distribution of anthropogenic co2 in the pacific ocean 1 this work presents an estimate of anthropogenic co2 in the pacific ocean based on measurements from the woce jgofs oaces global co2 survey these estimates used a modified version of the c technique modifications include a revised preformed alkalinity term a correction for denitrification and an evaluation of the disequilibrium terms using an optimum multiparameter analysis the total anthropogenic co2 inventory over an area from 120 e to 70 w and 70 s to 65 n excluding the south china sea the yellow sea the japan east sea and the sea of okhotsk was 44 5 5 pg c in 1994 approximately 28 pg c was located in the southern hemisphere and 16 5 pg c was located north of the equator the deepest penetration of anthropogenic co2 is found at about 50 s the shallowest penetration is found just north of the equator very shallow anthropogenic co2 penetration is also generally observed in the high latitude southern ocean one exception to this is found in the far southwestern pacific where there is evidence of anthropogenic co2 in the northward moving bottom waters in the north pacific a strong zonal gradient is observed in the anthropogenic co2 penetration depth with the deepest penetration in the western pacific the pacific has the largest total inventory in all of the southern latitudes despite the fact that it generally has the lowest average inventory when normalized to a unit area the lack of deep and bottom water formation in the north pacific means that the north pacific inventories are smaller than the north atlantic

late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

shredding of environmental signals by sediment transport 1 landscapes respond to climate tectonic motions and sea level but this response is mediated by sediment transport understanding transmission of environmental signals is crucial for predicting landscape response to climate change and interpreting paleo climate and tectonics from stratigraphy here we propose that sediment transport can act as a nonlinear filter that completely destroys shreds environmental signals this results from ubiquitous thresholds in sediment transport systems e g landsliding bed load transport and river avulsion this morphodynamic turbulence is analogous to turbulence in fluid flows where energy injected at one frequency is smeared across a range of scales we show with a numerical model that external signals are shredded when their time and amplitude scales fall within the ranges of morphodynamic turbulence as signal frequency increases signal preservation becomes the exception rather than the rule suggesting a critical re examination of purported sedimentary signals of external forcing citation jerolmack d j and c paola 2010 shredding of environmental signals by sediment transport geophys res lett 37 l19401 doi 10 1029 2010gl044638

late pennsylvanian glaciation evidence of icehouse conditions from canyon and cisco units midland basin texas abstract the late paleozoic has long been recognized a time of significant continental glaciation associated with high frequency high amplitude glacioeustasy although precise assessment of glacioeustatic amplitudes are difficult to extract from the stratigraphic record best approximations may be possible by analyzing spatial and temporal distributions of depositional facies utilizing several wells across the study area we used detailed sedimentologic description and depositional facies analysis from 12 wells and applied rigorous cycle stacking pattern analysis exposure surfaces recognition and wireline logs to correlate timelines across the wells on the basis of the high resolution sequence stratigraphic framework built for the scurry area canyon reef operators sacroc field a highly resolved glacioeustatic curve was generated for latest desmoinesian to the latest virgilian our eustatic curve suggests that the missourian and virgilian stages of the late pennsylvanian are characterized by high frequency high amplitude eustatic fluctuations the missourian stage was a period dominated grainstone capped cycles that are isopachous and conformable these cycles reflect a eustatic amplitude of at least 37 m with an average duration of 100 ka suggesting the dominance of short term eccentricity signal the virgilian stage is far more complicated and is characterized by highly shingled cycles compared to the missourian stage deeper water phylloid boundstone and calichified shoal complex grainstones are juxtaposed next to each other which suggests a stronger eustatic amplitude 40 m compared to the missourian stage although the eustatic amplitude of the virgilian cycles is similar to those of the missourian cycles they have a longer frequency 343 ka representative of long term eccentricity we conclude that the late pennsylvanian stratigraphy of the sacroc field in the midland basin records extensive continental glaciation during the missourian stage and increased and reached an acme during the virgilian stage

in situ calcium carbonate dissolution in the pacific ocean over the past several years researchers have been working to synthesize the woce jgofs global co2 survey data to better understand carbon cycling processes in the oceans the pacific ocean data set has over 35 000 sample locations with at least two carbon parameters oxygen nutrients cfc tracers and hydrographic parameters in this paper we estimate the in situ caco3 dissolution rates in the pacific ocean water column calcium carbonate dissolution rates ranging from 0 01 1 1 mmol kg1 yr1 are observed in intermediate and deepwater beginning near the aragonite saturation horizon in the north pacific intermediate water between 400 and 800 m caco3 dissolution rates are more than 7 times faster than observed in middle and deep water depths average 0 051 mmol kg1 yr1 the total amount of caco3 that is dissolved within the pacific is determined by integrating excess alkalinity throughout the water column the total inventory of caco3 added by particle dissolution in the pacific ocean north of 40s is 157 pg c this amounts to an average dissolution rate of approximately 0 31 pg c yr1 this estimate is approximately 74 of the export production of caco3 estimated for the pacific ocean these estimates should be considered tomore be upper limits for in situ carbonate dissolution in the pacific ocean since a portion of the alkalinity increase results from inputs from sediments less

water chemistry and caco3 dissolution in the saline part of an open flow mixing zone coastal yucatan peninsula mexico along the caribbean coast of the yucatan peninsula brackish ground water mixed fresh water and sea water is channeled through upper pleistocene limestone via fracture controlled caverns in caves cenotes and caletas at xcaret yalku and tancah this open flow coastal mixing zone comprises three major layers 1 an upper dilute zone of gradually increasing salinity with depth slow mixing 2 a thin intermediate zone of rapidly increasing salinity with depth rapid mixing and 3 a lower saline zone of gradually increasing salinity with depth the intermediate layer occurs at different absolute salinities at different localities and it generally corresponds to the level of a notch apparently related to dissolution in the wall rock of the caverns chemical composition of the mixed ground water is consistent with that predicted from theoretical conservative mixing of fresh water and sea water end members sampled in the yucatan coastal region inorganic c alkalinity mg ca and sr ca and 18o and 13c of the mixed water give no indication of dissolution or precipitation of cac03 as the ground water flows rapidly seaward field and petrographic observations however show that aragonite is preferentially dissolving throughout the modern mixing zone and in particular in the saline portion comparison of saturation indices to calculated mixing curves shows that the coastal mixing zone of the eastern yucatan peninsula is undersaturated with respect to cac03 over a wide range of salinity including mixtures of as much as 95 sea water for aragonite and 90 sea water for calcite supersaturation with respect to stoichiometric dolomite is maintained over the whole range of salinities but super saturation with respect to calcian dolomite ca57mg43 can be confined to high salinity mixtures depending on the thermodynamic data base used in calculations these data suggest that 1 dissolution of coastal limestone can take place in the sea water dominated portion of the mixing zone and 2 the mixing zone model for dolomitization can be extended to much higher salinities than is indicated by the widely accepted dorag model

depth distributions of alkalinity tco2 and δ13ctco2 at seats time series site in the northern south china sea abstract in this study measurements of titration alkalinity ta total dissolved carbon dioxide tco2 and 13c of tco2 13 c tco 2 throughout the water column at the southeast asian time series study seats site were investigated in order to understand better the fundamental processes controlling their vertical distributions in the south china sea scs the linear correlations between ta and salinity in the shallow waters as identified by the mixing line between the surface water and salinity maximum water suggested the predominant control of physical mixing on the variability of ta in contrast tco2 and 13 c tco 2 showed the non conservative behavior in the respective tco2 and 13 c tco 2 vs salinity plot due to the effect of biological production a stoichiometric model further showed that the depth profile of nta ta salinity 35 largely reflects the increase of preformed nta in the shallow waters whereas carbonate dissolution was responsible for the continuous increase of nta in the deep waters a one dimensional diffusion advection model further revealed that the carbonate dissolution could account for 28 of ntco2 tco2 salinity 35 increase in deep waters and the remaining 72 of ntco2 was from organic decomposition calculation of excess ta further showed that it emerged well above the aragonite and calcite saturation depths at 600 and 2500 m respectively indicating that some biologically chemically and physically mediated processes must be involved to provide excess ta into the shallow waters the decrease in 13 c tco 2 with depth primarily resulted from organic decomposition the influence of anthropogenic co2 throughout the water column was assessed with the carbon chemistry and the isotope based approach in this study both methods obtained nearly the same results in which the signal of anthropogenic co2 decreased exponentially with depth and its penetration depth were found to be at 1000 m the inventory of anthropogenic co2 in the water column was estimated to be 16 6 mol c m 2 which was less than that reported in the northwest pacific at the same latitude presumably due to the enhanced upwelling in the scs such an anthropogenic co2 penetration had led to decreases of the saturation levels of aragonite and calcite by 17 and 14 respectively in the surface water and an upward migration of aragonite saturation depth by 100 m since industrial revolution

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

isotopic fingerprints of milankovitch cycles in pennsylvanian carbonate platform top deposits the valdorria record northern spain sedimentary cyclic sequences deposited during the late palaeozoic ice age are widespread glacio eustatic control of the cyclic patterns is commonly accepted and the durations of the cyclothems generally match the short and long eccentricity milankovitch orbital parameters nevertheless geochemical fingerprints of orbital parameters are poorly documented in deep time sedimentary records here we report on well exposed bashkirian cyclothems of c 123 ka and c 400 ka durations from the valdorria platform the shorter term cyclothems can be grouped into longer term composite sequences that are consistent with generally accepted durations of c 125 ka and c 400 ka for milankovitch eccentricity cycles the stratigraphic pattern is mirrored by the isotope geochemical signals which show distinct recurring trends these trends are confirmed by statistical tests whereas intrinsic factors and or subaerial exposure related to sea level lowstands might have truncated cycle patterns in tectonically stable basins rapid subsidence of the valdorria platform s foreland basin appears to have contributed to a faithful recording of cyclothems of different orders the patterns and biostratigraphic constraint revealed in this study demonstrate the power of orbital forcing in imprinting sedimentary and geochemical signals in the rock record

differential dissolution of a pleistocene reef in the ground water mixing zone of coastal yucatan mexico a geochemical explanation is provided for the extensive dissolution observed along the carbonate coast of the yucatan peninsula mexico mixing of fresh ground water with subterranean caribbean seawater generates a highly reactive geochemical zone that enhances aragonite and calcite dissolution and permits neomorphism of aragonite mixing zone dissolution caused by ground water discharge is a major geomorphic process in developing caves coves and crescent shaped beaches along the yucatan coast such dissolution has probably been a significant control on permeability and porosity distribution in carbonate rocks in the geologic record

physical and chemical stratigraphy suggest small or absent glacioeustatic variation during formation of the paradox basin cyclothems the paradox basin cyclothems previously have been interpreted as milankovitch style glacial interglacial cycles from the late paleozoic ice age but an unambiguous test for a glacioeustatic origin has not been conducted a high resolution coupled chemical and physical stratigraphic analysis of two outcrop sections and three core segments provides new evidence that supports either minor sea level change of several meters or an autocyclic mechanism for parasequence formation high amplitude sea level change is ruled out by the scale of thin top negative isotopic meteoric diagenesis trends associated with parasequence tops and subaerial exposure fabrics isotopic gradients from shelf light to basin heavy indicate that parasequences are deposited diachronously with isotopes of more distal sections recording increased basin restriction these results support the idea that the late pennsylvanian was a prolonged period of relatively static eustasy agreeing with recent studies in the western usa the methods provide a new set of tools and context for extracting environmental information from cyclic upward shallowing carbonate parasequences

late paleozoic depositional sequences are synchronous and worldwide more than fifty transgressive regressive depositional sequences are present in carboniferous and permian shallow marine successions on stable cratonic shelves worldwide these were synchronous depositional events resulting from eustatic sea level changes that generally ranged from 100 to 200 m each transgressive regressive sequence is correlatable using current fossil knowledge they average about 2 m y and range from 1 2 to 4 m y in length the presence within these strata of numerous synchronous unconformities of considerable duration and worldwide extent suggests that the fossil record is very incomplete and that we are studying a punctuated fossil record and not a punctuated evolution based on a highly irregular mutation rate these late paleozoic transgressive regressive depositional sequences facilitate correlations because depositional histories of a rock succession can support interpretations of faunal assemblages and faunal similarities in evaluating age relationships

carbonate dissolution and precipitation in coastal environments laboratory analysis and theoretical consideration 1 we have conducted laboratory experiments to examine caco3 dissolution and precipitation in saltwater freshwater mixing zones with a view to understanding and predicting porosity changes in coastal environments mixing of seawater or saline subsurface water with fresh water can be of major importance in the chemical diagenesis of carbonate rocks and sediments we used artificial seawater and nacl solutions of different concentrations under different co2 partial pressures and with different mixing ratios two dimensional flow cells filled with glass beads and crushed calcium carbonate rock were used to measure calcium carbonate precipitation and dissolution respectively an important feature of these experiments is that the results are shown to agree well with a relatively simple transport theory describing mineral precipitation dissolution that results from the nonlinear dependence of caco3 saturation upon electrolyte concentration the theory demonstrates that the rate of dissolution or precipitation depends on the curvature and sign of the solubility as a function of salinity the square of the salinity gradient and the macroscopic dispersion coefficient the theory is largely scale independent and depends upon field parameters that can be determined analysis of data from three field sites yucatan peninsula bermuda and mallorca demonstrates excellent agreement between field observations and theory

heterogeneous distributions of co 2 may be more important for dissolution and karstification in coastal eogenetic limestone than mixing dissolution mixing dissolution a process whereby mixtures of two waters with different chemical compositions drive undersaturation with respect to carbonate minerals is commonly considered to form cavernous macroporosity e g flank margin caves and banana holes in eogenetic karst aquifers on small islands macroporosity commonly originates when focused dissolution forms globular chambers lacking entrances to the surface suggesting that dissolution processes are decoupled from surface hydrology mixing dissolution has been thought to be the primary dissolution process because meteoric water would equilibrate rapidly with calcium carbonate as it infiltrates through matrix porosity and because pco2 was assumed to be homogeneously distributed within the phreatic zone here we report data from two abandoned well fields in an eogenetic karst aquifer on san salvador island bahamas that demonstrate pco2 in the phreatic zone is distributed heterogeneously the pco2 varied from less than log 2 0 to more than log 1 0 atm over distances of less than 30 m generating dissolution in the subsurface where water flows from regions of low to high pco2 and cementation where water flows from regions of high to low pco2 using simple geochemical models we show dissolution caused by heterogeneously distributed pco2 can dissolve 2 5 to 10 times more calcite than the maximum amount possible by mixing of freshwater and seawater dissolution resulting from spatial variability in pco2 forms isolated globular chambers lacking initial entrances to the surface a morphology that is characteristic of flank margin caves and banana holes both of which have entrances that form by erosion or collapse after cave formation our results indicate that heterogeneous pco2 rather than mixing dissolution may be the dominant mechanism for observed spatial distribution of dissolution cementation and macroporosity generation in eogenetic karst aquifers and for landscape development in these settings copyright 2015 john wiley sons ltd

glacioeustasy meteoric diagenesis and the carbon cycle during the middle carboniferous middle carboniferous carbonates in the western u s have undergone pleistocene bahamas style meteoric diagenesis that may be associated with expanding late paleozoic ice sheets fourteen stratigraphic sections from carbonate platforms illustrate the regional distribution and variable intensity of physical and chemical diagenesis just below the middle carboniferous unconformity these sections contain top negative carbon isotope excursions that terminate in regional exposure surfaces that are associated with some combination of karst towers desiccation cracks fabric destructive recrystallization or extensive root systems the timing of the diagenesis is synchronous with similarly scaled top negative carbon isotope excursions observed by others in england kazakhstan and china the mass flux of negative carbon required to generate similar isotopic profiles across the areal extent of middle carboniferous platform carbonates is a significant component of the global carbon cycle we present a simple carbon box model to illustrate that the 13c of dissolved inorganic carbon in the ocean could be elevated by 1 4 as isotopically light carbon from the weathering of terrestrial organic matter reacts with exposed platforms before reaching the ocean and atmosphere these results represent an improvement on global biogeochemical models that have struggled to provide a congruent solution to the high 13c of the late paleozoic icehouse

an application of l band synthetic aperture radar to tide height measurement a method for measuring the tide height near the coast from l band synthetic aperture radar sar data is presented twenty one coherent interferograms have been successfully constructed from japanese earth resources satellite 1 jers 1 sar data obtained over oyster sea farming structures a coherence analysis of the 21 interferometric pairs showed that a perpendicular baseline of less than 3 km with a temporal baseline within 500 days are required to obtain a coherent pair with a coherence higher than 0 25 in the study area the coherent phases preserved in the interferograms showed a close relation with the sea level the problem of phase unwrapping to restore an absolute tide height was overcome by introducing normalized image intensities the radar measurements estimated by the proposed method were verified using tide gauge data and comparison of the two datasets yielded a correlation coefficient r sup 2 of 0 91 with a root mean square error of 5 76 cm the results demonstrate that radar interferometry can be applied for a tide height measurement near the coast given sufficient structures that return off nadir radar pulses to the antenna the multipolarized l band sar system will provide better results using only double bounced signals in the future

the influence of air sea exchange on the isotopic composition of oceanic carbon observations and modeling although the carbon isotropic composition of ocean waters after they leave the surface ocean is determined by biological cycling air sea exchange affects the carbon isotopic composition of surface waters in two ways the equilibrium fractionation between oceanic and atmospheric carbon increases with decreasing temperature in southern ocean surface waters this isotopic equilibrium enriches delta sup 13 c relative to the delta sup 13 c expected from uptake and release of carbon by biological processes alone similarly surface waters in the subtropical gyres are depleted in delta sup 13 c due to extensive air sea exchange at warm temperatures countering the tendency toward isotopic equilibration with the atmosphere a relatively slow process are the effects of the equilibration of co sub 2 itself a much faster process in regions where there is a net transfer of isotopically light co sub 2 from the ocean to the atmosphere e g the equator surface waters become enriched in sup 13 c whereas in regions where isotopically light co sub 2 is entering the ocean e g the north atlantic surface waters become depleted in sup 13 c a compilation of high quality oceanic delta sup 13 c measurements along with experiments performed using a zonally averaged three basin dynamic ocean model are used to explore these processes 40 refs 14more figs 1 tab less

diurnal and seasonal variations of carbonate system parameters on luhuitou fringing reef sanya bay hainan island south china sea the 3 day diurnal dynamics of carbonate system and related parameters on luhuitou fringing reef of sanya bay adjacent to the south china sea scs were observed in december of 2009 early winter april spring july summer and november late autumn of 2010 the luhuitou fringing reef ecosystem was generally dominated by macro and planktonic algae throughout the year except by coralline algae in winter the system parameters showed distinct diurnal trends in the four seasons averaged ranges of diurnal variation for dissolved oxygen and partial pressure of co2 pco 2 were higher in the autumn 4 67 mg l 1 and 218 2 mu atm respectively than other seasons averaged ranges of diurnal variation for normalized total alkalinity nta was higher in the winter 61 3 mu mol kg 1 and lower in the spring 16 0 mu nol kg 1 the diurnal variations are mainly controlled by biological activities especially by the processes of photosynthesis and respiration in the reef ecosystem in winter however calcification and dissolution contributed more to the diurnal variations compared with the other three seasons total alkalinity was largely related to seasonal changes in river inflow rates dissolved oxygen ph total co2 and aragonite saturation also showed seasonal variations these variations were mainly controlled by the seasonal changes of photosynthesis and respiration which were mainly affected by changes in benthic community structure temperature and river inflow rates the oversaturated pco 2 in the reef ecosystem with respect to the atmosphere in the winter and summer resulted in co2 discharge from the reef ecosystem to the scs the whole system served as net source of co2 to the atmosphere and the adjacent south china sea on an annual time scale c 2013 elsevier ltd all rights reserved

reconstructing the oceanic 13c suess effect the anthropogenic 13c change for the time period 1968 to 1991 was determined based on calculations of the preformed 13c 12c of dissolved inorganic carbon dic distributions on isopycnal surfaces in the main thermocline of the pacific north atlantic and south indian oceans the time rate of change of preformed 13c the 13c suess effect along isopycnals was calculated using cfc derived water ages and yields a time history of the surface water 13c change at the isopycnal outcrop location the surface ocean suess effect recorded on isopycnals decreased with increasing outcrop latitude from approximately 0 2 decade 1 within the subtropics to around 0 1 decade 1 in the subpolar oceans in the pacific ocean these surface 13c change rate reconstructions agree both in magnitude and meridional trend with direct observations of surface ocean 13c changes reported from time series measurements and from comparisons of surface water 13c of dic measurements in 1970 and 1993 a global ocean average surface 13c rate of change of 0 15 0 04 decade 1 is determined which is slightly smaller than a previous time series data and model based estimate 0 171 decade 1 bacastow etal 1996 depth integrations of the 13c reconstructions in the pacific indian and atlantic oceans when combined with these previous individual depth profile comparisons and geochemical ocean sections study bomb 14c inventories quay et al 1992 imply a global depth integrated 13c change rate of 9 7 2 4 m yr 1 over the time period 1970 1990 these results imply a net oceanic co2 uptake rate of 1 9 0 9 gt c yr 1 over the time period 1970 1990 when applied to an atmospheric 13co2 and 12co2 budget

predicting the thickness of fresh water lenses in carbonate paleo islands abstract fresh water lenses in carbonate sand and grainstone islands can be modeled using dupuit ghyben herzberg methods the results indicate that the thickness of the lens h in a homogeneous infinite strip island will be a function of the island s width a hydraulic conductivity k and the amount of recharge r the ratio of r k in most modern carbonate islands of holocene sands and pleistocene rocks is in the range of 10 4 to 10 6 this means h should be 1 to 3 the magnitude of a however vertical and lateral variations in k variations in island shape the presence of intra island evaporitic ponds and marshes and the presence of a mixing zone result in actual h a ratios that range from 0 2 to about 2 with 1 being the most representative value the thic ness of a paleo lens in an ancient carbonate shoal or reef complex can therefore be estimated if the width of the interpreted island can be approximated from facies or isopach maps an example from the late jurassic smackover formation in oaks field louisiana indicates that the estimated thickness of paleo lenses is identical to the thickness of the porosity zones in a series of off lapping oolite shoal complexes a second example from the late permian san andres formation in yates field west texas reveals that the estimated thickness of paleo lenses is essentially equivalent to the thickness of a phreatic cave system formed on paleo islands developed along the san andres shelf margin the h a method for estimating the thickness of paleo lenses and the possible extent of island stage fresh water diagenesis in ancient carbonates is more useful than the ghyben herzberg rule h 40 times the elevation of the water table because the gh rule requires estimation of paleo water table and paleo sea level positions to within a couple of centimeters such estimates are typically impossible in ancient rocks

calcium carbonate budget in the atlantic ocean based on water column inorganic carbon chemistry 1 recent independent lines of evidence suggest that the dissolution of calcium carbonate caco3 particles is substantial in the upper ocean above the calcite 100 saturation horizon this shallow water dissolution of carbonate particles is in contrast with the current paradigm of the conservative nature of pelagic caco3 at shallow water depths here we use more than 20 000 sets of carbon measurements in conjunction with cfc and 14c data from the woce jgofs oaces global co2 survey to estimate in situ dissolution rates of caco3 in the atlantic ocean a dissolution rate is estimated from changes in alkalinity as a parcel of water ages along an isopycnal surface the in situ caco3 dissolution increases rapidly at the aragonite 100 saturation horizon estimated dissolution rates north of 40on are generally higher than the rates to the south which is partly attributable to the production of exported caco3 being higher in the north atlantic than in the south atlantic as more caco3 particles move down the water column more particles are available for in situ dissolution the total water column caco3 dissolution rate in the atlantic ocean is determined on an annual basis by integrating estimated dissolution rates throughout the entire water column and correcting for alkalinity input of approximately 5 6 1012 mol c yr 1 from caco3 rich sediments the resulting water column dissolution rate of caco3 for the atlantic ocean is approximately 11 1 1012 mol c yr 1 this corresponds to about 31 of a recent estimate 35 8 1012 mol c yr 1 of net caco3 production by lee 2001 for the same area our calculation using a large amount of high quality water column alkalinity data provides the first basin scale estimate of the caco3 budget for the atlantic ocean

inorganic carbon in the indian ocean distribution and dissolution processes 1 this study uses nearly 25 000 carbon measurements from the woce jgofs global co2 survey to examine the distribution of dissolved inorganic carbon dic and total alkalinity ta in the indian ocean shallow and intermediate distributions of inorganic carbon do not strictly follow temperature and salinity because of differing surface gradients and vertical biological processes that work to modify the circulation derived features anthropogenic co2 has increased the shallow dic by as much as 3 decreasing the vertical dic gradient deep ocean dic and ta increase toward the north because of the decomposition and dissolution of organic and inorganic particles calcite saturation depths range from 2900 3900 m with the deepest saturation depth in the central indian ocean variations of aragonite saturation depth 200 1400 m are similar to calcite but the deepest saturations are in the southwestern indian ocean the shallowest aragonite saturation depths are found in the bay of bengal in the northern arabian sea and bay of bengal the current aragonite saturations are 100 and 200 m shallower respectively than in preindustrial times estimates of carbonate dissolution rates on isopycnal surfaces range from 0 017 to 0 083 mol kg 1 yr 1 in deep waters upper water column dissolution rates range from 0 to 0 73 mol kg 1 yr 1 with a local maximum occurring in intermediate waters just below the aragonite saturation horizon dissolution is also generally higher north of the chemical front at 10 20 s there is some evidence for significant sedimentary sources in the northern indian ocean

carbonate dissolution in the guts of benthic deposit feeders a numerical model abstract we present a numerical model to quantify calcite dissolution in the guts of deposit feeding invertebrates deposit feeder guts were modeled as constantly stirred reactors cstrs following terminology from digestion theory saturation state and dissolution of calcium carbonate were calculated from changes in total dissolved carbon dioxide and alkalinity resulting from sediment passage through the digestive tract while accounting for dissolution of calcite and respiration of organic carbon typical dissolution rates for a gut volume of 1 ml ranged between 0 5 4 mg calcite d 1 sensitivity analysis revealed gut ph sediment organic matter om content and om reactivity to be the critical parameters determining calcite dissolution rate carbonate dissolution rate was inversely related to gut ph however calcite dissolution was found to be possible even at alkaline gut ph due to respiration by intestinal microbes the kinetics of calcite dissolution had only marginal influence on daily calcite dissolution rates varying the calcite dissolution rate constant by six orders of magnitude affected calcite dissolution rates by less than a factor of 10 calcite dissolution rates were calculated for 4 different hydrographic regimes that differed in their content of sedimentary calcite and om and furthermore in their om reactivity highest dissolution rates were calculated for the shallow water setting where relatively high om content facilitated high microbial respiration rates depressing gut ph however dissolution rates for the deep sea setting were only slightly lower due to greatly elevated ingestion rates resulting from low om content as a consequence of much higher faunal abundances shallow water benthos is likely to contribute the vast majority of gut mediated carbonate dissolution nevertheless the fraction of sedimentary calcite that dissolves during one gut passage is probably too small to be observable by simple gravimetric analysis this may explain the notable scarcity of evidence for gut mediated carbonate dissolution in the literature to date assuming depth dependent calcite dissolution rates and deposit feeder abundances we estimate gut mediated carbonate dissolution to contribute approximately 5 of the annual global sedimentary carbonate dissolution rate which corresponds to an average calcite dissolution rate of approximately 0 5 mg m 2 d 1 for the entire ocean floor

biogeochemistry and dynamics of particulate organic matter in a shallow water hydrothermal field kueishantao islet ne taiwan abstract the particulate organic matter pom of shallow water hydrothermal fields has been studied in the context of food web reconstruction but the processes governing its biogeochemistry and dynamics are poorly explored here we investigate the pom in the kueishantao hydrothermal field using chemical and hydrodynamic approaches the depletion of total suspended matter lower c n ratios and higher carbon isotopic values of particulate organic carbon 13cpoc in the vertical plumes relative to values derived from si based models were attributed to the hydraulic sorting of the vented particles which tend to have more n and 13c in the fine fraction the particulate organic carbon poc unlike the total suspended matter was enriched in the vertical plumes and explained by physicochemical processes rather than biological addition the poc enriched plume top water was found to be a better endmember than the vent fluids to explain particle mixing in the lateral plume physical mixing played a steering role in shaping the particle chemistry of the lateral plumes but markedly 13c enriched poc was still observable in several near vent low to intermediate si plume waters implying locally enhanced primary production of at least 0 1 0 4 mg c m3 h the presence of eddies confirmed by flow field measurements should have contributed to the detection of biogeochemical anomalies via extending the retention time of plume water to 1 2 h the dominating mixing process resulted in decoupling between the 13cpoc signatures and carbonate chemistry in this shallow water hydrothermal plume

unsupervised classification of scattering behavior using radar polarimetry data the use of an imaging radar polarimeter data for unsupervised classification of scattering behavior is described by comparing the polarization properties of each pixel in an image to that of simple classes of scattering such as even number of reflections odd number of reflections and diffuse scattering for example when this algorithm is applied to data acquired over the san francisco bay area in california it classifies scattering by the ocean as being similar to that predicted by the class of odd number of reflections scattering by the urban area as being similar to that predicted by the class of even number of reflections and scattering by the golden gate park as being similar to that predicted by the diffuse scattering class it also classifies the scattering by a lighthouse in the ocean and boats on the ocean surface as being similar to that predicted by the even number of reflections class making it easy to identify these objects against the background of the surrounding ocean

polarimetric features of oyster farm observed by airsar and jers 1 the polarimetric features of an oyster farm in a coastal area are analyzed to verify the applicability of radar polarimetry and interferometry l band airborne synthetic aperture radar airsar data and japan earth resources satellite jers 1 data are used to examine the unique structure of an oyster farm located in south korea a specific feature of the oyster farm is the presence of numerous arrays of structures of various orientations that consist of exercise bar shaped poles protruding above sea level this paper demonstrates that tide level is strongly correlated with the double bounce scattering power from the vertical pole structures this phenomenon is also verified by laboratory measurements using a network analyzer in the laboratory experiment double bounce scattering and total power showed increasing trends with increased height of the vertical poles single bounce scattering is sensitive to the orientation of horizontal poles relative to antenna orientation hh polarization is the most effective technique for imaging oyster farms from l band polarimetric airsar data the authors were able to use a three component decomposition of the airsar data to distinguish an exposed tidal flat from a submerged tidal flat the characteristics of the exposed tidal flat are similar to those of the carbon sponge in the laboratory test except that the double bounce scattering power is slightly greater in the real world example the single bounce scattering component in airsar data is generally greater than that in laboratory measurements because of sea surface conditions and oyster growth when the horizontal pole was aligned normal to the radar look direction single bounce scattering was greater than the double bounce scattering even under water covered conditions while a difference in tide height of 10 cm contributed approximately 3 0 db in the laboratory experiment a difference in tide height of 20 cm contributed to only approximately 1 7 db in the jers 1 sar image intensity jers 1 sar image intensity for areas dominated by double and single bounce scattering was 0 78 and 0 56 respectively results confirm that polarimetric sar data are useful in selecting areas dominated by double bounce scattering in oyster farms

detection of oyster habitat in tidal flats using multi frequency polarimetric sar data abstract exposed oyster reefs in tidal flats have complex and rough surfaces because of their unique surface texture which are quite distinct from the surrounding mud or sand flats here we investigate the microwave signatures backscattered from naturally distributed oyster reefs in tidal flats utilizing the polarimetric analysis techniques to fully polarimetric radarsat 2 c band and alos palsar l band data the study areas include the tidal flats around jebu island and hampyung bay on the west coast of the korean peninsula we analyzed the microwave scattering mechanisms associated with oyster reefs and surrounding areas using the polarimetric target decomposition theorem and quantitatively measu hhvv red target depolarization effects the cross polarized ratio hv vv the co polarized correlation coefficient hhvv and the co polarized phase difference between hh and vv on the basis of a large increase in the cross polarized backscattering hv in the c band sar data one can observe strong volume or multiple scattering and depolarization effects over oyster reefs areas whereas only surface scattering was dominant in most parts of the background tidal areas in oyster reefs the proportion of volume scattering and the cross polarized ratio were greater than 0 7 and 8 db respectively these scattering characteristics were also verified from in situ measurements in the field using a ground based polarimetric scatterometer system however almost no difference was observed between the scattering signatures of oyster reefs and background mudflat areas from l band data which have a considerably longer wavelength than c band the study clearly suggests that multi frequency c and l band polarimetric sar systems can be used to detect the naturally distributed oyster reefs in tidal flats

depletion of 13c in seawater σc02 on modern carbonate platforms significance for the carbon isotopic record of carbonates seawater co2 from modern carbonate platforms bahama banks and florida is depleted in 13c by as much as 4 relative to open ocean water depletion in 13c is caused by isotopically light co2 input from respiration of marine and terrestrial organic matter during water mass residence on the bank as such depletion in 13c is related to changes in water chemistry driven by evaporation freshwater discharge and caco3 withdrawal deviation of modern platform seawater 13c values away from those of surface seawater suggests that 13c values of ancient cratonic carbonate must be cautiously interpreted initial depositional environment as well as alteration during diagenesis must be considered in extracting valid secular trends for oceanic 13c variation

quantifying the relationship between water depth and carbonate facies abstract carbonate facies often are used to define meter scale parasequence or cyclic structure in ancient sedimentary basins these parasequences constitute the fundamental stratigraphic unit in many studies of ancient climate and life on earth of interest is the uncertainty associated with the assumptions that underpin the parasequence definition and interpretation this work presents a method that uses modern maps of bathymetry and the geographic distribution of facies atop the great bahama bank to extract a signal of water depth change from facies transitions in vertically stacked carbonate strata this probabilistic approach incorporates the observed complexity in the water depth distribution of immediately adjacent modern carbonate environments and results in an impartial and explicit interpretation of stratigraphic data with quantified uncertainties specifically this analytical tool can distinguish sequences of facies that are likely to record information about changing water depths from sequences of facies that do not additionally the quantitative signal extracted from sequences of discrete or qualitative data can be used for the correlation of stratigraphic sequences by quantifying geologic observations through a lens of modern data the reproducibility and accuracy of sedimentary interpretations can be improved to build a more authentic picture of earth history

global dissolution effects on planktonic foraminiferal mg ca ratios controlled by the calcite saturation state of bottom waters mg ca ratios of planktonic foraminiferal tests are important tools for reconstructing past ocean temperatures at different levels of the upper water column yet numerous studies suggest a significant influence of calcite dissolution on mg ca ratios lowering their initial signal recorded within a planktonic foraminiferal habitat to determine the effect of dissolution this study presents mg ca ratios of eight planktonic foraminiferal species from the south china sea sediment surface continuously decreasing with increasing water depth the mg ca ratios also decrease with calcite saturation states close to and below saturation bottom water delta co32 40 mu mol kg 1 this preservation pattern compares well with examples of mg ca dissolution from the tropical atlantic ocean and is independent of the foraminiferal species merging a global data set by separate normalization of 79 mg ca data sets from the pacific atlantic and indian oceans which removes thermal differences between the ocean regions and foraminiferal species enabled us to quantify a global decrease in planktonic foraminiferal mg ca ratios of 0 054 0 019 mu mol mol 1 per mol kg 1 below a critical threshold for dissolution of 21 3 6 6 mu mol kg 1 the absolute decline in mg ca ratios which is similar for all species affects temperature estimates from sub thermocline species more strongly than those from shallow dwellers the water depth of this critical threshold in the global oceans shoals from 3 5 km in the north atlantic to 0 5 km in the north pacific based on calculations of the global calcite saturation state from 6321 hydrographic stations above this critical threshold mg ca ratios are well preserved and paleotemperature estimates are broadly unaffected by dissolution

coupled sedimentary and δ13c records of late mississippian platform to slope successions from south china insight into δ13c chemostratigraphy abstract variability in stratigraphic accumulation rates and distribution of stratal hiatuses along with strong endemism of index fossils hinder regional to global stratigraphic correlation of the visean serpukhovian v s boundary interval late mississippian and thus geological inferences regarding the onset of the late paleozoic ice age here we integrate high resolution 13c time series with detailed sedimentary facies analysis of late visean early serpukhovian v s carbonate platform to slope successions from south china to evaluate the influences of local depositional and diagenetic processes on 13ccarb and to address the correlation issue analysis of 11 sedimentary facies from 5 outcrop sections indicates a restricted platform setting yashui section dominated by bioclastic wacke packstone to lime mudstone in which paleokarst developed and contemporaneous carbonate slope settings dominated by thin bedded lime mudstones intercalated with slumps and calciturbidites based on vertical facies assemblages three depositional units are recognized recording a significant sea level drawdown across the v s boundary multiple negative 13c excursions 1 can be correlated across the v s boundary interval in several slope sections naqing luokun and narao sections variability in the v s boundary 13c record in some sections is interpreted to record truncation physically by submarine erosion by slumps or chemically during karstification a long term decrease in 13c values through the serpukhovian of the yashui section likely records local influences on carbon cycling in the restricted platform setting this negative 13c trend and associated depositional facies at the yashui section can be correlated to the arrow canyon section usa which together with other coeval global sedimentary and geochemical records indicate a widespread eustatic drawdown in the late visean with initial buildup of gondwanan ice sheets we conclude that integrated sedimentary facies analysis and 13c chemostratigraphy can be used for stratigraphic correlation when interpreted within a well constrained sedimentary and carbon isotope regional framework

nonhomogeneous seawater sr isotopic composition in the coastal oceans a novel tool for tracing water masses and submarine groundwater discharge here we present high precision 2 3 ppm 87sr 86sr measurements in coastal waters together with salinity to evaluate water mass mixing and the influence of submarine groundwater discharge sgd in coastal waters and marginal seas nonhomogeneous sr isotopic variations in water columns were documented in the southern okinawa trough sot south china sea and kao ping canyon kpc where seawater 87sr 86sr varied up to 70 ppm seawater sr isotopic composition changes only slightly in the upper 200 m of the sot but was detectable and highly correlated with salinity indicating a mixing between radiogenic north pacific tropical water high 87sr 86sr and high salinity at 100 150 m and a less radiogenic component with low 87sr 86sr and low salinity at 200 m vertical profiles of seawater 87sr 86sr along the kpc show significant variations suggesting dynamic mixing affected by continental inputs i e river runoff and sgd in this region these results highlight the potential use of seawater sr isotopes as a powerful tracer for determining mixing ratios and the dynamic mixing of oceanic water masses especially in coastal and marginal seas

evaluation of terrasar x observations for wetland insar application this paper assesses the potential of using spaceborne x band synthetic aperture radar sar data for monitoring water level changes over wetlands our analysis is based on three sets of terrasar x tsx observations acquired over south florida s everglades wetlands during an eight month period in 2008 the first set was acquired in single hh polarization stripmap mode over our northern study area consisting of managed wetlands and urban environments the second set was acquired in dual polarization stripmap mode over the western half of the same area consisting mostly of managed wetlands the third set was also acquired with dual polarization stripmap mode over our southern study area consisting of natural flow freshand salt water wetlands in the southern everglades the first data set was used for a proof of concept study to verify that x band data can generate coherent interferograms in wetland areas interferometric processing of this data set shows a high level of coherence 0 35 over both wetland and urban regions maintaining interferometric phase in all three interferograms spanning 11 days surprisingly phase is maintained over some of the wetlands even for interferograms spanning 33 days the other two data sets were used to evaluate interferometric coherence of all four polarization modes and to determine dominant scattering mechanism in each wetland environment our results show high coherence values 0 4 in all polarization modes with highest values in hh then vv and lowest in hv or vh interferograms calculated from multipolarization data show very similar fringe patterns regardless of the polarization type suggesting that the phase information in all polarization data reflects water level changes in wetlands and that volume scattering may be less important than commonly believed we also used the two multipolarization data sets to conduct the pauli decomposition finding a strong dependence of scattering mechanism on vegetation type the high interferometric coherence level of all polarization data suggests that a significant part of the x band scattered signal interacts with lower sections of the vegetation trunks and branches because scattering from wind affected canopies cannot support such a high coherence level the high spatial resolution of tsx combined with its 11 day repeat orbit makes this x band sensor surprisingly suitable for wetland interferometric sar applications

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

does carbon 13 track anthropogenic co2 in the southern ocean a multiparametric linear regression technique was used for waters in the southern ocean to estimate the change in both 13 c dic 13 c dic and dissolved inorganic carbon dic dic between 1978 and 1998 due to the accumulation of anthropogenic co 2 the observed decrease in 13 c dic at the surface the suess effect was 0 015 0 003 yr 1 in the sub antarctic zone and 0 005 0 003 yr 1 in the antarctic zone similar to values reported for the southern indian ocean gruber et al 1999 sonnerup et al 2000 to compare the 13 c dic with adic we used the ratio of these two anomalies rc 13 c dic dic mol kg 1 1 along the section arc ranged from 0 015 0 005 at 42 s to 0 007 0 005 mol kg 1 1 at 54 s the spatial variability in arc in the southern ocean reflects different timescales for processes controlling the uptake of 13 c from those controlling the uptake of 12 c and indicates that 13 c dic decouples from adic poleward of the sub antarctic zone the variations of arc along the section suggest that the 13 c dic anomaly is not a good predictor of the anthropogenic co 2 inventory in the southern ocean some methods for determining anthropogenic co 2 uptake both on the global and regional scale assume the penetration depths of 13 c dic to be the same as adic which implies a constant value for arc in the ocean at 0 016 mol kg 1 1 heimann and maier reimer 1996 ortiz et al 2000 bauch et al 2000 the use of a constant arc and the observed 13 c dic to estimate anthropogenic co 2 could lead to an underestimate in the inventory of anthropogenic co 2 for the southern ocean by 50

in situ calibration of mg ca ratio in planktonic foraminiferal shell using time series sediment trap a case study of intense dissolution artifact in the south china sea this study examines mg ca temperature equations through the use of planktonic foraminifers collected from continuous time series sediment traps at four water depths in the south china sea this deployment provides an opportunity to refine partial dissolution artifacts and to identify responses of shell chemistry to changes in ambient seawater conditions paired mg ca and 18o measurements on shells are strongly correlated with seasonal variability in terms of temperature at specific habitat depths however partial dissolution can significantly alter mg ca ratios even at depths well above the calcite lysocline or carbonate compensation depth of the three species studied neogloboquadrina dutertrei is the most sensitive species to dissolution relative to the other surface dwelling species globigerinoides ruber and globigerinoides sacculifer differences between the mg derived temperature equation here and those from previously established core top or sediment trap calibrations can be attributed to various degrees of dissolution and lateral advection thus highlighting the need for in situ empirical calibration for different ocean basins

the influence of air and sea exchange on the carbon isotope distribution in the sea we explore here the influence of the temperature dependence of isotope fractionation between atmospheric co2and ocean co2 on the distribution of carbon isotopes in the ocean this is accomplished by an analysis of departures from the expected redfield tie between po4 and 13c we find that for the surface ocean the temperature influence largely compensates for the biologic influence in the deep ocean the temperature influence imprinted at the sites of deepwater formation reduces somewhat the biologically induced difference between the carbon isotope ratios for deep waters produced in the northern atlantic and in the antarctic these same features are reproduced in the hamburg ocean model in order to assess the impact of changes in the ratio of ocean mixing rate to wind speed we have made a model run in which co2 exchange rates between air and sea were everywhere doubled as expected the influence of the thermodynamic effect on the oceanic carbon isotope distribution is magnified

carbon isotope records from extant caribbean and south pacific sponges evolution of δ13c in surface water dic stable isotope records of demosponges from the caribbean and coral sea are described for the purpose of studying the influence of fossil fuel co2 on the carbon isotopic composition of dissolved inorganic carbon dic in surface water the slow growing sponges precipitate calcium carbonate in isotopic equilibrium with ambient sea water and are used to detect changes in 13cdic from pre industrial times early 19th century to the present we observed similar shapes and ranges in 13c curves measured on caribbean specimens collected from water depths of 25 84 and 91 m as well as a specimen collected in shallow waters off new caledonia the records reveal a highly significant correlation with atmospheric 13cco2 13cdic values for caribbean and coral sea surface waters were calculated using the 13c sponge records while 13c of atmospheric co2 decreased by about 1 4 from the early 19th century to 1990 13cdic of caribbean and coral sea surface waters decreased by 0 9 0 2 and 0 7 0 3 respectively no isotopic equilibrium between surface water dic and atmospheric co2 was observed either during the pre industrial steady state or during the last 100 years the lower amount of depletion in the surface water 13cdic with respect to the atmospheric anthropogenic signal is explained by the dilution of the surface waters by biologically altered subsurface water dic the lower 13c decrease in the coral sea points to a stronger influence of the subsurface water source compared to the caribbean

carbon isotopic disequilibrium between seawater and air in the coastal northern south china sea over the past century six coastal sediment cores collected from the northern south china sea were dated by 210 pb and analyzed for stable carbon and oxygen isotope composition of planktonic foraminifer globigerinoides ruber d 13 cgr and d 18 ogr three of these cores were located east of hainan island and the other three off the pearl river estuary pre surface seawater d 18 o and dissolved inorganic carbon dic d 13 c were identified as the dominant factors controlling downcore variations of d 18 ogr and d 13 cgr respectively results of d 13 cgr were then used to study surface water d 13 cdic and its relation to d 13 c of atmospheric co2 d 13 catm over the past century downcore records showed rather constant d 13 cgr in cores off hainan island but moderate decreases of d 13 cgr at rates between 0 006 and 0 009 per year in cores off the pre isotopic disequilibrium between d 13 cdic and d 13 catm was observed with d 13 cdic apparently higher than expected at equilibrium with d 13 catm except at the site closest to the pre the relatively steady d 13 cgr values east of hainan island were explained by balanced vertical mixing and biological pump whereas the moderate d 13 cgr decreases with time off the pre were attributable to fluvial input of

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

the nature of the δ13c of periplatform sediments implications for stratigraphy and the global carbon cycle the carbon isotopic composition y 13 c of bulk carbonates obtained from a transect of sites drilled through platform and periplatform sediments of holocene to early miocene age has been compared to ascertain whether changes in the y 13 c can be correlated between sediments of equivalent ages and whether such changes can be related to global changes in the y 13 c of the dissolved inorganic carbon in the oceans over this time period five of the sites were drilled during leg 166 of the ocean drilling project 1003 1007 in a transect ranging from five km to 25 km away from the platform margin and penetrating sediments of holocene to oligocene age that are contained in 17 depositional sequences a q two shallow water sites clino and unda were situated on a extension of the same transect on great bahama bank in a water depth of 10 15 m with the exception of unda and clino the y 13 c of the carbonates ranges from 5x in the younger sequences to 1x in the early miocene in each of the sites the y 13 c is strongly positively correlated with the percentage of aragonite as a consequence the y 13 c of sequences a through f is strongly correlated reflecting the decreasing amount of aragonite with increasing depth in the two platform sites the y 13 c is significantly lower in the younger portions of the cores as a result of the influences of meteoric diagenesis during repeated exposure during the pleistocene although the y 13 c of the individual sequences can be correlated in most instances between the odp holes the changes are not related to global changes in the y 13 c of the oceans which in contrast to the y 13 c of the platform sediments become isotopically lower towards the present day instead variations in the y 13 c appear to be related to varying mixtures of y 13 c rich banktop sediments and pelagic material

a three component scattering model for polarimetric sar data an approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric sar observations the mechanisms are canopy scatter from a cloud of randomly oriented dipoles evenor double bounce scatter from a pair of orthogonal surfaces with different dielectric constants and bragg scatter from a moderately rough surface this composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers the model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from nasa jet propulsion laboratory s jpls airborne polarimetric synthetic aperture radar airsar system the model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas for example the model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature an advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric sar images furthermore it is shown that the contributions of the three scattering mechanisms to the hh hv and vv backscatter can be calculated from the model fit finally this model fit approach is justified as a simplification of more complicated scattering models which require many inputs to solve the forward scattering problem

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

study of the polarimetric characteristics of mud flats in an intertidal zone using c and x band spaceborne sar data abstract the polarimetric characteristics of a mud flat area in the intertidal zone near jiangsu china are analyzed under different environmental conditions using x band and c band spaceborne synthetic aperture radar sar data from the terrasar x tsx and radarsat 2 r2 satellites the dominant scattering mechanisms of different objects including mud flats and aquaculture facilities in the intertidal zone are studied based on the polarimetric target decomposition of fully polarimetric r2 data the polarimetric characteristics of different objects in the intertidal zone are quantitatively compared using the depolarization parameters derived from the r2 data which indicate that tides have different effects on the dominant scattering mechanisms of the mud flats and aquaculture farms furthermore comparisons of the c band and x band polarimetric characteristics of the mud flats and aquaculture farms in the intertidal zone are analyzed by combining the tsx and r2 data the results show that surface scattering is the dominant mechanism of the mud flats whereas different dominant mechanisms occur in the aquaculture areas present during different tides interestingly strikingly similar polarimetric characteristics of mud flats and aquaculture in x band and c band sar are observed and these novel results were achieved through a depolarization analysis based on the tsx and r2 data in synergy

steady state freshwater seawater mixing zone in stratified coastal aquifers summary the mixing zone between freshwater and intruding seawater which controls regional groundwater flow dynamics and reactive transport processes is the most important component in coastal aquifers laboratory experiments and numerical simulations were conducted to investigate the effects of aquifer stratification on the thickness of a steady state freshwater seawater mixing zone a series of experiments were implemented in a laboratory tank packed with three layers of coastal sands and manipulated by two flow cells for maintaining constant head boundary conditions packed aquifers included a homogenous aquifer a high hydraulic conductivity k low k high k stratified aquifer and a low k high k low k stratified aquifer both tank scale and field scale density dependent models were developed to simulate the laboratory experiments and to systematically investigate aquifer stratification effects on the thickness of a steady mixing zone with varying layer configurations results showed that when an aquifer layer with a low k overlies a layer with a relatively high k slanting upward flow of diluted saltwater and re circulated seawater flow are refracted at the interface between the two layers resulting in streamline separation and a broad mixing zone in the low k layer by contrast the mixing zone in a high k layer is slightly narrowed when it overlies a layer with a relatively low k because flow refraction squeezes the streamlines within the mixing zone the mixing zone profile in head controlled systems is a function of k contrast but independent of the magnitude of k our results demonstrated the significant impact of aquifer stratification on controlling groundwater flow and solute transport in coastal subsurface environments and would have significant implications for studying physical chemical and biological processes in coastal subsurface environments as aquifer stratification is naturally prevalent

distribution and constraining factors of planktonic and benthic foraminifers in bottom sediments of the southern south china sea abstract a total of 93 surface sediment samples were collected to analyze the environmental factors constraining the foraminiferal distribution pattern in the southern south china sea scs species distributions and stable isotopic compositions were combined to reveal the controlling factors such as depth salinity substrate runoff currents and cold seep activities water depth is the dominant factor controlling both assemblage composition and 18o of benthic foraminiferal tests the 1000 m isobath separates the sites into two clusters cluster a and b which are dominated by deep water species and shallow water species respectively the sites in the deep water zone cluster a are characterized by lower absolute abundances species richness and shannon index values a measure of diversity and higher proportions of planktonic foraminifers compared with the sites in the shallow water zone cluster b increasing proportions of agglutinated tests with depth and rapidly decreasing proportions of planktonic foraminifera in the nansha trough basin provide evidence of calcium dissolution occurring at a depth corresponding with previous reports oxygen stable isotopes 18ob of benthic foraminifera become more positive with depth only up to 1000 m and remain constant beyond differences in the proportion of agglutinated and porcelaneous tests in the shallow water zone suggest that terrestrial runoff from nearby river systems mekong river and northern borneo rivers and seasonal surface currents scs southern cyclonic gyre and scs southern anticyclonic gyre jointly influence the distribution patterns of foraminifera in the study area enrichment of planktonic 18o is a response to cold waters brought by the scs southern cyclonic gyre during winter an upwelling current winter natuna off shelf current containing higher amounts of organic matter nutrients contributes to the depleted 13c of planktonic foraminifera and to the abnormal abundance of foraminifera at the sites within its area of influence the dominance of the foraminifer melonis barleeanus at sites belonging to subcluster a1 and the stable isotope compositions of benthic foraminifera 18o 0 13c

morphological geochemical and ecological differences of the extant menardiform planktonic foraminifera globorotalia menardii and globorotalia cultrata taxonomic consistency is the prerequisite for any foraminiferal study in particular interpretation of planktonic foraminiferal geochemical data requires consistent selection of monospecific tests due to varying habitats of different species in order to exemplify the impact of slightly varying morphological characteristics on geochemical signatures we investigated three basic shape dimensions test weights stable isotope values and mg ca ratios of globorotalia menardii and globorotalia cultrata which are often grouped or referred to as synonyms along with visual distinction encrusted g menardii is distinguished from shiny g cultrata by its on average doubled test weight when referring to the same maximum diameter more elongated and flattened g cultrata calcifies within the deeper mixed layer which applies also for the initial calcification of g menardii final encrustration of g menardii after vertical migration is suggested to take place close to the bottom of the seasonal thermocline combined mg ca ratios versus calcification temperature calibration provides a reliable tool for monospecific thermal reconstructions for the seasonal thermocline g menardii and the deeper mixed layer g cultrata c 2010 elsevier b v all rights reserved