experimental reactions of amphibolite with boron bearing aqueous fluids at 200 mpa implications for tourmaline stability and partial melting in mafic rocks reactions between hornblende plagioclase amphibolite and acidic and alkaline b bearing aqueous fluids have been investigated by experiments at 475 600 c and 200 mpa at 600 c hornblende calcic plagioclase react to form tourmaline danburite clinopyroxene quartz in acidic fluids containing 0 5 1 0 wt b2o3 tourmaline is precipitated directly from acidic fluids and the reaction is driven by neutralization of fluids by na ca derived from the breakdown of reactant solids the concentration of b2o3 in fluids needed to stabilize tourmaline increases as ph increases above approximately 6 0 and tourmaline is unstable in alkaline fluids ph approximately 6 5 7 0 regardless of b concentration in addition to acid base relations tourmaline stability is favored by comparatively higher activity coefficients for al species in acidic fluids the concentrations of al and si in fluid increase with alkalinity with the eventual production of felsic borosilicate melts through partial melting of the plagioclase component of the amphibolite in seeded experiments tourmaline also contributes components to melt partial melting is evident in the range 500 525 c at 200 mpa in experiments with 8wt b2o3 in fluid as na2b4o7 the experimental results are applied primarily to metasomatic reactions between mafic rocks and borate fluids derived from granitic magmas but tourmaline stability and partial melting in mafic regional metamorphic systems are also discussed briefly

fluid inclusions in the harney peak granite black hills south dakota usa implications for solubility and evolution of magmatic volatiles and crystallization of leucogranite magmas abstract experimental and theoretical studies have shown that magmatic fluids have strong influence on phase equilibria of granitic systems a microthermometric study of fluid inclusions in the proterozoic harney peak granite black hills south dakota usa was undertaken to obtain direct evidence for the composition and evolution of magmatic fluids in a leucogranitic system and to evaluate their effect on liquid lines of descent of leucogranite magmas a previous stable isotopic study has demonstrated that the granite has not interacted with nonmagmatic fluids since its crystallization therefore fluids found in the inclusions are of magmatic origin and present an opportunity to directly sample magmatic fluids trapped during crystallization of a granitic magma and during subsolidus conditions the harney peak granite was emplaced as multiple sills dikes and small intrusions many of which differentiated into coupled aplite pegmatite layers three types of fluid inclusions are found in the granite type 1 consist of variable saline h 2 o c0 2 mixtures with minor ch 4 or other gases inclusions of this type are found in tourmaline and quartz in aplite layers are generally isolated and have negative crystal shapes they are interpreted to be primary there is a general increase in salinity and decrease in isochore temperature with decreasing co 2 h 2 o ratio of the inclusions the trend is ascribed to progressive change in fluid composition with crystallization due to the differential solubility of co 2 and h 2 o in the high silica magma isochores coupled with independently determined crystallization temperatures suggest entrapment pressure 3 5 kbar consistent with geobarometry in the wallrocks type 2 inclusions are carbonic fluids dominated by co 2 whereas type 3 inclusions are saline aqueous fluids without a detected carbonic component both types are mostly found along healed fractures in quartz they are interpreted to be secondary inclusions that formed as a result of unmixing of type 1 inclusions at subsolidus conditions during uplift and cooling of the harney peak granite dome freezing point depressions birefringent daughter crystals phase equilibria considerations and track mapping of b and li distribution in thin sections all indicate that both type 1 and type 3 inclusions contain solutes such as k li and b in addition to nacl using published solubility models for h 2 o and co 2 in granitic melts and the composition of the most co 2 rich type 1 inclusions x co 2 0 55 the initial h 2 o and co 2 concentrations in the harney peak granite magma are deduced to have been 3 5 wt and 1500 ppm respectively the relatively low water concentration is consistent with temperatures of dehydration melting reactions that produced the magma it is suggested that the aplite pegmatite segregations found in parts of the harney peak granite are the result of initial rapid near liquidus crystallization of minerals with high na k ratios including plagioclase and tourmaline along a wide range of increasing h 2 o aplite crystallization was followed by crystallization of relatively potassic residual liquid enriched in fluxing elements under conditions of high h 2 o

neritic and pelagic carbonate sedimentation in the marine environment ignorance is not bliss synthesis of available data allows us to define general patterns of late quaternary carbonate production and sedimentation in the global ocean during high stands of sea level the neritic and pelagic environments appear to sequester approximately similar amounts of carbonate whereas during low stands of sea level the decreased neritic zone produces and accumulates approximately an order of magnitude less carbonate assuming that global accumulation of deep sea carbonates remains more or less constant during glacially induced changes in sea level the ocean becomes depleted with respect to calcium carbonate during high stands and recharges during low stands before we can achieve a better understanding of the global carbonate system however we need a better understanding of key environments and processes a production and accumulation on continental shelves both as potential sinks accumulation and as sources export to the deep sea b a better measure of pelagic carbonate production and c late quaternary late pleistocene and holocene mass accumulation rates in the deep sea

is late quaternary climate change governed by self sustained oscillations in atmospheric co2 a simple earth system model is developed to simulate global carbon and phosphorus cycling over the late quaternary it is focused on the geological cycling of c and p via continental weathering volcanic and metamorphic degassing hydrothermal processes and burial at the seabed a simple ocean model is embedded in this geological model where the global ocean is represented by surface water thermocline and deep water boxes concentrations of dissolved phosphorus dissolved inorganic carbon and total alkalinity are calculated for each box the partial pressure of co2 in the atmosphere pco 2a is determined by exchange processes with the surface ocean and the continents it serves as key prognostic model variable and is assumed to govern surface temperatures and global sea level the model is formulated as autonomous system in which the governing equations have no explicit time dependence for certain parameter values the model does not converge towards a steady state but develops stable self sustained oscillations these free oscillations feature pco 2a minima and maxima consistent with the ice core record when vertical mixing in the ocean is allowed to vary in response to pco 2a controlled temperature change a stable 100 kyr cycle with a rapid transition from glacial to interglacial conditions is obtained when additional non linear equations are applied to calculate deep ocean mixing iron fertilization and the depth of organic matter degradation as function of pco 2a controlled surface temperature the delta c 13 value of carbon in the ocean atmosphere system calculated in these model runs is consistent with the benthic delta c 13 record however the simulated c 13 depletion in the glacial ocean is not driven by the decline in terrestrial carbon stocks but by sea level change controlling the rates of organic carbon burial and weathering at continental margins the pco 2a and delta c 13 oscillations develop without any form of external milankovitch forcing they are induced and maintained by sea level change generating persistent imbalances in the marine carbon and phosphorus budgets stable oscillations are also obtained when sea level change is allowed to lag temperature with a realistic time scale for ice sheet adjustment

evidence for a reduction in the carbonate ion content of the deep sea during the course of the holocene the paleo carbonate ion proxy proposed by broecker et al 1999 is applied in a search for trends in the holocene acidity of waters in the transition zone between north atlantic deep water and antarctic bottom water aabw a clear signal emerges that the carbonate ion content of waters in this zone declined during the past 8000 years in order to determine whether this decline represents a strengthening of the northward penetrating tongue of low co3 content aabw or a global reduction of co3 ion measurements were made on a core from the ontong java plateau in the western equatorial pacific evidence for a similar decline in co3 ion over the course of the holocene was obtained lending support of the latter explanation such a drop is consistent with the recent finding by indermuhle et al 1999 that the co2 content of the atmosphere as recorded in the taylor dome antarctica ice core rose by 20 25 ppm during the past 8000 years

global chemical erosion during the last glacial maximum and the present sensitivity to changes in lithology and hydrology geographically based calculations for 18 000 years ago 18 ka and today were made to examine the potential effects on terrestrial chemical erosion of changes in lithology and hydrology on glacial interglacial timescales runoff fields were derived from general circulation model predictions of precipitation minus evaporation then global lithologic maps were prepared so that empirical relationships for runoff versus bicarbonate flux for different rock types could be used to calculate global chemical erosion rates assuming that significant chemical erosion does not occur beneath ice sheets we find that chemical erosion in ice free areas at 18 ka was only slightly greater than today this result arises because the amount of land covered by ice sheets is roughly compensated for by exposed shelf areas and because there is little difference in global runoff the small 20 increase in the global chemical erosion rate during glacial conditions is due to exposure on the shelves of a relatively high proportion of carbonates which weather faster than average data on glacial interglacial movements of the calcite compensation depth ccd are inconclusive but seem to indicate little change whereas even a 20 increase in the riverine bicarbonate flux should cause an observable deepening if the ccd did not indeed change then our predicted increase in the bicarbonate flux from land during glaciations would have to be accommodated by other means such as increased carbonate productivity about half of the observed decrease in atmospheric pco2 at 18 ka could be explained if increased silicate chemical erosion accompanied increased total chemical erosion in ice free areas consideration of the maximum possible effect of meltwater at ice margins leads to an 80 increase in the global chemical erosion rate at 18 ka such an increase would lead to a larger and faster drop in atmospheric pco2 but also to an excessive deepening of the global ccd this scenario seems unrealistic our results are contrary to interpretations of a much higher silicate chemical erosion rate during glaciations based on recently published records of quaternary marine sr isotopic ratios therefore if these records are indeed globally representative and entirely due to increased silicate chemical erosion as opposed to changes in source areas or hydrothermal inputs then other factors such as a shift in the global weathering regime which we do not explicitly consider here may be involved sensitivity tests show that considering spatial heterogeneities in lithology and runoff leads to lower predictions of global chemical erosion rates than what one would obtain by considering only global averages in a non spatially resolved calculation

surface water temperature salinity and density changes in the northeast atlantic during the last 45 000 years heinrich events deep water formation and climatic rebounds we developed a new method to calculate sea surface salinities sss and densities ssd from planktonic foraminiferal 18o and sea surface temperatures sst as determined from planktonic foraminiferal species abundances sst sss and ssd records were calculated for the last 45 000 years for biogeochemical oceanic flux study bofs cores 5k and 8k recovered from the northeast atlantic the strongest feature is the dramatic drop in all three parameters during the heinrich ice rafting events we modelled the possibility of deepwater formation in die northeast atlantic from the ssd records by assuming that the surface waters at our sites cooled as they flowed further north comparison with modelled north atlantic deepwater densities indicates that there could have been periods of deepwater formation between 45 000 and 30 000 14c years b p interrupted by iceberg meltwater input of heinrich event 3 and 4 at 27 000 and 38 000 14c years b p and during the holocene no amount of cooling in the northeast atlantic between 30 000 and 13 000 years could cause deep water to form because of the low salinities resulting from the high meltwater inputs from icebergs our records indicate that after each heinrich event there were periods of climatic rebound with milder conditions persisting for up to 2000 years as indicated by the presence of warmer and more saline water masses after these warm periods conditions returned to average glacial levels these short term cold and warm episodes in the northeast atlantic are superimposed on the general trend towards colder conditions of the last glacial maximum lgm heinrich event 1 appears to be unique as it occurs as insolation rose and was coeval with the initial melting of the fennoscandian ice sheet we propose that meltwater input of heinrich event 1 significantly reduced north atlantic deep water formation reducing the heat exchange between the low and high latitudes thus delaying deglaciation by about 1500 radiocarbon years 2000 calendar years

ocean chemistry during glacial time abstract measurements of co2 to air ratios in the gas trapped in bubbles in ice of glacial age suggest that the co2 content of the atmosphere was considerably lower during peak glacial time than during holocene time the purpose of this paper is to show that such a change must in all likelihood be the result of alterations in the nutrient element chemistry of sea water two possible scenarios are presented one involves alternate storage and erosion of phosphorous leaving residues from shelf sediments the other involves changes in the c p ratio in the organic debris falling to the deep sea means of verifying the nutrient cycle hypothesis are also given it is shown that the 13c record as we know it in planktonic and benthic foraminifera the oxygen record as inferred from benthic foraminifera species distributions and the early post glacial caco3 preservation event as recorded by aragonitic pteropods are consistent with both of the hypotheses presented only if an early post glacial spike in the 13c record for planktonic shells could be found would it be possible to eliminate one of these hypotheses i e that involving shelf storage the implications of these nutrient hypotheses to climate theory are as follows if shelf storage is responsible for the glacial to interglacial co2 increase then the co2 change must be considered an amplifier of some primary cause the reason is that sea level changes are needed to drive deposition on and erosion from the shelves on the other hand if changes in the c p ratio for falling debris are responsible then the co2 change could either be an amplifier or a primary cause for the major glacial to interglacial climatic cycle the latter is possible as self sustained oscillations in ocean chemistry might be driven by interactions between ocean ecology and ocean nutrient chemistry

punctuated progradation of the seven mile beach holocene barrier system southeastern tasmania abstract prograded barriers are depositional coastal landforms which preserve past shoreline locations and have been studied in order to understand the fundamental drivers of barrier formation this paper reconstructs the holocene history of the seven mile beach prograded barrier in tasmania australia using optically stimulated luminescence osl dating ground penetrating radar gpr light detection and ranging lidar elevation models and sedimentological analyses shoreline progradation of the barrier commenced around 7300 years ago and continued to near present despite a 3000 pause in deposition between 6700 and 3600 years ago indicative of substantial changes in sediment availability gpr imaged subsurface structures contain a record of seaward dipping reflectors preserved as sediment supplied beaches and dunes leading to shoreline progradation in the past 500 years a large transgressive dune has formed built from reworked barrier sands and now dominates the eastern portion of the barrier implying that shoreline progradation has ceased this study reaffirms the notion that relict foredune ridges are strongly aligned with modal wave refraction patterns in planform and emphasises the importance of sediment delivery as a key driver of shoreline progradation through beachface and dune accretion the substantial pause in shoreline progradation on this barrier system as observed on others around the world requires further explanation although changes in sediment delivery have been inferred it may also be appropriate to reopen the debate on holocene sea level change in tasmania

links between iron supply marine productivity sea surface temperature and co2 over the last 1 1 ma received 3 july 2008 revised 9 october 2008 accepted 27 october 2008 published 14 february 2009 1 paleoclimatic reconstructions have provided a unique data set to test the sensitivity of climate system to changes in atmospheric co2 concentrations however the mechanisms behind glacial interglacial g ig variations in atmospheric co2 concentrations observed in the antarctic ice cores are still not fully understood here we present a new multiproxy data set of sea surface temperatures sst dust and iron supply and marine export productivity from the marine sediment core ps2489 2 odp site 1090 located in the subantarctic atlantic that allow us to evaluate various hypotheses on the role of the southern ocean so in modulating atmospheric co2 concentrations back to 1 1 ma we show that antarctic atmospheric temperatures are closely linked to changes in so surface temperatures over the last 800 ka and use this to synchronize the timescales of our marine and the european project for ice coring in antarctica epica dome c edc records the close correlation observed between iron inputs and marine export production over the entire interval implies that the process of iron fertilization of marine biota has been a recurrent process operating in the subantarctic region over the g ig cycles of the last 1 1 ma however our data suggest that marine productivity can only explain a fraction of atmospheric co2 changes up to around 40 50 ppmv occurring at glacial maxima in each glacial stage in this sense the good correlation of our sst record to the edc temperature reconstruction suggests that the initial glacial co2 decrease as well as the change in the amplitude of the co2 cycles observed around 400 ka was most likely driven by physical processes possibly related to changes in antarctic sea ice extent surface water stratification and westerly winds position

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

holocene sea level change on the southeast coast of australia a review a revised holocene sea level curve for the southeast coast of new south wales australia is presented based on a review of previously published geochronological results for fossil molluscs organi

holocene shoreline progradation and coastal evolution at guichen and rivoli bays southern australia prograded barrier systems record shoreline behaviour and palaeoenvironmental information the guichen bay holocene embayment fill succession in south australia has been subject to several prominent

dawsonite an inclusion mineral in quartz from the tin mountain pegmatite black hills south dakota dawsonite naal co 3 oh 2 was identified in primary fluid inclusions in quartz from the li rich tin mountain pegmatite black hills south dakota by petrography sem eds analysis and raman spectroscopy this is the first report of dawsonite as an inclusion mineral in a pegmatite the presence of dawsonite in the inclusions is evidence for the existence of carbonate ions in the complex pegmatite melt and or exsolved magmatic fluid the lack of dawsonite as a macroscopic mineral is attributed to its high solubility in the late pegmatite fluids and to the small fraction of carbonate ions in the melt however its common occurrence along with other carbonate and borate minerals in fluid inclusions suggests that carbonate and borate complexes play an important role in petrogenesis of pegmatites

ice age terrestrial carbon changes revisited n shackleton 1977 first proposed that changes in the marine 13 c record 13 c could be used to infer ice age changes in carbon storage on land the previously published best estimate from the marine record is equivalent to about 490 gt 0 32 13 c however adams et al 1990 utilized a pollen database to estimate a 1350 gt change in carbon storage which would cause a 13 c of about 0 90 the nearly trillion ton difference in estimates amounts to almost half of the total carbon stored on land to address the nature of this discrepancy i have reexamined the terrestrial carbon record based on a new pollen database compiled by r webb and the cooperative holocene mapping project cohmap group i estimate about 750 1050 gt glacial interglacial change in terrestrial carbon storage with the range reflecting uncertainties in carbon storage values for different biomes additional uncertainties apply to rainforest and wetland extent and presence of c4 plants which have a significantly different isotopic signature than c3 plants although some scenarios overlap a new estimate of carbon storage based on the oceanic 13 c record revised to 0 40 and 610 gt most estimates seem to fall outside the envelope of uncertainty in the marine record several possible explanations for this gap involve 1 a missing sink may be involved in land sea carbon exchange e g continental slopes 2 the geochemistry of the exchange process is not understood 3 carbon storage by biome may have changed under ice age boundary conditions or 4 the standard interpretation of whole ocean changes in the marine 13 c record requires reevaluation this latter conclusion receives some support from comparison of the 13 c records for 18 o stages 2 and 6 for the stage 6 glacial the 13 c changes are 50 60 larger than for the stage 2 glacial yet implications of increased aridity are not supported by longterm trends in atmospheric dust loading to summarize the above analysis implies that despite the uncertainties remaining in estimates of terrestrial carbon storage changes a case can be made that our understanding of the transfer process is incomplete and that the eventual explanation may require clarification of factors affecting the marine 13 c record

quantitative interpretation of atmospheric carbon records over the last glacial termination 1 the glacial interglacial rise in atmospheric pco2 is one of the best known changes in paleoclimate research yet the cause for it is still unknown forcing the coupled ocean atmosphere biosphere box model of the global carbon cycle bicycle with proxy data over the last glacial termination we are able to quantitatively reproduce transient variations in pco2 and its isotopic signatures 13c 14c observed in natural climate archives the sensitivity of the box model of the isotopic carbon cycle bicycle to high or low latitudinal changes is comparable to other multibox models or more complex ocean carbon cycle models respectively the processes considered here ranked by their contribution to the glacial interglacial rise in pco2 in decreasing order are the rise in southern ocean vertical mixing rates 30 ppmv decreases in alkalinity and carbon inventories 30 ppmv the reduction of the biological pump 20 ppmv the rise in ocean temperatures 15 20 ppmv the resumption of ocean circulation 15 20 ppmv and coral reef growth 5 ppmv the regrowth of the terrestrial biosphere sea level rise and the increase in gas exchange through reduced sea ice cover operate in the opposite direction decreasing pco2 during termination i by 30 ppmv according to our model the sequence of events during termination i might have been the following a reduction of aeolian iron fertilization in the southern ocean together with a breakdown in southern ocean stratification the latter caused by rapid sea ice retreat trigger the onset of the pco2 increase after these events the reduced north atlantic deep water nadw formation during the heinrich 1 event and the subsequent resumption of ocean circulation at the beginning of the bolling allerod warm interval are the main processes determining the atmospheric carbon records in the subsequent time period of termination i we further deduce that a complete shutdown of the nadw formation during the younger dryas was very unlikely changes in ocean temperature and the terrestrial carbon storage are the dominant processes explaining atmospheric 13c after the bolling allerod warm interval

late pleistocene evolution of the ocean s carbonate system abstract we demonstrate that the carbonate record from a single site ocean drilling program site 1089 in the deep south atlantic represents a qualitative high resolution record of the temporal evolution of the carbonate saturation state of the deep sea the record is especially notable because it is free from many of the complications that limit other records low sedimentation rates blurring by chemical erosion bioturbation etc the pattern of carbonate variability is characteristic of indo pacific cores with high carbonate glacials and low carbonate interglacials wt carbonate lags changes in benthic 18 o by an average of 7 6 kyr and carbonate variations are in phase with the rate of change first derivative of benthic 18 o intense dissolution occurs at the transition from interglacial to glacial periods and increased preservation occurs during deglaciations these observations represent two fundamentally different responses of the marine carbonate system the lagged response of carbonate to 18 o reflects a steady state mass balance process whereby the lysocline adjusts to maintain alkalinity balance between riverine input and marine burial the site 1089 carbonate signal is remarkably similar to inferred changes in the sr ca of seawater for the past 250 kyr which implies that both carbonate dissolution and seawater sr ca may be controlled by sea level induced changes in the location of carbonate deposition shelf basin fractionation during glacial to interglacial cycles the transient change in preservation during the transitions into and out of glacial stages reflects a response of the carbonate system to a redistribution of alkalinity and dic in the ocean i e carbonate compensation comparison of the site 1089 carbonate and vostok p co 2 records suggests a role of deep sea co 3 2 variations for governing at least some second order features of the atmospheric p co 2 signal in order to quantify this role however measurement of indices of dissolution along a true depth transect will be required to estimate the magnitudes of changes in deep sea co 3 2

the evolution of pleistocene climate a time series approach abstract in the later part of the pleistocene variations in global ice volume have been dominated by an approximate 100 000 year cycle analysis of 2 myr long oxygen isotope record from an equatorial pacific core indicates that this is true only for the last 900 000 years prior to this time the amplitude of the 100 000 year cycle is much reduced as is the variance of all oscillations with periods greater than 60 000 years based on results of time series analysis of this 2 myr long record the pleistocene glacial cycles can be divided into three sections 1 the late pleistocene 0 900 kyr b p where the variations in the isotope record are dominated by the 100 000 year cycle 2 the middle pleistocene 900 1450 kyr b p in which low frequency components are not as important as in the later period of the pleistocene and 3 the early pleistocene late pliocene 1450 2000 kyr b p where general reductions of importance at all frequencies is seen as compared to the later intervals recent modeling efforts which describe variations in global ice volume show that the dominant low frequency component observed in the late pleistocene can result from different time constants for the rate of glacial growth and decay in response to variations in the earth s orbital parameters it is hypothesized that during the early pleistocene the rate of growth and decay of glaciers were more similar and that continental erosion by successive glacial advances lowered the land surface in areas of ice cap formation to below sea level when the ice caps became marine based more rapid decay of the ice became possible

thin film dawsonite in jurassic coal measure strata of the yaojie coalfield minhe basin china a natural analogue for mineral carbon storage in wet supercritical co2 abstract a large amount of thin film dawsonite has developed in coal cleats and also in fractures within the roof sandstone in jurassic co 2 rich coal measure strata of the yaojie coalfield minhe basin china the co 2 in these strata has been in a supercritical state since natural emplacement in this study the yaojie coalfield is considered a natural analogue site for co 2 capture utilization and storage ccus the thin film dawsonite in coal measure strata was analyzed to investigate the evolution of carbon in supercritical co 2 after ccus as it provides a possible example of the formation of carbonate minerals from a wet supercritical co 2 fluid the cleat and fracture filling dawsonite takes the form of white or silver white radial thin film crystals generally 2 and co 2 derived from the decomposition of basement marble which resulted from dynamic thermal metamorphism of the f19 fault zone the carbon isotopic compositions of the cleat filling dawsonite from different carbon sources are transitional and the carbon source for all of the sandstone fracture filling dawsonite is the co 2 released from the decomposed basement marble the morphological and mineralogical characteristics of the thin film dawsonite show that it most likely nucleated and grew directly in the liquid like water film formed by wet supercritical co 2 on solid phase surfaces rather than by epitaxial growth on the rocks surrounding the cleats and fractures probably via layer by layer crystallization the sodium and aluminum in the dawsonite were derived from formation water the formation of dawsonite in the coal measure strata of the yaojie coalfield indicates that some of the free state co 2 which increases in content due to desorption of the coal matrix can ultimately be converted into carbonate minerals during ccus

late pleistocene and holocene sea level change along the australian coast abstract tectonically the australian continent is relatively stable and as such it provides a good platform for studying late pleistocene and holocene sea level change the observations indicate that present sea level was reached at about 6000 years ago and that since then level has remained constant to within a few metres considerable spatial variability in the amplitude of the emergence and in the time at which sea levels first reached their present values have been observed spatial variability has also been observed in the sea level during the last glacial maximum and during the late phase of the holocene transgression much of this variaiblity is the result of the earth s adjustment to the glacial melting in the late pleistocene early holocene time and the concomitant distribution of this meltwater into the oceans conclusions that are drawn from matching observations with this glacio hydro isostatic model include the following 1 the mantle viscosity increases with depth the average upper mantle viscosity is about 2 3 10 20 pa s and the average lower mantle defined as below 670 km depth viscosity is about 10 22 pa s the average lithospheric thickness for the coastal and offshore region is about 70 80 km lateral variations in these mantle parameters are indicated 2 the addition of melwater into the oceans did not cease 6000 years ago but continued at a reduced rate up to more recent times adding an amount of water equivalent to a 3 m sea level rise in this interval 3 the amplitude of the holocene emergence is a function inter alia of coastal geometry and significant variations occur over distances of a few hundred kilometres and more holocene highstands of 1 2 m are generally well developed at the continental margins but are less well developed or do not developed at all at offshore islands and reefs 4 variations in the time of maximum emergence also occur being earlier at upstream tidal river sites than at coastal sites at offshore reefs or islands the sea level curve lags the coastal curves by 1000 years or more 5 considerable spatial variability occurs in the sea levels at the time of the last glacial maximum with variations of up to 30 m occurring across the continental shelves 6 there is generally no need to invoke tectonic movements to explain the sea level data along the australian coast but possible exceptions occur for the perth region and for tasmania

reply to punctuated transgression comment on oliver t s n donaldson p sharples c roach m and woodroffe c d punctuated progradation of the seven mile beach holocene barrier system southeastern tasmania abstract our interpretation of the depositional history of the prograded barrier at seven mile beach in tasmania described in oliver et al 2017a was based on the morphology of ridges apparent in the lidar based digital elevation data and a sample of 14 optically stimulated luminescence osl ages dougherty 2018 has identified gaps in the chronology and speculated that progradation may have occurred as sea level fell from a mid holocene highstand inappropriately applying sea level curves from mainland australia despite a highstand being inferred by early research in tasmania glacio isostatic modelling and recent sea level studies adopted a prevailing view that excluded a highstand our observations led us to question this prevailing view and to suggest that it might be appropriate to reopen the debate on holocene sea level change in tasmania we welcome the renewed interest in the chronology and sea level history of this prograded barrier and look forward to further clarification based on new evidence the site may have the potential to become one of the more continuous and better constrained sea level records in southern australia

evaporitic carbonates in the pre salt of santos basin genesis and tectonic implications abstract since the first discoveries of oil accumulations in the carbonate reservoirs of the lower cretaceous barra velha formation of the santos basin their genesis has been the subject of intense discussion different depositional models have been proposed with some authors advocating a microbial origin while others an abiotic origin as travertines or travertine like rocks this search for a modern carbonate analogue for these unusual rocks may have disregarded an intriguing alternative an evaporative model supported by our petrographical and geochemical data evaporitic sediment patterns in endorheic basins in a depositional framework of brine drawdown are dominated by ephemeral salt pan hydrology bedded salt crusts form a stack of subaqueous aligned crystal beds at the sediment water interface salt grows diagenetically within saline and mud layers beneath the dry pan surface finally laminated sediments are deposited we observe a similar cyclic pattern in the pre salt core we described beds of shrub like crystals and diagenetic spherulites growing in magnesium clay matrix are followed by laminites the model we propose attempts to contribute solving the puzzle of pre salt carbonate deposition by integrating sedimentology and geochemistry with basin tectonics our observations and basin tectonics point to the exciting possibility that the sag phase carbonates of the santos campos basin were deposited as the initial transitional stage of a closed sub sea level evaporite basin whose rising salinities culminated in the deposition of halite and bittern salts carnallite sylvite tachyhydrite basinwide evaporites are singular events in the geological record they form when a giant sub sea level basin becomes a sump of continental marine and hydrothermal fluids producing unexpected brine compositions in unusual depositional settings present in ancient evaporitic basins but absent from most modern ones the novelty in this paper is that we apply to pre salt carbonate deposition the sedimentology hydrology and geochemistry of ancient evaporitic basins with this concept in mind we propose a geochemical model for the unusual pre salt carbonate precipitation of the santos basin regarding the walvis rio grande volcanic high as a topographic barrier during the aptian we suggest that the main sources of calcium to the barra velha paleolake were hydrothermal brines mostly from infiltrating seawater that reacted at depth with the basalts of the volcanic barrier hyperextension of the lithosphere with a shallow moho increased geothermal gradients to levels favorable for the generation of hydrothermal cacl2 brines a process facilitated by the already elevated ca ion and low sulfate concentration of the cretaceous ocean these cacl2 rich fluids would pass through the volcanic barrier into a sub sea level paleolake in the rift basin the high salinity paleolake would become saturated in calcium bicarbonate carbonate as internally drained nahco3 bearing alkaline waters formed by physical chemical weathering of penecontemporaneous basaltic rocks mix with the cacl2 bearing hot brines percolating through the barrier producing a hybrid brine 2nahco3 cacl2 ca hco3 2 2nacl such a depositional system integrating the geochemical depositional controls of sag phase carbonates with those of the south atlantic evaporites has important implications for unravelling the genesis of these exotic deposits

p t and fluid evolution of barren and lithium pegmatites from vlastějovice bohemian massif czech republic fluid inclusions mineral thermometry and stable isotope data from two types of mineralogically and texturally contrasting pegmatites barren ones and lithium ones from the moldanubian zone of the bohemian massif were studied in order to constrain p t conditions of their emplacement subsolidus hydrothermal evolution and to estimate composition of the early exsolved fluid and that of the parental melt despite the fact that the lithium pegmatites are abundant throughout the crystalline units of the bohemian massif data similar to this paper have not been published yet the studied pegmatites are hosted by iron rich calcic skarn bodies this specific setting allowed scavenging of calcium fluorine and some other elements from the host rocks into the pegmatitic melts and post magmatic fluids such contamination process was important namely in the case of barren pegmatites as can be deduced from the variation in anorthite contents in plagioclase and from the presence of fluorite hornblende with f content or garnet in the contact zones of pegmatite dykes fluid inclusions were studied mostly in quartz but also in fluorite titanite and apatite early aqueous carbonic and late aqueous fluids were identified in both pegmatite types the p t conditions of crystallization as well as the detailed composition of exsolved magmatic fluid however particularly differ the magmatic fluids associated with barren pegmatites correspond to h2o co2 low salinity fluids composition of which evolved from 20 to 23 to 5 mol co2 and from 2 to 4 6 mol nacl eq sudden decrease in the co2 content of the post magmatic fluids 5 mol co2 seems to coincide with the enrichment of the fluid in calcium from the contamination process and resulted in precipitation of calcites frequently found as trapped solid phases in fluid inclusions the fluids associated with lithium pegmatites are more complex h2o co2 n2 h3bo3 nacl the co2 content of early exsolved fluid is 26 20 mol co2 and remains the same in the next fluid generation the main difference between the magmatic and the first post magmatic fluids is the presence of 7 9 wt of h3bo3 identified as daughter mineral sassolite in the former the second post magmatic fluids are again co2 poor 4 mol and more saline 4 mol nacl eq the composition of exsolved fluid was further used to constrain volatile composition and content of the parental melts finally p t conditions of pegmatite crystallization are constrained 600 640 c and 420 580 mpa for the barren pegmatites and 500 570 c and 310 430 mpa for the lithium pegmatite while the emplacement of the former occurred in thermal equilibrium with the moldanubian host rock environment the emplacement of the later suggests substantial thermal disequilibrium

dissolved inorganic phosphorus export to the coastal zone results from a spatially explicit global model 1 here we describe test and apply a spatially explicit global model of river borne dissolved inorganic phosphorus dip export called news dip among the innovations in news dip are increased spatial resolution 0 5 0 5 explicit treatment of sewage fertilizer manure and weathering p sources and inclusion of reservoir retention and consumptive water use terms the news dip model performed better than pre existing global models in predicting dip yield for both calibration and validation basins r2 0 72 and 0 56 respectively news dip predicts that of the 34 tg of p yr 1 loaded on watersheds by human activity globally approximately 3 reaches river mouths as dip anthropogenic sources account for 65 0 71 tg yr 1 of the dip exported to the coastal zone with the remainder 0 38 tg yr 1 attributable to natural weathering processes dip yields range over 5 orders of magnitude from less than 0 01 to 1153 kg p km 2 yr 1 with highest predicted dip yields clustering in east asia europe and indonesia human sewage is the largest anthropogenic source of dip to the coastal zone on all continents and to all ocean basins news dip also suggests that despite regional variability at the global scale non point sources of dip such as inorganic p fertilizer and manure are much less important in determining coastal export of dip than point sources and natural weathering processes

consequences of pacing the pleistocene 100 kyr ice ages by nonlinear phase locking to milankovitch forcing 1 the consequences of the hypothesis that milankovitch forcing affects the phase e g termination times of the 100 kyr glacial cycles via a mechanism known as nonlinear phase locking are examined phase locking provides a mechanism by which milankovitch forcing can act as the pacemaker of the glacial cycles nonlinear phase locking can determine the timing of the major deglaciations nearly independently of the specific mechanism or model that is responsible for these cycles as long as this mechanism is suitably nonlinear a consequence of this is that the fit of a certain model output to the observed ice volume record cannot be used as an indication that the glacial mechanism in this model is necessarily correct phase locking to obliquity and possibly precession variations is distinct from mechanisms relying on a linear or nonlinear amplification of the eccentricity forcing nonlinear phase locking may determine the phase of the glacial cycles even in the presence of noise in the climate system and can be effective at setting glacial termination times even when the precession and obliquity bands account only for a small portion of the total power of an ice volume record nonlinear phase locking can also result in the observed quantization of the glacial period into multiples of the obliquity or precession periods

the miarolitic pegmatites from the konigshain a contribution to understanding the genesis of pegmatites in this paper we show that the crystallization of miarolitic pegmatites at konigshain started at about 700 c in melts containing up to 30 mass water such high water concentration at low pressures 1 3 kbar is only possible if the melts are peralkaline such peralkaline melts are highly corrosive and reacted with the wall rock here the granite host forming the graphic granite zone in part via a magmatic metasomatic reaction with cooling the water concentration in some melt fractions increased up to 50 mass h2o the melt dominated system ends below 600 c and passes into a fluid dominated system the beginning of which is characterized by strong pressure fluctuations caused by the change of oh and co32 in the melt to molecular water and co2 we note two generations of smoky quartz one crystallized above the transition of quartz 573 c and one below both of which contain melt inclusions this indicates that some melt fraction remains during at least the higher temperature portion of the growth of minerals into the miarolitic cavity contradicting the view that minerals growing into a pegmatite chamber only do so from aqueous fluids we show that the konigshain miarolitic pegmatites are part of the broad spectrum of pegmatite types and the processes active at konigshain are representative of processes found in most granitic pegmatites and are thus instructive in the understanding of pegmatite formation in general and constraining the composition and characteristics of pegmatite forming melts

multiple sea ice states and abrupt moc transitions in a general circulation ocean model sea ice has been suggested based on simple models to play an important role in past glacial interglacial oscillations via the so called sea ice switch mechanism an important requirement for this mechanism is that multiple sea ice extents exist under the same land ice configuration this hypothesis of multiple sea ice extents is tested with a state of the art ocean general circulation model coupled to an atmospheric energy moisture balance model the model includes a dynamic thermodynamic sea ice module has a realistic ocean configuration and bathymetry and is forced by annual mean forcing several runs with two different land ice distributions represent present day and cold climate conditions in each case the ocean model is initiated with both ice free and fully ice covered states we find that the present day runs converge approximately to the same sea ice state for the northern hemisphere while for the southern hemisphere a difference in sea ice extent of about three degrees in latitude between the different runs is observed the cold climate runs lead to meridional sea ice extents that are different by up to four degrees in latitude in both hemispheres while approaching the final states the model exhibits abrupt transitions from extended sea ice states and weak meridional overturning circulation to less extended sea ice and stronger meridional overturning circulation and vice versa these transitions are linked to temperature changes in the north atlantic high latitude deep water such abrupt changes may be associated with dansgaard oeschger events as proposed by previous studies although multiple sea ice states have been observed the difference between these states is not large enough to provide a strong support for the sea ice switch mechanism

atmospheric δ13co2 and its relation to pco2 and deep ocean δ13c during the late pleistocene the ratio of the stable carbon isotopes of atmospheric co2 13co2 contains valuable information on the processes which are operating on the global carbon cycle however current 13co2 ice core records are still limited in both resolution and temporal coverage as well as precision in this study we performed simulations with the carbon cycle box model bicycle with special emphasis on atmospheric 13co2 proposing how changes in 13co2 might have evolved over the last 740 000 years we furthermore analyze the relationship between atmospheric 13co2 pco2 and deep ocean 13c of dissolved inorganic carbon dic 13cdic in both our modeling framework and proxy records when available our analyses show that mean ocean and deep pacific 13cdic are mainly controlled by the glacial interglacial uptake and release of carbon temporarily stored in the terrestrial biosphere during warmer climate periods in contrast glacial interglacial changes in pco2 and 13co2 represent mainly a mixture of ocean related processes superimposed on the slow glacial interglacial change in terrestrial carbon storage the different processes influencing atmospheric 13co2 largely compensate each other and cancel all variability with frequencies of 1 100 kyr 1 large excursions in 13co2 can a priori be expected as any small phase difference between the relative timing of the dominant and opposite sign processes might create large changes in 13co2 amplitudes in 13co2 caused by fast terrestrial uptake or release during millennial scale climate variability depend not only on the amount of transferred carbon but also on the speed of these changes those which occur on timescales shorter than a millennium are not detectable in 13co2 because of gas exchange equilibration with the surface ocean the 13co2 signal of fast processes on the other hand is largely attenuated in ice core records during the firnification and gas enclosure we therefore suggest to measure 13co2 with priority on ice cores with high temporal resolution and select times with rather fast climatic changes

loss of carbon from the deep sea since the last glacial maximum deep ocean carbonate ion concentrations co32 and carbon isotopic ratios 13c place important constraints on past redistributions of carbon in the ocean land atmosphere system and hence provide clues to the causes of atmospheric co2 concentration changes however existing deep sea co32 reconstructions conflict with one another complicating paleoceanographic interpretations here we present deep sea co32 for five cores from the three major oceans quantified using benthic foraminiferal boron calcium ratios since the last glacial period combined benthic 13c and co32 results indicate that deep sea released co2 during the early deglacial period 17 5 to 14 5 thousand years ago was preferentially stored in the atmosphere whereas during the late deglacial period 14 to 10 thousand years ago besides contributing to the contemporary atmospheric co2 rise a substantial portion of co2 released from oceans was absorbed by the terrestrial biosphere

temperature induced marine export production during glacial period 1 proxy records indicate that export production was enhanced at the onset of the last glaciation we examine how glacial cooling affects marine export production through temperature dependent phytoplankton productivity and organic carbon remineralization using glacial climate simulation compared with the standard assumption of no temperature dependence as applied in existing paleoclimate models including temperature dependence enhances export production globally under glacial climate conditions the near freezing temperatures of antarctic seawater significantly reduce organic carbon remineralization less remineralization than production results in increasing carbon export to the deep ocean nutrients remaining near the surface at high latitudes are advected to lower latitudes via antarctic intermediate water enhancing primary production and hence export in temperate and tropical regions as well including temperature dependence improves the model s agreement with the glacial proxy records of export production and stable carbon isotopes even under stably stratified conditions with a weakening of north atlantic deep water

the oxygen geochemical cycle dynamics and stability abstract the first and possibly only major rise of atmospheric oxygen from p o 2 0 1 pal the present atmospheric level to p o 2 10 pal appears to have occurred sometime before 2 ga ago although the exact time of and the cause s for the rise have been hotly debated equally important questions on the atmospheric oxygen concern its stability especially the mechanisms regulating the atmospheric p o 2 level and the causes and magnitude of p o 2 variations since the first major rise of atmospheric oxygen previous efforts to model the p o 2 variation during the phanerozoic time have typically relied on secondary information such as the carbon and sulfur isotopic records of sedimentary rocks and on simple dynamics of the geochemical cycles of o c s and p based on box type models as a result many kinetic questions about the variation and stability of atmospheric oxygen could not have been answered here we quantitatively evaluate the dynamics and stability of atmospheric o 2 and co 2 using recent experimental data field observations and a new model for the c o coupled geochemical cycles we examine the change with time in the fluxes of various compounds o 2 co 2 phosphate organic c carbonate c c bearing reduced volcanic gases and c free reduced volcanic gases among the various reservoirs atmosphere soil surface ocean deep ocean the lower crust and mantle and upper crust under a variety of scenarios our model does not assume steady state fluxes for any of the reservoirs rather the model incorporates the kinetic experimental data on oxidation of coal a proxy for kerogen the dynamics of soil formation and erosion the kinetics of decomposition of organic matter in the oceans by aerobic and anaerobic bacteria the equilibrium ocean atmosphere carbonate model the observed relationships among the organic burial flux dissolved o 2 content of deep ocean and sedimentation rates and the three box model ocean the important parameters that strongly influence the dynamics of atmospheric o 2 are found to be a the total area of soil formation on earth b the average soil depth c the average rate of physical erosion of soils which is linked to the average rate of accumulation of clastic sediments in the oceans d the composition and flux of volcanic gas and e the level of atmospheric co 2 we develop kinetic equations linking these parameters to the production and consumption fluxes of atmospheric oxygen and also to stable p o 2 values considering the likely ranges of variations in these parameters in geologic history we suggest that the atmospheric p o 2 level is likely to have stayed within a very narrow range of 0 6 2 pal and that the entire ocean except for local euxinic basins is likely to have been basically oxygenated since the first major rise of atmospheric oxygen more than 2 ga ago

production and accumulation of calcium carbonate in the ocean budget of a nonsteady state present day production of caco3 in tne world ocean is calculated to be about 5 billion tons bt per year of which about 3 bt accumulate in sediments the other 40 is dissolved nearly half of the carbonate sediment accumulates on reefs banks and tropical shelves and consists largely of metastable aragonite and magnesian calcite deep sea carbonates predominantly calcitic coccoliths and planktonic foraminifera have orders of magnitude lower productivity and accumulation rates than shallow water carbonates but they cover orders of magnitude larger basin area twice as much calcium is removed from the oceans by present day carbonate accumulation as is estimated to be brought in by rivers and hydrothermal activity 1 6 bt suggesting that outputs have been overestimated or inputs underestimated that one or more other inputs have not been identified and or that the oceans are not presently in steady state one missing calcium source might be groundwater although its present day input is probably much smaller than that of rivers if as seems likely caco3 accumulation presently exceeds terrestial and hydrothermal input this imbalance presumably is offset by decreased accumulation and increased input during lowered sea level shallow water accumulation decreases by an order of magnitude with a 100 m drop in sea level while groundwater influx increases because of heightened piezometric head and the diagenesis of metastable aragonite and magnesian calcite from subaerially exposed shallow water carbonates

periodic mid cretaceous oceanic anoxic events linked by oscillations of the phosphorus and oxygen biogeochemical cycles 1 a series of oceanic anoxic events oaes occurred in the mid cretaceous warm period 120 80 ma that have been linked with high rates of organic carbon burial warm high and low latitude temperatures and sea level changes oaes have been studied individually but a causal mechanism that connects them has been lacking we show that peaks in phosphorus accumulation in marine sediments broadly coincide with oaes 1a 1b 1d 2 and 3 and exhibit a 5 6 myr periodicity which for reactive p is prominent over 100 80 ma oxic anoxic oscillations of this frequency are also found in a model of the coupled n p c and o2 biogeochemical cycles these oscillations are maintained by positive feedbacks between phosphate concentration biological productivity and anoxia in the global ocean and counteracting but slower negative feedbacks involving changes in atmospheric oxygen an increase in phosphorus weathering rate above a critical threshold can shift the system into self sustaining oscillation this could have been caused by tectonic and volcanic forcing increasing atmospheric co2 and global warmth 120 80 ma augmented by the rise of flowering plants around 100 ma with a plausible forcing scenario we are able to reproduce the approximate timing of oaes 1a 1b 1d 2 and 3 in the model

the sequence of events surrounding termination ii and their implications for the cause of glacial interglacial co2 changes events surrounding termination ii as preserved in the vostok ice core provide a number of clues about the mechanisms controlling glacial to interglacial climate change antarctic temperature and the atmosphere s co2 content increased together over a period of 8000 years this increase is bounded by a drop in dust flux at its onset and by a drop in the 18o of trapped air at its finish a similar lag between dust flux and foraminiferal 18o is seen in a southern ocean marine record suggesting that the 18o in air trapped in vostok ice is a valid proxy for ice volume the synchronous change of atmospheric co2 and southern hemisphere temperature thus preceded the melting of the northern hemisphere ice sheets this observation coupled with the fact that nutrient reorganization in the north atlantic occurs with or after the sea level rise eliminates many scenarios proposed to explain the co2 rise including those which rely on sea level change conveyor related nutrient redistribution or north atlantic cooling southern ocean scenarios become the front runners but the most popular mechanism iron fertilization has two problems in explaining the co2 rise before termination ii first much of the dust demise occurs prior to the change in co2 so if iron is the villain a threshold value of its supply must be called upon above which productivity does not continue to increase second the co2 rise continues for some 4 5 kyr after the dust flux has fallen to close to zero these problems may be solved if the increased iron supply in dust caused higher rates of nitrogen fixation during the glacial periods in this case the residence time of oceanic nitrate of a few thousand years would enable decreasing productivity to be a global rather than a local phenomenon and would explain the slow rampup of atmospheric co2

integrating millennial and interdecadal shoreline changes morpho sedimentary investigation of two prograded barriers in southeastern australia abstract prograded barriers are distinctive coastal landforms preserving the position of past shorelines as low relief shore parallel ridges composed of beach sediments and commonly adorned with variable amounts of dune sand prograded barriers have been valued as coastal archives which contain palaeoenvironmental information however integrating the millennial timescale geological history of barriers with observed inter decadal modern beach processes has proved difficult technologies such as airborne lidar ground penetrating radar gpr and optically stimulated luminescence dating osl were utilised at boydtown and wonboyn in southeastern australia and combined with previously reported radiocarbon dates and offshore seismic and sedimentological data to reconstruct the morpho sedimentary history of prograded barrier systems these technologies enabled reconstruction of geological timescale processes integrated with an inter decadal model of ridge formation explaining the gpr imaged subsurface character of the barriers both the boydtown and wonboyn barriers began prograding 7500 8000 years ago when sea level attained at or near present height along this coastline and continued prograding until the present day with an initially slower rate of shoreline advancement sources of sediment for progradation appear to be the inner shelf and shoreface with a large shelf sand body likely contributing to progradation at wonboyn the towamba river seems to have delivered sediment to twofold bay during flood events after transitioning to a mature estuarine system sometime after 4000 cal yr bp some of this material appears to have been reworked onto the boydtown barrier increasing the rate of progradation in the seaward 50 of the barrier deposited over the past 1500 years the gpr imaged beachfaces are shown to have similar geometry to beach profiles following recent storm events and a model of ridge formation involving cut and fill of the beachface and dune building in the backshore explains the character of the preserved beachface record and the morphology of the ridges this model is applicable to future management of individual beaches where such beaches are subject to ongoing cut and fill dune building processes and inherited sediment budget conditions

fluid immiscibility in natural processes use and misuse of fluid inclusion data ii interpretation of fluid inclusion data in terms of immiscibility abstract phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility in part i following from that point the major limits on the accuracy and even the validity of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed the practical implications of the general constraints temperature pressure topology of the fluid systems are envisaged emphasis is laid on some important consequences such as the use of isochore intercepts and the possible resulting interpretation of fluid mixing rather than unmixing the case of highly saline inclusions the identification and interpretation of heterogeneous trapping the composition and density constraints on coexisting fluids are presented and illustrated by natural examples taking into account all the measurable parameters in fluid inclusions volume temperature and nature of phase transitions more or less complete individual spectroscopic analyses all the available experimental data and all the theoretical constraints may be long and difficult however it is most generally very informative and productive although part of these data is often sufficient to deny unmixing nevertheless a final example on metamorphic fluids demonstrates how such an approach can prove and also characterize a fluid unmixing during a geologic process

glacial to postglacial drop in productivity in the western equatorial pacific mixing rate vs nutrient concentrations primary productivity in the western equatorial pacific was distinctly higher during the last glacial period than today judging from the abundance patterns of benthic foraminifers in box cores from the ontong java plateau the export of organic matter dropped by a factor of 1 7 during the last glacial to interglacial transition on the basis of global calibration of estimated export against accumulation rates of benthic foraminifers using detailed information on 13 c stratigraphy of planktic and benthic foraminifers for the past 20 ka together with a simple two box ocean model we calculate that upward mixing and diffusion of subsurface waters decreased by a factor of 1 4 while nutrient content decreased by a factor of 1 2 over this time span

carbon cycle instability as a cause of the late pleistocene ice age oscillations modeling the asymmetric response a dynamical model of the pleistocene ice ages incorporating many of the qualitative ideas advanced recently regarding the possible role of ocean circulation chemistry temperature and productivity in regulating long term atmospheric carbon dioxide variations has been constructed this model involves one additional term and free parameter beyond that included in a previous model b saltzman and a sutera 1987 providing the capacity for an asymmetic for example saw toothed response it is shown that many of the main features exhibited by the 18o derived ice record and the vostok core 13c derived carbon dioxide record in the late pleistocene can be deduced as a free oscillatory solution of the model including a rapid deglaciation during which a spike of high co2 and a rapid surge in north atlantic deep water production occurs it is expected that the addition of reasonable levels of external for example earth orbital forcing will enable the model to account for a significant amount of the remaining observed variance and covariance of the slow response climatic variables over the full pleistocene including the mid pleistocene transition

productivity records from the southern ocean and the equatorial pacific ocean testing the glacial shelf nutrient hypothesis abstract quantifying variations in oceanic nutrient mass balances is central to understanding the links between biological productivity carbon cycle variations and climate one challenge in mass balance determinations is in developing appropriate proxies and applying them in a number of oceanic settings on comparable time scales on glacial timescales it is important to separate nutrient variations driven by external processes e g continental weathering dust inputs from those driven by internal processes i e changing loci of upwelling changes in nutrient inventories here we compare several upwelling regions as a first order analysis of phosphorus p inventory variations in the ocean sea level variations should have a profound impact on the continental margin sink of this biolimiting nutrient on glacial timescales new estimates for a shorter response time of p in the ocean suggest that variations in the p cycle play a role on marine biological productivity and thus the carbon cycle during glacial interglacial intervals although this glacial transfer of nutrients from shelves to the deep sea was postulated over two decades ago few quantitative data have been produced to support or refute this hypothesis supported by a more thorough understanding of p sedimentary geochemistry we present here detailed records of variations in oceanic p cycling on glacial timescales showing that the redistribution of this nutrient from marginal to deep sea sinks during glacial lowstands has had an impact on the oceanic p cycle furthermore p based records of export production from the southern and equatorial pacific oceans indicate that this redistribution of p resulted in higher oceanic dissolved p concentrations and increased oceanic productivity toward the end of glacials and the beginning of subsequent interglacials a 10 20 kyr lag between p based export production records and sea level supports the newer estimates of the marine p response time and indicates that this nutrient lag may be a heretofore unrecognized driver of other biological paleoproductivity records

estimation of the global amount of submarine gas hydrates formed via microbial methane formation based on numerical reaction transport modeling and a novel parameterization of holocene sedimentation this study provides new estimates for the global offshore methane hydrate inventory formed due to microbial ch4 production under quaternary and holocene boundary conditions a multi 1d model for particular organic carbon poc degradation gas hydrate formation and dissolution is presented the novel reaction transport model contains an open three phase system of two solid compounds organic carbon gas hydrates three dissolved species methane sulfates inorganic carbon and one gaseous phase free methane the model computes time resolved concentration profiles for all compounds by accounting for chemical reactions as well as diffusive and advective transport processes the reaction module builds upon a new kinetic model of poc degradation which considers a down core decrease in reactivity of organic matter various chemical reactions such as organic carbon decay anaerobic oxidation of methane methanogenesis and sulfate reduction are resolved using appropriate kinetic rate laws and constants gas hydrates and free gas form if the concentration of dissolved methane exceeds the pressure temperature and salinity dependent solubility limits of hydrates and or free gas with a rate given by kinetic parameters global input grids have been compiled from a variety of oceanographic geological and geophysical data sets including a new parameterization of sedimentation rates in terms of water depth we find prominent gas hydrate provinces offshore central america where sediments are rich in organic carbon and in the arctic ocean where low bottom water temperatures stabilize methane hydrates the world s total gas hydrate inventory is estimated at 0 82 x 10sup13 m3 2 10 x 10sup15 m3 ch4 at stp conditions or equivalently 4 18 995 gt of methane carbon the first value refers to present day conditions estimated using the relatively low holocene sedimentation rates the second value corresponds to a scenario of higher quaternary sedimentation rates along continental margins our results clearly show that in situ poc degradation is at present not an efficient hydrate forming process significant hydrate deposits in marine settings are more likely to have formed at times of higher sedimentation during the quaternary or as a consequence of upward fluid transport at continental margins

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

a possible sequence of events for the generalized glacial interglacial cycle 1 there is not yet widespread agreement as to the underlying cause of the 80 100 ppmv roughly 100 kyr duration glacial interglacial cycles in atmospheric pco2 most of the mechanisms which have been proposed to account for the observed pco2 variations appear to in some way violate interpretations of paleo proxy data the inability of a single mechanism to explain the observed cycles in atmospheric co2 which show amazing similarity over the past 430 000 years is perplexing and leads us to consider whether a combination of mechanisms might be consistent with available evidence consistent with previous work we find that physical changes ocean circulation temperature mixing can only explain part of the observed atmospheric pco2 variability changes in ocean chemistry are invoked to explain the remainder in order to account for the initial pco2 drawdown from interglacial to intermediate levels we invoke physical changes in the ocean mixing temperature the transition from intermediate atmospheric pco2 levels to full glacial conditions involves a small increase in mean ocean nutrient levels and mean ocean alkalinity accomplished by falling sea level and subsequent erosion of organic rich shelf sediments the first part of the transition out of full glacial conditions is achieved through increased temperature and increased mixing in the southern ocean the final part of the atmospheric pco2 rise up to full interglacial conditions is accomplished through rising sea level and the subsequent change in mean ocean alkalinity and phosphate and a rise in the northern hemisphere temperature and ocean mixing the proposed sequence of events is consistent with most existing proxy evidence for paleo nutrient levels and changes in export production over the last glacial interglacial cycle furthermore it is consistent with evidence for a whole ocean shift in 13c toward significantly more negative values in the late glacial the proposed scenario is also consistent with ice core based timing constraints as summarized by broecker and henderson 1998 we show that we are able to explain the full magnitude of the glacial interglacial cycle in atmospheric pco2 without the need to invoke iron fertilization in the southern ocean

rapid coupling between ice volume and polar temperature over the past 150 000 years a new approach to dating a continuous sea level record using speleothem u th ages shows that past variations in global ice volume occurred within centuries of polar climate change with rates of sea level rise reaching at least 1 metre per century

b and li in proterozoic metapelites from the black hills u s a implications for the origin of leucogranitic magmas the abundance and distribution of b and li in metasedimentary rocks and in the harney peak granite hpg in the black hills south dakota u s a elucidate the behavior of these two elements during 1 regional metamorphism that began at 1760 ma 2 subsequent contact metamorphism associated with emplacement of the hpg and associated pegmatites at 1715 ma and 3 anatexis leading to production of the granite there is no clear evidence for changes in b and li concentrations with progressive regional metamorphism of the metapelites from chlorite biotite grade up to staurolite grade rocks outside the pegmatite aureole that surround the hpg have average b contents of 80 ppm there is no correlation of b with other elements in the pelitic schists which indicates that none of the major phases is the dominant host for b boron content is mainly controlled by small amounts of randomly distributed tourmaline that was identified in alpha track maps of thin sections in the aureole of the granite b concentrations are depleted in many samples the depletion is attributed to consumption of tourmaline during interaction of the rocks with alkalic fluids the average li contents in metapelites far away from the hpg are also 80 ppm near the hpg li concentrations reach roughly 190 ppm indicating significant metasomatism by fluids that emanated from the granite and pegmatites the concentrations of b and li in the low grade metapelites are sufficient to explain their abundances in the hpg if the granite formed by partial melting of the metapelites and if there was total breakdown of tourmaline stabilization of tourmaline in leucogranites is not necessarily related to sources enriched in b but may be related to its competition for fe and mg with biotite

determination of the h3bo3 concentration in fluid and melt inclusions in granite pegmatites by laser raman microprobe spectroscopy a method of determining the boric acid h3bo3 concentration in fluid inclusions and volatile rich glasses using laser raman microprobe spectroscopy is described the h3bo3 content of melt and fluid inclusions is determined with good accuracy and precision in the concentration range of 0 to 20 wt and with a minimum detection limit mdl of 0 05 wt h3bo3 the method is applicable to complex solutions that contain components such as nacl kcl rbcl or cscl which do not form stable hydrated borates with boric acid at room temperature this raman study demonstrates that boric acid is an abundant component in volatile rich melt inclusions and in genetically linked primary and pseudosecondary fluid inclusions particularly in tourmaline bearing granites and boron rich pegmatites in quenched pegmatite melt boron occurs predominantly as a trigonal coordinated b oh 3 complex the analytical method is applied to a series of melt and fluid inclusions from different localities and geological environments namely hydrothermal tin and tungsten deposits granite pegmatites and rhyolites special emphasis is given to the analysis of fluorine phosphorus and boron rich pegmatites of the variscan ehrenfriedersdorf complex central erzgebirge germany in this pegmatite system boron in combination with water fluorine and phosphorous is responsible for immiscibility of two coexisting silicate melts a silicate rich h2o poor melt and a silicate poor h2o rich melt accompanied by strong element fraction ation between the two boron fractionates into the water rich silicate melt by factors between 1 8 at 500 c and 1 0 at 712 c if at low pressure a vapor phase is additionally formed boron is partitioned into the vapor phase the utility of the developed method was also quantitatively tested by experiments with a hydrothermal diamond anvil cell

sea level and storm control on the evolution of a chenier plain firth of thames new zealand abstract geological controls on the evolution of the miranda chenier plain firth of thames new zealand are investigated using high resolution stratigraphic information obtained from geophysical surveys two previous studies of the miranda chenier plain have provided disparate conceptual models of its development over the holocene one study evokes sea level oscillations to form individual cheniers while the other offers an alternate model based on the observed transgression of the modern chenier both studies agree that sea level has dropped between 4000 and 1000 years bp but the elevation of the highstand and nature of the fall are contentious this paper extends previous interpretations using data obtained from ground penetrating radar surveys and historical aerial photographs stratigraphic interpretation of the continuous high resolution sub surface radar data was used to infer a sea level curve for miranda these data enable four new inferences 1 sea level fell from 2 m around 4000 years ago mid holocene highstand to present about 1000 years ago 2 falling sea level influenced chenier spacing with the onset of alongshore rather than across shore chenier plain development coinciding with the termination of sea level fall after the formation of ridge six 3 all cheniers initially transgressed producing similar resultant spit morphologies but the evolution of the more recent ridges 1 5 differed from older ridges 6 13 in that transgression occurred over embayed tidal flat sediments while the older cheniers stabilized on foreshore mudflats and 4 storms exert an important control in initiating chenier genesis the miranda chenier plain is a site of global significance for understanding chenier evolution in this study the high level of subsurface detail unimagined in past decades presents greater insight into the morphology and stratigraphy of the chenier ridges shedding new light on the role of sea level and storms on the evolution of the plain

nineteenth and twentieth century sea level changes in tasmania and new zealand positive deviations from linear sea level trends represent important climate signals if they are persistent and geographically widespread this paper documents rapid sea level rise reconstructed from sedimentary records obtained from salt marshes in the southwest pacific region tasmania and new zealand a new late holocene relative sea level record from eastern tasmania was dated by ams14c conventional high precision and bomb spike 137cs 210pb stable pb isotopic ratios trace metals pollen and charcoal analyses palaeosea level positions were determined by foraminiferal analyses relative sea level in tasmania was within half a metre of present sea level for much of the last 6000 yr between 1900 and 1950 relative sea level rose at an average rate of 4 2 0 1 mm yr during the latter half of the 20th century the reconstructed rate of relative sea level rise was 0 7 0 6 mm yr our study is consistent with a similar pattern of relative sea level change recently reconstructed for southern new zealand the change in the rate of sea level rise in the sw pacific during the early 20th century was larger than in the north atlantic and could suggest that northern hemisphere land based ice was the most significant melt source for global sea level rise

modeled estimates of global reef habitat and carbonate production since the last glacial maximum estimated changes in reef area and caco3 production since the last glacial maximum lgm are presented for the first time based on a model reefhab which uses measured environmental data to predict global distribution of reef habitat suitable reef habitat is defined by temperature salinity nutrients and the depth attenuated level of photosynthetically available radiation par caco3 production is calculated as a function of par when minimum par levels were chosen to restrict reef growth to 30 m depth and less modern reef area totaled 584 746 10 km global carbonate production which takes into account topographic relief as a control on carbonate accumulation was 1 00 gt yr 1 these values are close to the most widely accepted estimates of reef area and carbonate production and demonstrate that basic environmental data can be used to define reef habitat and calcification to simulate reef habitat changes since the lgm the model was run at 1 kyr intervals using appropriate sea level and temperature values these runs show that at the lgm reef area was restricted to 20 of that today and carbonate production to 27 due primarily to a reduction in available space at the lower sea level and secondarily to lower sea surface temperatures nonetheless these values suggest that reef growth prior to shelf flooding was more extensive than previously thought a crude estimate of reef released co2 to the atmosphere since the lgm is of the same order of magnitude as the atmospheric co2 change recorded in the vostok ice core which emphasizes the role of neritic carbonates within the global carbon cycle this model currently addresses only the major physical and chemical controls on reef carbonate production but it provides a template for estimating shallow tropical carbonate production both in the present and in the past as such the model highlights several long standing issues regarding reef carbonates particularly in terms of better defining the roles of light temperature aragonite saturation state and topography on reef calcification

the role of oceans and sea ice in abrupt transitions between multiple climate states the coupled climate dynamics underlying large rapid and potentially irreversible changes in ice cover are studied a global atmosphere ocean sea ice general circulation model with idealized aquaplanet geometry is forced by gradual multi millennial variations in solar luminosity the model traverses a hysteresis loop between warm ice free conditions and cold glacial conditions in response to 6 5wm 22 variations in global annual mean insolation comparison of several model configurations confirms the importance of polar ocean processes in setting the sensitivity and time scales of the transitions a sawtooth character is found with fasterwarmingandslowercooling reflectingtheopposingeffectsofsurfaceheatingandcoolingonupper ocean buoyancy and thus effective heat capacity the transition from a glacial to warm equable climate occurs in about 200 years in contrast to the freshwater hosing scenario transitions are driven by radiative forcing and sea ice feedbacks the ocean circulation and notably the meridional overturning circulation moc does not drive the climate change the moc and associated heat transport collapses poleward of the advancing ice edge but this is a purely passive response to cooling and ice expansion the moc does however play a key role in setting the time scales of the transition and contributes to the asymmetry between warming and cooling

petrology and isotopic geochemistry of dawsonite bearing sandstones in hailaer basin northeastern china abstract the co2 gas reservoir sandstones in the hailaer basin contain abundant dawsonite and provide an ideal laboratory to study whether any genetic relationship exists between dawsonite and the modern gas phase of co2 the origins of dawsonite and co2 in these sandstones were studied by petrographic and isotopic analysis according to the paragenetic sequence of the sandstones dawsonite grew later than co2 charging at 110 85 ma the dawsonite 18o value is 7 4 smow and the calculated 18o values of the water present during dawsonite growth are from 11 4 to 9 2 smow this combined with the nahco3 dominated water linked to dawsonite growth suggests meteoric water being responsible for dawsonite growth the 13c values of gas phase co2 and the ratios of 3he 4he of the associated he suggest a mantle magmatic origin of co2 rich natural gas in hailaer basin dawsonite 13c values are 5 3 to 1 5 average 3 4 and the calculated 13c values of co2 gas in isotopic equilibrium with dawsonite are 11 4 to 7 3 these c isotopic values are ambiguous for the dawsonite c source from the geological context the timing of events together with formation water conditions for dawsonite growth dawsonite possibly grew in meteoric derived water atmospherically derived co2 maybe or at least the dominant c source for dawsonite it seems that there are few relationships between dawsonite and the modern gas phase of co2 in the hailaer basin

phosphorus in sediments of the amazon river and estuary implications for the global flux of phosphorus to the sea abstract the distribution of various forms of p in suspended and depositional bank sediments of the amazon river and bottom sediments of the mixing and freshwater portions of the amazon estuary and shelf have been determined using a modified sequential extraction method forms of p distinguished are p associated with ferric oxides hydroxides fe p organic p org p p extracted with acetate buffer at ph 4 acet p and detrital apatite detr p results indicate that there is a distinct drop in fe p org p and total p after deposition of suspended sediment on the banks of the river similar results are found for sediment deposited on the freshwater portion river channel bottom of the continental shelf sediment deposited on estuarine portions of the shelf also shows a significant drop in total p due mostly to a drop in org p no appreciable change in acet p was found between river suspended sediments and those of either the river banks or of the estuarine shelf an inverse correlation is found for all sediments between concentrations of fe p and detr p because of the association of detrital apatite with the coarser fractions of the sediments and fe p with the finer fractions these results suggest that considerable amounts of p are added to the oceans by the bacterial decomposition of river transported organic matter and by the desorption of p from iron oxides hydroxides some desorption from al silicates may also occur the organic p is released to interstitial solution during early diagenesis and this p may be adsorbed by fe oxides in the sediment during frequent resuspension events the fe oxides are carried to the overlying water where the p is desorbed and thereby released to solution based on our amazon results the total global p flux to the oceans by rivers may be more than three times that carried only in solution by the rivers further work is needed on other river systems to check these preliminary results

insolation driven 100 000 year glacial cycles and hysteresis of ice sheet volume comprehensive climate and ice sheet models show that insolation and internal feedbacks between the climate the ice sheets and the lithosphere asthenosphere system explain the 100 000 year period on which the northern hemisphere ice sheets grow and shrink for the past million years earth s climate has been dominated by a 100 000 year cycle of glaciation involving the advance and retreat of the northern hemisphere ice sheets variations in insolation the solar radiation reaching earth s surface caused by constant changes in earth s orbit and orientation to the sun are closely associated with glaciations but the physical mechanisms driving the cycle have remained unclear now ayako abe ouchi and colleagues demonstrate that insolation variations interact with the size of the ice sheets and the solid earth to control the 100 000 year cycles their model shows that internal feedbacks between insolation climate and the elevation of the land beneath the ice sheet allows ice sheets to grow gradually until a maximum size is reached at that point the lowered ice sheet elevation caused by the delayed rebound of the solid earth means that a small increase in insolation can destroy the ice sheet in just a few thousand years the growth and reduction of northern hemisphere ice sheets over the past million years is dominated by an approximately 100 000 year periodicity and a sawtooth pattern1 2 gradual growth and fast termination milankovitch theory proposes that summer insolation at high northern latitudes drives the glacial cycles3 and statistical tests have demonstrated that the glacial cycles are indeed linked to eccentricity obliquity and precession cycles4 5 yet insolation alone cannot explain the strong 100 000 year cycle suggesting that internal climatic feedbacks may also be at work4 5 6 7 earlier conceptual models for example showed that glacial terminations are associated with the build up of northern hemisphere excess ice 5 8 9 10 but the physical mechanisms underpinning the 100 000 year cycle remain unclear here we show using comprehensive climate and ice sheet models that insolation and internal feedbacks between the climate the ice sheets and the lithosphere asthenosphere system explain the 100 000 year periodicity the responses of equilibrium states of ice sheets to summer insolation show hysteresis11 12 13 with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles the hysteresis loop of the north american ice sheet is such that after inception of the ice sheet its mass balance remains mostly positive through several precession cycles whose amplitudes decrease towards an eccentricity minimum the larger the ice sheet grows and extends towards lower latitudes the smaller is the insolation required to make the mass balance negative therefore once a large ice sheet is established a moderate increase in insolation is sufficient to trigger a negative mass balance leading to an almost complete retreat of the ice sheet within several thousand years this fast retreat is governed mainly by rapid ablation due to the lowered surface elevation resulting from delayed isostatic rebound14 15 16 which is the lithosphere asthenosphere response carbon dioxide is involved but is not determinative in the evolution of the 100 000 year glacial cycles

continental scale magmatic carbon dioxide seepage recorded by dawsonite in the bowen gunnedah sydney basin system eastern australia abstract dawsonite naalco3 oh 2 is widespread as a cement replacement and cavity filling in permo triassic sedimentary rocks of the bowen gunnedah sydney basin system eastern australia the origin of dawsonite in these rocks was studied by petrographic and stable isotope analysis dawsonite d13c pdb values range from 4 0 to 4 1 and are remarkably consistent throughout the bowen gunnedah sydney basin system these values indicate either a marine carbonate or magmatic source for carbon in the dawsonite a magmatic carbon source is considered more likely on the basis that 1 evidence of and the cause for widespread marine carbonate dissolution in the sedimentary successions are not apparen 2 dawsonite is widespread in both marine and nonmarine facies 3 the region has been the site of major igneous activity 4 other dawsonite deposits of similar carbon isotopic composition are linked to igneous activity and 5 magmatic co2 accumulations are known in parts of the bowen gunnedah sydney basin system the timing of igneous activity in the bowen basin constrains the timing of dawsonite formation in the bowen gunnedah sydney basin system to the tertiary consistent with textural relationships which indicate that dawsonite formed late during the burial history of the permo triassic sequences the distribution and interpreted origin of dawsonite implies magmatic co2 seepage in the bowen gunnedah sydney basin system on a continental scale

on the structure and origin of major glaciation cycles 2 the 100 000 year cycle climate over the past million years has been dominated by glaciation cycles with periods near 23 000 41 000 and 100 000 years in a linear version of the milankovitch theory the two shorter cycles can be explained as responses to insolation cycles driven by precession and obliquity but the 100 000 year radiation cycle arising from eccentricity variation is much too small in amplitude and too late in phase to produce the corresponding climate cycle by direct forcing we present phase observations showing that the geographic progression of local responses over the 100 000 year cycle is similar to the progression in the other two cycles implying that a similar set of internal climatic mechanisms operates in all three but the phase sequence in the 100 000 year cycle requires a source of climatic inertia having a time constant similar to 15 000 years much larger than the other cycles similar to 5 000 years our conceptual model identifies massive northern hemisphere ice sheets as this larger inertial source when these ice sheets forced by precession and obliquity exceed a critical size they cease responding as linear milankovitch slaves and drive atmospheric and oceanic responses that mimic the externally forced responses in our model the coupled system acts as a nonlinear amplifier that is particularly sensitive to eccentricity driven modulations in the 23 000 year sea level cycle during an interval when sea level is forced upward from a major low stand by a milankovitch response acting either alone or in combination with an internally driven higher frequency process ice sheets grounded on continental shelves become unstable mass wasting accelerates and the resulting deglaciation sets the phase of one wave in the train of 100 000 year oscillations whether a glacier or ice sheet influences the climate depends very much on the scale the interesting aspect is that an effect on the local climate can still make an ice mass grow larger and larger thereby gradually increasing its radius of influence

relating estimates of caco3 production export and dissolution in the water column to measurements of caco3 rain into sediment traps and dissolution on the sea floor a revised global carbonate budget 1 the global caco3 budget is constrained by new estimates of standing stocks fluxes through the water column and dissolution in the water column and on the sea floor previous estimates of carbonate production and export are indistinguishable within a large range of values 0 4 1 8 gt pic yr 1 globally excess alkalinity ta and water mass tracers indicate dissolution of 1 0 gt pic yr 1 between 200 and 1500 m suggesting production and export must at least equal this amount most water column dissolution occurs at high latitudes and alkalinity fluxes from outer shelf and upper slope sediments 100 1500 m only support 5 10 of the ta inventory below 2000 m the sinking flux of pic 0 6 gt pic yr 1 is consistent with the rate of sea floor dissolution 0 4 gt pic yr 1 plus burial 0 1 gt pic yr 1 this rain rate constrains the export value to 1 6 gt pic yr 1 satellite based estimates of standing stocks of caco3 indicate a decrease equatorward which is opposite in trend to sediment trap fluxes this observation may be explained by an equatorward decrease in sinking particle dissolution systematic changes in pic residence time with latitude or satellite retrieval problems globally averaged euphotic zone standing stock 5 4 mmol m 2 and export estimates indicate pic residence times of 5 18 days

punctuated transgression comment on oliver t s n donaldson p sharples c roach m and woodroffe c d punctuated progradation of the seven mile beach holocene barrier system southeastern tasmania abstract sea level rise is known to have emplaced incipient sandy barriers during post glacial marine transgression and these same barriers are forecast to erode or transgress as rising seas accelerate with global warming in order for a barrier to prograded over the intervening millennia a positive sediment budget must exist such that sand supplied to the coast is ample enough to fill the existing accommodation space embayment or a drop in sea level forced seaward progradation storms have long been understood to repeatedly punctuate progradation over days to decades oliver et al 2017a however present two periods of perceived pauses in progradation lasting centuries and millennia with each hiatus considered to have resulted from changes in sediment supply despite the sizable dataset the there are gaps in the stratigraphy and chronology of barrier formation during these two specific time periods in question 6500 to 3500 years ago and 500 years ago to present additionally the morphology representing barrier evolution during 6 5 3 5 ka is obscured by the selected rendering of the light detection and ranging lidar data and breaks in the topographic profiles extracted from the lidar reanalysis of this data within the context of existing literature indicate that seaward progradation slowed not paused between 6 5 to 3 5 ka while this is not surprising for a site with no active riverine or longshore sediment source the rapid progradation that follows is this transition and the timing do make sense within the context of a fall from a mid holocene highstand which is debated in this far field region of australia furthermore it is apparent that the last few centuries do not represent a hiatus in barrier deposition but rather a termination in progradation and transition to erosion and transgression the barrier is not likely to resume prograding seaward but continue to erode and transgress in the future due to the forecast acceleration in sea level rise and increase in storm intensity associated with global warming

experimental study of igneous and sedimentary apatite dissolution control of ph distance from equilibrium and temperature on dissolution rates apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of ph temperature solution saturation state and on non carbonated and carbonated apatite compositions igneous fluorapatite fap and sedimentary carbonate fluorapatite cfa respectively from 2 8 5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of fap for the cfa compositions studied the dissolution rate decreased with increasing ph from 4 ph 7 during early stages of the dissolution reaction for both fap and cfa mineral components were released in non stoichiometric ratios with reacted solution ratios of dissolved ca p and ca f being greater than mineral stoichiometric ratios suggesting that ca was preferentially released compared to p and f from the mineral structure during the early stages of dissolution an increase in reacted solution ph accompanies this early elevated release of ca as the dissolution reaction proceeded to steady state dissolution became congruent when normalized to bet measured surface area fap dissolved faster from 4 ph 7 compared to cfa the apparent arrhenius activation energy ea of fap dissolution over the temperature range of 25 55 c at ph 3 0 i 0 1 and pco2 0 is 8 3 0 2 kcal mol 1 both the apparent exchange of solution h for solid bound ca at low ph in the early stage of dissolution and the ea of dissolution suggest a surface and not a diffusion controlled dissolution reaction for fap and cfa the degree of undersaturation of the solution gr with respect to fap was important in determining the dissolution rate at ph 3 0 i 0 1 and pco2 0 the dissolution rate of fap was 5 greater in the far from equilibrium region compared to the near equilibrium slope region a simple apatite weathering model incorporating the experimental results from this study was constructed and numerical calculations suggest that during the phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the p weathering flux from apatite dissolution it is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early to mid paleozoic resulted in elevated p weathering fluxes which along with climatic evolutionary pressures of the neoproterozoic facilitated the radiation of multicellular organisms large scale phosphorite deposition and abundance of calcium phosphate shelled organisms during the early cambrian

physical mechanisms behind biogeochemical glacial interglacial co2 variations the atmospheric concentration ofco2 has un dergonesignicantandfairlyregularchangesonatimescale of 100 kyr during the at least last four glacial interglacial cycles here we present a novel coupled physical biogeo chemical mechanism for these variations previous studies had to arbitrarily specify the behavior of the physical cli matesysteminordertoinvokeabiogeochemical mechanism for the glacial co2 changes be it an arbitrarily specied changeintheverticaloceanmixing toggweiler 1999 orar bitrarily specied sea ice cover changes stephens and keel ing 2000 instead we present here a new self consistent qualitative physical mechanism for both the vertical mixing and sea ice cover changes in this mechanism the cooling of north atlantic deep water due to northern hemisphere glaciationistransportedsouthwardbythethermohalinecir culation andcoolsthedeepwaterupwellinginthesouthern ocean this in turn aects the southern ocean stratica tion reducesthe rate of vertical mixing of thesurface water with the deep water and increases the sea ice cover we also explain the continuous time evolution between glacial and interglacial states rather than treat them as two steady states and are able to model explicitly for the rst time the amplication of the glacial interglacial variability of the physical climate system by the ocean biogeochemistry

feedbacks between oceanic redox states and marine productivity a model perspective focused on benthic phosphorus cycling a new model for the marine cycles of particulate organic carbon poc oxygen nitrate and phosphorus has been developed and applied to explore the controls and constraints on marine productivity and nutrient inventories the coupled benthic pelagic model uses a new approach for the simulation of the reactive phosphorus turnover preac corresponding to the sum of organic p authigenic p and adsorbed phosphate in marine sediments the simulated poc preac burial ratio in shelf slope and rise and deep sea sediments increases under strongly reducing conditions in agreement with field observation the model runs revealed that the spread of anoxia in bottom waters may enhance the productivity of the global ocean by one order of magnitude if sufficient nitrate is provided by n2 fixation thus anoxic bottom waters promote eutrophic conditions and vice versa additional model runs showed that the productivity and nutrient inventory of the glacial ocean were probably enhanced due to the falling sea level marine regression induced a narrowing of the depositional areas on the continental shelves and thereby an increase in the fraction of poc exported to the deep ocean the accelerated poc delivery in turn decreased the oxygen contents of the deep water and thus favored the release of phosphate from deep sea and rise sediments enhanced recycling of phosphate at the seafloor promoted further poc export in a positive feedback loop

phosphorus imbalance in the global ocean the phosphorus budget of the pre human modern ocean is constrained applying the most recent estimates of the natural riverine eolian and ice rafted input fluxes the phosphorus burial in marine sediments and the hydrothermal removal of dissolved phosphate from the deep ocean this review of current flux estimates indicates that the phosphorus budget of the ocean is unbalanced since the accumulation of phosphorus in marine sediments and altered oceanic crust exceeds the continental input of particulate and dissolved phosphorus the phosphorus mass balance is further tested considering the dissolved phosphate distribution in the deep water column the marine export production of particulate organic matter rain rates of phosphorus to the seafloor benthic dissolved phosphate fluxes and the organic carbon to phosphorus ratios in marine particles these independent data confirm that the phosphate and phosphorus budgets were not at steadystate in the pre human global ocean the ocean is losing dissolved phosphate at a rate of 11 6 x 1010 mol yr 1 corresponding to a decline in the phosphate inventory of 4 5 kyr 1 benthic data show that phosphate is preferentially retained in pelagic deep sea sediments where extended oxygen exposure times favor the degradation of particulate organic matter and the up take of phosphate in manganese and iron oxides and hydroxides enhanced c p regeneration ratios observed in the deep water column 400 m water depth probably reflect the preferential burial of phosphorus in pelagic sediments excess phosphate is released from continental margin sediments deposited in low oxygen environments the dissolved oxygen threshold value for the enhanced release of dissolved phosphate is 20 m benthic phosphate fluxes increase drastically when oxygen concentrations fall below this value

southern ocean dust climate coupling over the past four million years dust plays a central part in ocean biogeochemical cycles by supplying iron and other essential micronutrients to regions where marine productivity is limited by the availability of iron martinez garcia et al present a marine record of dust and iron supply to the southern ocean during the past four million years the data derived from leaf waxes establish that previous records of dust flux from antarctic ice cores are broadly representative of a larger area importantly the dust and iron supply rose sharply 1 25 million years ago suggesting that increased dust supply may be a major influence on the more severe swings between the glacial and interglacial climate of the late pleistocene dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean1 2 indeed dust supply to the southern ocean increases during ice ages and iron fertilization of the subantarctic zone may have contributed up to 40 parts per million by volume p p m v of the decrease 80 100 p p m v in atmospheric carbon dioxide observed during late pleistocene glacial cycles3 4 5 6 7 so far however the magnitude of southern ocean dust deposition in earlier times and its role in the development and evolution of pleistocene glacial cycles have remained unclear here we report a high resolution record of dust and iron supply to the southern ocean over the past four million years derived from the analysis of marine sediments from odp site 1090 located in the atlantic sector of the subantarctic zone the close correspondence of our dust and iron deposition records with antarctic ice core reconstructions of dust flux covering the past 800 000 years refs 8 9 indicates that both of these archives record large scale deposition changes that should apply to most of the southern ocean validating previous interpretations of the ice core data the extension of the record beyond the interval covered by the antarctic ice cores reveals that in contrast to the relatively gradual intensification of glacial cycles over the past three million years southern ocean dust and iron flux rose sharply at the mid pleistocene climatic transition around 1 25 million years ago this finding complements previous observations over late pleistocene glacial cycles5 8 9 providing new evidence of a tight connection between high dust input to the southern ocean and the emergence of the deep glaciations that characterize the past one million years of earth history

holocene coastal evolution and evidence for paleotsunami from a tectonically stable region tasmania australia stratigraphic investigations of three coastal waterbodies in southeastern tasmania reveal major paleoenvironmental phases related to sea level change and anomalous deposits consistent with tsunami