boron incorporation into calcite during growth implications for the use of boron in carbonates as a ph proxy abstract current interest in boron incorporation into carbonates arises from the observation that the isotopic composition of carbonates depends on the ph of the fluid from which they precipitated this finding opened the possibility of using boron isotopic composition of natural carbonates as a paleo ph proxy in this study coprecipitation of boron by calcite was investigated using atomic force microscopy afm as a function of ph supersaturation and boron concentration in situ afm observations reported here provide experimental evidence of boron incorporation into calcite which takes place to a greater extent at high ph 9 5 and under close to equilibrium conditions moreover we report nanoscale observations that give indirect evidence of the incorporation of boron in non lattice sites step specific interactions of tetrahedrally coordinated boron with calcite obtuse steps during growth are revealed as a reduction in the obtuse step spreading rate as well as rounding and roughening of such steps our results suggest that together with changes in ph variations in the calcification rate or the calcite crystallographic form in which boron is incorporated are important factors to consider when using boron in carbonates as a ph proxy as these factors could also influence the amount of boron incorporated during growth and possibly the boron isotopic signature

seawater ph pco2 and co2 3 variations in the caribbean sea over the last 130 kyr a boron isotope and b ca study of planktic foraminifera abstract here a new analytical methodology is described for measuring the isotopic composition of boron in foraminifera using multicollector inductively coupled plasma mass spectrometry mc icpms this new approach is fast 10 samples analysed in duplicate per analytical session and accurate to better than 0 25 at 95 confidence with acceptable sample size requirements 1 3 mg of carbonate a core top calibration of several common planktic and two benthic species from geographically widespread localities shows a very close agreement between the isotopic composition measured by mc icpms and the isotopic composition of b oh 4 in seawater as predicted using the recently measured isotopic equilibrium factor of 1 0272 at the depth of habitat a down core and core top investigation of boron concentration b ca ratio shows that the partition coefficient is influenced by co2 3 complicating the application of this proxy nevertheless it is demonstrated that these two proxies can be used to fully constrain the carbonate system of surface water in the caribbean sea odp site 999a over the last 130 kyr this reconstruction shows that during much of the holocene and the last interglacial period surface water at site 999a was in equilibrium with the atmosphere with respect to co2 during the intervening colder periods although the surface water pco2 was lower than the holocene it was a minor to significant source of co2 to the atmosphere possibly due to either an expansion of the eastern equatorial atlantic upwelling zone or a more local expansion of coastal upwelling in the southern caribbean such reorganisation of the oceanic carbonate system in favour of a larger source of co2 to the atmosphere from the equatorial ocean may require mechanisms responsible for lowering atmospheric co2 during glacial periods to be more efficient than previously supposed

palaeozoic reefs and bioaccumulations climatic and evolutionary controls the geological record contains a fascinating diversity of reefs and shell accumulations as my other biosedimentary structures their facies characterization requires careful observation at outcrop and sample scale and in thin section to provide information about the global geometries fabrics and textures respectively this collection of papers encompasses the breadth of sedimentary geometries and facies displayed by palaeozoic reefs shell accumulations and transitional composite deposits the definition of reefs and shell concentrations has given rise to variations in nomenclature the papers in this volume cover specific problems regarding the nomenclature and facies characterization of reefs shell accumulations and transitional composite deposits however rather than attempt a complete revision of terms the authors have touched on some of the important issues at this stage of development in the field the main climatic environmental and evolutionary factors that controlled the palaeozoic development of shell accumulation and reefs

symbiont bleaching in planktic foraminifera during the middle eocene climatic optimum many genera of modern planktic foraminifera are adapted to nutrient poor oligotrophic surface waters by hosting photosynthetic symbionts but it is unknown how they will respond to future changes in ocean temperature and acidity here we show that ca 40 ma some fossil photosymbiont bearing planktic foraminifera were temporarily bleached of their symbionts coincident with transient global warming during the middle eocene climatic optimum meco at ocean drilling program odp sites 748 and 1051 southern ocean and mid latitude north atlantic respectively the typically positive relationship between the size of photosymbiont bearing planktic foraminifer tests and their carbon isotope ratios 13c was temporarily reduced for 100 k y during the peak of the meco at the same time the typically photosymbiont bearing planktic foraminifera acarinina suffered transient reductions in test size and relative abundance indicating ecological stress the coincidence of minimum 18o values and reduction in test size 13c gradients suggests a link between increased sea surface temperatures and bleaching during the meco although changes in ph and nutrient availability may also have played a role our findings show that host photosymbiont interactions are not constant through geological time with implications for both the evolution of trophic strategies in marine plankton and the reliability of geochemical proxy records generated from symbiont bearing planktic foraminifera

pennsylvanian early triassic stratigraphy in the alborz mountains iran new fieldwork was carried out in the central and eastern alborz addressing the sedimentary succession from the pennsylvanian to the early triassic a regional synthesis is proposed based on sedimentary analysis and a wide collection of new palaeontological data the moscovian qezelqaleh formation deposited in a mixed coastal marine and alluvial setting is present in a restricted area of the eastern alborz transgressing on the lower carboniferous mobarak and dozdehband formations the late gzhelian early sakmarian dorud group is instead distributed over most of the studied area being absent only in a narrow belt to the se the dorud group is typically tripartite with a terrigenous unit in the lower part toyeh formation a carbonate intermediate part emarat and ghosnavi formations the former particularly rich in fusulinids and a terrigenous upper unit shah zeid formation which however seems to be confined to the central alborz a major gap in sedimentation occurred before the deposition of the overlying ruteh limestone a thick package of packstone wackestone interpreted as a carbonate ramp of middle permian age wordian capitanian the ruteh limestone is absent in the eastern part of the range and everywhere ends with an emersion surface that may be karstified or covered by a lateritic soil the late permian transgression was directed southwards in the central alborz where marine facies nesen formation are more common time equivalent alluvial fans with marsh intercalations and lateritic soils qeshlaq formation are present in the east towards the end of the permian most of the alborz emerged the marine facies being restricted to a small area on the caspian side of the central alborz there the permo triassic boundary interval is somewhat similar to the abadeh shahreza belt in central iran and contains oolites flat microbialites and domal stromatolites forming the base of the elikah formation the p t boundary is established on the basis of conodonts small foraminifera and stable isotope data the development of the lower and middle part of the elikah formation still early triassic in age contains vermicular bioturbated mudstone wackestone and anachronostic facies like gastropod oolites and flat pebble conglomerates three major factors control the sedimentary evolution the succession is in phase with global sea level curve in the moscovian and from the middle permian upwards it is out of phase around the carboniferous permian boundary when the dorud group was deposited during a global lowstand of sealevel when the global deglaciation started in the sakmarian sedimentation stopped in the alborz and the area emerged therefore there is a consistent geodynamic control from the middle permian upwards passive margin conditions control the sedimentary evolution of the basin which had its depocentre s to the north climate also had a significant role as the alborz drifted quickly northwards with other central iran blocks towards the turan active margin it passed from a southern latitude through the aridity belt in the middle permian across the equatorial humid belt in the late permian and reached the northern arid tropical belt in the triassic

assessing the impact of diagenesis on δ11b δ13c δ18o sr ca and b ca values in fossil planktic foraminiferal calcite the geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo climatic oceanographic and ecological changes however dissolution of biogenic calcite and precipitation of inorganic calcite overgrowth and recrystallization at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test biasing any resulting paleoenvironmental reconstruction the 11b of planktic foraminiferal calcite is a promising ocean ph proxy but the effect of diagenesis is still poorly known here we present new 11b 13c 18o sr ca and b ca data from multiple species of planktic foraminifera from time equivalent samples for two low latitude sites clay rich tanzanian drilling project tdp site 18 from the indian ocean containing well preserved glassy foraminifera and carbonate rich ocean drilling program odp site 865 from the central pacific ocean hosting recrystallized frosty foraminifera our approach makes the assumption that environmental conditions were initially similar at both sites so most chemical differences are attributable to diagenesis planktic foraminiferal 18o and 13c records show offsets in both relative and absolute values between the two sites consistent with earlier findings that these isotopic ratios are strongly influenced by diagenetic alteration sr ca and b ca ratios in planktic foraminiferal calcite are also offset between the two sites but there is little change in the relative difference between surface and deep dwelling taxa in contrast 11b values indicate no large differences between well preserved and recrystallized foraminifera suggesting that despite extensive diagenetic alteration the 11b of biogenic calcite appears robust potentially indicative of a lack of free exchange of boron between pore fluids and the recrystallizing caco3 our finding may remove one potential source of uncertainty in 11b based ph reconstructions and provide us with greater confidence in our ability to reconstruct ph in the ancient oceans from at least some recrystallized foraminiferal calcite however further investigations should extend this approach to test the robustness of our findings across a range of taphonomies ages and burial settings

wuchiapingian early lopingian permian global brachiopod palaeobiogeography a quantitative approach abstract a global presence absence database of 212 wuchiapingian early lopingian permian brachiopod genera from 30 stations is analysed by cluster analysis nonmetric multidimensional scaling and minimum spanning tree to document the global palaeobiogeographical patterns five core groups are revealed by the quantitative analysis and interpreted as representing five marine biotic provinces they are the cathaysian tropical western tethyan tropical himalayan warm temperate austrazean cold temperate and greenland svalbard provinces cold temperate the cathaysian province is composed of many isolated or semi isolated islands situated in the palaeotethys whereas the other four provinces occurred mainly on the continental shelves of pangea the western tethyan province along the western coast of the palaeotethys the himalayan province on the northern margin of gondwanaland the austrazean province along the southeastern margin of gondwanaland and the greenland svalbard province on the northern margin of pangea in addition nonmetric multidimensional scaling helped to identify key biogeographic determinants latitude related thermal gradient appears to have accounted for most of the variance in the data geographic distance and ocean circulation may have also played a major but subordinate role in the delineation and or enhancement of some of the provinces comparison with early and middle permian global marine provincialism indicates that marine biotic provinces had significantly reduced during the lopingian late permian in the lead up to the end permian mass extinction

evaluation of the biogeochemical controls on b ca of globigerinoides ruber white from the oceanic flux program bermuda a b s t r a c t boron to calcium b ca ratios in planktonic foraminifera is suggested to be a proxy for the surface oceanic carbonate system the reliability of the proxy has been questioned due to conflicting reports from culture and sediment calibrations on the influence of temperature on b ca to assess this issue b ca and mg ca ratios and 18 ow ere measured in tests of the symbiont bearing surface dwelling planktonic foraminifer globigerinoides ruber white collected by the oceanic flux program ofp time series sediment traps located approximately 75 km se of bermuda b ca ratios in the 300 400 m size fraction of g ruber were approximately 10 20 higher than those in the 200 300 m size fraction in contrast mg ca ratios and 18 ov alues do not exhibit any relationship to test size which indicates that the size effect observed for b ca is not due to differences in depth habitat but to vital effects seasonal variation in the b ca ratio was similar in both size fractions and ranged by 20 30 mol mol this range is larger than that predicted by seasonal variations in seawater b oh hco the proposed boron species incorporated into planktonic foraminiferal calcite and indicates that b ca in g ruber is influenced by an additional variable s the seasonal cycle of b ca in g ruber white was more strongly correlated with light intensity than with temperature both observations suggest that the presence of symbionts in g ruber and seasonal variability in their photosynthetic activity act to modify the internal ph during calcification by up to 0 2u nits relative to ambient seawater 2014 elsevier b v all rights reserved

rapid and sustained surface ocean acidification during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been associated with the release of several thousands of petagrams of carbon pg c as methane and or carbon dioxide into the ocean atmosphere system within 10 kyr on the basis of the co occurrence of a carbon isotope excursion cie widespread dissolution of deep sea carbonates and global warming in theory this rapid carbon release should have severely acidified the surface ocean though no geochemical evidence has yet been presented using boron based proxies for surface ocean carbonate chemistry we present the first observational evidence for a drop in the ph of surface and thermocline seawater during the petm planktic foraminifers from a drill site in the north pacific ocean drilling program site 1209 show a 0 8 decrease in boron isotopic composition 11b at the onset of the event along with a 30 40 reduction in shell b ca similar trends in 11b are present in two lower resolution records from the south atlantic and equatorial pacific these observations are consistent with significant global acidification of the surface ocean lasting at least 70 kyr and requiring sustained carbon release the anomalies in the b records are consistent with an initial surface ph drop of 0 3 units at the upper range of model based estimates of acidification

geochemical investigation of gametogenic calcite addition in the planktonic foraminifera orbulina universa abstract several species of planktonic foraminifera precipitate a final layer of calcite onto the shell surface immediately prior to gamete release at the end of the foraminifera life cycle here we present the results of carbon 13 oxygen 18 and thermal labeling experiments conducted under high hl and low light ll regimes that vary symbiont photosynthetic activity mean experimental group data show that gametogenic gam calcite contributes between 4 17 and 14 20 to final shell mass for high and low light experiments respectively these data indicate that past studies of gam calcite addition have overestimated the amount of gam calcite on foraminifera shells by 30 55 calculations indicate that the mass of gam calcite added to the o universa shell 4 2 2 0 g and 4 0 2 4 g is constant in the hl and ll groups respectively we propose that the production of gam calcite may be the result of the discharge of a relatively constant volume cytoplasmic pool of either ca 2 or alkalinity carbon pool that increases the calcite saturation state in the microenvironment adjacent to the foraminifera shell just prior to gamete formation and release results from these experiments indicate that the geochemistry of thin walled o universa from deep sea sediments is composed of 80 ontogenetic calcite that was precipitated in the primary near surface habitat of this species

effects of seawater carbonate ion concentration and temperature on shell u mg and sr in cultured planktonic foraminifera we investigate the sensitivity of u ca mg ca and sr ca to changes in seawater co3 and temperature in calcite produced by the two planktonic foraminifera species orbulina universa and globige rina bulloides in laboratory culture experiments our results demonstrate that at constant temperature u ca in o universa decreases by 25 7 per 100 mol co3 k g 1 as seawater co3 increases from 110 to 470 mol kg 1 results from g bulloides suggest a similar relationship but u ca is consistently offset by 40 at the same environmental co3 in o universa u ca is insensitive to temperature between 15 c and 25 c applying the o universa relationship to three u ca records from a related species globigerinoides sacculifer we estimate that caribbean and tropical atlantic co3 was 110 70 mol kg 1 and 80 40 mol kg 1 higher respectively during the last glacial period relative to the holocene this result is consistent with estimates of the glacial interglacial change in surface water co3 based on both modeling and on boron isotope ph estimates in settings where the addition of u by diagenetic processes is not a factor down core records of foraminiferal u ca have potential to provide information about changes in the ocean s carbonate concentration below ambient ph ph 8 2 mg ca decreased by 7 5 o universa t o 16 6 g bulloides per 0 1 unit increase in ph above ambient ph the change in mg ca was not significant for either species this result suggests that mg ca based paleotemperature estimates for the quaternary during which surface ocean ph has been at or above modern levels have not been biased by variations in surface water ph sr ca increased linearly by 1 6 0 4 per 0 1 unit increase in ph shell mg ca increased exponentially with temperature in o universa where mg ca 0 85 exp 0 096 t whereas the change in sr ca with temperature was within the reproducibility of replicate measurements copyright 2004 elsevier ltd

tethyan oceanic currents and climate gradients 300 m y ago we reconstruct the oceanic circulation pattern of the tethys ocean 300 m y ago by placing late carboniferous early permian climate sensitive biotic associations from gondwana and laurasia on a pangea paleogeography constrained by selected paleomagnetic data warm climate fossils and facies from iran located at that time along the gondwanan margin of arabia are compatible with the existence in the tethys ocean of a warm subtropical surface current gyre whereas cold surface currents swept the glaciated gondwanan margin at higher southern latitudes redistributing cold biota toward the tropics this tethyan surface current system and the associated narrow zonal barrier show similarities to recent glacial climate patterns when placed on a large scale paleogeographic reconstruction of pangea of the b type it neatly explains the otherwise problematic observation that the carboniferous permian biota of iran and northern arabia is dominated by warm euramerican and or russian taxa that are strikingly different from typical cold gondwanan associations

influence of solution chemistry on the boron content in inorganic calcite grown in artificial seawater abstract the ratio of boron to calcium b ca in marine biogenic carbonates has been proposed as a proxy for properties of seawater carbonate chemistry applying this proxy to planktic foraminifera residing in the surface seawater largely in equilibrium with the atmosphere may provide a valuable handle on past atmospheric co 2 concentrations however precise controls on b ca in planktic foraminifera remain enigmatic because it has been shown to depend on multiple physicochemical seawater properties to help establish a firm inorganic basis for interpreting the b ca records we examined the effect of a suite of chemical parameters ca 2 ph dic salinity and po 4 3 on b ca in inorganic calcite precipitated in artificial seawater these parameters were primarily varied individually while keeping all others constant but we also tested the influence of ph and dic at a constant calcite precipitation rate r by concurrent ca 2 adjustments in the simple ca 2 ph and dic experiments both r and b ca increased with these parameters in the ph ca 2 and dic ca 2 experiments at constant r on the other hand b ca was invariant at different ph and decreased with dic respectively these patterns agree with the behavior of solution b total dic ratio such that at a fixed b total it is independent of ph but decreases with dic based on these results r and b total dic ratio appear to be the primary controls on b ca in inorganic calcite suggesting that both b oh 4 and b oh 3 are possibly involved in b incorporation moreover b ca modestly increased with salinity and po 4 3 inorganic calcite precipitated at higher r and in the presence of oxyanions such as so 4 2 and po 4 3 in growth solutions often undergoes surface roughening due to formation of crystallographic defects vacancies and occasionally amorphous hydrous caco 3 these non lattice sites may provide additional space for b particularly b oh 3 consequently besides the macroscopic influence of r and bulk solution chemistry molecular scale processes associated with calcite nucleation can be an important consideration for b incorporation especially in complex ionic solutions lastly the covariance of b ca with dic and salinity observed here qualitatively agrees with those in planktic foraminifers it follows that their impact on foraminiferal b ca is partly inorganically driven which may explain why the effect is evident across different species

controls on boron incorporation in cultured tests of the planktic foraminifer orbulina universa culture experiments with living planktic foraminifers reveal that the ratio of boron to calcium b ca in orbulina universa increases from 56 to 92 mol mol 1 when ph is raised from 7 61 0 02 to 8 67 0 03 total scale across this ph range the abundances of carbonate bicarbonate and borate ions also change 530 500 and 170 mol kg 1 respectively thus specific carbonate system control s on b ca remain unclear complicating interpretation of paleorecords b ca in cultured o universa also increases with salinity 55 72 mol mol 1 from 29 9 35 4 and seawater boron concentration 62 899 mol mol 1 from 4 40 ppm b suggesting that these parameters may need to be taken into account for paleorecords spanning large salinity changes 2 and for samples grown in seawater whose boron concentration b sw differs from modern by more than 0 25 ppm while our results are consistent with the predominant incorporation of the charged borate species boh4 into foraminiferal calcite the behavior of the partition coefficient kd defined as b ca calcite boh4 hco3 seawater cannot be explained by borate incorporation alone and suggests the involvement of other ph sensitive ions such as co32 for a given increase in seawater boh4 the corresponding increase in b ca is stronger when boh4 is raised by increasing b sw than when it is raised by increasing ph these results suggest that b incorporation controls should be reconsidered additional insight is gained from laser ablation icp ms profiles which reveal variable b ca distributions within individual shells

core top calibration of b ca in pacific ocean neogloboquadrina incompta and globigerina bulloides as a surface water carbonate system proxy abstract practical methods for reconstructing past ocean carbonate chemistry are needed to study past periods of ocean acidification and improve understanding of the marine carbonate system s role in the global climate cycles planktic foraminiferal b ca may fill this role but requires better understanding and improved proxy calibrations we used pacific ocean core top sediments to generate new calibrations of the b ca proxy for past carbonate system parameters in two upwelling subpolar species of asymbiotic planktic foraminifera globigerina bulloides and neogloboquadrina incompta both species show significant positive correlation of b ca with calcite saturation calcite and carbonate ion concentration co 3 2 across a broad range of environmental conditions this suggests a calcification rate control on b ca incorporation as calcite regulates calcification rate in agreement with recent inorganic calcite studies this is also consistent with a surface entrapment model of trace element incorporation into caco3 in neither species is b ca significantly correlated with ph suggesting that ph does not directly regulate boron incorporation and that calculation of ph directly from foraminiferal b ca is not suitable correlations between b ca and b oh 4 b oh 4 hco3 and b oh 4 dic are weaker than with calcite boron partition coefficients k d b ca solid b oh 4 hco 3 seawater show little or no correlation with co32 or temperature and vary widely providing no support for application of kd to calculate carbonate system parameters from b ca we also discuss potential effects of depth related dissolution temperature and salinity on b ca these empirical calibrations linking foraminiferal calcite b ca with calcite provide a strong tool for reconstructing the past ocean carbonate system and improve our understanding of the proxy s geochemical basis

the universal ratio of boron to chlorinity for the north pacific and north atlantic oceans abstract we report seawater boron concentration mg kg 1 and chlorinity values measured in seawater samples n 139 collected at various depths in the north pacific and north atlantic oceans and the east japan sea located in the western temperate north pacific our results indicate that variations in seawater boron concentration are strongly coupled to variations in chlorinity and salinity yielding a mean boron to chlorinity ratio of 0 2414 0 0009 mg kg 1 1 boron to salinity ratio 0 1336 0 0005 mg kg 1 1 this ratio was surprisingly universal throughout the water column in the three marine basins and across widely different ocean surface regimes but differs from the generally accepted ratio of 0 232 0 005 mg kg 1 1 determined by uppstrom 1974 which was based on only 20 measurements at four sites in the tropical pacific ocean in converting total alkalinity to carbonate alkalinity and vice versa for thermodynamic calculations the difference between these two ratios leads to a difference of 5 mol kg 1 in estimates for ocean surface waters where the contribution of borate to total alkalinity is typically greatest we suggest the use of the new boron to chlorinity ratio for predicting seawater boron concentrations using chlorinity or salinity data

evaluating the utility of b ca ratios in planktic foraminifera as a proxy for the carbonate system a case study of globigerinoides ruber b ca ratios in foraminifera have attracted considerable scientific attention as a proxy for past ocean carbonate system however the carbonate system controls on b ca ratios are not straightforward with inline image inline image in situ inline image at saturation correlating best with b ca ratios in benthic foraminifera rather than ph inline image or inline image as a simple model of boron speciation in seawater and incorporation into caco3 would predict furthermore culture experiments have shown that in planktic foraminifera properties such as salinity and b sw can have profound effects on b ca ratios beyond those predicted by simple partition coefficients here we investigate the controls on b ca ratios in g ruber via a combination of culture experiments and core top measurements and add to a growing body of evidence that suggests b ca ratios in symbiont bearing foraminiferal carbonate are not a straightforward proxy for past seawater carbonate system conditions we find that while b ca ratios in culture experiments covary with ph in open ocean sediments this relationship is not seen in fact our b ca data correlate best with inline image a previously undocumented association and in most regions salinity these findings might suggest a precipitation rate or crystallographic control on boron incorporation into foraminiferal calcite regardless our results underscore the need for caution when attempting to interpret b ca records in terms of the ocean carbonate system at the very least in the case of mixed layer planktic foraminifera

water contents of early cretaceous mafic dikes in the jiaodong peninsula eastern north china craton insights into an enriched lithospheric mantle source metasomatized by paleo pacific plate subduction related fluids abstractthe early cretaceous lithospheric mantle beneath the jiaodong peninsula has been recognized as ancient and enriched mantle with widespread mafic dike swarms however the enriching agent an

a novel determination of calcite dissolution kinetics in seawater we present a novel determination of the dissolution kinetics of inorganic calcite in seawater we dissolved 13 c labeled calcite in unlabeled seawater and traced the evolving 13 c composition of the fluid over time to establish dissolution rates this method provides sensitive determinations of dissolution rate which we couple with tight constraints on both seawater saturation state and surface area of the dissolving minerals we have determined dissolution rates for two different abiotic calcite materials and three different grain sizes near equilibrium dissolution rates are highly nonlinear and are well normalized by geometric surface area giving an empirical dissolution rate dependence on saturation state of rate g cm 2 day 7 2 0 6 10 4 1 3 9 0 1 this result substantiates the non linear response of calcite dissolution to undersaturation the bulk dissolution rate constant calculated here is in excellent agreement with those determined in far from equilibrium and dilute solution experiments plots of dissolution versus undersaturation indicates the presence of at least two dissolution mechanisms implying a criticality in the calcite seawater system finally our new rate determination has implications for modeling of pelagic and seafloor dissolution nonlinear dissolution kinetics in a simple 1 d lysocline model indicate a possible transition from kinetic to diffusive control with increasing water depth and also confirm the importance of respiration driven dissolution in setting the shape of the calcite lysocline

a continental shelf perspective of ocean acidification and temperature evolution during the paleocene eocene thermal maximum a rapid and large injection of isotopically light carbon into the ocean atmosphere reservoirs is signaled by a negative carbon isotope excursion cie at the paleocene eocene boundary 56 m y ago to better understand the extent of ocean warming and acidification associated with the carbon injection we generated elemental and isotopic records of surface and thermocline planktonic foraminifera across the paleocene eocene boundary from an expanded section along the mid atlantic coastal plain new jersey usa ocean temperatures derived from magnesium calcium paleothermometer document a lag in thermocline warming relative to surface waters implying a progressive deepening of the mixed layer in addition to global warming a similar magnitude of acidification as recorded by boron calcium b ca on the shelf compared with open ocean sites confirms widespread acidification of the surface ocean an increase in seawater alkalinity after the cie as recorded by b ca in planktonic foraminifera likely played an important role in neutralizing the added carbon possibly minimizing benthic extinction along the shelf

trace element proxies for surface ocean conditions a synthesis of culture calibrations with planktic foraminifera abstract the trace element composition of planktic foraminiferal calcite provides a useful means of determining past surface ocean conditions we have assembled the results of culture experiments for three species of symbiont bearing planktic foraminifera globigerinoides ruber globigerinoides sacculifer and orbulina universa and one symbiont barren species globigerina bulloides to evaluate their responses to temperature salinity ph carbonate ion and dissolved inorganic carbon dic growth conditions trace element ratios li ca b ca mg ca sr ca mn ca cd ca ba ca na ca and u ca were measured simultaneously on samples grown with the same culture techniques which provides robust relatable calibrations that may be used together in multi proxy paleoceanographic studies our data confirm that temperature is the dominant control on foraminiferal mg ca under the ranges of conditions studied and that the potential effects of salinity and co32 on mg ca of these tropical species across late pleistocene glacial cycles are relatively small carbonate system experiments suggest that sr ca may be useful for reconstructing large dic changes na ca increases with salinity in g ruber pink but not in g sacculifer as these emerging proxy relationships become more firmly established the synthesis of multiple trace element ratios may help paleoceanographers isolate the effects of different environmental parameters in paleo records calcification rates g day vary among species and do not respond consistently to any experimental parameter comparison of our calcification rates with those observed in inorganic calcite precipitation experiments suggest that foraminifera calcify 100 more slowly than inorganic calcites grown in similar solutions we suggest that calcification rate does not typically exert a dominant control on trace element partitioning in planktic foraminiferal calcite though it may play a role for some elements under certain circumstances differences in average growth rate cannot explain composition differences among species pointing to alternative controls that may be biological in origin

oceanic calcium changes from enhanced weathering during the paleocene eocene thermal maximum no effect on calcium based proxies 1 during the paleocene eocene thermal maximum petm 55 myr ago prominent climatic and biogeochemical changes took place in the atmosphere ocean and on land for example deep sea temperatures rose by 5 c to 6 c while sea surface temperatures at high latitudes increased by up to 9 c in the sedimentary record the onset of the petm is marked by widespread dissolution of calcium carbonate on the seafloor in addition there is evidence for globally higher humidity precipitation and increased weathering during the petm both calcium carbonate dissolution and enhanced weathering probably affected the seawater calcium concentration here we investigate implications that possible changes in the ocean s calcium inventory may have had on boron calcium b ca and magnesium calcium mg ca ratios which are used as proxies for deep water carbonate chemistry and temperature respectively we also examine effects on 44ca of seawater which is used as an indicator for variations in the marine calcium cycle we focus on the magnitude of change in the ocean s calcium ion concentration as a result of the carbon perturbation which resulted in increased weathering fluxes and the dissolution of calcite on the ocean floor during the petm different ranges of carbon input scenarios and their effect on ocean chemistry were examined using the long term ocean atmosphere sediment carbon cycle reservoir loscar model we found that under the most plausible scenario the calcium ion concentration change ca2 was less than 0 7 and around 2 in the most extreme scenario our results show that b ca and mg ca proxies were not affected within analytical precision by changes in oceanic calcium due to weathering and carbonate dissolution during the petm the most extreme scenario ca2 2 would result in 4 mol kg 1 uncertainty in reconstruction of co32 the same scenario affects the temperature reconstruction by 0 2 c the effect on the ocean s calcium isotope budget was insignificant as well resulting in 44casw of less than 0 05

capitanian late guadalupian permian global brachiopod palaeobiogeography and latitudinal diversity pattern a global database containing 3365 occurrences 821 species and 251 genera of the capitanian late guadalupian permian brachiopod faunas from 24 stations has been analyzed by cluster analysis using the jaccard and otsuka coefficients and the probabilistic index of similarity nonmetric multidimensional scaling and minimum spanning tree two supergroups three groups and six subgroups are revealed and interpreted as representing respectively two biotic realms the palaeoequatorial and gondwanan realms two regions and six provinces an additional realm the boreal realm based on the fauna from spitsbergen also appears recognizable although it also shows considerable similarities with southwestern north america and the northern margin of gondwana as revealed by the statistical analysis the palaeoequatorial realm can be further subdivided into the north america region and the asian tethyan region the six biotic provinces are the cathaysian province in the palaeotethys and mesotethys the greenland svalbard province in the arctic region the austrazean province in eastern australia and new zealand the grandian province in western north america and the two transitional zones the himalayan province in the southern temperate zone and the sino mongolian japanese province in the northern temperate zone polynomial regression analysis and rarefaction analysis indicate that the generic diversities of brachiopod faunas during the capitanian peaked in the palaeoequatorial cathaysian province and the two transitional zones himalayan province and sino mongolian japanese province but fell dramatically in the polar regions the generic diversity of the palaeoequatorial grandian province is apparently lower than in the two transitional zones of temperate palaeolatitudes suggesting that the generic diversity of capitanian brachiopod faunas does not exhibit a strict negative correlation with palaeolatitudes this in turn would suggest that biogeographical determinants such as geographical barriers inhabitable area and ocean currents other than latitude related temperature control may also have played an important role in the dispersal of some brachiopods and the characterization of some local provinces and high diversities the capitanian global brachiopod palaeobiogeography is generally comparable with those in the wuchiapingian and changhsingian but with some notable differences these include 1 that the grandian province of the capitanian in western north america vanished after the end guadalupian regression 2 that the western tethyan province of the lopingian could not be distinguished in the capitanian and 3 that the austrazean province was larger in area than either in the wuchiapingian or in the changhsingian

a core top assessment of proxies for the ocean carbonate system in surface dwelling foraminifers we have assessed the reliability of several foraminifer hosted proxies of the ocean carbonate system 11b b ca and u ca using holocene samples from the atlantic and pacific oceans we examined chemical variability over a range of test sizes for two surface dwelling foraminifers globigerinoides sacculifer and globigerinoides ruber measurements of 11b in g ruber show no significant relationship with test size in either atlantic or pacific sites and appear to provide a robust proxy of surface seawater ph likewise there is no significant variability in the 11b of our atlantic core top g sacculifer but we find that 11b increases with increasing test size for g sacculifer in the pacific these systematic differences in 11b are inferred to be a consequence of isotopically light gametogenic calcite in g sacculifer and its preferential preservation during postdepositional dissolution the trace element ratio proxies of ocean carbonate equilibria u ca and b ca show systematic increases in both g ruber and g sacculifer with increasing test size possibly as a result of changing growth rates this behavior complicates their use in paleoceanographic reconstructions in keeping with several previous studies we find that mg ca ratios increase with increasing size fraction in our well preserved atlantic g sacculifer but not in g ruber in contrast to previous interpretations we suggest that these observations reflect a proportionally larger influence of compositionally distinct gametogenic calcite in small individuals compared to larger ones as with 11b this influences g sacculifer but not g ruber which has negligible gametogenic calcite

timing and mechanism for intratest mg ca variability in a living planktic foraminifer abstract geochemical observations indicate that planktic foraminifer test mg ca is heterogeneous in many species thereby challenging its use as a paleotemperature proxy for paleoceanographic reconstructions we present mg ca and ba ca data collected by laser ablation icp ms from the shells of orbulina universa cultured in controlled laboratory experiments test calcite was labeled with ba spiked seawater for 12 h day or night calcification periods to quantify the timing of intratest mg banding across multiple diurnal cycles results demonstrate that high mg bands are precipitated during the night whereas low mg bands are precipitated during the day data obtained from specimens growing at 20 c and 25 c show that mg ca ratios in both high and low mg bands increase with temperature and average test mg ca ratios are in excellent agreement with previously published empirical calibrations based on bulk solution icp ms analyses in general mg band concentrations decrease with increasing ph and or co2 3 but this effect decreases as experimental temperatures increase from 20 c to 25 c we suggest that mitochondrial uptake of mg2 from the thin calcifying fluid beneath streaming rhizopodial filaments may provide the primary locus for mg2 removal during test calcification and that diurnal variations in either mitochondrial density or activity produce mg banding these results demonstrate that mg banding is an inherent component of test biomineralization in o universa and show that the mg ca paleothermometer remains a fundamental tool for reconstructing past ocean temperatures from fossil foraminifers

latest on the absolute age of the paleocene eocene thermal maximum petm new insights from exact stratigraphic position of key ash layers 19 and 17 abstract we constructed a precise early eocene orbital cyclostratigraphy for dsdp site 550 leg 80 goban spur north atlantic utilizing precession related cycles as represented in a high resolution x ray fluorescence based barium core log based on counting of those cycles we constrain the exact timing of two volcanic ash layers in site 550 which correlate to ashes 19 and 17 of the fur formation in denmark the ashes relative to the onset of the paleocene eocene thermal maximum petm are offset by 862 kyr and 672 kyr respectively when combined with published absolute ages for ash 17 the absolute age for the onset of the petm is consistent with astronomically calibrated ages using the current absolute age of 28 02 ma for the fish canyon tuff fct standard for calibrating the absolute age of ash 17 is consistent with tuning option 2 in the astronomically calibrated paleocene time scale of westerhold et al 2008 westerhold t rohl u raffi i fornaciari e monechi s reale v bowles j and evans h f 2008 astronomical calibration of the paleocene time palaeogeography palaeoclimatology palaeoecology v 257 p 377 403 using the recently recalibrated absolute age of 28 201 ma for the fct standard is consistent with tuning option 3 in the astronomically calibrated paleocene time scale the new results do not support the existence of any additional 405 kyr cycle in the early paleocene astronomically tuned time scale

b ca in planktonic foraminifera as a proxy for surface seawater ph boron isotope systematics indicate that boron incorporation into foraminiferal caco3 is determined by the partition coefficient k d frac left rm b rm ca right rm caco3 left rm b left rm oh right 4 rm hco 3 right rm seawater and b oh 4 hco3 seawater providing in principle a method to estimate seawater ph and pco2 we have measured b ca ratios in globigerina bulloides and globorotalia inflata for a series of core tops from the north atlantic and the southern ocean and in globigerinoides ruber white from ocean drilling program odp site 668b on the sierra leone rise in the eastern equatorial atlantic b ca ratios in these species of planktonic foraminifera seem unaffected by dissolution on the seafloor k d shows a strong species specific dependence on calcification temperature which can be corrected for using the mg ca temperature proxy a preliminary study of g inflata from southern ocean sediment core chat 16k suggests that temperature corrected b ca was 30 higher during the last glacial correspondingly ph was 0 15 units higher and aqueous pco2 was 95 atm lower at this site at the last glacial maximum the covariation between reconstructed pco2 and the atmospheric pco2 from the vostok ice core demonstrates the feasibility of using b ca in planktonic foraminifera for reconstructing past variations in ph and pco2

remobilization of metasomatized mantle lithosphere a new model for the jiaodong gold province eastern china the 120 ma jiaodong province in the north china craton composed of abundant mesozoic granites that intrude precambrian metamorphic basement is bordered by the sulu orogenic belt which formed through the collision between the north china and yangtze cratons in the triassic insights on the geodynamic setting and source of gold and fluids in the jiaodong gold province are based on a detailed study of the sanshandao deposit the 13cpdb and 18o values of hydrothermal calcite from this deposit range from 4 3 to 6 5 and 11 4 to 15 1 respectively which are compatible with a mantle source pre ore mafic dykes in the deposit show typical arc like geochemical features suggesting that the mantle source was metasomatized prior to the basic magmatism the 34s values of gold related pyrite from sanshandao and other large deposits in the province range from 10 9 to 11 5 and are higher than those of the country rocks but consistent with the signature of orogenic gold deposits sourced from a neoproterozoic sedimentary reservoir these high positive 34s values are interpreted to be inherited from auriferous neoproterozoic sedimentary rocks of the northern yangtze craton which were subducted into the mantle lithosphere beneath the north china craton during the formation of eclogite in the adjacent sulu orogenic belt in the triassic the syn ore lower cretaceous mafic dykes display oceanic island basalt like geochemical features suggesting that asthenosphere upwelling triggered the release of gold and sulfur from an enriched and fertilized mantle lithosphere contributing to the auriferous fluid which formed the widespread gold mineralization in the jiaodong province at ca 120 ma

evaluating the planktic foraminiferal b ca proxy for application to deep time paleoceanography abstract the cenozoic era has been characterized by large perturbations to the oceanic carbon cycle and global climatic changes but quantifying the magnitude and cause of these shifts is still subject to considerable uncertainty the boron calcium b ca ratio of fossil planktic foraminifera shells is a promising tool for reconstructing surface ocean carbonate chemistry during such events previous studies indicate that symbiont bearing planktic foraminiferal b ca depends on the b oh 4 dic ratio of seawater and potentially when combined with foraminiferal 11 b proxy reconstructions of b oh 4 an opportunity to reconstruct surface ocean dic in the geologic past there are however two barriers towards interpreting records from the pre pleistocene era 1 changes in seawater major ion chemistry in the past might have affected foraminiferal b ca and 2 modern foraminifera species show variable b ca calibration sensitivities that cannot be constrained in now extinct species here we address these challenges with new experiments in which we have cultured modern symbiont bearing foraminifera globigerinoides ruber pink and trilobatus sacculifer in seawater with simulated early cenozoic seawater chemistry high ca low mg and low b t we explore mechanisms that can account for the inter species trends that are observed in foraminiferal b ca and propose a framework that can be used to apply b ca calibrations to now extinct species for reconstructing climate perturbations under varying seawater chemistries

surface water conditions and calcium carbonate preservation in the fram strait during marine isotope stage 2 28 8 15 4 kyr 1 we present a high resolution record of calcium carbonate preservation alongside the distribution pattern of planktic foraminifera from the fram strait the record covers the marine isotope stage mis 2 28 8 to 15 4 kyr including the last glacial maximum lgm and the early deglaciation in multidecadal temporal resolution the investigation is based on the distribution patterns of planktic foraminifera stable isotopes mean shell weight of neogloboquadrina pachyderma the degree of fragmentation of planktic shells caco3 content and geochemical and sedimentological data the dissolution proxies indicate long lasting periods of markedly reduced preservation of calcium carbonate at 28 8 27 2 24 1 23 2 and 16 6 15 4 kyr in addition to a number of short lasting periods 300 year during the lgm these periods are accompanied by a simultaneous and significant reduction in specimens of subpolar planktic foraminifera indicating a southward expansion of arctic surface water masses prolonged periods with high abundances of subpolar foraminiferal species and good preservation of calcium carbonate are attributed to increased influence of atlantic water masses which appears to persist throughout most of the mis 2 comparison to holocene mis 1 shell weight records shows that the preservation during mis 2 was overall better even during the events of dissolution this was probably a reflection of the low concentration of atmospheric co2 at the time

the late palaeozoic trilobites of iran and armenia and their palaeogeographical significance the iranian territory is composed of a mosaic of tectonic units several of which underwent in the permian and triassic periods a migration from northern gondwana to southern laurussia associated with the opening of the neo tethys ocean although this broad outline of permo triassic palaeogeographical evolution of iranian microplates is now widely accepted the individual timing of migration of these blocks and their biogeographical relationships remain insufficiently known here i review the late palaeozoic record of trilobites in iran and armenia and discuss their palaeobiogeographical affinities in an attempt to shed light on the permian palaeogeographical evolution of iranian and armenian terranes seven iranian or armenian localities representative of five tectonic units have yielded carboniferous and permian trilobites ten species are recognized including two new taxa persia praecox gen nov sp nov and pseudophillipsia s l parvizii sp nov p praecox is the only carboniferous tournaisian species the others are wordian to wuchiapingian in age and can be separated into three morphological groups probably representing clades one is composed of representatives of acropyge while the two others armenica group and paffenholzi group comprise species of pseudophillipsia only p s l parvizii sp nov from the zagros mountains arabian plate is not attributed to one of these groups the distribution of trilobites in iran and armenia strongly suggests that the alborz central iran and transcaucasia microplates represented a single biogeographical unit in middle and late permian times special relationships of this biochore with south china can also be stressed

changing atmospheric co2 concentration was the primary driver of early cenozoic climate the early eocene climate optimum eeco which occurred about 51 to 53 million years ago was the warmest interval of the past 65 million years with mean annual surface air temperature over ten degrees celsius warmer than during the pre industrial period subsequent global cooling in the middle and late eocene epoch especially at high latitudes eventually led to continental ice sheet development in antarctica in the early oligocene epoch about 33 6 million years ago however existing estimates place atmospheric carbon dioxide co2 levels during the eocene at 500 3 000 parts per million and in the absence of tighter constraints carbon climate interactions over this interval remain uncertain here we use recent analytical and methodological developments to generate a new high fidelity record of co2 concentrations using the boron isotope 11 b composition of well preserved planktonic foraminifera from the tanzania drilling project revising previous estimates although species level uncertainties make absolute values difficult to constrain co2 concentrations during the eeco were around 1 400 parts per million the relative decline in co2 concentration through the eocene is more robustly constrained at about fifty per cent with a further decline into the oligocene provided the latitudinal dependency of sea surface temperature change for a given climate forcing in the eocene was similar to that of the late quaternary period this co2 decline was sufficient to drive the well documented high and low latitude cooling that occurred through the eocene once the change in global temperature between the pre industrial period and the eocene caused by the action of all known slow feedbacks apart from those associated with the carbon cycle is removed both the eeco and the late eocene exhibit an equilibrium climate sensitivity relative to the pre industrial period of 2 1 to 4 6 degrees celsius per co2 doubling 66 per cent confidence which is similar to the canonical range 1 5 to 4 5 degrees celsius indicating that a large fraction of the warmth of the early eocene greenhouse was driven by increased co2 concentrations and that climate sensitivity was relatively constant throughout this period

late permian limestones and the permain triassic boundary new biostratigraphic palaeobiogeographical and geochemical data in caucasus and eastern europe

the effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid base chemistry implications for eocene and cretaceous ocean carbon chemistry and buffering reconstructed changes in seawater calcium and magnesium concentration ca2 mg2 predictably affect the ocean s acid base and carbon chemistry yet inaccurate formulations of chemical equilibrium constants are currently in use to account for these changes here we develop an efficient implementation of the miami ionic interactionmodel to predict all chemical equilibrium constants required for carbon chemistry calculations under variable ca2 and mg2 we investigate the impact of ca2 and mg2 on the relationships among the ocean s ph co2 dissolved inorganic carbon dic saturation state of caco3 and buffer capacity increasing ca2 and or mg2 enhances ion pairing which increases seawater buffering by increasing the concentration ratio of total to free uncomplexed carbonate ion an increase in ca2 however also causes a decline in carbonate ion to maintain a given thereby overwhelming the ion pairing effect and decreasing seawater buffering given the reconstructions of eocene ca2 and mg2 ca2 20mm mg2 30mm eocene seawater would have required essentially the same dic as today to simultaneously explain a similar to modern and the estimated eocene atmospheric co2 of 1000 ppm during the cretaceous at 4 times modern ca2 ocean buffering would have been at a minimum overall during times of high seawater ca2 caco3 saturation ph and atmospheric co2 were more susceptible to perturbations of the global carbon cycle for example given both eocene and cretaceous seawater ca2 and mg2 a doubling of atmospheric co2 would require less carbon addition to the ocean atmosphere system than under modern seawater composition moreover increasing seawater buffering since the cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and co2 concentration mechanisms that aid photosynthesis

ordovician pterygometopidae trilobita of north america pterygometopidae are common trilobites in middle and upper ordovician rocks of north america northern europe and siberia and they have considerable biogeographic usefulness the subfamilies ptery

the cimmerian evolution of the nakhlak anarak area central iran and its bearing for the reconstruction of the history of the eurasian margin new structural sedimentological petrological and palaeomagnetic data collected in the region of nakhlak anarak provide important constraints on the cimmerian evolution of central iran the olenekian upper ladinian succession of nakhlak was deposited in a forearc setting and records the exhumation and erosion of an orogenic wedge possibly located in the present day anarak region the triassic succession was deformed after ladinian times and shows south vergent folds and thrusts unconformably covered by upper cretaceous limestones following the late jurassic neo cimmerian deformation palaeomagnetic data obtained in the olenekian succession suggest a palaeoposition of the region close to eurasia at a latitude around 208n in addition the palaeopoles do not support large anticlockwise rotations around ver tical axes for central iran with respect to eurasia since the middle triassic as previously suggested the anarak metamorphic complex amc includes blueschist facies metabasites associated with discontinuous slivers of serpentinized ultramafic rocks and carboniferous greenschist facies variscan metamorphic rocks including widespread metacarbonates the amc was formed at least partially in the triassic its erosion is recorded by the middle triassic baqoroq formation at nakhlak which consists of conglomerates and sandstones rich in meta morphic detritus the amc was repeatedly deformed during post triassic times giving origin to a complex structural setting characterized by strong tectonic fragmentation of previously formed tectonic units based on these data we suggest that the nakhlak anarak units represent an arc trench system developed during the eo cimmerian orogenic cycle different tectonic scenarios that can account for the evolution of the region and for the occurrence of this orogenic wedge in its present position within central iran are critically discussed as well as its relationships with a presumed variscan metamorphic event the cimmerian orogeny affecting the southern eurasian margin between turkey and thailand is related to the collision of several microplates most of which detached from northern gondwana in the early permian during the opening of the

the drift history of iran from the ordovician to the triassic new late ordovician and triassic palaeomagnetic data from iran are presented these data in conjunction with data from the literature provide insights on the drift history of iran as part of cimmeria during the ordovician triassic a robust agreement of palaeomagnetic poles of iran and west gondwana is observed for the late ordovician earliest carboniferous indicat ing that iran was part of gondwana during that time data for the late permian early early tri assic indicate that iran resided on subequatorial palaeolatitudes clearly disengaged from the parental gondwanan margin in the southern hemisphere since the late early triassic iran has been located in the northern hemisphere close to the eurasian margin this northward drift brought iran to cover much of the palaeotethys in approximately 35 ma at an average plate speed ofc 7 8 cm year 21 and was in part coeval to the transformation of pangaea from an irvin gian b to a wegenerian a type configuration

an integrated mineral system model for the gold deposits of the giant jiaodong province eastern china abstract the giant jiaodong gold province with more than 5000 t of proven gold resources is unique in that its mesozoic gold deposits are hosted in a precambrian basement block there has long been debate on the source of gold the mechanism for its extreme enrichment and a holistic genetic model for these spectacular deposits in order to improve understanding of these factors a mineral system model is proposed for the jiaodong gold deposits for the first time it is based on a detailed review of the architecture and composition of the underlying mantle lithosphere the geodynamic setting at the time of gold mineralization the geological and geochemical features of the deposits themselves and mechanisms of their preservation regional geodynamic reconstructions combined with the nature of mesozoic magmatic systems show that late mesozoic breakoff of the subduction slab and rollback of the paleo pacific plate caused asthenosphere upwelling and lithosphere extension and thinning robust geochronological studies demonstrate that the jiaodong gold deposits formed at ca 120 ma during a change of subduction direction of the paleo pacific plate and the synchronous transition of tectonic regime from regional compression to transpression or transtension prior to peak extension caused by thinning of the lithosphere geophysical exploration data and hf nd isotope mapping of the jiaodong peninsula reveal a relatively simple ancient crustal structure cut by near vertical shear or fault zones including the lithosphere scale tan lu and wulian yantai faults that provided the first order architecture for emplacement of mantle magmas and sub crustal fluids in terms of fertility the significant older pre mineralization crustal metamorphism combined with sulfur lead and strontium isotope ratios indicate a dominant sub crustal source for the ore components for the jiaodong gold deposits consistent with evidence for volatile and gold fertilized metasomatized mantle lithosphere beneath the north china block helium ar and c o isotope ratios implicate mantle sources of ore fluids with contamination by crustal components en route to crustal depositional sites in terms of crustal architecture combined geophysical structural mineralogical fluid inclusion and geochemical studies show that the deeply sourced ore fluids and metals advected upwards through lithosphere scale faults to deposit gold via sulfidation and phase separation in crustal scale nne ne trending fault systems at mid to upper crustal levels preservation of disseminated to stockwork style deposits and auriferous quartz pyrite vein deposits was enhanced by deep crustal formation combined with limited uplift and exhumation of the province the jiaodong gold deposits although commonly hosted in granite intrusions clearly post date them on the basis of robust and reliable geochronology the spatial but non temporal relationships of gold deposits with granites their strong structural control and their other characteristics clearly place them in the orogenic gold group it is suggested because of their uniqueness that they be termed jiaodong type orogenic gold deposits

calibration of the b ca proxy in the planktic foraminifer orbulina universa to paleocene seawater conditions the b ca ratio of planktic foraminiferal calcite a proxy for the surface ocean carbonate system displays large negative excursions during the paleocene eocene thermal maximum petm 55 9 ma consistent with rapid ocean acidification at that time however the b ca excursion measured at the petm exceeds a magnitude that modern ph calibrations can explain numerous other controls on the proxy have been suggested including foraminiferal growth rate and the total concentration of dissolved inorganic carbon dic here we present new calibrations for b ca versus the combined effects of ph and dic in the symbiont bearing planktic foraminifer orbulina universa grown in culture solutions with simulated paleocene seawater elemental composition high ca low mg and low total boron concentration b t we also investigate the isolated effects of low seawater b t high ca reduced symbiont photosynthetic activity and average shell growth rate on o universa b ca in order to further understand the proxy systematics and to determine other possible influences on the petm records we find that average shell growth rate does not appear to determine b ca in high calcite saturation experiments in addition our paleocene calibration shows higher sensitivity than the modern calibration at low b oh 4 dic given a large dic pulse at the petm this amplification of the b ca response can more fully explain the petm b ca excursion however further calibrations with other foraminifer species are needed to determine the range of foraminifer species specific proxy sensitivities under these conditions for quantitative reconstruction of large carbon cycle perturbations

environmental versus biological controls on mg ca variability in globigerinoides ruber white from core top and plankton tow samples in the southwest pacific ocean 1 laser ablation inductively coupled plasma mass spectrometry was used to analyze the individual chambers from tests of foraminiferal fossil and plankton tow globigerinoides ruber from the southwest pacific ocean from latitudes 3 s to 42 s the variability of mg ca between chambers of an individual intraindividual and individuals of the same population interindividual is such that when converted to temperature the extent of intra individual and interindividual variability appears to exceed that attributable to either calcification or seasonal temperature variability the pooled mean chamber mg ca from each core top and plankton tow site demonstrates a significant p 0 05 positive correlation with temperature we derive chamber specific calibrations where mg cach f 2 0 798 exp0 070 t mg cach f 1 0 891 exp0 067 t and mg cach f 0 590 exp0 072 t we do not observe any bias between the two morphotypes gs ruber ruber and gs ruber pyramidalis the chamber specific calibrations potentially offset mg ca based temperature reconstructions if used on bulk whole test mg ca or applied to misidentified chambers nevertheless these calibrations can be used to reliably estimate sea surface temperature although there is a general overriding temperature control on mg ca we show that removal of the effect of temperature at each site reveals a lognormal mg ca distribution this suggests that mg ca variability at each site is also affected by biological mechanism s that may control the distribution of interindividual mg ca in addition other te ca data al ca and mn ca from laser ablation trace element depth profiles can be used to identify detrital or diagenetic phases that may bias the trace element ca signal

silicate weathering and north atlantic silica burial during the paleocene eocene thermal maximum during the paleocene eocene thermal maximum petm ca 56 ma thousands of gigatons of carbon were released into the ocean and atmosphere over several thousand years offering the opportunity to study the response of ocean biogeochemistry to a carbon cycle perturbation of a similar magnitude to projected anthropogenic co 2 release petm scenarios typically invoke accelerated chemical weathering of terrestrial silicate rocks as a significant negative feedback driving the recovery and termination of the event however the implications of this mechanism for the geochemical cycling of silica during the petm have received little attention i use back of the envelope calculations and a simple two box geochemical model of the marine silica cycle to demonstrate that the sequestration of thousands of gigatons of carbon by enhanced silicate weathering during the petm would have dramatically increased the riverine supply of dissolved silica h 4 sio 4 to the oceans this would have elevated seawater h 4 sio 4 encouraging both increased opal sio 2 production by siliceous organisms and enhanced preservation of sio 2 in the water column and sediments both of these factors would have promoted a prompt due to the relatively short oceanic residence time of silica increase in sedimentary opal burial thus balancing the marine silica budget several recently recovered deep sea sedimentary records from the central north atlantic demonstrate elevated sio 2 content across the paleocene eocene boundary which i argue is the result of enhanced production and or preservation of sio 2 in response to elevated h 4 sio 4 in the north atlantic representing the ultimate fate of excess si weathered from the continents during the petm

early permian pangea b to late permian pangea a the pre drift wegenerian model of pangea is almost universally accepted but debate exists on its pre jurassic configuration since tedirving introd ucedpangea b by placing gond wana farther to the east by v3000 km with respect to laurasia on the basis of paleomagnetic data new paleomagnetic data from radiometrically dated early permian volcanic rocks from parts of adria that are tectonically coherent with africa gondwana integrated with published coeval data from gondwana and laurasia again only from igneous rocks fully support a pangea b configuration in the early permian the use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for pangea b the ultimate option to reject pangea b is to abandon the geocentric axial dipole hypothesis by introducing a significant non dipole zonal octupole component in the late paleozoic time averaged geomagnetic field we demonstrate however by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from gondwana as well as laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for pangea b in the early permian we therefore regard the paleomagnetic evidence for an early permian pangea b as robust the transformation from pangea b to pangea a took place during the permian because late permian paleomagnetic data allow a pangea a configuration we therefore review geological evidence from the literature in support of an intra pangea dextral megashear system the transformation occurred after the cooling of the variscan mega suture andlasted v20 myr in this interval the neotethys ocean opened between india arabia and the cimmerian microcontinents in the east while widespread lithospheric wrenching and magmatism took place in the west around the adriatic promontory the general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right lateral shear couple between gondwana and laurasia during the permian transcurrent plate boundaries associated with the pangea transformation reactivated variscan shear zones andwere subsequently exploitedby the opening of western neotethyan seaways in the jurassic

environmental controls on b ca in calcite tests of the tropical planktic foraminifer species globigerinoides ruber and globigerinoides sacculifer abstract the ratio of boron to calcium b ca in the calcite tests of planktic foraminifers may serve as a proxy for past seawater chemistry but controls on b incorporation are not yet certain here we present the results of laboratory culture experiments with live specimens of globigerinoides ruber pink and globigerinoides sacculifer which provide new insight into b incorporation controls we find that in g sacculifer b ca increases with increasing ph lower hco3 higher co32 and b oh 4 but decreases with increasing total dissolved inorganic carbon dic higher hco3 and co32 constant b oh 4 this suggests competition between aqueous boron and carbon species for inclusion into the calcite lattice similar to previous experiments with the subtropical temperate orbulina universa b ca increases with salinity but not with temperature we evaluate possible carbonate system control parameters and compare our tropical culture calibrations with new and published core top data