historical wave height trends in the south and east china seas 1911 2010 this study reconstructs 6 hourly significant wave heights hs in the south and east china seas for the period 1871 2010 using the twentieth century reanalysis ensemble of mean sea level pressure slp fields and a multivariate regression model to represent the hs slp relationship in each study area the regression model was calibrated and validated using the era interim reanalysis of hs and slp for the period 1981 2010 these reconstructions were found to reproduce reasonably well the seasonal mean and maximum hs climates as represented by the era40 and era interim wave reanalyses for each study area an ensemble of 56 members of 6 hourly hs was reconstructed for each grid point the regional mean series of the ensemble mean of the reconstructed consecutive monthly mean hs was tested for temporal homogeneity which identified a few discontinuities in the pre 1946 period and led to the exclusion of the reconstructed hs for 1871 1910 from trend analysis due to data uncertainty and inhomogeneity each 6 hourly hs time series for the period 1911 2010 was homogenized for the identified discontinuities before being used to derive annual and seasonal mean and maximum hs for trend analysis the trend analysis results show that in both study areas the 1911 2010 wave height trends are dominantly negative with the exception that the seasonal maximum significant wave heights seem to have increased in summer and spring in the central south china sea and in summer in the east china sea

palaeoenvironmental reconstruction of a middle miocene alluvial fan to cyclic shallow lacustrine depositional system in the calatayud basin ne spain the middle miocene sedimentary fill of the calatayud basin in north eastern spain consists of proximal to distal alluvial fan floodplain and shallow lacustrine deposits four main facies groups characteristic of differentsedimentary environments are recognized 1 proximal and medial alluvial fan facies that comprise clast supported gravel and subordinate sandstone and mudstone the latter exhibiting incipient pedogenic features 2 distal alluvial fan facies formed mainly of massive mudstone carbonate rich palaeosols and local carbonate pond deposits 3 lake margin facies which show two distinct lithofacies associations depending on their distribution relative to the alluvial fan system i e front lithofacies a comprising massive siliciclastic mudstone and tabular carbonates or lateral lithofacies b showing laminated and or massive siliciclastic mudstone alternating with tabular and or laminated carbonate beds and 4 mudflat shallow lake facies showing a remarkable cyclical alternation of green grey and or red siliciclastic mudstone units and white dolomitic carbonate beds the cyclic mudflat shallow lake succession as exposed in the orera composite section ocs is dominantly composed of small scale mudstone carbonate dolomite cycles the mudstone intervals of the sedimentary cycles are interpreted as a result of sedimentation from suspension by distal sheet floods the deposits evolving either under subaerial exposure or water saturated conditions depending on their location on the lacustrine mudflat and on climate the dolomite intervals accumulated during lake level highstands with mg rich waters becoming increasingly concentrated lowstand to highstand lake level changes indicated by the mudstone dolomite units of the small scale cycles reflect a climate control from dry to wet conditions on the sedimentation in the area the spatial distribution of the different lithofacies implies that deposition of the small scale cycles took place in a low gradient shallow lake basin located in an interfan zone the development of the basin was constrained by gradual alluvial fan aggradation additional support for the palaeoenvironmental interpretation is derived from the isotopic compositions of carbonates from the various lithofacies that show a wide range of 1 8 o and 1 3 c values varying from 7 9 to 3 0 pdb and from 9 2 to 1 7 pdb respectively more negative 1 8 d and 1 3 c values are from carbonate rich palaeosols and lake margin carbonates which extended in front of the alluvial fan systems whereas more positive values correspond to dolomite beds deposited in the shallow lacustrine environment the results show a clear trend of 1 8 o enrichment in the carbonates from lake margin to the centre of the shallow lake basin thereby also demonstrating that the lake evolved under hydrologically closed conditions

spherulites in calcrete laminar crusts biogenic caco 3 precipitation as a major contributor to crust formation abstract spherulites calcitic fibro radial spherulitic polycrystals are a major component of calcite layers in quaternary calcrete laminar crusts to explain the formation of spherulites petrographic and chemical studies were performed on pleistocene calcrete laminar crusts holocene biological crusts and laboratory in vitro cultures of cyanobacterial strains spherulites were found to be formed of acicular and radiating crystals either smooth and regular edged or twisted and irregular edged spherulites were composed of low mg calcite the concentration of mg in the spherulites increasing from nucleus to periphery the shape and chemistry of the in vitro spherulites and laminar crust spherulites were identical the structure elementary crystal shape and size of spherul tes can be used to differentiate them from microcodium with which they are commonly confused in the literature spherulite genesis can be linked to cyanobacterial activity involving photosynthetic uptake of hco 3 leading to caco3 precipitation the bicarbonate causing release of equivalent amounts of oh in the mucilaginous sheath the main steps in cyanobacteria biomineralization producing spherulites are 1 uptake of co2 and or hco 3 from the medium as the inorganic carbon source for photosynthesis 2 release of oh in the sheath 3 carbonate ion formation resulting from the reaction of oh and hco 3 followed by 4 caco3 precipitation this process involves two steps in desert environments during dry spells the cyanobacterial mat calcifies leading to spherulite production and the fo mation of thin clear microsparitic layers during wet periods a thin sedimentary deposit forms mixing micrite detrital particles and inherited or new tiny spherulites with the mucilaginous mat of cyanobacteria which traps all of this material an organo micritic layer forms during the following dry spell the process is repeated and the laminar crust is formed in conclusion the presence of spherulites in the laminar crust is indicative of subaerial exposure the crust being a terrestrial stromatolite

palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record interest in palustrine carbonates and calcretes has increased over the last 20 years since they contain significant environmental information much of the work performed in this area has focused on either of two types of terrestrial carbonate palustrine carbonates or calcretes pedogenic and groundwater yet their simultaneous study shows there may be a gradual transition from one form to the other revealing the interplay between pedogenic sedimentary and diagenetic processes three main factors control the formation of these carbonates the position of the water table the host rock and the period of sub aerial exposure in pedogenic calcretes precipitation of carbonate takes places mostly in the vadose zone above the water table and within a previous host rock or sediment in groundwater calcretes the precipitation of carbonate also occurs within a previous host rock and around the groundwater table in palustrine carbonates however the precipitation of lime mud occurs in a lacustrine water body palustrine carbonates necessarily form on previous lacustrine mud whereas both types of calcretes may form on any type of sediment or soil the sub aerial exposure time needed to form palustrine carbonates may by relatively short even a season whereas pedogenic calcretes need more time several years to millions of years groundwater calcretes do not form on the topographic surfaces so there is no need of sub aerial exposure however stable surfaces favour the development of thick groundwater calcretes small fluctuations in the water table cause gradual transitions of these three types of terrestrial carbonates and the subsequent mixture of their characteristic features causing difficulties in the interpretation of these carbonates the formation of these carbonates is controlled by palaeoenvironmental factors both commonly form in semi arid climates arid climates are also suitable for calcretes but sub humid conditions are more suitable for palustrine carbonates more indications of climatic conditions may be obtained through the analysis of the d18o content of both calcretes and palustrine carbonates and from the depth of the horizon containing carbonate nodules in pedogenic calcretes vegetation is also important in the formation of these types of carbonates data on the prevailing vegetation can be obtained from the analysis of the micro and macrofabric as well as from the d13c signal of the primary carbonates which in pedogenic carbonates has also been used to estimate atmospheric pco2 during the phanerozoic these terrestrial carbonates are widely distributed on floodplains and distal areas of alluvial basins their presence and characteristics can be used as indicators of aggradation subsidence or accommodation rates and therefore as indicators of different tectonic regimes even though the study of these carbonates has notably increased in recent years much less is known about them than about marine carbonates presently there is much emphasis on obtaining a general model for sequence stratigraphy in terrestrial basins with a need to include the carbonates analysed in this paper

zonal jets in the equatorial atlantic ocean abstract we use position data from argo floats smoothed out over 400 km 200 km zonal ellipses and interpolated onto a 0 5 grid to investigate the zonal jet structure of the flow field at the sea surface and on three subsurface layers central waters cw 200 m antarctic intermediate waters aaiw 1000 m upper north atlantic deep waters unadw 1500 m in the equatorial atlantic ocean 15 s to 15 n the annual mean fields exhibit narrow zonal jets typically 4 5 wide at the sea surface and only 2 at the subsurface levels with directions alternating in latitude and maximum speeds about 0 5 m s 1 at the surface 0 1 m s 1 at cw and unadw and 0 03 m s 1 at aaiw the available data also allows us to explore the seasonal variability of these jets at the surface and aaiw levels the surface currents are dominated by an annual cycle between 4 n and 10 n and to a lesser degree by a semi annual contribution close to the equator this variability is an outcome of evolving zonal recirculations with the north equatorial countercurrent necc arising from the diversion of the northern branch of the south equatorial current nsec the diversion begins in the eastern atlantic and propagates west between april and august following the inter tropical convergence zone itcz the aaiw current field is largely affected by westward propagating anomalies most visible near 3 s 0 3 n and 7 n which give rise to current reversals annual averaging produces the illusion of more 5 instead of 3 and slower peak values about 0 03 m s 1 instead of 0 1 m s 1 jets than found on any month

authigenic trioctahedral smectites controlling ph alkalinity silica and magnesium concentrations in alkaline lakes abstract the mineralogical composition of salts and the chemical composition of brines of lake yoa ounianga el kebir northern chad both reveal the neoformation of stevensite a trioctahedral smectite accompanied by aragonite the coprecipitation of these two minerals clearly controls the evolution of ph alkalinity and ca mg and silica concentrations in alkaline brines the geochemical evolution characterized by a strong depletion of ca and mg in solution and an increase in alkalinity and ph is confirmed as the dominant process governing the formation of soda alkaline lakes

groundwater dolocretes in a lake marginal environment an alternative model for dolocrete formation in continental settings danian of the provence basin france in the long continental history of the provence basin which extended from santonian to oligocene times a major period of palaeosol development occurred in the danian dolocretes developed within floodplain silts and partly from palustrine limestones dolocretes are overlain by pedogenic facies calcretes and palustrine limestones gradational lower and upper limits of profiles succession of nodular coalescent and massive horizons the epigenesis of quartz by dolomite the unimodal crystal size and the euhedral dolomite fabric as well as the absence of biogenic structures and vadose cements show that dolocretes formed in the phreatic zone the exclusive occurrence of dolocretes around the palaeolake or playa suggests that dolocrete formed by the mixing of groundwaters and lake brines which infiltrated the phreatic zone during periods of strong evaporation and lake level lowering the term halo dolocrete is proposed to describe this type of dolocrete deposit subsequent alteration of the dolocrete includes leaching of the central core of dolomite crystals and calcitization calcitization was either fabric destructive type i or fabric preserving type ii and took place during very early diagenesis i e concomitant with calcrete formation or palustrine limestone deposition fabric destructive calcitization is attributed to a drop in the lake level when the upper part of the dolocrete was subjected to vadose zone processes whereas the fabric preserving calcitization resulted from reactions with dilute lake and groundwaters during rise in lake level

root calcretes and uranium bearing silcretes at sedimentary discontinuities in the miocene of the madrid basin toledo spain abstract this paper reports a detailed study of the calcrete and silcrete profiles in the miocene detrital deposits in the western area of madrid at the boundary of two main sedimentary units the aims of this work were to better understand the pedogenic and diagenetic environments in which these profiles formed and to determine the cause s of their enrichment in uranium calcrete and silcrete duricrusts are characteristic features of closed continental basins in semiarid climates this paper discusses the significance of duricrusts as indicators of important change in such basins the detailed macromorphological micromorphological and geochemical study of three duricrust profiles revealed the sequence of pedogenic vadose and groundwater processes responsible for their formation during the first stage of their development carbonate laminae formed a white grill like structure within the detrital parent materials the microstructure and macrostructure of the carbonate which includes alveolar septal structures and needle fiber calcite indicates the important role of roots and their associated microorganisms in calcrete formation early silicification occurred in the pedogenic vadose environment affecting the detrital parent material roots and calcretes forming an early silcrete defined by opaline glaebules and silica rhizoliths the detailed preservation of the cells in the silicified roots denotes the early replacement of root organic matter the green or green yellowish fluorescence of the silicified root structures under short wavelength uv shows their preferential enrichment in uranium calcitization and silicification coexisted in the pedogenic vadose environment leading to several reversible replacements of calcite and silica later the rise of the water table promoted silicification under phreatic conditions as indicated by the good preservation of the texture of the detrital host rocks and calcretes other silcrete textures such as ovoidal opaline accumulations intraclasts produced by autobrecchification and vadose silica cements indicate later vadose environments and consequently variations in the water table the geochemical features of the calcretes and silcretes major minor and rare earth elements were inherited from their parent materials the rare earth element patterns of some silcretes show them to have a positive ce anomaly suggesting that oxidizing conditions reigned during their formation the good correlation between silica and uranium suggests that the silica phases acquired uranium through the direct silicification of roots that had fixed uranium from organic matter this study shows that calcrete silcrete duricrusts provide detailed information regarding the processes occurring in semiarid continental basins in the studied basin roots played a key role in both the development of the duricrust profiles and their enrichment in uranium these duricrusts provide important information for understanding the overall stratigraphy of the studied basin and its large scale sequential evolution

petrographic and geochemical evidence for the formation of primary bacterially induced lacustrine dolomite la roda white earth pliocene central spain upper pliocene dolomites white earth from la roda spain offer a good opportunity to evaluate the process of dolomite formation in lakes the relatively young nature of the deposits could allow a link between dolomites precipitated in modern lake systems and those present in older lacustrine formations the la roda mg carbonates dolomite unit occur as a 3 5 to 4 m thick package of poorly indurated white massive dolomite beds with interbedded thin deposits of porous carbonate displaying root and desiccation traces as well as local lenticular gypsum moulds the massive dolomite beds consist mainly of loosely packed 1 to 2 m sized aggregates of dolomite crystals exhibiting poorly developed faces which usually results in a subrounded morphology of the crystals minute rhombs of dolomite are sparse within the aggregates both knobbly textures and clumps of spherical bodies covering the crystal surfaces indicate that bacteria were involved in the formation of the dolomites in addition aggregates of euhedral dolomite crystals are usually present in some more clayey sepiolite interbeds the thin porous carbonate mostly dolomite beds exhibit both euhedral and subrounded bacterially induced dolomite crystals the carbonate is mainly ca dolomite 51 54 mol caco3 showing a low degree of ordering degree of ordering ranges from 0 27 to 0 48 calcite is present as a subordinate mineral in some samples sr mn and fe contents show very low correlation coefficients with mg ca ratios whereas sio2 and k contents are highly correlated 18o and 13c values in dolomites range from 3 07 to 5 40 pdb mean 0 06 1 75 and from 6 34 to 0 39 pdb mean 3 55 1 33 respectively samples containing significant amounts of both dolomite and calcite do not in general show significant enrichment or depletion in 18o and 13c between the two minerals the correlation coefficient between 18o and 13c for dolomite is extremely low and negative r 0 05 whereas it is higher and positive r 0 47 for calcite the lacustrine dolomite deposit from la roda is interpreted mainly as a result of primary precipitation of dolomite in a shallow hydrologically closed perennial lake the lake was supplied by highly saturated hco3 co32 groundwater that leached dolomitic mesozoic formations precipitation of dolomite from alkaline lake waters took place under a semi arid to arid climate however according to our isotopic data strong evaporative conditions were not required for the formation of the la roda dolomite a significant contribution by bacteria to the formation of the dolomites is assumed in view of both petrographic and geochemical evidence

soil landscape and climatic relationships in the middle miocene of the madrid basin the miocene alluvial lacustrine sequences of the madrid basin spain formed in highly varied landscapes the presence of various types of palaeosols allows assessment of the effects of local and external factors on sedimentation pedogenesis and geomorphological development in the northern more arid tectonically active area soils were weakly developed in aggrading alluvial fans dominated by mass flows reflecting high sedimentation rates in more distal parts of the fans and in playa lakes calcretes and dolocretes developed the former were associated with mg poor fan sediments while the latter formed on mg rich lake clays exposed during minor lake lowstands the north east part of the basin had a less arid climate alluvial fans in this area were dominated by stream flood deposits sourced by carbonate terrains floodplain and freshwater lake deposits formed in distal areas the high local supply of calcium carbonate may have contributed to the preferential development of calcretes on the fans both the fan and floodplain palaeosols exhibit pedofacies relationships and more mature soils developed in settings more distant from the sediment sources palaeosols also developed on pond and lake margin carbonates and led to the formation of palustrine limestones the spatial distributions and stratigraphies of palaeosols in the madrid basin alluvial fans suggest that soil formation was controlled by local factors these palaeosols differ from those seen in quaternary fans which are characterized by climatically induced periods of stability and instability

dolomite in caves recent dolomite formation in oxic non sulfate environments castanar cave spain abstract dolomite is a common mineral in the rock record but rare in recent superficial environments where it does occur it is related to anoxic sulfate rich environments and microbial activity the occurrence of some dolomite deposits in caves however indicates that dolomite formation is also possible in oxic non sulfate settings dolomite is forming at 17 c and in oxic vadose conditions on the host rocks and aragonite speleothems of the castanar cave caceres spain it appears as spheroids and dumbbells 50 300 m in diameter that internally consist of micron sized rhombic to rounded crystals initially this dolomite is ca rich non stoichiometric and poorly ordered mg rich solutions allow the precipitation of metastable mg rich carbonates such as huntite this soon transforms into this ca rich dolomite which later ages to form a more stoichiometric dolomite these dolomites show similarities to those grown under anoxic sulfate rich conditions and their presence in caves provides a different setting that may contribute to the understanding of the dolomite problem including their initial formation and later recrystallization processes

the recent increase in north atlantic wave heights the nature and causes of the recent increase in north atlantic wave heights are explored by combining a numerical hindcast with a statistical analysis the numerical hindcast incorporates a 10 yr history 1980 89 of north atlantic twice daily wind analyses to generate a monthly averaged significant wave height swh history the hindcast compares favorably with published monthly averaged swh observations the link between modelgenerated wintertime monthly swh and monthly averaged sea level pressure slp data is determined by means of a canonical correlation analysis cca within the analysis domain most of the variance in swh and slp is captured by two pairs of joint patterns the leading pair consists of a slp dipole resembling the north atlantic oscillation nao and a swh dipole in spatial quadrature relation to it using the cca results an extended statistical hindcast of monthly wave fields is generated from sea level pressure data and used to quantitatively estimate the systematic increase in wave heights since the 1960s it is shown that an increasing trend in swh at several northeast atlantic locations since 1960 or so is related to the systematic deepening of the icelandic low and intensification of the azores high over the last three decades the analysis suggests that wave height south of 408n has decreased during the same period

aerobic microbial dolomite at the nanometer scale implications for the geologic record microbial experiments are the only proven approach to produce experimental dolomite under earth s surface conditions although microbial metabolisms are known to induce dolomite precipitation by favoring dolomite growth kinetics the involvement of microbes in the dolomite nucleation process is poorly understood in particular the nucleation of microbially mediated dolomite remains a matter for investigation because the metabolic diversity involved in this process has not been fully explored herein we demonstrate that halomonas meridiana and virgibacillus marismortui two moderately halophilic aerobic bacteria mediate primary precipitation of dolomite at low temperatures 25 35 c this report emphasizes the biomineralogical implications for dolomite formation at the nanometer scale we describe nucleation of dolomite on nanoglobules in intimate association with the bacterial cell surface a combination of both laboratory culture experiments and natural samples reveals that these nanoglobule structures may be 1 the initial step for dolomite nucleation 2 preserved in the geologic record and 3 used as microbial tracers through time and or as a proxy for ancient microbial dolomite as well as other carbonate minerals

measurements of the offshore wave climate around the british isles by satellite altimeter satellite altimetry gives a new perspective on ocean wave climate measurements around the british isles show a strong seasonality with exceptionally large average wave heights to the west and north of the british isles in the winter furthermore the interannual variability of winter wave climate is very high most of this variability can be described by a strong linear dependence on the north atlantic oscillation nao index this relationship may largely explain observations of increasing wave heights in the northeastern atlantic and northern north sea during the latter decades of the 20th century coincident with a long term rise in the nao

variability and predictability of the north atlantic wave climate wave climate across the ocean basins can be described using satellite altimetry here we concentrate on the north atlantic region waves in the north atlantic are strongly seasonal and peak in the winter season the northeastern sector of the atlantic and adjoining shelf seas also exhibit exceptionally high interannual variability in the winter with monthly average significant wave height varying by up to a factor of 2 from one year to the next the strength and geographical distribution of variability is broadly consistent throughout the winter months december march a large fraction of these wave height anomalies is associated with a single pattern of pressure anomalies that resembles the north atlantic oscillation nao a predictor based on nao dependence is trained from relatively recent satellite data and then tested against earlier satellite and in situ data the predictor is successful in large areas of the north atlantic confirming a robust relationship between wave height anomalies and the nao over the last few decades a substantial rise up to 0 6 m in monthly mean wave heights on the northeastern atlantic during the latter part of the twentieth century is attributable to changes in the nao substantial residual anomalies in wave heights exist after the influence of the nao has been subtracted these are partly explained by a second pair of north atlantic patterns in wave height anomalies and sea level pressure anomalies this east atlantic pattern is particularly influential in midwinter and affects the southern part of the northeastern sector including the region of seven stones light vessel

overlapping of pedogenesis and meteoric diagenesis in distal alluvial and shallow lacustrine deposits in the madrid miocene basin spain the miocene distal alluvial fan and palustrine deposits of the madrid basin paracuellos de jarama area were examined to establish the sequence of its pedogenic diagenetic processes and the main factors controlling them in this area the diagenetic processes operated not only on carbonates as commonly studied but also in high magnesium clays and opaline cherts this paper provides a dynamic model for saline alkaline lake margins that complements the existing freshwater palustrine model three sections ber pel and upc containing limestones sepiolite dolostones and opaline cherts were examined these represent the entire transition from alluvial fan deposit to lake environment the alluvial fan deposits pel section show the most complex sequence of processes after a weak edaphic imprint the primary mudstone and siltstones are affected by silicification opaline levels formed mainly by selective replacement of sepiolites and later dolomitization several types of dolomite are present rounded crystals spherules and globular bodies being the most characteristic in the ponds situated at the foot of the alluvial fans or in interfan areas sepiolite precipitated within free water bodies ber section and an intense pedogenesis led to the formation of palustrine sepiolite deposits later the intense silicification of the sepiolite produced lenticular opaline levels that were locally transformed to quartz by aging in the shallow lakes upc section palustrine limestones and sepiolite were deposited the carbonates are partially affected by silicification the sepiolite becoming completely silicified the opaline levels clearly preserve the structure of the limestones and sepiolite host rocks all the opaline levels show local aging processes the silicification processes were different in the three settings due to the interplay of groundwater with sedimentary environments and facies in the distal alluvial fan sediments of the pel section the initial host rock affected by silicification is not preserved due to the later dolomitization that erased both it and its textures the silicification environment was therefore not easy to determine in the ber and upc section the main silicification took place in groundwater influenced environments but evidence was seen of cements and silicifications in vadose environments in all study settings the overlapping of pedogenic vadose and groundwater processes was controlled by changes in the position of the water table four stages were concluded to explain the transformation from the primary deposits to the later dolomitization process and the formation of vadose cements the majority of the silicifications seen occurred as responses to changes in the water table position linked to the aggradation of this closed basin in all the studied environments the sepiolite deposits were preferentially silicified their fibrous structure and high absorption capacity helping to retain interstitial fluids moreover sepiolite and opal are stable under relatively similar geochemical conditions in arid environments the dissolution of the sepiolite caused an increase in silica in the interstitial fluids favouring silicification and ruling out the need of a biogenic source the replacement of limestones by silica is usually driven by variations in ph and salinity which are very common in surface environments such as shallow lakes and soils

cenozoic calcretes from the teruel graben spain microstructure stable isotope geochemistry and environmental significance in the teruel graben northeast spain laminar and nodular calcretes formed in a variety of cenozoic deposits ranging in age from palaeogene to pleistocene these calcretes developed in a relatively small area under the influence of the same highlands consequently differences in their microstructure and isotopic composition c and o must be related to differences in host rock climate vegetation and duration of development nine profiles developed in different sedimentary settings from proximal areas to lacustrine environments were studied to determine whether the microstructure and stable isotope composition changed during the cenozoic these characteristics might be used as indicators of the prevailing climate and vegetation and reveal any changes that occurred during this time most of the laminar calcretes studied are compound profiles that formed on hard substrates e g jurassic limestones or coarse detrital deposits e g palaeogene pliocene and plio pleistocene sandstones and conglomerates these profiles formed in proximal areas of the basin and also in fluvial terraces microstructures include biogenic features such as alveolar septal structures root tubes calcified root cells and calcified organic filaments underside coatings of micrite and fibrous vadose cements are common around gravel clasts on the other side spherulites are only preserved at the very top of the youngest calcretes nodular calcretes developed on fine detrital substrates e g on palaeogene miocene and pliocene red mudstones and sandy mudstones of distal alluvial and floodplain environments and in some places grade vertically into palustrine limestones the nodules consist of micrite and were elongated vertically show desiccation cracks and mottling micritic coatings some alveolar septal structures and root traces microcodium of type 1 occurs in both laminar and nodular calcretes but only in those of palaeogene age while calcified root cells microcodium of type 3 are seen in the pliocene calcretes the stable isotope composition covers a wide range 8 23 18o 4 29 pdb and 7 29 13c 3 42 pdb nodular laminar and palustrine facies occupy overlapped isotopic fields displaying an overall negative covariant trend location within the basin prevailing climate and density of vegetation are responsible for differences in isotope values the palaeogene samples show a wide range of values and are difficult to separate from the others however there is as significant change to lighter carbon values from the miocene to the pliocene profiles this change may be related to the cooler climatic conditions that prevailed during the pliocene and is reverse to the expected shift to heavier 13c values which is related to the increase of c4 vegetation that occurred in many areas of the world during the miocene or to the transit to the pliocene the formation of these calcretes seems to have occurred in semi arid conditions with prevailing c3 vegetation

northern hemisphere winter circulation associated with the north atlantic oscillation and stratospheric polar night jet the interannual variability of the atmospheric winter circulation as characterized by the geopotential height at 500 hpa and temperature at 850 hpa associated with the north atlantic oscillation nao and stratospheric polar night jet pnj is examined it is suggested that the wintertime atmospheric circulation related to the nao index can be separated into two different modes of variability one is a regional mode characterized by a meridional dipole type pattern in the 500 hpa geopotential height anomaly field over the atlantic region the other having more zonal structure extends over wider region of the northern hemisphere this is also related to the lower stratospheric polar night jet air temperature near the surface over the eastern part of the eurasian continent is more closely correlated with the above mentioned hemispheric mode of variability than the regional nao

dolomitization and silicification in low energy lacustrine carbonates paleogene madrid basin spain abstract repetitive sequences of carbonate deposits occurrence include in the lower part of the paleogene carbonate unit northeast border of the madrid basin have been studied defining regressive lacustrine sequences and early diagenetic processes binocular microscopic examination scanning electron microscopic energy dispersive x ray observations and x ray diffraction analyses joint to isotopic studies 18 o and 13 c have been used to characterise the facies and environments the sequences consist of a lower uncemented carbonate mud unit calcitic or dolomitic in composition and an upper carbonate unit arenites bioclastic limestones and microbial laminated limestones with cherts visual features vertical prismatic structures fissures massive nodulization rhizoliths brecciation and microscopic features micrite micronodules vug porosity circumgranular cementation gypsum lenticular crystals outline pedogenic processes these features found locally in bioclastic and microbial laminated limestones or in dolomite uncemented muds define respectively palustrine limestones or dolocretes facies analysis allows us to define several lacustrine sub environments basinal littoral eulittoral and supralittoral and characterises different types of shallowing upward lacustrine sequences either with or without subaerial exposure the isotopic values of the bioclastic and microbial laminated limestone from 5 77 to 6 78 for 13 c and from 5 25 to 5 53 for 18 o and those of uncemented calcitic muds from 5 80 to 7 01 for 13 c and from 4 98 to 5 58 for 18 o establish that both types of carbonates precipitated in equilibrium with meteoric waters in the palustrine carbonate deposits the 13 c values suggest a strong organic contribution the dolomitization that only affected the uncemented carbonate muds is early interpreted because of the structural and compositional characteristics of the dolomite micro rhombic dolomicrite nearly stoichiometric and poorly ordered and because the calculated average 18 o dol cal for calcitic and dolomitic uncemented muds is about 6 the 18 o isotopic values indicate that the dolomite precipitated from water that was slightly more enriched in heavy isotopes than the calcite because of an increase in evaporation rates nodules and nodular levels of cherts occur in the upper units of littoral and eulittoral sequences probably as a consequence of the existence of microbial mats that could include the silica source according to their mineralogy opal ct and quartz moganite and structures double nodules lamination and bioturbation three types of chert are described tb mb and wo these types define three general stages of silicification during the early diagenesis from the recently buried to the postcompactation of carbonate deposits the 18 o values of quartz show that the silicification and ageing of opaline phases occurred from meteoric waters which were lighter than the calcite or dolomite precipitating waters the cherts included in palustrine limestones show 18 o values of quartz that record more evaporated waters than those of the general stages of silicification

seasonal variability of the global spectral wind wave climate our understanding of the seasonal variability in the global wind wave field is revisited here using a novel analysis that resolves the directional wave spectra empirical orthogonal function analysis was applied to modeled wave spectral data from a wavewatch iii hindcast across a sparse global grid to identify the main patterns of the climatological wave spectral variability at each grid point prior methods have focused on the variability of two modes of the wave field locally generated sea and the primary swell component our results also consider additional wave modes at each location enabling us to track the passage of the less dominant swell modes consistent with existing climatological knowledge the main modes of wave spectral variability at high latitudes are related to eastward propagating waves that disperse equatorward as swell following great circle paths however despite being the less energetic mode the northern hemisphere generated swell is found to propagate into the southern hemisphere further than the more energetic southern hemisphere swell which propagates northward in the equatorial zone a complex multimodal wave climate is found with the spectra variability modulated by remotely generated swell and higher frequency waves associated with the prevailing winds the evolution of these patterns throughout the year is clearly depicted overall our approach captures a more complete picture of the seasonal variability of the global wave field by accounting for all the wave modes observed in the spectra at each location together with their temporal variability

wave driven sea level anomalies at the midway tide gauge as an index of north pacific storminess over the past 60 years 1 sixty years of sea level data collected in the interior lagoon of midway atoll in the northern hawaiian islands are used to examine short term 2 days high amplitude up to 1 m sea level anomaly sla events that occur during the winter months a combination of wind and wave model hindcasts satellite altimetry product and in situ water level data confirms that these high sla events are driven primarily by the arrival of energetic swell waves generated by storms in the north pacific as breaking waves on the northwest side of the atoll lead to the setup of the lagoon the number of high sla events recorded in midway during each winter season correlates well with the storminess in the central north pacific defined as the mean seasonal wave height this leads us to conclude that the seasonal number of high sla events measured at this specific tide gauge in midway can be used as an index of storminess in the central north pacific over climatic time scales our midway based index of storminess correlates well with the pacific decadal oscillation pdo index and its observed increase over the past 60 years is attributed to variability associated with the pdo rather than a long term trend

two faces of enso induced surface waves during the tropical cyclone season abstract the response of the wave climate to tropical cyclones tcs is investigated using the significant wave height swh observed from satellites and the wavewatch iii ww3 model tropical cyclone wind generates local waves wind seas under the tc and longer period waves swells that propagate long distances the genesis location intensity and frequency of tropical cyclones over the global ocean are strongly affected by the phases of the el nino southern oscillation enso it is shown that the interannual variation of global ocean surface waves in the subtropics during summer is dominated by enso related tc activity in particular in the subtropical western north pacific the wind power is stronger in the tc season before an el nino and weaker before a la nina these enso related tc variations are shown through composite and empirical orthogonal function analyses as well as modeling to dominate the spatial distribution and temporal variation of the swh over the western north pacific the model confirms that longer period waves swells are driven into northern south china sea toward japan in mid latitudes and toward the central pacific along the equator due to enso related tc activities the wind power and swh over the subtropical western north pacific lead and regress well with the enso index suggesting that they may potentially serve as useful enso predictors

late permian continental sediments in the se iberian ranges eastern spain petrological and mineralogical characteristics and palaeoenvironmental significance abstract a detailed mineralogical and petrological study and the analysis of paleosol profiles in continental alluvial sediments of the late permian in the se iberian ranges spain allow us to infer the significant environmental changes that occurred during this time period three parts have been distinguished in the late permian sediments alcotas formation the lower part includes abundant and well preserved carbonate paleosol profiles and fine grained sediments made up by quartz feldspar hematite and illite with scarce kaolinite the preservation of dolomicrite in some paleosols suggests that they originally developed as dolocretes in an arid to semi arid climate with marked seasonality a change towards more humid and acid conditions can be deduced from the presence of siderite and goethite in paleosols in the middle part of the alcotas formation moreover the presence of plant remains coal beds and or carbonaceous shales at the top of the middle part and the lack of carbonate paleosols in the upper part of the formation would indicate a further step towards acid conditions these conditions would increase until the early triassic as indicated by the lack of carbonates and the presence of sr rich aluminium phosphate sulphates aps minerals at the base of the triassic canizar formation which clearly indicates extreme acid conditions during the permian triassic transition of the study area

ocean swells along the global coastlines and their climate projections for the twenty first century abstractremotely generated swell waves are the dominant contributor of the coastal wind wave climate along most of the world coastlines in this work we describe the characteristics of swells from

wind and wave climate in the arctic ocean as observed by altimeters abstracttwenty years 1996 2015 of satellite observations were used to study the climatology and trends of oceanic winds and waves in the arctic ocean in the summer season august september the atlantic side seas exposed to the open ocean host more energetic waves than those on the pacific side trend analysis shows a clear spatial regional and temporal interannual variability in wave height and wind speed waves in the chukchi sea beaufort sea near the northern alaska and laptev sea have been increasing at a rate of 0 1 0 3 m decade 1 found to be statistically significant at the 90 level the trend of waves in the greenland and barents seas on the contrary is weak and not statistically significant in the barents and kara seas winds and waves initially increased between 1996 and 2006 and later decreased large scale atmospheric circulations such as the arctic oscillation and arctic dipole anomaly have a clear impact on the variation of winds and waves in the atlantic sector comparison

the madrid basin and the central system a tectonostratigraphic analysis from 2d seismic lines abstract data from deep boreholes seismic surveys and surface geology are used to reconstruct the sedimentary infilling of the cenozoic madrid basin eight main depositional sequences and seismic units are recognised from the paleogene the latter four of these sedimentary sequences were deposited in a continental environment under the influence of tectonic activity in the central system the toledo mountains the iberian chain and the sierra de altomira the sedimentary infill shows an overall coarsening upward trend from upper cretaceous formations to syn tectonic conglomerate deposits followed by a fining upward sequence and moderate reactivation of some faults during the late miocene pliocene the syn tectonic sediments are oligocene early miocene in age the foredeep is oriented northeast southwest and shows a sediment thickness of up to 3800 m in areas close to the central system several types of tectonic structures are recognised including imbricate thrust systems thrust triangle zones fault propagation folds back thrust systems and pop up structures the frontal thrusts were subjected to significant erosion and late miocene sediments onlap the anticlines of the onshore foreland nw se trending positive flower structures have been recognised in the eastern part of the basin the total northwest southeast shortening across the contact between the madrid basin and the central system is approximately 5 km of which 2 3 km occurred across the southern border thrust the simultaneous basement uplift of the central system and the tectonic escape of the sierra de altomira have been interpreted as a consequence of constrictive deformation within the pyrenean foreland of the iberian microplate

evidence for a recent change in the link between the north atlantic oscillation and arctic sea ice export evidence for a recent change in the link between the north atlantic oscillation nao and arctic sea ice export through fram strait during wintertime djfm is presented from the analysis of simulated arctic sea ice and observations for the period 1958 1997 whereas no correlation between the two time series is found from 1958 to 1977 r 0 1 the correlation increased significantly thereafter r 0 7 1978 1997 the increased coherency between the nao and arctic sea ice export through fram strait during the last two decades resulted from anomalous meridional wind components near fram strait which were associated with the more easterly position of the nao s centers of interannual variability compared to 1958 1977

last century changes in ocean wind wave height from global visual wave data 1 centennial time series of visually observed wave height were derived from the international comprehensive ocean atmosphere data set along the major ship routes in the world ocean and homogenized they demonstrate positive trends in significant wave height over the north pacific with a maximum of 8 10 cm decade in the northeast pacific in the north atlantic and other basins significant upward changes up to 14 cm decade are observed only for the last 50 years and not for centennial records long term changes in wind wave height are closely associated with the north atlantic oscillation in the atlantic and with north pacific oscillation and el nino southern oscillation in the pacific

variability of the winter wind waves and swell in the north atlantic and north pacific as revealed by the voluntary observing ship data this paper analyses secular changes and interannual variability in the wind wave swell and significant wave height swh characteristics over the north atlantic and north pacific on the basis of wind wave climatology derived from the visual wave observations of voluntary observing ship vos officers these data are available from the international comprehensive ocean atmosphere data set icoads collection of surface meteorological observations for 1958 2002 but require much more complicated preprocessing than standard meteorological variables such as sea level pressure temperature and wind visual vos data allow for separate analysis of changes in wind sea and swell as well as in significant wave height which has been derived from wind sea and swell estimates in both north atlantic and north pacific midlatitudes winter significant wave height shows a secular increase from 10 to 40 cm decade 1 during the last 45 yr however in the north atlantic the patterns of trend changes for wind sea and swell are quite different from each other showing opposite signs of changes in the northeast atlantic trend patterns of wind sea swell and swh in the north pacific are more consistent with each other qualitatively the same conclusions hold for the analysis of interannual variability whose leading modes demonstrate noticeable differences for wind sea and swell statistical analysis shows that variability in wind sea is closely associated with the local wind speed while swell changes can be driven by the variations in the cyclone counts implying the importance of forcing frequency for the resulting changes in significant wave height this mechanism of differences in variability patterns of wind sea and swell is likely more realistic than the northeastward propagation of swells from the regions from which the wind sea signal originates

trends of atlantic wave extremes as simulated in a 40 yr wave hindcast using kinematically reanalyzed wind fields abstract in this study seasonal extremes of wave height in the north atlantic are analyzed the analysis is based on a 40 yr 1958 97 numerical wave hindcast using an intensive kinematic reanalysis of wind fields changes in the ocean wave extremes are identified by performing the mann kendall test and are further related to changes in the atmospheric circulation sea level pressure by means of redundancy analysis the relationship between sea level pressure and ocean wave extremes is also used to reconstruct the seasonal wave statistics for the last century back to 1899 consistent with previous studies this high resolution atlantic wave hindcast also shows that the northeast north atlantic ocean has experienced significant multidecadal variations in the last century and it has indeed roughened in winters of the last four decades the winter wave height increases are closely related to changes in the north atlantic oscillation during the last four decades while showing trend patterns similar to

tectonics magmatism and paleo fluid distribution in a strike slip setting insights from the northern termination of the liquine ofqui fault system chile this study addresses the interplay between strain stress fields and paleo fluid migration in the southern andean volcanic zone svz the svz coexists with the margin parallel liquine ofqui fault system lofs and with nw striking andean transverse faults atf to tackle the role of different fault fracture systems on deformation distribution and magma fluid transport we map the nature geometry and kinematics of faults veins and dikes at various scales fault slip data analysis yields stress and strain fields from the full study area data base regional scale and fault zones representative of each fault system local scale regional scale strain analysis shows kinematically heterogeneous faulting local strain analyses indicate homogeneous deformation with ne trending shortening and nw trending extension at nne striking liquine ofqui master fault zones strain axes are clockwise rotated at second order fault zones with ene trending shortening and nnw trending stretching the atf record polyphasic deformation conversely stress field analysis at regional scale indicates a strike slip dominated transpressional regime with n64 e trending 1 and n30 w trending 3 deformation is further partitioned within the arc through nne striking dextral reverse faults ne striking dextral normal faults and nw striking sinistral reverse faults with normal slip activation the regional tectonic regime controls the geometry of ne striking dikes and volcanic centers ne striking faults record local stress axes that are clockwise rotated with respect to the regional stress field nne and ne striking faults are favorably oriented for reactivation under the regional stress field and show poorly developed damage zones conversely nw striking fault systems misoriented under the regional stress field show multiple fault cores wider damage zones and dense vein networks deformation driven by oblique subduction is partially partitioned into strike slip and shortening components the trench parallel component is mostly accommodated by ns striking right lateral faults of the lofs trench perpendicular shortening is accommodated by sinistral reverse atf and dextral reverse nne striking faults we conclude that the svz records a deformation history coeval with magma fluid migration

spectra of long term series for wind speed and wave height in the indian ocean area the spectra of long term series of wind velocity and significant wave height were built in two domains of variability scales from one day to one year d1 and from one year to 15 years d2 surface wind data from the era interim reanalysis in the indian ocean io area for the period of 1979 2015 years and wave heights simulated with the improved wam model were used for this purpose in order to study the spatial variability of the spectral shapes spectra of wind speed and wave height were calculated at two sections located along the meridians and three sections located along latitudes with a step of 3 for the d1 domain the existence of three ranges of variability scales r1 r2 r3 are shown in which both types of spectra have the well defined and visibly different power like slopes varying in dependence on the offset from the equator the navier stokes equations were analyzed in order to design a theoretical interpretation of the spectral shapes features found in the d1 domain for the d2 domain no unified system of isolated frequencies has been revealed which is expected for the entire indian ocean among the set of selected periods the most stable one is the variability period of around 5 5 years results presented in this work are discussed

ocean waves and teleconnection patterns in the northern hemisphere abstractunderstanding long term ocean wave climate variability is important to assess climate change impacts on coastal and ocean physics and engineering teleconnection patterns can represent wave climate variability in the context of climate change the objective of this study is to identify how large scale spatial distributions of wave heights vary on a monthly basis and how they are influenced by various teleconnection patterns using reanalysis datasets the wave height climate responses to teleconnection patterns in the eastern part of the north pacific and north atlantic are more sensible than in the corresponding western parts the dominant spatial patterns of monthly averaged wave height variability in winter were obtained by empirical orthogonal function analysis the three dominant patterns in the north pacific and north atlantic are similar it is remarkable that one of the three dominant patterns a band shaped pattern exhibits a strong relation to the teleconnection pattern in each ocean t

characteristics of the recent eastward shift of interannual nao variability recent observational studies have shown that the centers of action of interannual variability of the north atlantic oscillation nao were located farther eastward during winters of the period 1978 97 compared to previous decades of the twentieth century in this study which focuses on the winter season december march new diagnostics characterizing this shift are presented further the importance of this shift for nao related interannual climate variability in the north atlantic region is discussed it is shown that an nao related eastward shift in variability can be found for a wide range of different parameters like the number of deep cyclones near surface air temperature and turbulent surface heat flux throughout the north atlantic region by using a near surface air temperature dataset that is homogenous with respect to the kind of observations used it is shown that the eastward shift is not an artifact of changes in observational practices that took place around the late 1970s finally an eof based monte carlo test is developed to quantify the probability of changes in the spatial structure of interannual nao variability for a relatively short 20 yr time series given multivariate white noise it is estimated that the likelihood for differences in the spatial structure of the nao between two independent 20 yr periods which are similar as measured by the angle and pattern correlation between two nao patterns to the observed differences to occur just by chance is about 18 from the above results it is argued that care has to be taken when conclusions about long term properties of nao related climate variability are being drawn from relatively short recent observational data e g 1978 97

influence of the pacific south american modes on the global spectral wind wave climate in this study we analyse the influence of the pacific south american modes psa 1 and psa 2 on the global wind wave climate using wave data derived from a wavewatch iii global wave hindcast we apply an empirical orthogonal function analysis to daily averaged directional wave spectra to extract the two main patterns of interannual wave spectral variability these are related to changes in the wave spectral density levels variability in the wave heights and to rotations of the wave signal variability in wave direction the psa 1 mode is positively correlated with the wave height variability in the southeast pacific and negatively correlated in the indian ocean sector of the southern ocean the psa 2 mode presents a strong negative correlation with wave heights in the central south pacific moreover the psa modes are significantly correlated with changes in modelled wave direction in the south pacific region composite maps of wind anomalies during positive stages of psa 1 and psa 2 provide a compelling explanation for the observed correlation patterns the methodology applied in this study is also used to assess the influence of other climate modes on the global wind wave climate namely the southern annular mode arctic oscillation north atlantic oscillation el nino southern oscillation and the pacific north american mode while our results are consistent with previous studies we provide more clarity as to how different atmospheric modes influence the variability of specific components of the wave spectrum importantly we assess the how these climate modes would modulate the interannual variability of wave direction

sedimentation on the distal reaches of the okavango fan botswana and its bearing on calcrete and silcrete ganister formation the distal reaches or flood plain of the okavango alluvial fan of northern botswana are characterized by gently undulating topography with local relief generally less than two meters the entire area is blanketed by eolian sand although the area is semiarid with evapotranspiration exceeding precipitation the area is subject to seasonal flooding by annual influx of floodwater from subtropical angola to the north distributary channels on the flood plain are poorly defined and consist of sinuous depressions lacking normal fluvial characteristics such as levees bars or incision the flood water has very little suspended load higher ground on the flood plain forms islands during the seasonal flood elevated tracts arise by displacive subsurface crystallization of carbonate and silica which is induced by trees that grow on the higher ground sedimentation on lower lying areas occurs by a combination of 1 accumulation of fine clastic material derived from the flood water and phytolithic silica both of which are mixed into the sandy substrate by illuviation and bioturbation and 2 precipitation of fine grained amorphous silica from the groundwater induced by transpiration by aquatic grasses and sedges accumulation of silica in the soil profile produces a proto silcrete this sequence grades laterally into carbonate dominated island soils the ultimate cause of this association is an abundance of water with low suspended load in an environment with a high evapotranspiration rate ganisters in ancient rocks may have a similar origin

carbonate microbialites and hardgrounds from manito lake an alkaline hypersaline lake in the northern great plains of canada abstract manito lake is a large perennial na so 4 dominated saline to hypersaline lake located in the northern great plains of western canada significant water level decrease over the past several decades has led to reduction in volume and surface area as well as an increase in salinity the salinity has increased from 10 ppt to about 50 ppt tds this decrease in water level has exposed large areas of nearshore microbialites these organogenic structures range in size from several cm to over a meter and often form large bioherms several meters high they have various external morphologies vary in mineralogical composition and show a variety of internal fabrics from finely laminated to massive in addition to microbiolities and bioherms the littoral zone of manito lake contains a variety of carbonate hardgrounds pavements and cemented clastic sediments dolomite and aragonite are the most common minerals found in these shoreline structures however calcite after ikaite monohydrocalcite magnesian calcite and hydromagnesite are also present the dolomite is nonstoichiometric and calcium rich the magnesian calcite has about 17 mol mgco 3 ams radiocarbon dating of paired organic matter and endogenic carbonate material confirms little or no reservoir affect although there is abundant evidence for modern carbonate mineral precipitation and microbialite formation most of the larger microbialites formed between about 2300 and 1000 cal bp whereas the hardgrounds cements and laminated crusts formed about 1000 500 cal bp

biogenic silica storage in soils the role of plants in soil development has become of crucial interest in quantifying global weathering processes on the volcanic reunion island indian ocean a 15 cm thick phytolith rich horizon biogenic opal a developed at the expense of trachytic ashes between 3820 85 and 335 90 yr b p then 97 138 t km 2 yr of sio 2 were biogeochemically recycled from the weathering of parent rocks through a past forest of bamboos nastus borbonicus this rate is in the same range as the present chemical weathering rates of silica in the area considered to be among the highest in the world these results demonstrate that the storage of biogenic silica in soils may be significant and may retard the output of silica to rivers and ocean

microcodium revisited root calcification products of terrestrial plants on carbonate rich substrates abstract microcodium is a problematic calcitic microfeature of many calcretes and calcareous paleosols in the cretaceous and tertiary continental and marine successions of the peri tethyan realm the main controversy about the microcodium structures is their origin and possible relation with calcified plant roots microcodium and rhizogenic root formed microfabrics were studied in calcrete profiles within the paleocene shallow marine carbonate succession in southwestern slovenia the prominent laminar calcrete horizons contain abundant calcite aggregates 150 m to 1 cm in size with perfectly preserved structural details of plant root tissues morphology and structure of these aggregates indicate that they formed through biologically controlled precipitation of calcium carbonate within the root cortical cells the morphologies intermediate between the typical microcodium aggregates composed of a single layer of individual elongate pyramidal or prismatic crystals of calcite measuring 100 500 m in length and 20 70 m in width and calcified roots with multilayer arrangement of isodiametric cells were observed and this supports previous rhizogenic interpretations of microcodium structures intermediate forms show that the typical microcodium aggregates formed through morphological transformation of the root tissue by growth of the calcite within the cortical cells which distorted the cell shape calcification of roots and the creation of microcodium structures can be explained as an effective nutrient acquiring mechanism used by certain types of terrestrial plants inhabiting nutrient poor calcareous substrates the widespread occurrence of microcodium in almost unaltered shallow marine limestones indicates that its formation took place during early stages of paleosol development probably reflecting specific types of vascular plants of a pioneer community that were able to colonize carbonate substrates during the early phases of subaerial exposure

isotopic evidence for dolomite formation in soils abstract dolomite formation in soils constitute a particular challenge because of 1 scant magnesium content in continental environments as opposed to the marine medium 2 the kinetic problem related to the incorporation of magnesium into the carbonate and 3 the unknown role of soil dolomites in the global carbon cycle pedogenic dolomite formed at deeper soil levels subsoil before the development of petrocalcic horizon barriers was investigated in a semiarid region of se spain guadix baza basin mineralogical characterization textural relationships and isotopic data concerning soil dolomite together with the results of a precipitation experiment provided fuller knowledge of the processes and conditions governing neoformation of dolomite in these soils in the study case dolomite enrichment occurs beyond the limit of major biological activity which coincides with the rooting depth of native perennial plants in the semiarid soils studied textural studies reveal the corrosion of inherited dolomite crystals in the upper soil horizons and the formation of dolomite in depth in relation to a clayey material composed mainly of smectites stable isotope distribution in dolomites throughout the profiles indicates a fractionation with depth this is explained by the formation of dolomites after the dissolution of the pedogenic calcite the calcite detected in the subsoil is interpreted here as a precursor of the neoformed dolomites that transport the isotopic signal associated with biological activity of soils to deeper layers dolomite formation appears to be favoured by the presence of clay minerals in the precipitation media clays retain water during evapotranspiration stages which drastically change the transport properties of the media and promote the incorporation of mg into the structure of the neoformed ca mg carbonate as confirmed by laboratory experiments diffusion controlled crystal growth processes lead to the formation a precursory protodolomite with disordered ca mg distribution from a fluid locally supersaturated in dolomite

initial stages of laminar calcrete formation by roots examples from the neogene of central spain thin carbonate laminae formed by root activity are common within miocene detrital deposits of the duero and madrid basins the laminae are about 3 cm thick extending several metres laterally and displace the original detrital sediment which ranges in grain size from fine gravel to sandy clay the thickness morphology microstructure and stable isotope compositions of the laminae indicate that they formed by the activities of roots and associated microorganisms within the soil the laminae are similar to those commonly recognised in thick laminar calcrete profiles three types of laminae are recognised differences in the micromorphology of the laminae are explained as reflecting the different organisms involved and whether calcification occurred when the root was alive or decaying the first type occurs in a profile at paracuellos the jarama where the laminae consist of a mosaic of 20 mm calcite crystals whose arrangement indicates that calcification took place in the medulla of the root and probably occurred while the plant was alive in a second type in the villacadima profile laminae comprise calcified root mats whose formation indicates the interplay of roots and fungi calcification of the cell walls and intracellular spaces took place in the cortices of the roots and not in the medullas as revealed by the presence of central pores in every calcified root a third type of lamina is recognised in profiles at vin egra de moran a and consists of mucilaginous sheets coated by needle fibre calcite crystals the occurrence of associated small root casts indicates that formation of the laminae occurred while the root was decaying and was also influenced by fungal activity these laminae occur within poorly developed soils and their formation was controlled by the relationship between sedimentation erosion and soil formation processes thus the occurrence of these laminae interbedded with detrital sediments reflects environments where sedimentation was relatively low and episodic so after the detrital sediment input surfaces were stable and root mats were able to develop renewed sedimentation accounted for the death of the root mats and the development of new ones on the new surfaces where the sedimentation rate is lower the laminae tend to amalgamate and thicker laminar calcrete profiles form with little or no interbedded detrital sediment

endomycorrhizae in miocene paleosols implications in biotite weathering and accumulation of dolomite in plant roots sw madrid basin spain abstract this work provides evidence of arbuscular mycorrhizae or endomycorrizhae and their role in mineral weathering and soil carbonate production from miocene paleosols formation of the paleosols bearing mycorrhizae took place in marginal lacustrine and distal fan deposits in the madrid basin endomycorrizhae fossils are preserved as carbonate in biotite filled rhizoliths fossilized mycorrhizae are morphologically identical to those of living counterparts and consist of two linked parts the extraradicular segment surrounding the root is represented by a calcitic mycelium comprising spores and two types of hyphae that are seen to attach and to corrode the mineral grains the intraradicular part is made of a network of branched filaments hyphal coils arbuscules and likely vesicles that are mixed with the cortical root cells of the plants fossilized as dolomicrosparite aggregates the preferential formation of the dolomite aggregates on biotite grains in rhizoliths is interpreted to reflect a focused interest of the plants on this mineral and indicates the mineral may have been used as a source of plant nutrients the close association of the carbonate with the silicate further suggests that the precipitation of dolomite in the root cells and the weathering of the biotite resulted from interrelated processes main mechanisms to produce mineral dissolution include organic acids and chelate secretions by the plant roots and fungi which would remove nutrients these results confirm that carbonate paleosols provide an excellent reservoir of information on ecological interactions and biogeochemical cycling and expand the range of biogenic processes and their resultant products involved in the formation of carbonate soils this approach has broad applications given the abundance of carbonate paleosols and the endomycorrhiza record dating back 400 million years

the decay rate of ocean swell observed by altimeter abstractaltimeter data from transects across the southern ocean are analyzed to determine the decay of oceanic swell the resulting decay rate is shown to be proportional to wavenumber squared and swell amplitude cubed such a decay relationship is consistent with turbulent interaction with the background either in the air or water the present data cannot distinguish between these two cases the results are consistent with the limited previous studies and present a source term suitable for use in wave prediction models

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

seasonal wetland carbonate sequences and dynamic catenas a re appraisal of palustrine limestones abstract palustrine carbonate cyclothems are compared directly to well documented peritidal carbonate cyclothems in the case of the latter the trend of increasing degree of exposure seen vertically through a cyclothem has been interpreted as due to the aggradation of the sediment surface relative to the semi diurnal tidal regime palustrine cyclothems also show similar increases in the degree of exposure and this is interpreted as the effect of sediment aggradation in a seasonal wetland regime the resulting changes in the drainage characteristic revealed in a palustrinc cyclothem reflect a type of seasonally variable catenary relationship referred to here as a dynamic catena this model explains the key features of palustrine cyclothems and suggests the importance of seasonal wetland environments in ancient continental settings

modern and late holocene dolomite formation manito lake saskatchewan canada abstract major advances have occurred in our understanding of modern dolomite formation and penecontemporaneous dolomitization over the past several decades manito lake located in west central saskatchewan canada is a large 65 km 2 deep z max 22 m perennial saline 45 ppt tds lake in which modern and late holocene dolomite coexists with other endogenic and authigenic carbonate precipitates including aragonite monohydrocalcite calcite and mg calcite like many other lacustrine dolomites manito lake dolomite is microcrystalline less than 1 m to 5 m ca rich and poor to moderately ordered it occurs as relatively pure hardgrounds and as a component of nearshore microbialites it also forms isopachous cements in consolidated siliciclastic shoreline sediments manito lake dolomite is most likely forming by mainly biomediated precipitation at or near the sediment water interface i in pore spaces of coarse siliciclastic sediments i e beachrock ii as fine laminae associated with microbialites and iii as a major component of mudstone hardgrounds and pavements

microbial fossilization in carbonate sediments a result of the bacterial surface involvement in dolomite precipitation recent dolomitic sediment samples from lagoa vermelha brazil were examined microscopically to study the process of bacterial fossilization in carbonate sediments bacteria like bodies were intimately associated with carbonate mineral surfaces and coatings on the former demonstrate the calcification of single bacterial cells the bacterial fossilization process in lagoa vermelha sediments was simulated in the laboratory by cultivation of mixed and pure cultures of sulphate reducing bacteria which were isolated from the lagoa vermelha sediments these cultures produced carbonate minerals that were studied to provide insight into the initiation of the fossilization process in mixed culture experiments bacterial colonies became calcified whereas in pure culture experiments single bacterial cells were associated with dolomite surfaces dolomite nucleated exclusively in bacterial colonies intimately associated with extracellular organic matter and bacterial cells electrophoretic mobility measurements of the bacterial cells in electrolyte solutions demonstrated the specific adsorption of ca 2 and mg 2 onto the cell surfaces indicating the role of the bacterial surface in carbonate nucleation and bacterial fossilization the affinity of the cells for mg 2 was related to the capability of the strains to mediate dolomite formation combined with sulphate uptake which dissociates the mgso 4 o ion pair and increases the mg 2 availability the concentration of mg 2 ions in the microenvironment around the cells where the conditions are favourable for dolomite precipitation may be the key to overcome the kinetic barrier to dolomite formation these results demonstrate that bacterial fossilization is a consequence of the cell surface involvement in carbonate precipitation implying that fossilized bacterial bodies can be used as a tool to recognize microbially mediated carbonates

are the northern hemisphere winter storm tracks significantly correlated abstract in this study the correlation between the northern hemisphere winter pacific and atlantic storm tracks is examined using the ncep ncar reanalysis and the 40 yr ecmwf re analysis era 40 as well as unassimilated aircraft observations by examining month to month variability in the 250 hpa meridional velocity variance the correlation between the two storm track peaks is found to be as high as 0 5 during the winters between 1975 76 and 1998 99 here it is shown that the correlation between the two storm tracks can be clearly detected from the aircraft data further analyses of the reanalysis data show that the correlation can also be seen in other eddy variance and covariance statistics including the poleward heat flux at the 700 hpa level the correlation between the two storm tracks as seen in both reanalysis datasets is shown to be much weaker during the period 1957 58 1971 72 suggesting a possible regime transition from largely uncorrelated storm tracks to highly correlated storm tracks

mineralogy and origin of rhizoliths on the margins of saline alkaline lake bogoria kenya rift valley abstract a wide range of rhizoliths occurs around the margins of lake bogoria kenya these include root casts moulds tubules rhizocretions and permineralised root systems these rhizoliths are variably composed of opaline silica calcite zeolites mainly analcime fluorite and possibly fluorapatite either alone or in combinations some rhizoliths are infilled moulds with detrital silicate grains most rhizoliths are in situ showing both vertical and horizontal orientations reworked rhizoliths have been concentrated locally to form dense rhizolites hot spring fluids concentrated by evapotranspiration and capillary evaporation have provided most of the silica for the permineralisation of the plant tissues precipitation involved the growth of silica nanospheres and microspheres that coalesced into homogeneous masses calcite rhizoliths formed following evaporative concentration evapotranspiration and or co2 degassing of ca bearing runoff water that infiltrated the sediment or by mixing of runoff with saline alkaline groundwater fluorite precipitated in areas where mixing of hot spring and meteoric waters occurred or possibly where hot spring fluids came into contact with pre existing calcite zeolitic rhizoliths formed during a prolonged period of aridity when capillary rise and evaporative pumping brought saline alkaline waters into contact with detrital silicate minerals around roots

reworked calcretes their significance in the reconstruction of alluvial sequences permian and triassic minorca balearic islands spain the permian and triassic of minorca balearic islands consists of a 670 m thick red alluvial succession that includes in situ calcrete profiles and reworked calcrete material in the permian succession the calcretes vary from laminar forms developed on the carboniferous basement to weakly developed nodular calcretes in fluvial sediments the palaeosols in the triassic are mostly dolomitic and the profiles reach up to stage iii of soil development spec pap geol surv am 203 1995 1 the clasts formed through reworking of the palaeosol profiles are about 0 5 10 cm across and include mosaics of calcite dolomite crystals brecciated clasts rhizolith fragments and aggregates of clay and or silt these clasts appear in three different types of deposits type 1 corresponds to lenticular bodies that fill small scour surfaces and consists only of intraformational conglomerates these deposits are interpreted as ephemeral channels and sheet floods that represent the interfluvial drainage systems that captured only the precipitation falling on the alluvial plain type 2 includes sand dune 3 d bodies with flat bottoms and convex tops these bodies are about 20 cm high and 2 m wide and were formed by floodwaters that flowed down the levees of the major streams type 3 channel deposits contain reworked calcretes and extrabasinal clasts which overlie erosive surfaces and are found in layers within cross bedded sandstones and conglomerates these are interpreted as channel floor lag deposits of major channels that entered from distant uplands and drained the alluvial plain variations in the aggradation rates of the floodplain resulted in five different infill stages in the lowstand to early transgressive interval as in stages i p1 and iv b1 the fluvial deposits filled palaeovalleys calcretes and reworked calcrete deposits were of difficult formation apart from terraces and preservation accommodation space was at its greatest in the transgressive stages ii p2 and v b2 this caused the greatest aggradation of the floodplains which are formed of thick sequences of fine grained sediments isolated meandering channels weakly developed calcretes compound and reworked calcrete deposits mostly of types 1 and 2 the density of channels notably increased in stage iii p3 highstand interval because of the reduction of accommodation space this could favour the formation of composite or even cumulative palaeosols but of difficult preservation reworked calcrete deposits are mostly of type 3 but types 1 and 2 are also recognised the reworked calcrete deposits are an important part of the permian and triassic fluvial sediments and their occurrence and characteristics are important in order to interpret the infill of terrestrial basins and the construction of floodplains

discriminating between tectonism and climate signatures in palustrine deposits lessons from the miocene of the teruel graben ne spain the upper miocene vallesian turolian unit ii of the teruel graben comprises at its top a 25 m thick sequence of palustrine deposits deposition of the entire unit commenced some 9 to 7 ma ago in a halfgraben basin here via a recent quarry we examine in detail the lateral and vertical distribution of unit ii s palustrine facies and their features to determine the palaeogeography and main controls on deposit formation our findings suggest the deposits formed at a low gradient lake margin with different energy levels these energy levels controlled the type of primary deposit within the lake wackestone to packstone sediments formed in low energy conditions whereas cross bedded rudstones to floatstones formed under higher energy conditions by erosion and redeposition of prior lacustrine deposits pedogenic and diagenetic modifications of the primary sediments took place during sedimentary discontinuities sd when the lacustrine sediments were subaerially exposed these processes serve to explain the formation of eight different palustrine limestones limestones with root traces mottled limestones brecciated limestones flat pebble breccias granular limestones micro karstified limestones with laminar calcretes carbonate mounds and clayey limestones with laminar calcretes based on the features and thicknesses of the modified sediments five different morphological stages i to v of palustrine carbonates are defined stage i is characterized by incipient mottling and brecciation stage ii shows mottling and strong brecciation that lead to the formation of intraclast breccias in which the fragments are mostly in situ in stage iii the primary fabric is totally changed intraclasts have moved and may have lost their initial morphology this stage iii may also be characterized by the formation of micro karst stage iv is typified by the presence of coated grains and thin root mats the chronological data available suggest that the formation of stage iii lacustrine deposition palustrine modification would require about 40 000 yr facies and the sd record changes across short horizontal distances and thus reflect the topography of prior sedimentation modification events small 50 cm highs with micro karst have their sd counterparts in lower areas of the lake in which the sd is indicated by desiccation and mottling the topographic differences of the micro karst were filled by intraclastic rudstones sourced by the adjacent carbonate flats the example examined not only clearly sketches the morphology of ancient palustrine systems or wetlands it also provides evidence that recycling of previous carbonate deposits played an important role as a sediment source apart from biogenic or physical chemical production processes our geochemical data indicate lmc low magnesian calcite as the main component and fe contents lower than 1 except for the mottled areas that are richer in feo stable isotope compositions provide 18o values close to 6 5 vpdb and more varied 13c 3 39 to 6 97 pdb oxygen and carbon values reveal no covariation and clear trends are lacking the homogeneity of 18o values reflects the intense effects of meteoric waters the deposition of these palustrine limestones took place under suitable semi arid to sub humid climates climate could also have a role in determining subaerial exposure periods however its imprint is not easy to detect neither in the geochemical signals nor in the vertical arrangement of the facies this could be attributed to climate changes probably occurring over shorter periods than those that can be recorded in this type of sediment such as the astronomical precession cycles and suggests the unsuitability of palustrine carbonates for detailed palaeoclimate analyses tectonism controlled the location of the main lacustrine depocentre close to the basin s main fault the activity of this normal fault during the sedimentation of unit ii determined long and short term sedimentary sequences such sequences are the response to small scale subsidence pulses followed by the infill of the created accommodation space by shallow lacustrine deposits which underwent early pedogenic and diagenetic processes after subaerial exposure

groundwater dolocretes from the upper triassic of the paris basin france a case study of an arid continental diagenetic facies thick dolomite cemented horizons dolocretes occur within a fluvial sandstone mudstone sequence of late triassic age in the western part of the paris basin france two types of dolomites can be distinguished a nodular dolomitic beds less than a few metres thick which formed within mottled overbank siltstones and mudstones and b massive dolomite up to 16 m thick which occurs in coarse grained channel sandstones and conglomerates the majority of the dolomite consists of a finely crystalline groundmass of dolomicrospar and less commonly dolomicrite glaebules irregular spar filled cracks spheroidal dolomite silicification and vuggy porosity are locally abundant in the massive dolomite in contrast biologically induced micromorphological features such as rhizocretions and alveolar septal fabrics were observed in the thin nodular dolomite beds the dolomite is near stoichiometric well ordered and non ferroan 18o values range from 7 7 to 0 4 o pdb and 18o values range from 5 1 to 1 8 0 pdb and no obvious difference in the stable isotopic composition between both types of dolomites was observed sr isotope ratios range from 0 7101 to 0 7126 and are invariably higher than the contemporary triassic sea water a vadose pedogenic origin for the thin dolocrete layers is indicated by the occurrence of rhizocretions and other biological structures several features however argue against a pedogenic origin for the massive carbonates most notably the absence of biologically induced structures the occurrence in coarse grained channel and not overbank deposits and the great thickness these units are thus interpreted as groundwater in origin phreatic calcretes of quaternary age widespread in inland australia are regarded as a modern analogue for the triassic paris basin dolocretes petrographic observations argue in favour of primary proto dolomite precipitation although early diagenetic replacement of calcite by proto dolomite cannot be ruled out strontium and carbon isotope data of early diagenetic dolocrete cements and oxygen isotope data of early diagenetic silica indicate an entirely non marine continental origin for the groundwaters the poorly ordered and non stoichiometric protodolomite probably underwent stabilization upon further burial resulting in a near stoichiometric well ordered dolomite that clearly lacks evidence for pervasive recrystallization

morphology and origin of dolomite in paleosols and lacustrine sequences examples from the miocene of the madrid basin the northern madrid basin contains paleosols and lacustrine sequences composed of ordered dolomite smectite rich mudstones with analcime deposited in distal alluvial fans affected by pedogenic processes mudstones contain dolomite and silica laminae interpreted as mineralized root mats dolostones with prismatic structure constitute stage iii dolocretes homogeneous lacustrine dolomudstones show some features indicative of subaerial exposure dolomite textures include microcrystalline dolomite coarse crystalline mosaics located in root cavities dolomite dumbbells and dolomite spheroids replacing clays dolomudstones or opal mol values of mgco3 of dolomites vary between 47 67 and 53 34 mol 18o values range between 3 65 and 5 51 vpdb 13c values range between 7 19 and 8 38 vpdb dolomicrite formed in alkaline lakes by direct precipitation and replacement of clays in soils the rhizosphere was favorable for dolomite mosaic and dumbbells formation spheroidal dolomite replaced clays and opal under early phreatic diagenesis trioctahedral smectites silica and analcime indicate that these pedogenic and lacustrine environments were alkaline smectites and or carboxyl groups acted as a catalyst favoring the incorporation of mg into dolomite in these non saline settings the kinetic barriers for dolomite precipitation lowered by high ph and mg enrichment ordered dolomite formation occurred under biogenic and abiogenic conditions during sedimentation pedogenesis and early diagenesis

palustrine sedimentation and associated features grainification and pseudo microkarst in the middle miocene intermediate unit of the madrid basin spain abstract a rather thick sequence 50 75 m of lacustrine limestones forms the uppermost part of the intermediate unit middle miocene in the ne part of the madrid basin central spain a gradual change from distal alluvial to open lake facies is recorded in this area red mudstones passing vertically to strongly mottled limestones are typical of the transition from distal alluvial to marginal lake deposits a wide variety of facies occur in the marginal lacustrine facies association all of them showing pedogenic features e g root traces alveolar septal structures pseudo microkarst micrites and biomicrites are interpreted as open lacustrine deposits although not as strongly pedogenically modified as the marginal lacustrine facies they still show evidence of subaerial exposure the carbonate sequence was deposited in a low gradient shallow lake system in which slight fluctuations in the water level caused extensive emergence pedogenic processes affected most of the lake deposits but modification was more intense in the marginal facies biogenic activity and mechanical reworking at lake margins led to the formation of pedogenic diagenetic pseudo microkarst and peloidal and or intraclastic limestones

the morphology of calcite crystals grown in a porous medium doped with divalent cations calcite crystals were grown in the presence of small concentrations 50 200 and 600 ppm of divalent cations ba2 sr2 co2 and mn2 in a silica hydrogel medium the calcite crystals grown in the presence of cations larger than ca2 ba2 or sr2 developed rhombohedral habits defined by 101 4 form similar to the morphology of calcite grown in a pure gel sem images show that growth on 101 4 occurs by lateral advancement of layers bounded by macroscopic dendritic or jagged steps in the case of calcite crystals grown in a gel doped with cations smaller than ca2 co2 or mn2 a variety of morphologies was obtained ranging from blocky crystals at lower concentrations 50 and 200 ppm to peanut like aggregates spheres and spherulites at 600 ppm the macroscopic morphological characteristics of such doped calcite crystals reflect closely the growth behaviour of calcite 101 4 surface at a nanoscale reported by previous afm studies morphological features have been interpreted on the basis of the modification of growing steps characteristics as a consequence of asymmetrical cation incorporation the use of such morphologies as a criterion of biological activity is therefore unreliable

the origin and significance of pedogenic dolomite from the upper permian of the south urals of russia pedogenic carbonate nodules from six sections spanning the continental permian triassic boundary in the south urals russia were analysed morphological petrographic sem and xrd analyses have demonstrated that many of the latest permian palaeosols are dolomitic this dolomite forms the microcrystalline 5 16 m groundmass of the nodules later diagenetic phases represented by coarser crystalline textures were identified as calcite isotopic analysis of the microcrystalline dolomite has revealed it to be similar in isotopic composition to authigenic dolomite forming today in saline soils in alberta canada these data indicate that the dolomite found in these nodules is pedogenic and formed in equilibrium with the atmosphere upper permian pedogenic dolocretes in the studied sections are most frequent in a palaeosols that formed on palaeo highs and b in the latest permian period changhsingian which may indicate that there was an increase in seasonality and evaporation in the south urals region at this time the presence of only calcitic palaeosols in the earliest triassic may reflect a subsequent dramatic change in the basin conditions possibly relating to the permian triassic mass extinction which stopped the conditions that are necessary for dolomite formation