interest in pedogenic carbonates has increased in recent decades because they are a useful tool for reconstructing paleoclimatic conditions 13 c and 18 o and past atmospheric co 2 concentrations as well as for radiocarbon dating of soils for such investigations the recrystallization rate of primary caco 3 by pedogenic carbonate formation and the dependence of the recrystallization rate on environmental factors are essential but still unquantified factors the recrystallization rate of primary caco 3 of loess at three co 2 concentrations was estimated by isotopic exchange between primary caco 3 and the 14 c of artificially labeled co 2 loess was used for the study as a parent substrate for soil formation to simulate initial rates of caco 3 recrystallization co 2 concentrations of 380 ppm 5000 ppm and 50 000 ppm lead to recrystallization rates of 4 1 10 7 day 1 8 1 10 7 day 1 and 16 9 10 7 day 1 respectively the relation between co 2 concentrations and recrystallization rates was described by a saturation curve under the tested experimental conditions complete 95 recrystallization of loess carbonate and formation of pedogenic carbonate would take 4 9 20 0 10 3 years strongly depending on co 2 concentration we expect faster recrystallization rates under field conditions because of permanent co 2 supply by root and rhizomicrobial respiration this impedes the equilibrium between the inorganic c pools in solid liquid and gaseous phases

kinematic history of a reactivated oceanic suture the mamonia complex suture zone sw cyprus the mamonia complex suture zone in sw cyprus marks an arcuate tectonic suture between an upper cretaceous oceanic microplate of supra subduction zone origin troodos complex and a deformed triassic passive margin sequence mamonia complex mapping of the serpentinite filled fault zones that define the suture zone combined with microstructural studies of its constituent fault rocks has revealed evidence of three main tectonic events of upper cretaceous age 1 high temperature c 600 c transform related dextral strike slip and localized metamorphism of mamonia complex units c 90 83 ma 2 retrograde hydration c 83 73 ma 3 regional contractional reactivation at low temperatures which ceased by the latest maastrichtian c 65 ma the present day structural geometries are interpreted as the result of maastrichtian contractional reactivation of a pre existing steep and irregular structural architecture that formed during transtension the resultant orientation of finite strain axes and thrust displacements display a radial distribution documenting near fault normal contraction along the whole length of the arcuate suture zone this pattern of displacements suggests a model whereby the troodos microplate impinged on the mamonia complex during westerly to southwesterly directed plate motion contractionally reactivating the mechanically weak suture zone

comparison of multiple proxy records of holocene environments in the midwestern united states we compare four emerging approaches to reconstructing holocene vegetation and climate from south of the glacial border in northeastern iowa united states pollen plant macrofossils carbon isotopic 13 c values from alluvial organic matter and carbon isotopic values in stalagmites from a nearby cave all show similar paleovegetational and paleoclimatic trends during the holocene pollen and plant macrofossils show a rapid change from forest to prairie about 6000 cal yr b p followed by a return of oaks to a presumably savanna like community about 3500 cal yr b p the 13 c values in alluvial organic matter and the percentage of c 4 plants both increase ca 6300 cal yr b p and then decrease in the last 3500 years in the cave 13 c values rise beginning at 6000 cal yr b p to a broad peak ca 4500 to 3000 cal yr b p and decrease thereafter pollen and plant macrofossils record the composition of the vegetation that produced the isotopic signals and verify c 3 c 4 interpretations based on the isotopic records we demonstrate that these methods are complementary but that any single method will provide an accurate reconstruction of past environments