the effect of antarctic sea ice on the southern hemisphere atmosphere during the southern summer this study examines the influence of antarctic sea ice distribution on the large scale circulation of the southern hemisphere using a fully coupled gcm where the sea ice submodel is replaced by a climatology of observed extremes in sea ice concentration three 150 year simulations were completed for maximum minimum and average sea ice concentrations and the results for the austral summer january march were compared using the surface temperatures forced by the sea ice distributions as a filter for creating the composite differences the results indicate that in the austral summer the polar cell expands contracts under minimum maximum sea ice conditions with corresponding shifts in the midlatitude ferrell cell we suggest that this response occurs because sea ice lies in the margin between the polar and midlatitude cells the polarity of the southern hemisphere annular sam mode is also influenced such that when sea ice is at a minimum maximum the polarity of the sam tends to be negative positive

a possible enso signal in the ross sea an examination of the observational record in the ross sea over the period 1982 1994 indicates that there is a statistically significant relationship between the ross sea sea surface temperature sst and the enso signal in the tropical pacific during this period the ross sea ssts lag the enso signal by 2 4 months with the highest correlation coefficient occurring with a lag of 3 months observations of the sea ice concentration during 1982 1994 also indicate a relation between the sea ice concentration in the ross sea and the enso cycle with reduced sea ice concentrations in el nino years

constraints on palaeoenvironments in the lower cretaceous wealden of southern england from the geochemistry of sphaerosiderites abstract sphaerosiderites are millimetre scale concretions of feco 3 that form predominantly in waterlogged environments and are of use in palaeoenvironmental and palaeohydrological studies we present petrographic elemental and stable isotopic 13 c 18 o data from sphaerosiderites collected from the lower cretaceous wealden sediments of southern england the sphaerosiderites are composed of very pure feco 3 with only small amounts of ca mg and mn present suggesting that they are well preserved and were precipitated from fresh groundwater 13 c values display a relatively large range from about 5 to 30 vpdb in contrast 18 o values are relatively invariant 1 0 83 with an average of 3 01 vpdb the relationship between carbon and oxygen suggests that the sphaerosiderites faithfully record palaeo groundwater 18 o likely 18 o values for groundwater were calculated using a published experimentally derived siderite water fractionation equation and plausible assumed values for palaeotemperature the average estimate was 4 9 smow the wealden sphaerosiderite oxygen isotope values are comparable with other early cretaceous data from similar palaeolatitudes but lower than estimated holocene values for equivalent latitudes this observation may indicate greater rainfall at 30 n during the cretaceous relative to the holocene and also suggests relative stability of palaeoclimatic conditions during the early cretaceous at this palaeolatitude

seasonal relationships between large scale climate variability and antarctic sea ice concentration abstractthe observed relationships between anomalous antarctic sea ice concentration sic and the leading patterns of southern hemisphere sh large scale climate variability are examined as a function of season over 1980 2008 particular emphasis is placed on 1 the interactions between sic the southern annular mode sam and el nino southern oscillation enso and 2 the contribution of these two leading modes to the 29 yr trends in sea ice regression composite and principal component analyses highlight a seasonality in sh sea ice atmosphere interactions whereby antarctic sea ice variability exhibits the strongest linkages to the sam and enso during the austral cold season months as noted in previous work a dipole in sic anomalies emerges in relation to the sam characterized by centers of action located near the bellingshausen weddell and amundsen eastern ross seas the structure and magnitude of this sic dipole is found to vary considerably as a function of season consistent with the season

modulation in interannual sea ice patterns in the southern ocean in association with large scale atmospheric mode shift 1 we verified that the synchronous propagations of the spatial patterns of sea ice concentration sic of wave number 2 around the antarctic occurred only for the period 1984 to 1994 an empirical orthogonal function eof analysis of satellite data for 1979 2003 objectively demonstrates that the spatial pattern of sic propagated eastward only in 1984 1994 in other years it did not our results show that interannual variations in sic patterns are associated with differences in the dominant large scale atmospheric patterns in nonpropagating years variance of the tropospheric antarctic oscillation aao predominated however in propagating years the aao variance was subdominant to that of the pacific south american psa teleconnection pattern having a 4 year period such periodic psa enables the sic anomalies to propagate eastward with a periodically reinforced dipole pattern the shift of large scale atmospheric variability is one possible cause of the modulation in the sic pattern the switch of the atmospheric eof leading mode from the psa pattern to the aao in the mid 1990s corresponded to the modulation in the sic pattern and supports the presence of the atmospheric climate shifts

relationships between the interannual variability of antarctic sea ice and the southern oscillation abstract a climatology of antarctic sea ice extent based on 20 years of data 1973 1992 is presented including measures of interannual variability and extrema in the first half of the year the greatest variability is found in the western hemisphere particularly in the weddell and ross sea regions while in the second semester the variability displays a considerable degree of zonal symmetry we have used this dataset to explore the possible links between antarctic sea ice extent and the southern oscillation index soi to do this we have calculated their correlation for all pairings of calendar months as well as with the soi taken from the year before and subsequent to that of the time of the sea ice data most of the correlations assume their largest magnitude when the soi leads the anomalies in the sea ice but these differ considerably between the three ocean basins the extent of indian ocean sea ice in the months april through july is positively correlated with the soi during most of the previou

carbon oxygen and sulphur isotope variations in concretions from the upper lias of n e england carbon oxygen and sulphur isotope data for transects across two pyrite bearmg carbonate concretions and their host sediments from the upper lias of n e england show symmetrical zonation 13cpdb values of the calcite cement 12 9 to 15 4 indicate that most of it originated from organic matter by bacterial reduction of sulphate augmented with marine and to a lesser extent fermentation derived carbonate organic carbon 13cpdb 26 1 to 37 0 reflects the admixture of allochtho nous terrestrial organic matter with marine material and the selective preservation of isotopically light organic material through microbiological degradation two phases of pyrite are present in each concretion the earlier framboidal pyrite formed throughout the sediment prior to concretionary growth and has 34scd values of 22 to 26 indicating formation by open system sulphate reduction the later euhedral phase is more abundant and reaches values of 2 5 to 5 5 at concretion margins this phase of sulphate reduction provided the carbonate source for concretionary growth and occurred in a partially closed system the 13c and 34s data are consistent with mineralogical and chemical evidence which suggest that both concretions formed close to the sediment surface the 18o values of the calcite in one concretion 18opdb 2 3 to 4 8 indicate precipitation in pore waters whose temperature and isotopic composition was close to that of overlying seawater the other concretion is isotopically much lighter 18opdb 8 9 to 9 9 and large 18o differences between concretions in closely spaced horizons imply that local factors control the isotopic composition of pore waters

petrography and microanalysis of pennsylvanian coal ball concretions herrin coal illinois basin usa bearing on fossil plant preservation and coal ball origins abstract petrographic analyses of 25 coal balls from well studied paleobotanical profiles in the middle pennsylvanian herrin coal westphalian d illinois basin and five select coal balls from university collections indicate that herrin coal ball peats were permineralized by fibrous and non fibrous carbonates fibrous carbonates occur in fan like to spherulitic arrays in many intracellular within tissue pores and are best developed in relatively open extracellular between plant pore spaces acid etched fibrous carbonates appear white under reflected light and possess a microcrystalline texture attributable to abundant microdolomite scanning electron microscopy x ray diffraction and electron microprobe analysis demonstrate that individual fibers have a distinct trigonal prism morphology and are notable for their magnesium content 9 15 mol mgco 3 non fibrous carbonates fill intercrystalline spaces among fibers and pores within the peat as primary precipitates and neomorphic replacements in the immediate vicinity of plant cell walls non fibrous carbonates cut across fibrous carbonates as a secondary neomorphic phase attributed to coalification of plant cell walls dolomite occurs as diagenetic microdolomite associated with the fibrous carbonate phase as sparite replacements and as void filling cement maximum dolomite 50 59 wt is in the top of seam coal ball zone at the sahara mine which is overlain by the marine anna shale coal ball formation in the herrin coal began with the precipitation of fibrous high magnesium calcite the trigonal prism morphology of the carbonate fibers suggests rapid precipitation from super saturated meteoric pore waters carbonate precipitation from marine waters is discounted on the basis of stratigraphic paleobotanical and stable isotopic evidence most non fibrous carbonate is attributable to later diagenetic events including void fill replacements recrystallization and post depositional fracture fills evidence suggests that co 2 degassing was important in coal ball formation in the herrin coal which mainly occurred sequentially upward with peat accumulation in the sites studied

antarctic sea ice climatology variability and late twentieth century change in ccsm4 abstracta preindustrial control run and an ensemble of twentieth century integrations of the community climate system model version 4 ccsm4 are evaluated for antarctic sea ice climatology modes of variability trends and covariance with related physical variables such as surface temperature and sea level pressure compared to observations the mean ice cover is too extensive in all months this is in part related to excessively strong westerly winds over 50 60 s which drive a large equatorward meridional ice transport and enhanced ice growth near the continent and also connected with a cold bias in the southern ocean in spite of these biases in the climatology the model s sea ice variability compares well to observations the leading mode of austral winter sea ice concentration exhibits a dipole structure with anomalies of opposite sign in the atlantic and pacific sectors both the el nino southern oscillation and the southern annular mode sam project onto this mode in twentieth century inte

southern hemisphere circulation features associated with el nino southern oscillation events abstract composite seasonal mean and anomaly fields prepared from operational numerical analyses have been used to describe the southern hemisphere sh circulation features associated with el nino southern oscillation enso events the period of analyses available 1972 83 has limited the composites to include only three enso events the reliability and stability of the composites has been tested using multiple permutation methods and by comparison with the results obtained using a longer period 1950 79 of sh rawinsonde station data in the sh winter a weak equivalent barotropic wavetrain pattern of anomalies extends over australia and the south pacific ocean to south america this wavetrain pattern is quite variable in amplitude and location between enso events although it is more stable over the subtropical pacific in the sh summer the circulation anomalies are more zonally symmetric with increased height at low and high latitudes and decreased height in middle latitudes the circulation anoma

the antarctic dipole and its predictability this study investigates the nature of interan nualvariability ofantarcticseaiceanditsrelationshipwith the tropical climate we nd that the dominant interan nual variance structure in the sea ice edge and surface air temperature elds is organized as a quasi stationary wave which we call the antarctic dipole adp it is charac terized by an out of phase relationship between the ice and temperature anomalies in the central eastern pacic and atlantic sectors of the antarctic the dipole consists of a strong standing mode and a weaker propagating motion within each basin s ice eld it has the same wavelength as the antarctic circumpolar wave acw and dominates the acw variance the dipole is clearly associated with tropical enso events it can be predicted with moderate skill using linear regression involving surface temperature two to four months ahead the prediction performs better in extreme warm cold years and best in la ni na years

remapping the thickness distribution in sea ice models in sea ice models with multiple thickness categories the ice thickness distribution evolves in time the evolution of the thickness distribution as ice grows and melts is analogous to one dimensional fluid transport and can be treated by similar numerical methods one such method remapping is applied here thickness categories are represented as lagrangian grid cells whose boundaries are projected forward in time the thickness distribution is approximated as a linear or quadratic polynomial in each displaced category and ice area and volume are transferred between categories so as to restore the original boundaries in simple test problems and in a single column model with forcing typical of the central arctic remapping performs significantly better than methods previously used in sea ice models it is less diffusive than a scheme that fixes the ice thickness in each category and behaves better numerically than a scheme that represents the thickness distribution as a set of delta functions also remapping converges faster i e with fewer thickness categories than the alternative schemes with five to seven categories the errors due to finite resolution of the thickness distribution are much smaller than the errors due to other sources linear remapping performs as well as the more complex quadratic version and is recommended for climate modeling its computational cost is minimal compared to other sea ice model components

pore water evolution during sediment burial from isotopic and mineral chemistry of calcite dolomite and siderite concretions abstract coal measures often contain concretions segregations of diagenetic minerals originally formed within unconsolidated sediments three different types calcite pyrite dolomite pyrite and siderite occurring spatially quite close together in the central pennine region of england vary widely in carbon isotope composition 10 35 13c 21 49 and in major cation chemistry ca mg fe mn within some siderite concretions very high mn fe ratios were found in central subsamples these were also most enriched in 13c the fe mg ratio decreases systematically from centre to edge early shallow to deeper later precipitation the calcite pyrite and dolomite pyrite concretions developed completely prior to significant burial both have high mn fe ratios but negative 13c values calcite 21 49 dolomite 8 67 to 10 48 all of these patterns can be equated precisely with theories of pore water evolution developed on the basis of geochemical investigations of modem sediments microbial processes sulphate reduction methanogenesis contributed significantly as did thermal decarboxylation to siderite precipitated at considerable burial depth mn iv and fe iii acted differentially as oxidants producing co2 and increasing alkalinity the interplay of fresh and marine depositional waters is seen most obviously in the presence or absence of sulphate reduction this controlled mineral type iron sulphide or carbonate as well as isotopic and mineral chemistry

the pedogenic formation of coal balls by co2 degassing through the rootlets of arborescent lycopsids coal balls are calcium carbonate accumulations that permineralized peat in paleotropical permo carboniferous 320 250 ma mires the formation of coal balls has been debated for over a century yet a widely applicable model is lacking two observations have been particularly challenging to explain 1 the narrow temporal occurrence of coal balls and 2 their typical elemental high mg and isotopic low 18o composition that paradoxically indicate marine and freshwater origins respectively we evaluate a new model in which coal balls formed as co2 escaped from the peat by diffusion through unusual air filled spaces in the rootlets of lycopsid trees critically these trees were very common in paleotropical mires and their evolutionary range matches the temporal range of coal balls the episodic delivery of seawater and marine carbonate sediment to coastal mires is the first step in our model although other pathways for the delivery of divalent cations are permissible subsequent dilution by freshwater and dissolution of these carbonates at the elevated co2 of the mire subsurface is followed by the transport of co2 through the rootlet airspaces and into the overlying water and atmosphere which drives carbonate mineral precipitation in the sediment we show that dilution by freshwater because it minimally affects mg ca ratios can result in relatively low pore water 18o values while allowing high mg calcite formation this model thus explains the restriction of coal balls to the permo carboniferous and resolves the discrepancy between elemental and isotopic compositions of coal ball carbonate minerals furthermore we show with a 3d reactive transport model that co2 could escape rapidly enough through the rootlets to fill 25 percent of the peat pore spaces with calcite before substantial burial top decimeter of peat explaining the exceptional preservation of coal swamp flora therefore we suggest that coal balls are pedogenic in origin and that the disappearance of these pedogenically permineralized histosols represents the first documented decrease in soil diversity on a vegetated planet the rock record may thus provide important context for the modern loss and degradation of soils

analysis origin and significance of mineral matter in coal an updated review abstract the material classed as mineral matter in coal embraces crystalline mineral materials as well as a range of inorganic elements that occur in non crystalline form this review outlines the methods that may be used to evaluate the percentage of mineral matter for a coal sample as opposed to the ash yield and to identify the minerals their individual percentages and their modes of occurrence within the coal the principal techniques include low temperature oxygen plasma ashing quantitative evaluation of x ray diffraction data observation using optical microscopy and a combination of observation chemical analysis and in some cases mapping based on scanning electron microscopy and related methods a range of other techniques may also be used to provide additional information on particular mineral matter components processes responsible for mineral matter formation include detrital input biogenic activity and authigenic precipitation at different stages of the coal s depositional and post depositional history differential migration of non mineral inorganic elements may also occur in lower rank coals and expulsion of non mineral inorganics may take place with rank advance knowledge of the mineral matter may be of assistance in understanding the modes of trace element occurrence with implications for assessing possible environmental impacts and also the potential for recovery of economic products from coal the behaviour of different mineral matter components at high temperatures is also discussed as well as methods for mineralogical analysis of ashes and other coal utilization products information from mineral matter studies may provide an improved basis for understanding coal formation and for evaluating the response of particular coals to different combustion gasification and coking processes

lithospheric shear zones and mantle crust connections abstract a crustal scale ductile shear zone network in the precambrian granulite facies crust of madagascar is examined to determine the nature of the connections between the mantle and lower crust based on three independent data sets field and satellite mapping c and o isotope geochemistry and gravimetry this crust is divided into three zones 1 outside of shear zones 2 minor shear zones that are 350 km long up to 1000 km and 20 35 km wide the mantle is uplifted by about 10 km beneath the major shear zones the major shear zones are rooted in and are inferred to be controlled by the mantle they directly tapped mantle derived co 2 the small scale minor shear zones were controlled by crustal processes and focused crustally derived h 2 o rich co 2 fluids the regular distribution of the shear zones on a crustal scale is in agreement with models of buckling of the continental lithosphere in a compressional context the propagation of these mechanical instabilities promoted and channelled fluid flow these major pan african shear zones thinned the crust and were reactivated during the subsequent drifting of madagascar and opening of the indian ocean during jurassic to cretaceous times they also controlled many of the brittle fault zones in the overlying sedimentary basins mantle rooted large scale shear zones are inferred to be a general feature of cratonic areas reactivated by shear zone systems

displacement and strain patterns from naturally occurring shear zone terminations abstract strain distribution patterns are described from several naturally occurring ductile shear zone terminations and a two fold classification is suggested type i termination patterns show a symmetrical decrease in strain area and intensity and are associated with very low shear strain values in the main shear zone the more common type ii termination patterns show a symmetrical increase in strain area with decrease in strain intensity some brittle ductile examples of type ii terminations contain secondary shears that resemble splay faults all the available evidence suggests that the deformation near the terminations of these shear zones is not plane strain nor do the observed strain patterns readily fit the existing theoretical models

sea ice atmosphere signal of the southern oscillation in the weddell sea antarctica abstract composite analysis of weekly ship and shore observations of the weddell sea pack ice for extreme events of the southern oscillation so occurring in the 1929 62 period reveals strong variations in ice water concentrations in the early and late summer melt season substantially reduced ice concentrations more open water occur in december and early january of warm el nino events yr0 compared with the summer before yr 1 and appear connected with the change to a stronger cyclonic atmospheric circulation over higher latitudes of the south atlantic similarly consistent meteorology sea ice associations appear to characterize the mid to late summer of warm so events yr0 compared with yr0 of cold events there is some evidence that the regionally dependent pressure and wind reversals and possibly the associated sea ice concentration changes in the weddell sector have become more marked during so events occurring since about the early 1950s some corroboration of changes in the sea ice

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

observations of large scale ocean atmosphere interaction in the southern hemisphere abstract the authors provide a detailed examination of observed ocean atmosphere interaction in the southern hemisphere sh focus is placed on the observed relationships between variability in sh extratropical sea surface temperature sst anomalies the southern annular mode sam and the el nino southern oscillation enso results are examined separately for the warm november april and cold may october seasons and for monthly and weekly time scales it is shown that the signatures of the sam and enso in the sh sst field vary as a function of season both in terms of their amplitudes and structures the role of surface turbulent and ekman heat fluxes in driving seasonal variations in the sam and enso related sst anomalies is investigated analyses of weekly data reveal that variability in the sam tends to precede anomalies in the sst field by 1 week and that the e folding time scale of the sam related sst field anomalies is at least 4 months the persistence of the sam related sst anomalies is

twentieth century simulation of the southern hemisphere climate in coupled models part ii sea ice conditions and variability we examine the representation of the mean state and interannual variability of antarctic sea ice in six simulations of the twentieth century from coupled models participating in the intergovernmental panel on climate change fourth assessment report the simulations exhibit a largely seasonal southern hemisphere ice cover as observed there is a considerable scatter in the monthly simulated climatological ice extent among different models but no consistent bias when compared to observations the scatter in maximum winter ice extent among different models is correlated to the strength of the climatological zonal winds suggesting that wind forced ice transport is responsible for much of this scatter observations show that the leading mode of southern hemisphere ice variability exhibits a dipole structure with anomalies of one sign in the atlantic sector associated with anomalies of the opposite sign in the pacific sector the observed ice anomalies also exhibit eastward propagation with the antarctic circumpolar current as part of the documented antarctic circumpolar wave phenomenon many of the models do simulate dipole like behavior in sea ice anomalies as the leading mode of ice variability but there is a large discrepancy in the eastward propagation of these anomalies among the different models consistent with observations the simulated antarctic dipole like variations in the ice cover are led by sea level pressure anomalies in the amundsen bellingshausen sea these are associated to different degrees in different models with both the southern annular mode and the el nino southern oscillation enso there are indications that the magnitude of the influence of enso on the southern hemisphere ice cover is related to the strength of enso events simulated by the different models

strain and shape fabric variations associated with ductile shear zones abstract the foliated and compositionally banded granitic orthogneisses in the central core of the maggia nappe a lower pennine basement nappe of the central swiss alps are shown to be the sheared equivalent of late hercynian age granitic intrusions these ductile shear zones show mineral assemblages in amphibolite facies are alpine in age and form an anastomosing network enclosing remnant lozenge shaped pods of relatively undeformed rock the foliation developed within the shear zones concomitantly with a change in shape of quartz grain aggregates from initially equidimensional through tear drop shapes to ribbon like aggregates these shape changes occurred by intracrystalline glide together with intercrystalline slip on deformation induced planar surfaces

simulating the ice thickness distribution in a coupled climate model climate simulations in a global coupled model are investigated using a dynamic thermodynamic sea ice and snow model with sophisticated thermodynamics and a subgrid scale parameterization for multiple ice thicknesses in addition to the sea ice component the model includes a full primitive equation ocean and a simple energy moisture balance atmosphere we introduce a formulation of the ice thickness distribution that is lagrangian in thickness space the method is designed to use fewer thickness categories because it adjusts to place resolution where it is needed most and it is free of diffusive effects that tend to smooth eulerian distributions experiments demonstrate that the model does reasonably well in simulating the mean arctic climate we find the climate of the arctic and northern north atlantic is sensitive to resolving the ice thickness distribution when comparing the model results to a simulation with a two level sea ice model the ice thickness distribution causes ice export through fram strait to be more variable and more strongly linked to meridional overturning in the north atlantic ocean the lagrangian formulation of the ice thickness distribution allows for the inclusion of a vertical temperature profile with relative ease compared to an eulerian method we find ice growth rates and ocean surface salinity differ in our model with a well resolved vertical temperature profile in the ice and snow and an explicit brine pocket parameterization compared to a simulation with semtner zero layer thermodynamics although these differences are important for the climate of the arctic the effects of an ice thickness distribution are more dramatic and extend into the northern north atlantic sensitivity experiments indicate that five ice thickness categories with 50 cm vertical temperature resolution capture the effects of the ice thickness distribution on the heat and freshwater exchange across the surface in the presence of sea ice in these simulations

mechanisms forcing an antarctic dipole in simulated sea ice and surface ocean conditions abstract the mechanisms forcing variability in southern ocean sea ice and sea surface temperature from 600 years of a control climate coupled model integration are discussed as in the observations the leading mode of simulated variability exhibits a dipole pattern with positive anomalies in the pacific sector associated with negative anomalies in the atlantic it is found that in the pacific ocean circulation changes associated with variable wind forcing modify the ocean heat flux convergence and sea ice transport resulting in sea surface temperature and sea ice anomalies the pacific ice and ocean anomalies persist over a number of years due to reductions in ocean shortwave absorption reinforcing the initial anomalies in the atlantic sector no single process dominates in forcing the anomalies instead there are contributions from changing ocean and sea ice circulation and surface heat fluxes while the absorbed solar radiation in the atlantic is modified by the changing surface albedo the anomalies

calcite cementation during bacterial manganese iron and sulphate reduction in jurassic shallow marine carbonates faunally restricted argillaceous wackestones from the middle jurassic of eastern england contain evidence of early diagenetic skeletal aragonite dissolution and stabilization of the carbonate matrix closely followed by precipitation of zoned calcite cements and precipitation of pyrite distinctive cathodoluminescence and trace element trends through the authigenic calcites their negative 13c compositions and the location of pyrite in the paragenetic sequence indicate that calcite precipitation took place during sequential bacterial mn fe and sulphate reduction calcite 18o values are compatible with cementation from essentially marine pore fluids although compositions vary owing to minor contamination with 18o depleted late cements mg and sr concentrations in the calcites are lower than those in recent marine calcite cements this may be a result of kinetic factors associated with the shallow burial cementation microenvironments bicarbonate for sustained precipitation of the authigenic calcites was derived largely from aragonite remobilization augmented by that produced through anaerobic organic matter oxidation in the metal and sulphate reduction environments aragonite dissolution is thought to have been induced by acidity generated during aerobic bacterial oxidation of organic matter distinction of post oxic metal reduction and anoxic sulphate reduction diagenetic environments in modern carbonate sediments is uncommon outside pelagic settings and early bacterially mediated diagenesis in modern platform carbonates is associated with extensive carbonate dissolution high detrital fe contents of the jurassic sediments and their restricted depositional environment were probably the critical factors promoting early cementation these precipitates constitute a unique example of calcite authigenesis in shallow water limestones during bacterial mn and fe reduction

interpretation of recent antarctic sea ice variability 1 trends in the satellite derived antarctic sea ice concentrations 1979 2002 show pronounced increase decrease in the central pacific sector bellingshausen western weddell sector by 4 10 per decade confidence levels for these regional trends exceed 95 positive polarities of the antarctic oscillation aao lead to more less ice in the eastern ross amundsen sector bellingshausen northern weddell sector which are qualitatively opposite to the impacts of positive polarities of the el nino southern oscillation enso the mechanisms responsible for the covariability between the ice and the a aao and b enso are demonstrated over the last 24 years a positive aao trend and a slightly negative enso trend produce a spatial pattern of ice changes similar to the regional ice trends however the magnitude of the ice changes associated with the aao and enso is much smaller than the regional ice trends more local or less understood large scale processes should be investigated for the explanations

significance of crustal scale shear zones and synkinematic mafic dykes in the nagssugtoqidian orogen sw greenland a re examination the published accounts of the structural geology and tectonic evolution of the early proterozoic nagssugtoqidian orogen sw greenland require modification in several fundamental respects the geometry of the orogen has been attributed to important displacements on major conjugate shear zones and thrust zones from new field observations we are unable to confirm that crustal scale shear zones have played an important role in nagssugtoqidian tectonics the dextral component of conjugate shear zones is demonstrably sinistral and transpressive strike slip shear zones are incipient and a major thrust zone within the orogen cannot be confirmed at its projected inland location the sinistral strike slip nordre stromfjord shear zone is an order of magnitude smaller than previously thought it comprises an array of non linked segments of annealed mylonite and cannot have accommodated large displacements the dextral itivdleq shear zone is characterised by heterogeneous sinistral noncoaxial flow but compared with deformation elsewhere in the orogen it is not a large scale zone of strain localisation ikertoq thrust zone is not an orogen scale shear zone but appears to be part of a large scale rheological boundary application of an en relais fracture array model to what is classically identified as the kanga miut mafic dyke swarm suggests that the sinistral vorticity determined throughout much of the nagssugtoqidian orogen is detectable in the archean foreland up to 150 km south of the orogenic front

great slave lake shear zone canadian shield reconstructed vertical profile of a crustal scale fault zone abstract the great slave lake shear zone gslsz of the northwestern canadian shield a 25 km wide early proterozoic transcurrent dextral mylonite zone is a type example of a crustal scale fault zone profile with time 1 1 the metamorphic grade decreased from granulite to greenschist facies 2 2 the locus of high strain narrowed and jumped laterally abandoning relatively older mylonites progressively younger mylonites represent both cooler temperatures and lower pressures thus the sequence of narrowing mylonite belts represents a series of progressively shallower seated sections through the gslsz 3 3 deformation evolved through the brittle ductile transition initially producing non dilational penetrative breccias followed first by discrete non dilational faulting and subsequently by dilational quartz stockworks developing crustal scale shear zones grow to an optimum width dictated by the requirement of minimum geologically reasonable strain rates for given conditions of wall rock rheology and displacement rate independent of variations in relative plate motion mature shear zones change width and migrate laterally as a function of inferred thermally activated rheological changes within the wall rocks

theoretical strain patterns in ductile zones simultaneously undergoing heterogeneous simple shear and bulk shortening abstract structures observed in ductile shear zones show that deformation is continuous and strain is heterogeneous this leads us to define a simple model for shear strain rate when a shear zone simultaneously undergoes simple shearing and pure shearing contraction or extension the condition of continuity of deformation shows that must be a function of time integration of the deformation rate equations yields the particle paths in the deforming body from these we can determine at any time and at any point in the body the finite strain tensor lengths and orientations of the axes of the finite strain ellipsoid we can therefore define the finite strain trajectories and compare them with orientations of internal structures schistosity tension gashes the particle paths also allow us to study the progressive deformation of passive strain markers

on the link between the two modes of the ocean thermohaline circulation and the formation of global scale water masses a close link between the formation of global scale water masses such as north atlantic deep water nadw and antarctic intermediate water aaiw and two stable modes of the thermohaline circulation thc is investigated in a coupled model in the upper 2 3 km of the atlantic the thc modes are characterized by meridional overturning circulations of opposite sign with either a dominance of the aaiw cell over the nadw cell off thc mode or vice versa on thc mode a transition between these thc modes is controlled by the relationship between the densities in the source regions of formation of aaiw and nadw water masses this is shown by applying a freshwater perturbation in the region of enhanced aaiw formation in the southern ocean to obtain a hysteresis loop of the nadw circulation transitions between the two modes of the thc occur when the densities in the source regions of aaiw and nadw become comparable to each other

first description of phanerozoic radiaxial fibrous dolomite abstract the petrographic analysis and crystallographic analysis of concretionary carbonate cements coal balls from carboniferous paralic swamp deposits reveal the presence of length fast radiaxial fibrous dolomite rfd a fabric not previously reported from the phanerozoic this finding is of significance as earlier reports of phanerozoic radiaxial fibrous carbonates are exclusively of calcite mineralogy dolomite concretions described here formed beneath marine transgressive intervals within palustrine coal seams this is of significance as seawater was arguably the main source of mg2 ions for dolomite formation here data from optical microscopy cathodoluminescence electron backscattered diffraction x ray diffraction and geochemical analyses are presented to characterize three paragenetic dolomite phases and one calcite phase in these concretions the main focus is on the earliest diagenetic non stoichiometric degree of order 0 41 0 46 phase i characterized by botryoidal dolomite constructed of fibres up to 110 m wide with a systematic undulatory extinction and converging crystal axes petrographic and crystallographic evidence clearly qualifies phase i dolomite as radiaxial fibrous conversely fascicular optical fabrics were not found carbon isotope ratios 13c are depleted between 11 8 and 22 1 as expected for carbonate precipitation from marine pore fluids in organic matter rich paralic sediment oxygen isotope 18o ratios range between 1 3 and 6 0 the earliest diagenetic nature of these cements is documented by the presence of ubiquitous non compacted fossil plant remains encased in phase i dolomite as well as by the complex zoned luminescence patterns in the crystals and is supported by crystallographic and thermodynamic considerations it is argued that organic matter and specifically carboxyl groups reduced thermodynamic barriers for dolomite formation and facilitated mg caco3 precipitation the data shown here reveal a hitherto unknown level of complexity with respect to radiaxial fibrous carbonates and are of importance for those concerned with dolomite and carbonate petrography in general

origin and diagenetic evolution of ca mg fe carbonates in some coalfields of japan carbonate concretions lenses and bands in the pleistocene palaeogene and upper triassic coalfields of japan consist of various carbonate minerals with varied chemical compositions authigenic carbonates in freshwater sediments are siderite calcite ankerite dolomite ferroan magnesite in brackish water to marine sediments in the coal measures calcite dolomite ankerite siderite ferroan magnesite and in the overlying marine deposits calcite dolomite siderite most carbonates were formed progressively during burial within a range of depths between the sediment water interface and approximately 3 km the mineral species and the chemical composition of the carbonates are controlled primarily by the initial sedimentary facies of the host sediments and secondarily by the diagenetic evolution of pore water during burial based on the regular sequence and burial depth of precipitation of authigenic carbonates in a specific sedimentary facies three diagenetic stages of carbonates are proposed carbonates formed during stage i 2000 m are fe calcite and extremely high ca mg siderite the latter is exclusively in marine mudstones the supply of ca is partly from the alteration of silicates in the sediments at elevated burial temperatures after uplift calcite with low mg content precipitates from percolating groundwater and fills extensional cracks

analysis of the projected regional sea ice changes in the southern ocean during the twenty first century using the set of simulations performed with atmosphere ocean general circulation models aogcms for the fourth assessment report of the intergovernmental panel on climate change ipcc ar4 the projected regional distribution of sea ice for the twenty first century has been investigated averaged over all those model simulations the current climate is reasonably well reproduced however this averaging procedure hides the errors from individual models over the twentieth century the multimodel average simulates a larger sea ice concentration decrease around the antarctic peninsula compared to other regions which is in qualitative agreement with observations this is likely related to the positive trend in the southern annular mode sam index over the twentieth century in both observations and in the multimodel average despite the simulated positive future trend in sam such a regional feature around the antarctic peninsula is absent in the projected sea ice change for the end of the twenty first century the maximum decrease is indeed located over the central weddell sea and the amundsen bellingshausen seas in most models changes in the oceanic currents could play a role in the regional distribution of the sea ice especially in the ross sea where stronger southward currents could be responsible for a smaller sea ice decrease during the twenty first century finally changes in the mixed layer depth can be found in some models inducing locally strong changes in the sea ice concentration

decadal changes in the southern hemisphere sea surface temperature in association with el nino southern oscillation and southern annular mode the spatial structure of el nino southern oscillation enso and the southern annular mode sam which are the two most important climate modes affecting sea surface temperature sst variability in the southern hemisphere sh appear to have changed since 1999 the characteristic features of the enso and sam related atmospheric and oceanic variability in the sh are compared between two sub periods 1979 1998 and 1999 2012 using cyclostationary empirical orthogonal function analysis during the earlier period of 1979 1998 the enso is characterized by conventional eastern pacific type in which the signals in the sh constitute the pacific south america teleconnection pattern in contrast due to a shift of the active center of enso to the central pacific in the later period 1999 2012 atmospheric circulation and sst variability over the sh significantly vary moreover the sam related sst variability also shows remarkable differences before and after 1998 1999 this difference is primarily attributed to differences in the non annular spatial component of the sam between the two periods due to the changes in the spatial structure of the sam as well as those of the enso sst variability in the sh displays a marked change between the two periods detailed descriptions of the decadal changes of the sh sst in terms of interaction in the oceanic and atmospheric variability are presented along with the possible implications of this change

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

echinoderm skeletal preservation calcite aragonite seas and the mg ca ratio of phanerozoic oceans abstract the alternation between abiotic calcite and aragonite precipitation in shallow seawater and the oscillation of seawater mg ca ratio throughout the phanerozoic are both popular hypotheses echinoderms with well preserved stereom provide new empirical evidence that supports both these hypotheses analyses are reported from 29 specimens cambrian to eocene age containing ossicles preserved either as mg calcite 3 3 to 8 mole mgco3 or as mixed calcite and dolomite 5 to 12 5 mole mgco3 echinoderms with high mole mgco3 occur in the early cambrian and late carboniferous to triassic low values come from the silurian and jurassic to cretaceous the average composition of echinoderms with preserved stereom does not fall below 3 5 mol mgco3 during the phanerozoic and reaches its highest mean value of 16 0 mol mgco3 today an empirical partition coefficient of 0 03182 for modern tropical echinoids is used to indicate the mg ca ratio of ancient seawater from the mg ca ratio of fossil stereom some assumptions are involved and a likely error is calculated from the mg2 variation of modern echinoids high mean seawater mg ca ratios are calculated for early cambrian 3 3 and the late carboniferous to triassic 2 3 but never reached today s value of 5 2 low mg ca ratios 1 1 are indicated from jurassic to cretaceous echinoderms the 29 echinoderm samples plot close to first order mg ca seawater oscillations derived from geochemical models and mg ca ratios determined from fluid inclusions but considerable discrepancies exist when shorter 106 myr time intervals are considered further data and improved understanding of mg partitioning is required before accurate secular variation in the mg ca of seawater can be determined from echinoderms however they are an underused resource in this context and provide an excellent seawater archive

the influence of the large scale atmospheric circulation on antarctic sea ice during ice advance and retreat seasons antarctic sea ice a key component of the southern hemisphere climate system is influenced by several large scale modes of the atmospheric circulation antarctic sea ice variability is spatially heterogeneous and links between the atmospheric circulation modes and the sea ice variability are unclear using the observed sea ice concentration data this research isolates distinct regions of sea ice variability around antarctica and determines the advance and retreat periods for each of them the latter are then statistically linked with the observed geopotential height data to determine the atmospheric circulation pattern associated with the variability in the sea ice for each period and region the results clarify which circulation mechanism is of primary importance to sea ice variability during critical periods of the ice lifecycle in the different regions around antarctica and have potential for making estimates of past sea ice extent using the observed geopotential height data

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

micromechanisms of shear zone propagation at the brittle viscous transition our investigation of progressively strained rock samples from the margins of greenschist facies shear zones utilizes a space for time approach to reveal how the mylonitic overprint of metapsammitic and pelitic host rocks at the cap de creus involved brittle fracturing we present a set of microscale observations indicating that microfractures formed immediately prior to or coevally with a fine grained mylonite microfracturing dominated early stages of strain localization on the scale of the shear zones on the microscale centimeter long fractures facilitated strain softening by allowing enhanced fluid access thereby accelerating the dynamic recrystallization of quartz and a metamorphic reaction of biotite as these two processes produce a polyphase matrix of small dislocation poor grains that eventually form an interconnected rheologically weak phase fractures become inactive this represents a strain dependent brittle viscous transition we outline this transition in a conceptual model for the rheological evolution of mid crustal shear zones

reestablishing the circumpolar wave in sea ice around antarctica from one winter to the next remarkable correlation exists between warm water poleward winds over the ocean and low sea ice concentrations and extents over the winter sea ice pack around antarctica even to the point of continuing paterns across the ice sea boundary since the wind stress associated with poleward wind is expected to compact the ice during sea ice edge retraction we conclude that the memory of the antarctic circumpolar wave in the sea ice pack is carried from one austral winter to the next by the neighboring water temperatures since the sea ice pack retracts nearly to antarctica in austral summer

processes controlling upper ocean heat content in drake passage 1 a 16 year record of expendable bathythermograph transects across drake passage is used to examine variability in upper ocean heat content that is not associated with the annual cycle links between upper ocean heat content and anomalous heat fluxes winds two large scale climate indices and mesoscale eddies and meanders are examined results suggest that interannual variations in surface heat fluxes explain 5 to 10 of the variance in upper ocean heat content anomalous surface heat fluxes are linked to meridional wind anomalies upstream of drake passage which in turn are linked to forcing by el nino southern oscillation enso and the southern annular mode sam enso and sam are correlated with upper ocean heat content at near zero lags and statistically significant correlations occur at longer time lags as well the impact of mesoscale eddies and meanders on upper ocean heat content is explored with the use of a tracked eddy database an empirical relationship is constructed relating upper ocean heat content anomalies to eddy length scales and amplitudes eddies and meanders are estimated to account for more than one third of the nonannual cycle variance in drake passage upper ocean heat content

flow and strain patterns at the terminations of tapered shear zones with the help of corner flow theory this paper numerically analyzes the deformation pattern at the terminations of tapered shear zones the walls of which are rigid and move parallel to each other in opposite directions the overall flow pattern is characterized by curvilinear particle paths that show convexity towards and opposite to the tapering direction respectively for low 10 inclinations of the wall verging opposite to the sense of wall movement in tapered shear zones there are two distinct fields of instantaneous shortening and extension parallel to the direction of wall movement numerical models reveal that the finite strain distributions are generally asymmetrical with larger strain concentration occurring near the wall verging opposite to sense of wall movement the s foliation trajectories show a curvilinear pattern convexing against the tapering direction the analysis of rotationality vorticity indicates that the sense of vorticity near the synthetically verging wall is reverse to the sense of wall movement however wk is one everywhere within the shear zone

fossil plants from the eocene london clay the use of pyrite textures to determine the mechanism of pyritization pyritized twigs and roots from the eocene london clay of se england were studied to gain a better understanding of the process of pyritization by investigating pyrite textures in relation to cell type and quality of preservation highly polished sections and fractured surfaces taken from 124 specimens were examined using optical microscope and sem the latter equipped to map pyrite and carbon pyrite textures include microcrystalline framboidal massive polycrystalline and subhedral or euhedral forms the highest fidelity of preservation is always associated with microcrystalline pyrite precipitation on wall surfaces with subsequent infilling of cells with framboids or polyhedra preventing compression during burial but contributing nothing to actual ultrastructural preservation ultrastructurally parenchymatous cell walls are coalified whereas microcrystalline pyrite plus coalified material were observed within lignified cell walls in all four stages of pyritization are documented observations are interpreted in the light of recent experiments on pyritization of living material and the chemistry of pyrite formation in anoxic environments involving an aqueous and hence mobile fes cluster complex as a precursor the complexity of the fossilization process is reflected in the presence of different textures in adjacent cells of the same tissue this demonstrates the development of isolated chemical microenvironments as ph and eh vary in response to decay and mineralization and pyrite overgrowths within a cell indicate local microenvironmental changes through time

coupled ocean atmosphere feedback in the southern annular mode abstract previous studies have demonstrated that while the southern annular mode sam is an intrinsic feature of the atmosphere it projects strongly onto the ocean and sea ice properties and circulation this study investigates the extent of back interaction whereby these oceanic sam anomalies feed back to the atmosphere a comparison between atmosphere only and full coupled climate models demonstrates that air sea interactions in the coupled system act to increase the persistence of the sam in the atmosphere to identify the nature of feedback from the ocean to the atmosphere ensemble experiments are carried out in both atmosphere only and full coupled models whereby a continuous sam like sea surface temperature sst anomaly is imposed both coupled and uncoupled experiments show a direct thermal response that affects the lower tropospheric temperature and surface meridional winds an indirect upper troposphere wide response is also seen whose characteristics are sensitive to the coupling for the

x ray photoelectron emission spectromicroscopic analysis of arborescent lycopsid cell wall composition and carboniferous coal ball preservation abstract two alternative processes complicate understanding of the biochemical origins and geochemical alteration of organic matter over geologic time selective preservation of original biopolymers and in situ generation of new geopolymers one of the best constrained potential sources of bio and geochemical information about extinct fossil plants is frequently overlooked permineralized anatomically preserved plant fossils allow analysis of individual cell and tissue types that have an original biochemical composition already known from living plants the original composition of more enigmatic fossils can be constrained by geochemical comparisons to tissues of better understood fossils from the same locality this strategy is possible using synchrotron based techniques for submicron scale imaging with x rays over a range of frequencies in order to provide information concerning the relative abundance of different organic bonds with x ray absorption near edge spectroscopy in this study x ray photoelectron emission spectromicroscopy x peem was used to analyze the tissues of lepidodendron one of the lycopsid trees that were canopy dominants of many pennsylvanian coal swamp forests its periderm or bark the single greatest biomass contributor to many late paleozoic coals is found to have a greater aliphatic content and an overall greater density of organic matter than lignified wood because x peem allows simultaneous analysis of organic matter and matrix calcite in fully mineralized fossils this technique also has great potential for analysis of fossil preservation including documentation of significant traces of organic matter entrained in the calcite crystal fabric that fills the cell lumens

geochemistry of autochthonous and hypautochthonous siderite dolomite coal balls foord seam bolsovian upper carboniferous nova scotia canada abstract the 11 13 m thick foord seam in the fault bounded stellarton basin nova scotia is the thickest seam from the euramerican floral province known to contain coal balls in addition to the first discovery of autochthonous coal balls in the foord seam nova scotia its shale parting also contains hypautochthonous coal balls with histologically preserved plant structures the coal ball discovery helps fill a stratigraphic gap in coal ball occurrences in the upper carboniferous bolsovian of euramerica the autochthonous and hypautochthonous coal balls have a similar mineralogical composition and are composed of siderite 81 100 dolomite ankerite 0 19 minor quartz and illite and trace amounts of calcite similar is also their permineralizing mineralogy which consists of dolomite ankerite and siderite their low pyrite content and carbonate mineralogy and nonmarine origin differentiates the foord seam coal balls from other euramerican coal ball occurrences a preliminary geochemical model which is based on oxygen and carbon isotopic data indicates that siderite in both the autochthonous and hypautochthonous coal balls is of very early diagenetic nonmarine origin from 13 c enriched bicarbonate derived from bacterial methanogenesis of organic matter

theoretical and natural strain patterns in ductile simple shear zones abstract a simple empirical model representing the variation of shear strain throughout a simple shear zone allows us to determine the evolution of finite strain as well as the progressive shape changes of passive markers theoretical strain patterns intensity and orientation of finite strain trajectories deformed shapes of initially planar equidimensional and non equidimensional passive markers compare remarkably well with patterns observed in natural and experimental zones of ductile simple shear intensity and orientation of schistosity shape changes of markers foliation developed by deformation of markers the deformed shapes of initially equidimensional and non equidimensional passive markers is controlled by a coefficient p the product of 1 1 the ratio between marker size and shear zone thickness 2 2 the shear gradient across the zone for small values of p approximately p p lead to retort shaped markers this theoretical study also allows us to predict throughout a simple shear zone various relationships between the principal finite strain trajectory planar passive markers and foliations developed by deformation of initially equidimensional passive markers

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

ocean circulation variations associated with the antarctic circumpolar wave altimeter data analysis indicates persistent sea surface height ssh anomalies propagating eastward about the antarctic continent the spatial and temporal characteristics match variations in the atmosphere and sea surface temperature sst that are associated with the antarctic circumpolar wave acw during the observation time period the ssh appears quasiperiodic with a dominant 4 year period and 180 longitude wavelength thus the ssh signature of the acw appears as two anomalies on opposite sides of the antarctic continent propagating eastward at 10 cm s the ssh response to observed wind forcing agrees in terms of amplitude and phase with simple quasigeostrophic dynamics

formation of secondary pyrite and carbonate minerals in the lower williams lake tailings basin elliot lake ontario canada the lower williams lake tailings which resulted from u milling operations during the late 1950s and early 1960s cover an area of 2 ha in a small bog under partial water cover the tailings are underlain by a sand unit containing decaying organic material above the natural base consisting of sand till and gravel the tailings are composed predominantly of quartz muscovite k feldspar plagioclase and clinochlore residual pyrite grains displaying angular to subangular particles measuring less than 1 to 250 m occur in concentrations ranging from trace to approximately 6 wt framboidal pyrite has formed within the tailings basin in association with organic rich material the appearance of framboidal pyrite in the tailings indicates a reversal of the oxidation process and reprecipitation of fe sulfides in addition the tailings include calcite calcian siderite fe oxyhydroxides and fe si oxyhydroxides as secondary precipitates and replacement products groundwaters in the tailings and the underlying units are saturated with respect to gypsum and siderite these and the other saturation indices calculated for calcite goethite and barite are consistent with the secondary mineralogy of the tailings conditions promoting the formation of pyrite can be described as neutral to weakly alkaline and reducing assisted by microbial activity this study provides the first account of secondary carbonates and framboidal pyrite in the elliot lake tailings the existing environmental conditions at the site are favorable for the desired site rehabilitation

the impacts of el nino on the observed sea ice budget of west antarctica we assess the impact of el nino induced wind changes on seasonal west antarctic sea ice concentrations using reanalysis data and sea ice observations a novel ice budget analysis reveals that in autumn a previously identified east west dipole of sea ice concentration anomalies is formed by dynamic and thermodynamic processes in response to el nino generated circulation changes the dipole features decreased increased concentration in the ross sea amundsen and bellingshausen seas thermodynamic processes and feedback make a substantial contribution to ice anomalies in all seasons the eastward propagation of this anomaly is partly driven by mean sea ice drift rather than anomalous winds our results demonstrate that linkages between sea ice anomalies and atmospheric variability are highly nonlocal in space and time therefore we assert that caution should be applied when interpreting the results of studies that attribute sea ice changes without accounting for such temporally and spatially remote linkages

are coal balls rare a cyclostratigraphic analysis of coal ball occurrence in north america abstract from the perspective of phanerozoic time coal balls are rare apparently limited to a 24 m y interval 323 299 ma in the pennsylvanian and earliest permian yet within this interval coal balls occur in many coals approximately 82 transgressive regressive sedimentary cycles have been described for the midcontinent illinois and appalachian basins of north america during the mid to late pennsylvanian one third 27 82 have coal balls including 57 of major cycles 36 of intermediate cycles and 16 of minor cycles coal ball occurrence in the donets basin is similar over an interval of about 4 m y 315 311 ma latest bashkirian to mid moscovian 39 11 28 of transgressive regressive cycles have coal balls as north american paleoclimate became drier tree ferns replaced lycopsids as the dominant plant in peat swamps at the desmoinesian missourian boundary and coal ball occurrence declined overall 47 of cycles 19 40 with lycopsid or cordaitean dominance have coal balls whereas 19 8 42 of cycles with tree fern dominance have coal balls p this pattern may reflect the relative abundance of coal in the late pennsylvanian with drier paleotropical climates in the missourian virgilian leading to less paleotropical coal fewer mines and a lower probability of discovering missourian and virgilian coal balls however average cycle duration decreased from 150 kyr in the desmoinesian to 100 kyr in the missourian and virgilian and faster rates of relative sea level rise could have affected coal ball abundance particularly if coal balls formed in marine swamps with more rapid transgression leading to thinner coals or to freshwater coals directly overlain by marine sediments rygel et al 2008 suggested that missourian virgilian cycles recorded more erosional relief than desmoinesian cycles consistent with increased amplitude and rates of sea level rise during each glacial eustatic cycle changes in missourian virgilian cycles may have been augmented by stratigraphic attenuation as sediment filled the antecedent topography

cordaiteans in paleotropical wetlands an ecological re evaluation abstract cordaiteans in cordaite dominated permineralized peat from pennsylvanian coals in iowa have been reconstructed as mangroves using root anatomy peat taphonomy and geochemical data macrofloral palynofloral and conodont biostratigraphy indicate that these peats come from the latest atokan blackoak coal and earliest desmoinesian cliffland coal mid moscovian both in the kalo formation thus their depositional setting can be used to evaluate the mangrove hypothesis in recent mires thick mangrove peats have accumulated in tropical to subtropical carbonate systems in contrast thick tropical freshwater peats have accumulated in siliclastic systems kalo formation coals which we interpret as freshwater deposits formed in siliciclastic depositional settings similar to those of modern tropical freshwater peat and to other pennsylvanian coals in north america interpreted as freshwater deposits in the late atokan and earliest desmoinesian mid moscovian cordaiteans and tree ferns predominated in the western interior and illinois basins lycopsids and cordaiteans predominated in the appalachian and donets basins the scarcity of lycopsid only mires in north america during the late atokan earliest desmoinesian mid moscovian suggests drier climates than during the mid to late desmoinesian late moscovian rather than indicating mangrove swamps cordaite dominated peat may indicate climates with a low rain season although most plants in cordaite dominated peat probably grew in freshwater coastal mires in climate zones with seasons of low rain may harbor mangrove taxa the changuinola swamp of panama a modern peat accumulating wetland that has a low rain season is a possible analog of ancient cordaite dominated mires in changuinola most plants require freshwater however mangroves sustained by salt water influx into the swamp grow along the seaward edge and along blackwater creeks the low rain season hypothesis has implications for understanding rainfall amount and continuity during pennsylvanian cyclothem deposition the floral succession in diverse cordaite coals from cordaiteans to tree ferns to lycopsids suggests increasingly wet climate during coal accumulation the position of these coals immediately above the sequence boundary suggests humid climate during early glacial melting for these cyclothems

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

carbonate petrology and geochemistry of pennsylvanian coal balls from the kalo formation of iowa abstract coal balls are carbonate and pyrite concretions enclosing uncompressed peat primarily found in pennsylvanian and earliest permian paleotropical coals petrographic and microprobe analysis of coal balls from the mid moscovian latest atokan or earliest desmoinesian williamson no 3 mine kalo formation from lucas county iowa indicates that pyrite was the earliest mineral to form followed by high mg calcite average 13 9 mol mgco 3 which is also high in sr 700 1500 ppm suggesting that the kalo formation coal balls formed in response to the incursion of marine water into the mire the high mg calcite has an unusual growth habit radiating arrays of bladed polycrystals which look like distorted triangles with elongated apices when cut parallel to the basal plane these high mg calcite polycrystals have low mg non ferroan calcite rims consistent with diagenesis in meteoric water the presence of early high mg and low mg non ferroan calcite in the williamson no 3 coal balls suggests that these coal balls formed in a hydrologically dynamic environment most of the remaining cements in the kalo formation coal balls are low mg ferroan calcite consistent with burial diagenesis these cements retain regions of low mg and high mg calcite suggesting that they are neomorphs of the early high mg calcite cement fibers in the vascular bundle supports of cordaites principalis leaves have narrow rims of dolomite that appear unique to this species the presence of high mg calcite in the williamson no 3 coal balls supports the stopes and watson phil trans roy soc london b 1909 200 167 218 model of coal ball formation as a result of incursions of marine water into coastal mires it conflicts with stable isotopic data which suggests that most coal ball cements formed in meteoric water however in our samples the most common cement is diagenetically altered low mg ferroan calcite which might yield meteoric oxygen isotopic values excellent preservation of plant fossils in coal balls is not necessarily correlated with the presence of original cement

slow oceanic teleconnections linking the antarctic circumpolar wave with the tropical el nino southern oscillation a case study for the period 1982 1994 shows that a major source for the antarctic circumpolar wave is in the western subtropical south pacific where interannual anomalies in sea surface temperature sst and precipitable water prwat form once established these interannual anomalies in tandem with anomalies in sea level pressure slp move south toward the southern ocean the system then migrates east around the globe through a combination of oceanic advection with the antarctic circumpolar current and ocean atmosphere coupling the coincidence of interannual anomalies in sst slp and prwat indicates the extratropical ocean and atmosphere are tightly linked on these timescales large portions of the interannual sst anomalies branch advectively northward into the south atlantic and indian oceans ultimately reaching the tropics in each basin some 6 8 years after appearing in the low latitude pacific this constitutes a slow oceanic teleconnection that is unique in climate dynamics made possible by the continuity of earth s oceans via the southern ocean in the tropical indian ocean these interannual anomalies move east and arrive at the indo pacific transition in advance of the trans pacific propagation of the respective el nino southern oscillation enso phases the interannual sst and prwat anomalies that appear in the subtropical south pacific are directly linked with the enso cycle on the equator through anomalous vertical convection and a regional overturning cell in the troposphere the same cell that initiates fast planetary waves in the atmosphere that carry enso signals around the southern hemisphere on much shorter timescales

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

catchment processes and the quantity and composition of sediment delivered to terminal basins discussion although the quantities of sediment exported to the sea by large rivers are relatively well known information on mineralogical and geochemical characteristics is less readily available quantity and composition are strongly influenced by tectonic environment and also by both present and past climate an analysis of diagenetic processes in fine grained clastic sediments suggests that bed parallel changes in the intensity of diagenetic modification reflected in phenomena such as cemenstone horizons and marked changes in authigenic mineral assemblages sulphides carbonates silicates could be explained by changes in sediment supply rate driven by climatic fluctuations it is less easy to explain fluctuations in detrital sediment composition diagenetic reorganization would appear to be the most common cause of marked local compositional contrast in mudstones

what sets the mean transport through drake passage twelve experiments with two coarse resolutions of a global ocean model using a variety of surface forcings are analyzed to address the question of what sets the mean transport through drake passage seven of the experiments do not have an active sea ice model but the remaining five do previous theories have suggested that the drake passage transport is governed by the cape horn sverdrup transport or alternatively is proportional to the square root of the meridional ekman transport at the latitude of drake passage the results presented here do not support either of these theories the drake passage transport depends quite strongly on the isopycnal diffusivity parameter in the model and less strongly on the background vertical diffusivity and horizontal viscosity parameters however when the magnitudes of these parameters are fixed the results show a very strong correlation between drake passage transport and both the strength of the meridional ekman transport at the latitude of drake passage and the thermohaline circulation off the antarctic shelf the relationships are monotonic but not linear the best estimate is that the meridional ekman transport drives 100 sv of drake passage transport while the remaining 30 sv are driven by the global thermohaline circulation

spherulitic siderites in the holocene coastal deposits of korea eastern yellow sea elemental and isotopic composition and depositional environment abstract siderite concretions are recovered from both freshwater unit ii and tidal unit i deposits in the holocene macrotidal flat of kyunggi bay west coast of korea siderites from both units show a spherulitic and well rounded texture and well developed equant rhombs on the external surfaces the size of the concretions in unit ii 50 150 m in diameter is normally larger than that in unit i 10 20 m the siderites in unit ii are chemically pure and highly enriched in fe whereas those of unit i are relatively impure and distinctly zoned demarcating high mn up to 69 1 mol in the core and high fe up to 75 9 mol in the margin within siderites of unit i substitution for fe by ca and mg reaches up to 20 3 mol mean 15 1 mol and 16 1 mol mean 12 6 mol respectively bulk 18 o values 0 7 to 1 3 peedee belemnite pdb for siderites in unit i are relatively higher than those 7 1 to 0 5 pdb in unit ii regardless of units siderite 13 c values 21 3 to 11 2 pdb are persistently low indicating microbially mediated precipitation at shallow burial depth extensive mn ca and mg substitution coupled with enrichment of 18 o in the siderites of unit i seems to reflect marine influence during the holocene transgression the occurrence of early diagenetic siderites provides supporting evidence on the depositional environment marine vs non marine of the holocene muddy coastal deposits of korea eastern yellow sea

observed evidence of an impact of the antarctic sea ice dipole on the antarctic oscillation abstracta lagged maximum covariance analysis mca is applied to investigate the linear covariability between monthly sea ice concentration sic and 500 mb geopotential height z500 in the southern hemisphere sh the dominant signal is the atmospheric forcing of sic anomalies throughout the year but statistically significant covariances are also found between austral springtime z500 and prior sic anomalies up to four months earlier the mca pattern is characterized by an antarctic dipole adp like pattern in sic and a positively polarized antarctic oscillation aao in z500 such long lead time covariance suggests the forcing of the aao by persistent adp like sic anomalies the leading time of sic anomalies provides an implication for skillful predictability of springtime atmospheric variability

the antarctic circumpolar wave in a coupled ocean atmosphere gcm abstract a phenomenon called the antarctic circumpolar wave acw suggested earlier from fragmentary observational evidence has been simulated realistically in an extended integration of a max planck institute coupled general circulation model the acw both in the observations and in the model constitutes a mode of the coupled ocean atmosphere sea ice system that inhabits the high latitudes of the southern hemisphere it is characterized by anomalies of such climate variables as sea surface temperature sea level pressure meridional wind and sea ice that exhibit intricate and evolving spatial phase relations to each other the simulated acw signal in the ocean propagates eastward over most of the high latitude southern ocean mainly advected along in the antarctic circumpolar current on average it completes a circuit entirely around the southern ocean but is strongly dissipated in the south atlantic and in the southern indian ocean just marginally maintaining statistical significance in these areas

on the mechanism of the antarctic circumpolar wave abstract the variability in the subpolar southern hemisphere is studied with a coupled atmosphere ocean sea ice model the ecbilt after having reached an approximate statistical equilibrium in coupled mode without flux corrections a subsequent 1000 yr integration is performed and analyzed a singular value decomposition of austral winter sst anomalies and 800 hpa geopotential height in the antarctic circumpolar current region reveals a mode of covariability that resembles the observed antarctic circumpolar wave subsequent analysis of this mode shows that it is basically an oscillation in the subsurface of the ocean additional experiments suggest that it is generated by the advective resonance mechanism the oscillation is excited by the dominant modes of variability in the atmosphere whereas the timescale is set by the ratio of the horizontal scale of these atmospheric modes and the advection velocity of the mean oceanic currents the atmospheric response mainly consists of a local temperature adjus

anatomically preserved plants in siderite concretions in the shale split of the foord seam mineralogy geochemistry genesis upper carboniferous canada abstract a shale split in the well studied foord seam upper carboniferous stellarton basin nova scotia provides a rare opportunity to study little known siderite concretions with anatomically preserved plants from a limnic basin siderite concretions occur throughout the split commonly as sheet like inter connected lepidodendrid logs or less frequently as spherical masses they are typically vuggy a sample of 14 stratigraphically oriented concretions in the split shows that primary siderite varies from 45 to 80 wt due to selective replacement by 5 to 40 ferroan dolomite or ankerite in plant tissues these two minerals show large mg fe and mg ca variability and are fezoned clay content ranges from trace to 20 and quartz from 5 to 10 partial cell wall destruction by erosion and changeable oxic anoxic conditions prior to siderite permineralization resulted in preservation mainly of the more resistant plant tissues on average carbon from siderite is isotopically heavier 4 8 1 9 0 00 than that from dolomite 7 2 1 1 0 00 the distribution of and the positive correlation between 13 c and 18 o probably reflects the two fractionation processes associated with methanogenesis and dolomitization respectively in the genetic history of the siderite concretions in the split siderite concretions formed diagenetically early from bicarbonate under reducing conditions in a slightly alkaline freshwater environment that precluded calcite deposition

orientation of nucleating faults in anisotropic media insights from three dimensional deformation experiments abstract physical experiments have been undertaken to investigate the influence of planar rheological anisotropy on the orientation of fault structures in three dimensional flow associated with layer normal shortening the experimental results indicate that plane strain is a special case characterised by the lowest angle between the faults and the principal extension direction for any combination of rheology and flow type during progressive pure shear a model is proposed wherein the role of the anisotropy appears to be two fold first it determines that shear bands operate internally by a mechanism involving rotating slip surfaces during fault nucleation the initial orientation of the faults is determined by the optimisation of the driving processes in the propagating shear bands as a partial function of the angle they make with the external anisotropy second it induces directionally dependent variation in the resistance to flow which manifests itself differently according to the symmetry of the strain ellipsoid in three dimensions x y 1 z in flattening flow it is proposed that anisotropy induced geometrical hardening leads to an increase in the angles made by the shear bands with the principal extension directions of the deformation in constriction the same effect is seen in xz sections but in yz sections it is suggested that the wide range of fault orientations observed is due to anisotropy induced geometrical softening it is possible that the low angle of dip of crustal scale extensional detachment faults may reflect anisotropic behaviour of the lower continental crust

on the interannual variability of ocean temperatures around south georgia southern ocean forcing by el nino southern oscillation and the southern annular mode abstract the ocean around south georgia in the southwest atlantic sector of the southern ocean is highly productive with large stocks of antarctic krill supporting extensive colonies of marine and land based predators the operation of this ecosystem is strongly influenced by physical forcings and the role of the el nino southern oscillation enso phenomenon has been highlighted previously here we examine in detail the transmission of enso signals to south georgia and investigate other sources of interannual variability enso variability generates anomalies in sea surface temperature sst across the south pacific via atmospheric teleconnections these anomalies are advected toward south georgia within the antarctic circumpolar current acc and previous studies have focussed on long period advection order of 2 3 years from the southwest pacific we observe here however that the region close to the antarctic peninsula in the southeast pacific is especially susceptible to enso forcing via anomalous meridional winds this induces sst anomalies that are advected to south georgia on a much more rapid timescale order 5 6 months the phasing of these teleconnections is such that anomalies that reach the southeast pacific from farther west tend to be reinforced here by air sea ice interaction we also find an important role for the southern annular mode sam in determining sst variability at south georgia this is a circumpolar mode of climate variability and thus can readily influence local sst at south georgia directly the sam is however not perfectly zonally symmetric and like enso has a particular impact on meridional winds in the southeast pacific the average timescale for sam influence on south georgia sst is shorter than that of enso since it includes a stronger component of direct local forcing the south georgia ecosystem is not self sustaining with import of krill from breeding and nursery grounds upstream in the acc being important we speculate here that these varying meridional winds close to the antarctic peninsula play a direct role in promoting restricting the injection of shelf waters and the krill therein into the acc following which anomalies in krill density would be advected toward south georgia this offers a dynamical mechanism that might contribute to interannual changes in biological communities at south georgia in addition to existing theories both sam and enso have shown long period changes in recent decades with enso exhibiting a higher preponderance of el nino events compared with la nina events and the sam showing a marked trend toward a higher index state such long period behaviour is likely to induce changes in the south georgia ecosystem via their impacts on advection and sst for which an understanding of the physical mechanisms elucidated here will be key to unravelling

terminations of ductile shear zones abstract we propose a plane strain model for ductile shear zone terminations in rocks that otherwise record no visible shear strain this model may explain the strain distribution patterns in naturally occurring terminations of shear zone which show in the xz plane of finite strain 1 a decrease in the area of finite strain and in strain intensity ellipsoidal or lens like feature and 2 an increase in the strained area as strain intensity decreases splay like or horse tail feature

geochemistry of meteoric calcite cements in some pleistocene limestones in this study the stable isotope and trace element geochemistries of meteoric cements in pleistocene limestones from enewetak atoll western pacific ocean cat island bahamas and yucatan were characterized to help interpret similar cements in ancient rocks meteoric calcite cements have a narrow range of 18o values and a broad range of 13c values in each geographical province these pleistocene cements were precipitated from water with stable oxygen isotopic compositions similar to modern rainwater in each location enewetak calcite cements have a mean 18o composition of 6 5 0 pdb and 13c values ranging from 9 6 to 0 4 0 pdb sparry calcite cements from cat island have a mean 18o composition of 4 1 0 and 13c values ranging from 6 3 to 1 1 0 sparry cements from yucatan have a mean 18o composition of 5 7 0 and 13c values of 8 0 to 2 7 0 the mean 18o values of these pleistocene meteoric calcite cements vary by 2 4 0 due to climatic variations not related directly to latitude the 13c compositions of meteoric cements are distinctly lower than those of the depositional sediments variations in 13c are not simply a function of distance below an exposure surface meteoric phreatic cements often have 13c compositions of less than 4 0 0 which suggests that soil derived co2 and organic material were washed into the water table penecontemporaneous with precipitation of phreatic cements concentrations of strontium and magnesium are quite variable within and between the three geographical provinces mean strontium concentrations for sparry calcite cements are for enewetak atoll 620 ppm 510 ppm for cat island 1200 ppm 980 ppm and for yucatan 700 ppm 390 ppm equant cements intraskeletal cements and bahamian cements have higher mean strontium concentrations than other cements equant and intraskeletal cements probably precipitated in more closed or stagnant aqueous environments bahamian depositional sediments had higher strontium concentrations which probably caused high strontium concentrations in their cements magnesium concentrations in pleistocene meteoric cements are similar in samples from enewetak atoll mean 1 00 mol mgco3 0 60 mol mgco3 and cat island mean 0 84 mol mgco3 0 52mol mgco3 but yucatan samples have higher magnesium concentrations mean 2 20 mol mgco3 0 84mol mgco3 higher magnesium concentrations in some yucatan cements probably reflect precipitation in environments where sea water mixed with fresh water

comments on southern mid to high latitude variability a zonal wavenumber 3 pattern and the antarctic circumpolar wave in the csiro coupled model abstract variability in the southern atmospheric circulation at mid to high latitudes with a dominant quasi stationary wavenumber 3 pattern has been reported in many observational studies the variability is barotropic in nature with signals in the middle troposphere as well as at the atmosphere ocean interface moreover there are preferred fixed centers for the strongest anomalies these features are well reproduced by the commonwealth scientific and industrial research organisation coupled model on various timescales on the interannual timescale an index of the modeled wavenumber 3 pattern shows little correlation with the modeled southern oscillation index suggesting that the variability associated with wavenumber 3 anomalies is separate to modeled enso like events however the variation of the pattern index is strikingly similar to and highly correlated with the modeled oceanic variability the associated oceanic anomalies move eastward and are similar to those of the observed antarctic circum

forcing of the antarctic circumpolar wave by el nino southern oscillation teleconnections we address several issues regarding the antarctic circumpolar wave acw these include the extent to which the acw is related to el nino southern oscillation enso cycles and the need to reconcile differences between the observed zonal wavenumber 2 pattern and the wavenumber 3 pattern found in coupled ocean atmosphere models in the present study we revisit the sea surface temperature sst signal of the observed acw we find that the associated sst variations may be decomposed into several empirical orthogonal functions eofs that are linearly independent the first four eofs describe 84 of the total variance on timescales of 3 7 years and superposition of sst signals of the four eofs reproduces sst signals of the observed acw given that eof analysis can only describe standing oscillations we then employ complex eof ceof analysis suitable for studying propagating waves the first two ceofs denoted ceofsst1 and 2 account for 70 of the total variance and the sst variability reconstructed from them again reproduces the observed acw the real part of ceofsst1 44 of the total variance is similar to the first real eof eofsst1 both eofsst1 and ceofsst1 may be identified with enso and have a wavenumber 2 zonal pattern in the southern middle to high latitudes ceofsst1 is the major constituent of the acw in the period of 1981 1997 the associated atmospheric circulation displays a pacific south america psa pattern statistical analyses demonstrate that the psa pattern teleconnected to enso is the major mechanism that forces this principal constituent of the acw ceofsst2 26 of the total variance has a zonal wavenumber 3 pattern in the same latitude band similar to that simulated by several coupled models we suggest that if enso is not adequately resolved in coupled models but structures with zonal wavenumber 3 pattern are then the modeled acw would appear to have a zonal wavenumber 3 pattern

origin and significance of compositional layering in late precambrian sediments blue ridge province north carolina u s a abstract basal arkosic sandstones of the late precambrian grandfather mountain formation contain smallscale deformation zones usually 1 mm thick and spaced 5 to 10 mm apart the deformation zones are composed of green phengitic muscovite which concentrated in the deformation zones during pressure solution removal of quartz assuming plane strain the deformation zones have lost 34 of their area due to solution of quartz and axial ratios of strain ellipses are on the order of 16 1 in the principal plane the deformation zones and associated tight to isoclinal folds in the basal arkoses form a structural style which is transitional between ductile deformation zones in the crystalline basement and kink style folding in the interbedded siltstones and arkoses of the upper grandfather mountain formation since deformation zones may be more common in sedimentary rocks and low grade metasediments than previously realized one should exercise caution when using penetrative fabrics to unravel the structural history of multiply deformed rocks small scale deformation zones can be misinterpreted as a crenulation cleavage cutting an earlier penetrative fabric

formation and distribution of coal balls in the herrin coal pennsylvanian franklin county illinois basin usa large areas of concentrated coal balls permineralized peat up to 4 m thick obstructed longwall mining in the herrin coal at the old ben no 24 mine the largest coal ball area mapped contained 1500 m 3 several areas contained 400 m 3 of coal balls in mine mapping established that there were two types of roof freshwater and marine and that the coal balls were spatially correlated with the marine roof units regional studies and local data revealed that the younger freshwater energy shale mud originally covered all of the peat deposited at the mine but the mud was locally removed during a period of erosion the great majority of coal balls are found within the coal seam where they were permineralized in situ by carbonates some coal balls are found exposed on the eroded coal surface and others are within the channel fill associated with the erosion which predates any marine sedimentation thus the mineralization of the coal balls was synchronous with the erosion of the energy shale mud data from c and o isotope geochemical and mineralogical analyses of coal balls and associated materials were used to refine a depositional model of coal ball formation the concentrated coal ball areas were created by the triggered degassing of co 2 from partially decomposed peat in the presence of cations from fresh waters 13 c 12 c ratios in these coal balls average 23 9 13 c 12 c ratios as low as 34 occurring in the most concentrated coal balls are consistent with co 2 produced by anaerobic oxidation of methane top of seam coal balls were formed later and show slight to strong marine influence their 13 c 12 c ratios average 10 8

manganese fluxes from mississippi delta sediments abstract massive sediment deposition on the mississippi river delta establishes reducing conditions sufficient to bring about mn dissolution in the top millimeters of sediment as a result significant fluxes of dissolved mn pass from the delta sediments to the overlying water column this process is examined by study of chemical partitioning of mn in river particulates and delta sediments and from interstitial water chemistry remobilized mn is actively transported away from the delta area with aluminosilicate detritus thereby providing excess mn to the deep gulf of mexico at the expense of the delta sediments

the southern hemisphere evolution of enso during 1981 99 abstract improvements in observing systems over the last two decades now permit more detailed examinations of variability in the mid and high latitude southern hemisphere circulation in this study the leading modes of variation in the extratropical sea surface temperature are identified from the reynolds optimal interpolation oi dataset between november 1981 and december 1999 although attempts were made to exclude the strong contribution due to el nino southern oscillation enso by confining the analysis between 60 and 15 s the three leading modes were all enso related the first eof with 13 9 of the monthly variance lags the southern oscillation index soi by 2 months and depicts sea temperature variations characteristic of mature enso events the second eof accounting for 8 8 of the variance shows a precursor pattern that is strongly correlated with the soi and with eof1 which it leads by 9 10 months this pattern is characterized by anomalies west and east of australia extending north

origin and incremental evolution of brittle ductile shear zones in granitic rocks natural examples from the southern abitibi belt canada abstract metre scale shear zones developed in the mooshla granitic pluton exhibit a plethora of internal mesoand microstructures revealing their mode of nucleation growth and termination the subvertical e w brittle ductile shear zones are developed in the most isotropic part of the intrusion and consist of phyllonites characterized by mylonitic fabrics and well developed down dip mineral lineations they are exposed on a single large and flat outcrop perpendicular to the mineral lineation these brittle ductile shear zones are in close spatial association with a fracture system along which they have nucleated and propagated joints fractures and brittle faults contain abundant evidence of ductilely deformed and recrystallized minerals suggesting that they underwent ductile shearing after their formation the deformation was accompanied by the influx of a metasomatic fluid which altered original fe mg bearing minerals and plagioclase into quartz epidote chlorite sericite and carbonate that precipitated in dilatant fractures and narrow breccia zones we recognize two different types of lateral terminations i shear zones that terminate into joints and fractures that are parallel or oblique to the shear direction and ii curved segments of shear zones that connected with neoformed splay fractures at high angle to the shear direction in the latter case sharp bending and severe perturbation of the shear zone orientation occur at the shear zone termination where ductile shearing is transfered into an adjacent shear zone via dilatational fractures this demonstrates that shear zones tended to grow towards each other and coalesce to form a well developed anastomosing network we propose that narrow dilatational fractures and joints acted as paleo weakness planes along which fluid rock interaction and resulting reaction softening occurred the deformation scenario involves episodic fluid drawn into dilatant sites responsible for cyclic fluid pressure fluctuation in the system dilatancy related fracturing and reaction softening lead to deformation under brittle to plastic conditions and to shear strain localization