seismic anisotropy tracing plate dynamics in the mantle elastic anisotropy is present where the speed of a seismic wave depends on its direction in earth9s mantle elastic anisotropy is induced by minerals that are preferentially oriented in a directional flow or deformation earthquakes generate two seismic wave types compressional p and shear s waves whose coupling in anisotropic rocks leads to scattering birefringence and waves with hybrid polarizations this varied behavior is helping geophysicists explore rock textures within earth9s mantle and crust map present day upper mantle convection and study the formation of lithospheric plates and the accretion of continents in earth history

cementation in cold water bryozoan sand tasmania australia cold water 3 11 c carbonate is the predominant sediment on the tasmanian shelf calcitic skeletal grains bryozoa foraminifera echinoderms etc predominate over aragonitic gastropods etc ones non skeletal grains are mostly micritic intraclasts with some pellets fibrous spherulitic and rhombohedral calcite submarine cements range up to 90 in the bryozoan sand x ray analyses show that the bryozoan sand is characterized by a spectrum of calcites low to high magnesian and some aragonite a uniform spread of mg concentrations from 0 06 to 2 48 wt indicates 3 10 c ambient water temperatures the mn 10 360 ppm and fe 176 2499 ppm concentrations increase with increasing mg values due to the formation of impure caco3 phases the sr content in bryozoan sand bryozoa 3200 ppm sr decreases with increasing rhombohedral calcite cement as low mg calcite precipitating from 3 c sea water would have 1350 ppm sr the bryozoan sand grains with fibrous spherulitic calcite cements have high sr concentrations 4470 7000 ppm in the same range as in aragonitic detected only by x ray analyses bryozoan sand grains the spherulitic calcite cements are either pseudomorphs after original aragonite cements or these calcite cements and aragonite were inverted from fibrous spherulitic vaterite a predominant caco3 polymorph at temperatures 10 c

six decades of glacier mass balance observations a review of the worldwide monitoring network glacier mass balance is the direct and undelayed response to atmospheric conditions and hence is among the essential variables required for climate system monitoring it has been recognized as the largest non steric contributor to the present rise in sea level six decades of annual mass balance data have been compiled and made easily available by the world glacier monitoring service and its predecessor organizations in total there have been 3480 annual mass balance measurements reported from 228 glaciers around the globe however the present dataset is strongly biased towards the northern hemisphere and europe and there are only 30 reference glaciers that have uninterrupted series going back to 1976 the available data from the six decades indicate a strong ice loss as early as the 1940s and 1950s followed by a moderate mass loss until the end of the 1970s and a subsequent acceleration that has lasted until now culminating in a mean overall ice loss of over 20 m w e for the period 1946 2006 in view of the discrepancy between the relevance of glacier mass balance data and the shortcomings of the available dataset it is strongly recommended to 1 continue the long term measurements 2 resume interrupted long term data series 3 replace vanishing glaciers by early starting replacement observations 4 extend the monitoring network to strategically important regions 5 validate calibrate and accordingly flag field measurements with geodetic methods and 6 make systematic use of remote sensing and geo informatics for assessment of the representativeness of the available data series for their entire mountain range and for the extrapolation to regions without in situ observations and 7 make all these data and related meta information available

on the separation of crustal component from subducted oceanic lithosphere near the 660 km discontinuity the recent mineral physics observations suggest that the crustal and mantle components of subducted oceanic lithosphere have distinct densities and viscosities the deformation of such chemically stratified oceanic lithosphere as it collides with the 660 km discontinuity is examined using a simple analytical model it is shown that the separation of the crustal component can occur through a small scale folding 10 20 km if the viscosity of the crustal garnetite layer is significantly higher than the surrounding mantle 1021 pa s but is less than 1023 pa s leading to a garnet enriched transition zone behind subduction zones

strength and elasticity of ringwoodite at upper mantle pressures the differential stress supported by a natural iron bearing ringwoodite was determined using energy dispersive synchrotron x ray diffraction in a radial geometry in a diamond anvil cell the yield strength of ringwoodite was found to increase nearly linearly from 5 8 5 gpa at a pressure of 6 2 gpa to 10 2 9 gpa at a pressure of 27 0 gpa when scaled by the shear modulus silicate yield strengths are systematically higher than metals oxides and halides at pressures up to 30 gpa for silicates the yield strength is 5 7 of the shear modulus in this pressure range whereas for the other classes of solids the yield strength is typically less than 2 of the shear modulus the results show that ringwoodite has a small postive elastic anisotropy over this pressure range

transformation of aragonite dominated lime muds to microcrystalline limestones scanning electron microscopy of textures in several well lithified pleistocene micrites mixed micrite and microspar from south florida and the bahamas shows significant diagenetic alteration of the lime mud precursors the dominance of aragonite in those precursor muds is supported by the surprising presence of abundant aragonite relics in the neomorphic calcite crystals confirmed by feigl stain x ray and electron diffraction polished very lightly etched surfaces of neomorphic calcite crystals even in the microspar show aragonite relics and pits both absent in coexisting void fill cements similarities between micrite and microspar crystals indicate their common origin through a one step neomorphic process of calcitization that is the mud did not first calcitize to micrite and then alter to microspar by aggrading neomorphism this conclusion has more general implications for the interpretation of the origins of other older microsparitic carbonates both early calcitization and concurrent early meteoric cementation were significant in producing the florida bahamas micrites studied which have low porosities similar to those found in most ancient fine grained limestones these low porosities despite the absence of significant overburden indicate that major porosity reduction without compaction can occur in calcitized aragonite dominated muds

sector zoning in calcite cement crystals implications for trace element distributions in carbonates abstract compositional sector zoning in calcite cement crystals from a sedimentary limestone is represented by differences of mg content of over 1300 ppm or 95 and of sr and mn contents of up to 400 ppm or roughly 50 and 80 respectively between crystallographically nonequivalent time synchronous growth sectors 10 1 1 sectors are enriched with both mg and mn relative to 10 1 4 sectors and other sectors show both greater and lesser enrichment this systematic zoning pattern requires effective distribution coefficients for these trace elements to have been different for growth on different faces differential growth rate effects for nonequivalent faces are shown to be unimportant relative to differential growth face element preferences surface crystal structure and differing coordination environments are regarded as the principal factors influencing sector related elemental partitioning differences in calcite and dolomite

mass balance observations and reconstruction for haxilegen glacier no 51 eastern tien shan from 1999 to 2015 haxilegen glacier no 51 43 731 n 84 391 e cn5y741c0051 is located in the kuytun river basin erenharbirga range eastern tien shan this study presents the annual mass balance of haxilegen glacier no 51 for 7 hydrological years and uses a temperature index and an accumulation model to reconstruct the annual mass balance from 1999 to 2015 the model is calibrated against annual altitudinal mass balance measurements and then applied to the period with no measurements we find an accumulated mass balance of 6 06 0 88 m w e a 1 over the period of 16 hydrological years with an average annual value of 0 32 0 22 m w e a 1 the mean glacier wide annual summer and winter balances for 1999 to 2015 are 0 37 0 54 and 0 16 0 22 m w e a 1 respectively with a high correlation coefficient r 0 95 p 0 001 between annual balance and summer balance the calculated mass balance sensitivity of the glacier to temperature is 0 51 m w e a 1 c 1 and to precipitation is 0 08 m w e a 1 for a 10 increase the sensitivity of seasonal mass balance indicates that temperature during the melt season may august and annual precipitation are the major contributors to mass balance fluctuation

garnet yield strength at high pressures and implications for upper mantle and transition zone rheology 1 garnet helps control the mechanical behavior of the earth s crust mantle and transition zone here measurements are presented suggesting that garnet long considered to be a high viscosity phase is actually weaker than the other dominant components in the transition zone the mechanical behavior of garnet at high pressures was examined using radial diffraction techniques in the diamond anvil cell the yield strength of grossular garnet was inferred from synchrotron x ray measurements of differential lattice strains the differential stress was found to increase from 1 3 0 6 gpa at a hydrostatic pressure 5 8 1 1 gpa to 4 1 0 4 gpa at 15 7 1 0 gpa where it was level to 19 gpa the strength results are consistent with inferred strength values for majorite garnet from measurements in the diamond cell normal geometry bolstering the idea that garnet structured materials may all have similar strengths in this low temperature high differential stress regime garnet is shown to be significantly weaker than anhydrous ringwoodite and to have a strength similar to hydrous ringwoodite this result suggests that the presence of water in the transition zone may not be required to explain a weak rheology and therefore models of transition zone behavior built assuming that garnet is the high strength phase may need to be revised

seasonal variability of ionic concentrations in surface snow and elution processes in snow firn packs at the pgpi site on urumqi glacier no 1 eastern tien shan china to investigate the effects of both non meltwater and meltwater related post depositional processes on chemical species within the snow firn pack a research program the program for glacier processes investigation was initiated in july 2002 by the tien shan glaciological station chinese academy of sciences the seasonal variability of the ionic concentrations in surface snow samples and ion elution behavior in the snow firn pack were assessed from surface samples collected year round and 1011 samples collected from a snow pit at weekly intervals from september 2003 through september 2004 the results indicate that elevated ionic concentrations in spring and summer result from asian dust storm derived aerosol input and other aerosols entrained in precipitation potential sources of these chemical species are explored using correlation and factor analyses the elution sequence through the snow firn pack was determined to be so4 2 c a 2 n a n o3 c l k m g 2 n h4 the elution of ions at the sampling site was found to be driven primarily by air temperature and became evident when a diurnal mean temperature of 3 68c was attained at 0 38c all of the year round new ionic input was leached from the snow

sr mg ratios of modern marine calcite empirical indicators of ocean chemistry and precipitation rate holocene biotic and abiotic marine calcite have a similar range of mg contents 0 to 22 and 4 to 21 mol mgco3 respectively yet biotic calcite has sr2 concentrations that are consistently 1250 ppm higher than those of abiotic calcite as in laboratory experiments a positive linear relation is observed between dsr and calcite mg content this produces two distinct linear trends on a plot of sr2 vs mg2 concentrations principal axes of variation for both trends have similar slopes yet distinctly different sr2 concentration intercepts biotic y 0 024x 1298 r2 0 70 abiotic y 0 027x 47 r2 0 77 the similar slopes of these trends reflect the constancy of mgca and srca ratios of modern seawater equations describing the dependence of dsr on calcite mg content are derived from both trends biotic dsr 3 16 x 10t 6 ppm mg 0 169 abiotic dsr 3 52 x 10 6 ppm mg 0 0062 characterization of sr mg trends for holocene materials allows comparison with analogous trends from ancient samples to estimate relative changes in seawater mgca and srca ratios the relatively high sr contents of biotic calcite result from rapid precipitation rates associated with shell accretion in marine organisms calcites precipitated from seawater in laboratory experiments have dsr values that are similar to those of biotic marine calcite suggesting that both precipitate at approximately the same rate our estimates of surface area normalized precipitation rates in planktonic and benthonic foraminifera are comparable to those of seeded ph stat experiments we conclude that the dsr values for biotic and experimental marine calcite are kinetically controlled whereas the lower precipitation rates of abiotic marine calcite yield dsr values that approximate equilibrium conditions experimentally derived equations describing the relation between dsr and calcite precipitation rate indicate that the offset in sr content between biotic and abiotic calcite is the result of abiotic precipitation rates that are two to five orders of magnitude lower than those of biotic precipitates however observations of naturally occurring marine cements suggest that the five order of magnitude offset best represents natural system processes

plastic deformation of garnets systematics and implications for the rheology of the mantle transition zone abstract plastic properties of materials with garnet structure have been studied under wide temperature conditions ranging from room temperature to 95 of the melting temperatures using uniaxial compression and hot microhardness tests garnets studied include single crystals of oxide garnets y 3 al 5 o 12 gd 3 ga 5 o 12 and y 3 fe 5 o 12 and silicate garnets various solid solutions including grossular almandine andradite pyrope spessartine and uvarovite both uniaxial compression and hot hardness tests indicate that there is a general trend in the plasticity of garnets when the data are compared at normalized conditions t t m and and that the resistance to plastic deformation in garnets is significantly higher than most of the other minerals in the earth s mantle based on both stress dip tests and microstructural observations it is proposed that the creep strength of garnet is largely controlled by the resistance to dislocation glide rather than by recovery processes this conclusion is consistent with the high peierls stress inferred from the hot hardness tests the high peierls stress in garnets is presumably due to the large unit cell i e long burgers vectors and or the bcc packing which are common to all garnets we postulate therefore that the present results can be applied to the strength of high pressure garnet majorite and suggest that garnet rich layers in the earth such as subducted oceanic crust in the transition zone or a possibly garnet rich bottom part of the transition zone will be considerably stronger than surrounding regions

mass balance characteristics of urumqi glacier no 1 tien shan china the temporal and spatial variations of mass balance on different timescales were analyzed to identify their response to climate change using long term observed mass balance data covering the period 1959 2002 at urumqi glacier no 1 at the headwaters of the urumqi river tien shan china the results show that the accumulated glacier mass balance has decreased by 9599 mm w e which is equivalent to about 10 m mean thickness reduction the negative mass balance has been accentuated in recent years with a mean mass balance during the period 1997 2002 of 739 6 mm a 1 the glacier mass balance shows a clear periodicity with positive and negative alternations of 7 and 15 years during the past several decades annual mass balance shows a significant negative correlation with summer air temperature from june to august it is influenced more by annual air temperature than by annual precipitation the temperature increase preceded the precipitation increase as an influence on the mass balance furthermore monthly mass balance shows a negative correlation with monthly air temperature significant at the 99 confidence level in july and august monthly mass balance is negatively correlated with precipitation in may and august at the 95 confidence level but positively and insignificantly correlated with precipitation in june and july the negative relationship between mass balance and precipitation might be related to concurrent increases of precipitation and temperature

the strength of mantle silicates at high pressures and room temperature implications for the viscosity of the mantle the rheological properties of the upper mantle important in convective and tectonic processes have long been studied through low pressure creep experiments on olivine1 5 in comparison our understanding of deformation in the deep earth is incomplete because there are few experimental constraints on the rheology of the transition zone 400 670 km depth and the lower mantle estimates of the viscosity at these depths have had to rely on geophysical models of for example post glacial uplift the geoid and changes in the earth s rate of rotation6 13 recently we developed techniques for measuring solid state creep at mantle pressures14 and here we use these methods to make direct laboratory measurements of the strength of key mantle minerals we study mg fe 2sio4 olivine representative of about 60 of the upper mantle mg fe 2sio4 spinel which constitutes a large fraction of the transition zone and mg fe sio3 perovskite and perovskite mg fe o magnesiowiistite assemblages which comprise most of the lower mantle all at room temperature and pressures of up to 60 gpa our results suggest that the transition zone may form a layer of relatively high viscosity or strength between the upper and lower mantle a simple theological model shows that this behaviour may be compatible with current geophysical observations

mass balance and recession of urumqi glacier no 1 tien shan china over the last 45 years observations of urumqi glacier no 1 at the headwaters of the urumqi river tien shan show remarkable changes between 1959 and 2003 the cumulative mass balance of the glacier is 10 032 mm equivalent to 11 1 m of glacier ice or 20 of the glacier volume showing particular sensitivity to temperature change the speed of glacier flow has gradually declined especially since the 1980s from 1980 to 2003 the flow speed of the east and west branches of the glacier decreased by about 21 and 43 respectively the glacier continuously retreated from 1962 to 2003 its length has decreased by about 180 m 7 5 and its area has diminished by 0 23 km 2 11 8 analyses show that summer precipitation is negatively correlated with mass balance and positively associated with runoff these relationships are reasonable as higher precipitation leads to higher runoff and lower glacier melt on the other hand summer temperature is negatively correlated with mass balance and positively associated with runoff as higher temperatures lead to higher glacier melt and thus higher runoff with summer temperatures controlling mass balance variation over the past 45 years the negative mass balance caused by higher ablation than accumulation is associated with precipitation increase and temperature warming over the study area

rapid decrease of observed mass balance in the urumqi glacier no 1 tianshan mountains central asia the mass balance of urumqi glacier no 1 located in tianshan mountains of central asia has been monitored since 1959 based on the long term climate and glacier mass balance observation data for the period 1959 2010 analyses show that the glacier mass balance has decreased rapidly the equilibrium line altitude ela has ascended significantly and the glacier terminus has retreated continuously in response to climate change the cumulative mass balance was 14 883 mm w e equivalent to glacier thinning of 16 5 m with a mean value of 0 32 m y the ela showed a significant ascending trend ascending about 90 m the averaged ela was 4067 m a s l and analysis shows the steady state ela ela 0 was 4018 m a s l with the mass balance gradient alpha 5 9 mm m the glacier terminus retreated by 199 3 m at the east branch and 241 3 m at the west branch linear regression analysis results suggest that 1 c degrees summer temperature increases leads to 440 6 mm mass balance decrease mass balance increases by 120 mm when annual precipitation increases by 100 mm mass balance decrease was controlled mainly by summer temperature if such increased warming continues in the future the glacier mass balance will form a strongly negative balance the glacier will shrink and the glacier terminus will continue to retreat c 2013 elsevier ltd and inqua all rights reserved

tem observations of several spinel garnet assemblies toward the rheology of the transition zone in order to better identify the mineral phase which controls the rheology of the transition zone between 410 and 660 km depth transmission electron microscopy observations were made on several coexisting spinel garnet assemblies alkremite xenolith pyrope rich mgo 1 1al2o3 spinel assembly deformed at 1173k 800 mpa in a griggs apparatus mg fe 3 al mg si 2si3o12 majorite mg fe 2sio4 spinel assembly synthesized in a laser heated diamond anvil cell it was found that garnet crystals systematically remain undeformed while spinel crystals are plastically deformed these results are in accord with the assumption that the rheology of majorite is stronger than the rheology of spinel in the conditions of the transition zone

origin of anhedral sr rich calcite in deep water mixed sediment north east australia at burial depths of 800 1000 m within the epicontinental queensland trough of north east australia odp site 823 microcrystalline inter and intraskeletal mosaics of anhedral loaf shaped rounded calcite have sr2 values ranging from below microprobe detection limits 400 500 m depths petrographic observations illustrate that the calcite microfabric formed through coalescing crystal growth resulting from one or a combination of displacive growth in clay porphyroid neomorphism of aragonite vaterite and clay replacement by calcite sr2 mean concentrations in calcite between depths of 800 and 1000 m are similar to an expected equilibrium pore water concentration using a dsr of 0 06 and may indicate active calcite precipitation however sr2 variation 2000 5000 ppm within and among crystals and concentrations that range well above predicted equilibrium values for a given depth illustrate either variable sr2 retention during recrystallization of shelf derived aragonite and authigenic local vaterite or relative uptake of sr2 during calcite precipitation with burial within the context of calcite formation during burial to 1 km diagenetic attributes that affect the latter process include increased concentrations of pore water sr2 with depth associated with aragonite recrystallization dissolution upward migration of sr rich pore water and increased dsr related to local variation in precipitation recrystallization rates differential crystal sector growth rates and or microvariation in aragonite distribution

superplasticity in garnet from eclogite facies shear zones in the haram gabbro haramsoya norway study of garnet adjacent to and within shear zones that underwent synkinematic eclogitization reveals microstructures and textures that for the first time indicate grain boundary sliding as the main deformation mechanism in garnet monomineralic garnet layers exhibit characteristic features of superplastic behavior and show little strength contrast to the surrounding minerals the low strength is caused by the synkinematic growth of garnet limiting the grain size to tens of micrometers this behavior may significantly influence rheologic properties of high and ultrahigh pressure shear zones in subduction environments and may play a role during the formation of garnet in the transition zone of the mantle

mass balance reconstruction for glacier no 354 tien shan from 2003 to 2014 this study presents a reconstruction of the seasonal mass balance of glacier no 354 located in the akshiirak range kyrgyzstan from 2003 to 2014 we use a distributed accumulation and temperature index melt model driven by daily air temperature and precipitation from a nearby meteorological station the model is calibrated with in situ measurements of the annual mass balance collected from 2011 to 2014 the snow cover depletion pattern observed using satellite imagery provides additional information on the dynamics of mass change throughout the melting season two digital elevation models derived from high resolution satellite stereo images acquired in 2003 and 2012 are used to calculate glacier volume change for the corresponding period the geodetic mass change thus derived is used to validate the modelled cumulative glacier wide balance for the period 2003 12 we find a cumulative mass balance of 0 40 10mw e a 1 this result agrees well with the geodetic balance of 0 48 0 07mw e a 1 over the same period

plastic flow of pyrope at mantle pressure and temperature despite the abundance of garnet in deforming regions of the earth such as subduction zones its rheological properties are not well defined by laboratory measurements here we report measurements of steady state plastic properties of pyrope in its stability field temperature up to 1573 k pressure up to 6 8 gpa strain rate approx 10 5 s 1 using a deformation dia apparatus d dia coupled with synchrotron radiation synthetic pyrope py100 and natural pyrope py70alm16gr14 are both studied in a dry environment transmission electron microscopy tem investigation of the run products indicates that dislocation glide assisted by climb within grains and dynamic recrystallization for grain boundary strain accommodation is the dominant deformation process in pyrope both synthetic and natural pyropes stress and strain rate data as measured in situ by x ray diffraction and imaging are best fitted with the single flow law

twentieth century warming preserved in a geladaindong mountain ice core central tibetan plateau high resolution 18 o records from a geladaindong mountain ice core spanning the period 1477 1982 were used to investigate past temperature variations in the yangtze river source region of the central tibetan plateau tp annual ice core 18 o records were positively correlated with temperature data from nearby meteorological stations suggesting that the 18 o record represented the air temperature in the region a generally increasing temperature trend over the past 500 years was identified with amplified warming during the 20th century a colder stage spanning before the 1850s was found to represent the little ice age with colder periods occurring during the 1470s 1500s 1580s 1660s 1700s 20s and 1770s 1840s compared with other temperature records from the tp and the northern hemisphere the geladaindong ice core record suggested that the regional climate of the central tp experienced a stronger warming trend during the 20th century than other regions in addition a positive relationship between the geladaindong 18 o values and the north atlantic oscillation index combined with a wavelet analysis of 18 o records indicated that there was a potential atmospheric teleconnection between the north atlantic and the central tp

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

elasticity and strength of hydrous ringwoodite at high pressure oh bearing hydrous ringwoodite compressed non hydrostatically in a diamond anvil cell supports a differential stress that increases from 2 9 to 4 5 gpa over the pressure range of 6 7 13 2 gpa at room temperature this result suggests a significant water weakening effect when compared with results from similar experiments on the anhydrous counterpart kaver and duffy geophys res lett 28 2001 2691 2694 the elastic anisotropy 2c44 c11 c12 of hydrous ringwoodite is measured to be 0 87 7 throughout this pressure range similar to measured values for anhydrous ringwoodite kaver and duffy geophys res lett 28 2001 2691 2694 this lattice anisotropy cannot be explained by anelastic effects such as faulting and twinning within the structure these results suggest that hydrous minerals in the upper mantle and transition zone may have higher ductile strain rates for a fixed shear stress at high temperature resulting in stronger preferred lattice orientation this in turn may be seismically detectable which opens the possibility of using seismic anisotropy as a marker for local volatile containing areas within the upper mantle and transition zone

the geochemistry of carbonate diagenesis the past present and future stable carbon and oxygen isotopes 18o and 13c values and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years as valuable as these insights have been many problems regarding the interpretation of geochemical signals within mature rocks remain for example while the 18o values of carbonate rocks are dependent both upon the temperature and the 18o value of the fluid and additional information including trace element composition aids in interpreting such signals direct evidence of either the temperature or the composition of the fluids is required such information can be obtained by analysing the 18o value of any fluid inclusions or by measuring the temperature using a method such as the clumped isotope technique such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well known tendency for 18o values of carbonate rocks to decrease with increasing age unlike the 18o 13c values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time however many studies have not sufficiently emphasized the effects of diagenesis and other post depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored finally many additional proxies are poised to contribute to the interpretation of carbonate diagenesis although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods care should be taken to understand both old and new proxies before applying them to the ancient record

neomorphism and cementation in ancient deep water limestones cow head group cambro ordovician western newfoundland canada abstract lithification of thinly bedded lime mudstones and grainstones in the cow head group resulted mainly from precipitation of calcite cement and neomorphic spar at shallow burial depths below the sea floor these crystals are predominantly non ferroan although the iron content and the size of neomorphic spar commonly increase near the margins of nodular and continuous beds of lime mudstone displacive fringes of ferroan fibrous calcite represent the last stage of carbonate precipitation in some limestones most calcite 13c values range between 0 and 3 pdb but 13c values as negative as 15 indicate that bacterial degradation of orgnaic matter variably influenced pore water composition serial analyses from the centres to the margins of nodular and continuously bedded lime mudstones suggest that many of the limestones in this sequence were lithified prior to the precipitation of calcite having the prominent negative 13c values typical of concretionary carbonate calcite 18o values range from 5 to 8 pdb indicating precipitation from 18o depleted pore waters of uncertian origin cathodoluminescence shows that aggrading neomorphism in the lime mudstones did not take place by porphyroid or coalescive consumption of a more finely crystalline mosaic to yield a more coarsely crystalline mosaic instead scattered crystals enlarged by precipitation of progressively younger and eventually ferroan calcite especially at the margins of nodular and continuous limestone beds the cathodoluminescence zoning in calcite crystals is similar to that observed in meteorically altered limestones where pore waters were initially oxidizing but became progressively more reducing with time the preservation of trace element zoning crystal growth microfabrics and 13c values in authigenic calcite suggest collectively that recrystallization did not occur during subsequent burial