first reported sedimentary occurrence of berlinite alpo4 in phosphate bearing sediments from cioclovina cave romania this paper describes the first reported occurrence of berlinite alpo 4 formed entirely under sedimentary conditions berlinite appears as grayish or colorless fine crystals in vacuoles and along cracks in heavily compacted phosphate rich sediments within the cioclovina cave in romania the x ray powder diffraction pattern and the hexagonal unit cell of the cioclovina berlinite specimen compare well with other published determinations the lattice parameters are a 4 94 4 c 10 87 1 a v 230 1 3 a 3 microprobe analyses confirmed a nearly ideal formula for berlinite in situ guano combustion is responsible for the transformation of taranakite and for the dehydration of variscite into berlinite berlinite was successfully synthesized from these two minerals at atmospheric pressure and temperatures ranging from 350 to 600 c

geochemical characteristics of deep sea sediments from the arabian sea a high resolution study abstract five deep sea cores from the arabian sea covering a time interval of 170 ky were sampled at high resolution and analysed for major and trace elements the stratigraphy of the cores was obtained by comparing the ba al ratio with the specmap data this method is based on the close correlation between ba concentrations or ba al ratios and oxygen isotope ratios 18o of foraminifera in arabian sea sediments ba al ratios used as a productivity proxy are variable but high in all deep sea cores of the arabian sea indicating a basin wide influence of nutrient rich water masses compared to glacial intervals the warmer periods are characterised by higher element al ratios of proxies which are directly ba ca sr p i e hard parts of organisms or indirectly u 230thex related to biological productivity 230thex provides evidence for intense boundary scavenging caused by high productivity due to enhanced upwelling and terrigenous input from the indus fan the mn distribution in a core from the western arabian sea shows enrichments during interglacial periods and may indicate mn export owing to the presence of a stronger oxygen minimum zone several processes limit the applicability of proxies intercalated turbidites in the deep sea cores can be identified by means of si al ti al and zr al ratios versus depth due to the enrichment of quartz ti minerals and zircon in the basal layer these elements are also important for the reconstruction of the history and extent of the eolian dust input diagenetic redistribution of redox sensitive elements occurs at the boundaries between turbidites and normal pelagic sedimentation and may mask or destroy primary signals

oxygen minimum zone controlled mn redistribution in arabian sea sediments during the late quaternary 1 accumulation of labile mn is related to bottom water oxygen concentrations in this study we investigate the relation between oxygen minimum zone omz intensity and mn burial in arabian sea during the late quaternary mn carbonates in sediments of the deep arabian basin indicate that this part of the basin remained oxygenated for at least the last 185 kyr sequential leaching showed manganese carbonate enrichments with concentrations up to 3750 ppm in deep basin sediments these mn spikes must have formed diagenetically during periods of increased mn oxide fluxes to the deep basin associated with vertical extension of the omz this extension caused remobilization of mn oxides from a previously oxic slope resulting in increased mn accumulation in the deep basin mn relocation is evidenced by synchronous mn depletions in organic rich intervals in slope sediments mn records from the deep basin can thus be used as a qualitative proxy to reconstruct intermediate water oxygenation

238u234u230th disequilibrium in hydrogenous oceanic femn crusts palaeoceanographic record or diagenetic alteration abstract a detailed tims study of 234uexc 238u 230th 232th and th u ratios have been performed on the outermost margin of ten hydrogenous fe mn crusts from the equatorial pacific ocean and west central indian ocean th u concentration ratios generally decrease from the crust s surface down to 0 5 1 mm depth and growth rates estimated by uranium and thorium isotope ratios are significantly different in fe mn crusts from the peru basin and the west central indian ocean fe mn crusts from the same geographical area define a single trend in plots of ln 234uexc 238u vs ln 230th 232th and th u ratios vs age of the analysed fractions results suggest that l hydrogenous fe mn crusts remain closed systems after formation and consequently 2 the discrepancy observed between the 230th and 234u chronometers in fe mn crusts and the variations of the th u ratios through the margin of femn crusts are not due to redistribution of uranium and thorium isotopes after oxyhydroxide precipitation but rather to temporal variations of both th u and initial thorium activity ratios recorded by the fe mn layers implications of these observations for determination of fe mn crust growth rates are discussed variations of both th u and initial th activity ratios in fe mn crusts might be related to changes in particle input to seawater and or changes in ocean circulation during the last 150 ka

sedimentation at manop site h eastern equatorial pacific over the past 400 000 years climatically induced redox variations and their effects on transition metal cycling gravity cores recovered from manganese nodule project site h 6 33 n 92 49 w show marked downcore variations in the abundance of calcium carbonate organic carbon opal manganese and other components deposited over the past 400 000 years variations in the downcore abundance of organic carbon which ranges from 0 2 to 1 0 can be used to hindcast redox conditions in the surface sediments over this time the results indicate that the depth to the manganese redox boundary varied from about 5 to 25 cm below the seafloor during four major cycles downcore variations in solid phase mn ni and cu can be produced by such changes in redox conditions a model which predicts that solid phase mn can be trapped and buried when the mn redox boundary migrates rapidly upward is consistent with the observed organic carbon and mn records and supports the reconstructed redox variations the history of redox variations at site h can be explained by changes with time in surface water productivity major productivity variations at the site occur over 100 kyr cycles with relatively higher productivity occurring during glacial stages thus quaternary climate changes influence surface water productivity redox conditions in sediments and the cycling of transition metals

the ti al molar ratio as a new proxy for tracing sediment transportation processes and its application in aeolian events and sea level change in east asia abstract ti al molar ratios of sediments in various sedimentary environments are used to explain sediment transportation from source regions to sink areas samples were collected from outcrops soils fluvial lake and marine sediment environments initial ti al molar ratios of sediments are controlled by those of parent soils or rocks these ratios tend to decline gradually as a result of heavy mineral gravity fractionation during transportation sedimentary ti al molar ratios in sink areas such as lakes and pelagic environments are lower than those in source regions in this study for the changjiang river huanghe river and kaoping river ti al molar ratios decline considerably from downstream to estuary environments additionally well sorted aeolian sands have extremely low ti al molar ratios in northern china the ti al molar ratios of aerosol particles found in taiwan and the east china sea show reduced ratios as a result of asia dust storm episodes furthermore lower ti al molar ratios in deep ocean sediments were discovered by tracing the distribution of sedimentary ti al molar ratios in the south china sea when sea levels dropped during glacial periods the river estuary was closer to deep marine areas and carried more terrestrial sediments into deep marine environments the closer estuary with relatively higher ti al ratio would lead increase of ti al molar ratios in deep sea sediments in this study ti al molar ratio is promoted as a new proxy to help with understanding changes in sedimentary environments

climatic influence in nrm and 10be derived geomagnetic paleointensity data abstract one can determine geomagnetic paleointensities from natural remanent magnetizations nrm and by inverting production rates of cosmogenic isotopes such as 10 be and 14 c recently two independently derived 200 kyr stacks y guyodo j p valet relative variations in geomagnetic intensity from sedimentary records the past 200 000 years earth planet sci lett 143 1996 23 36 m frank b schwarz s baumann p w kubik m suter a mangini a 200 kyr record of cosmogenic radionuclide production rate and geomagnetic field intensity from 10 be in globally stacked deep sea sediments earth planet sci lett 149 1997 121 129 were compared and the good agreement was suggested to validate the use of sedimentary cores for studies both compilations use mainly the astronomically forced and climatically controlled oxygen isotope stratigraphy to date and synchronize the sedimentary records while this very curve has several coherent features with the supposedly pure geomagnetic records an nrm relative paleointensity record which was included in the conventional paleointensity stack shows correspondence with climatic features which is explained by an inadequacy in the normalization technique therefore it is possible that the extraction of the pure paleointensity signal from marine sediments has not always been accomplished

variations in solar magnetic activity during the last 200 000 years is there a sun climate connection abstract the production of 10be in the earth s atmosphere depends on the galactic cosmic ray influx that in turn is affected by the solar surface magnetic activity and the geomagnetic dipole strength using the estimated changes in 10be production rate and the geomagnetic field intensity variations in solar activity are calculated for the last 200 ka large variations in the solar activity are evident with the sun experiencing periods of normal enhanced and suppressed activity the marine 18o record and solar modulation are strongly correlated at the 100 ka timescale it is proposed that variations in solar activity control the 100 ka glacial interglacial cycles however the 10be production rate variations may have been under estimated during the interval between 115 ka and 125 ka and may have biased the results future tests of the hypothesis are discussed

response of manganese in the ocean to the climatic cycles in the quaternary profiles of the 230th concentration in mn crusts from the central pacific ocean measured at extremely high depth resolution reveal that the growth rates of mn crusts are influenced by climate based on a constant flux model the sections of maximum 230th concentration correspond to periods of slow growth during glacial stages fast growth occurred during interglacial stages 1 5 and 7 probably due to a larger supply of mn oxides from the water column high resolution profiles of 230th and 10be in sediment cores from high biological productivity areas display radioisotope maxima in the interglacial stages and minima during glacial periods the ratio of the fluxes of 10be 230th being 4 the only exceptions are observed at 135 and 270 kyr b p where the ratio of the fluxes is as low as 0 1 to 0 3 we presume that this 230th anomaly reflects short periods of time at the end of glacials when precipitation of mno2 occurred this hypothesis is confirmed by peaks of mn observed in sediment cores mainly at the transitions from glacial to interglacial stages the standing crops of mn in these layers suggest release of mn2 from the sediments during glacial stages and buildup of mn in the water column to concentrations of up to 10 mol l

what do we learn from peaks of uranium and of manganese in deep sea sediments abstract uranium and manganese are two redox sensitive trace elements with complementary behavior under anoxic conditions u is immobile while reduced mn is dissolved in pore water of sediments uranium diffuses from sea water into reducing sediments and is enriched there the depth of the reducing layers and the sediment accumulation rate determine the enrichment of authigenic uranium on the contrary mn is dissolved in the reducing sediment sections diffuses in pore water and forms peaks of mn oxide as soon as oxygen is available thus the profiles of both mn and authigenic u record the depth of the redoxcline during periods of oxygen limitation in the sediments estimates of the depth of incorporation of uranium during the last glacial were derived for several cores at localities in the atlantic numerical modeling of the redoxcline as a function of the oxygen content of the water column and of the flux of organic matter to the sediments constrains these values during periods of extreme shallow redoxcline depths burn down of organic matter and deepening of the redoxcline during the holocene may have significantly altered the organic matter and uranium signals of glacial sediments at present day conditions sediments accumulating at rates smaller than 2 cm ky 1 may have lost the u signals peaks of manganese are then the only reliable record for a less ventilated sediment column in the past

first reported sedimentary occurrence of berlinite alpo4 in phosphate bearing sediments from cioclovina cave romania comment in a recent work onac and white 2003 reported on berlinite but also chlorellestadite and churchite from the bivouac room cioclovina cave romania our analyses of materials collected from this site failed to identify berlinite chlorellestadite or churchite due to the nature of the samples collected from the bat guano deposit at cioclovina many possible sources of confusion can occur for example separates from a mixture of taranakite quartz and minor illite could give the same analytical results as those reported by onac and white 2003 for berlinite for this reason we consider that the occurrence of berlinite at cioclovina as well as the occurrence of other exotic species such as chlorellestadite or churchite is not well enough substantiated and their report must be regarded with caution arguments to support this point of view are problems identified with the analytical techniques empa xrd the failure of the experimental synthesis of berlinite in dry conditions at atmospheric pressure and the geochemical context from cioclovina

sedimentology of seismo turbidites off the cascadia and northern california active tectonic continental margins northwest pacific ocean abstract holocene turbidites from turbidite channel systems along the active tectonic continental margins of the cascadia subduction zone offshore vancouver island to mendocino triple junction and the northern san andreas transform fault the triple junction to san francisco bay have been analyzed for sedimentologic features related to their seismic origin centimeter thick silt sand beds turbidite base capped by mud layers turbidite tail and interbedded with hemipelagic silty clay intervals with high biogenic content have been characterized by visual core descriptions grain size analysis x ray radiographs and physical properties along the northern california margin in upstream single tributary canyons and channels most turbidites are uni pulsed classic fining up whereas downstream below multiple tributary canyon and channel confluences most deposits are stacked turbidites because each set of stacked turbidites has no hemipelagic sediment between each turbidite unit and each unit has a distinct mineralogy from a different tributary canyon we interpret that a stacked turbidite is deposited by several coeval turbidity currents fed by multiple tributary canyons and channels with synchronous triggering from a single san andreas fault earthquake the cascadia margin is characterized by individual multi pulsed turbidites that contain multiple coarse grained sub units without hemipelagic sediment between pulses because the number and character of multiple coarse grained pulses for each correlative multi pulsed turbidite is almost always constant both upstream and downstream in different channel systems for 600 km along the margin we interpret that the earthquake shaking or aftershock signature is usually preserved for the much stronger cascadia 9 mw compared to weaker california 8 mw earthquakes which result in upstream uni pulsed turbidites and downstream stacked turbidites consequently both the strongest 9 mw great earthquakes and downstream confluences cause multi pulsed and stacked turbidites that are typical for seismo turbidites generated by a single great earthquake along both margins earthquake triggering and multi pulsed or stacked turbidites become an alternative explanation for amalgamated turbidite beds in active tectonic margins and show that multiple grain size pulses and reverse grading are not unique criteria for hyperpycnites thalweg levee turbidites or mini basin margin turbidites the analyses of the turbidites along the cascadia and northern california margins reveal common sedimentologic characteristics of turbidites triggered by great earthquakes that can be used to distinguish seismo turbidites in other active tectonic margins around the world

post depositional manganese mobilization during the last glacial period in sediments of the eastern clarion clipperton zone pacific ocean abstract numerous studies have provided compelling evidence that the pacific ocean has experienced substantial glacial interglacial changes in bottom water oxygenation associated with enhanced carbon dioxide storage in the glacial deep ocean under postulated low glacial bottom water oxygen concentrations o 2 bw redox zonation biogeochemical processes and element fluxes in the sediments must have been distinctively different during the last glacial period lgp compared to current well oxygenated conditions in this study we have investigated six sites situated in various european contract areas for the exploration of polymetallic nodules within the clarion clipperton zone ccz in the ne pacific and one site located in a protected area of particular environmental interest apei3 north of the ccz we found bulk sediment mn maxima of up to 1 wt in the upper oxic 10 cm of the sediments at all sites except for the apei3 site the application of a combined leaching protocol for the extraction of sedimentary mn and fe minerals revealed that mobilizable mn iv represents the dominant mn oxyhydr oxide phase with more than 70 of bulk solid phase mn steady state transport reaction modeling showed that at postulated glacial o 2 bw of 35 m the oxic zone in the sediments was much more compressed than today where upward diffusing pore water mn2 was oxidized and precipitated as authigenic mn iv at the oxic suboxic redox boundary in the upper 5 cm of the sediments transient transport reaction modeling demonstrated that with increasing o 2 bw during the last glacial termination to current levels of 150 m 1 the oxic suboxic redox boundary migrated deeper into the sediments and 2 the authigenic mn iv peak was continuously mixed into subsequently deposited sediments by bioturbation causing the observed mobilizable mn iv enrichment in the surface sediments such a distinct mobilizable mn iv maximum was not found in the surface sediments of the apei3 site which indicates that the oxic zone was not as condensed during the lgp at this site due to two to threefold lower organic carbon burial rates leaching data for sedimentary fe minerals suggest that fe iii has not been diagenetically redistributed during the lgp at any of the investigated sites our results demonstrate that the basin wide deoxygenation in the ne pacific during the lgp was associated with 1 a much more compressed oxic zone at sites with carbon burial fluxes higher than 1 5 mg corg m 2 d 1 2 the authigenic formation of a sub surface mobilizable mn iv maximum in the upper 5 cm of the sediments and 3 a possibly intensified suboxic diagenetic growth of polymetallic nodules as our study provides evidence that authigenic mn iv precipitated in the surface sediments under postulated low glacial o 2 bw it contributes to resolving a long standing controversy concerning the origin of widely observed mn rich layers in glacial deglacial deep sea sediments

beryllium 10 thorium 230 and protactinium 231 in galapagos microplate sediments implications of hydrothermal activity and paleoproductivity changes during the last 100 000 years biogenic particle fluxes from highly productive surface waters boundary scavenging and hydrothermal activity are the main factors influencing the deposition of radionuclides in the area of the galapagos microplate eastern equatorial pacific in order to evaluate the importance of these three processes throughout the last 100 kyr concentrations of the radionuclides 10be 230th and 231pa and of mn and fe were measured at high resolution in sediment samples from two gravity cores klh 068 and klh 093 high biological productivity in the surface waters overlying the investigated area has led to 10be and 231pa fluxes exceeding production during at least the last 30 kyr and probably the last 100 kyr however during periods of high productivity at the up welling centers off peru and extension of the equatorial high productivity zone a relative loss of 10be and 231pa may have occurred in these sediment cores because of boundary scavenging the effects of hydrothermal activity were investigated by comparing the 230thex concentrations to the mn fe ratios and by comparing the fluxes of 230th and 10be which exceed production the results suggest an enhanced hydrothermal influence during isotope stages 4 and 5 and to a lesser extent during isotope stage 1 in core klh 093 during isotope stages 2 and 3 the hydrothermal supply of mn was deposited elsewhere probably because of changes in current regime or deep water oxygenation a strong increase of the mn fe ratio at the beginning of climatic stage 1 which is not accompanied by an increase of the 230thex concentration is interpreted to be an effect of mn remobilization and reprecipitation in the sediment

mount mazama eruption calendrical age verified and atmospheric impact assessed geochemical identification of mount mazama ash in the greenland ice sheet project 2 gisp2 ice core gives a calendrical age of 7627 150 cal yr b p 5677 150 b c for the eruption thus providing a more accurate early holocene stratigraphic time line than previously available the gisp2 record of volcanically derived sulfate suggests a total stratospheric aerosol loading between 88 and 224 mt spread over an 6 yr period following the eruption of mount mazama taking into account the likelihood of some tropospheric aerosol transport to greenland realistic estimates of the resulting atmospheric optical depth range from 0 6 to 1 5 these values may have produced a temperature depression of 0 6 to 0 7 c at mid to high northern latitudes for 1 3 yr after the eruption these results indicate that the 5677 b c eruption of mount mazama was one of the most climatically significant volcanic events of the holocene in the northern hemisphere we also calculate a maximum stratospheric cl release of 8 1 mt by the eruption which may have led to substantial stratospheric ozone depletion

a 250 000 year climatic record from great basin vein calcite implications for milankovitch theory a continuous record of oxygen 18 18o variations in the continental hydrosphere during the middle to late pleistocene has been obtained from a uranium series dated calcitic vein in the southern great basin the vein was deposited from ground water that moved through devils hole an open fault zone at ash meadows nevada between 50 and 310 ka thousand years ago the configuration of the 18o versus time curve closely resembles the marine and antarctic ice core vostok 18o curves however the u th dates indicate that the last interglacial stage marine oxygen isotope stage 5 began before 147 3 ka at least 17 000 years earlier than indicated by the marine 18o record and 7 000 years earlier than indicated by the less well dated antarctic 18o record this discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine 18o chronology may need revision and that orbital forcing may not be the principal cause of the pleistocene ice ages

diffusion and supply rates of 10be and 230th radioisotopes in two manganese encrustations from the south china sea ages of two mn encrustations estimated by their 230th and 10be distributions are compared with k ar ages and micropaleontological datings of their nuclei to discuss possible diffusion and supply effects of the radioisotope distribution and their influence on the reliability of age determinations based on comparable results obtained by the different methods the effective diffusion coefficient of 10be can be calculated as d 1 0 10 8cm2 y this coefficient is 3 8 times smaller than the best estimates available at present in both nodules we observe lower 10be concentrations in the uppermost 2 3 mm 1 3 m y which suggests that 10be uptake has been reduced since the middle pleistocene the 2 7 fold increase of the growth rate starting 3 2 m y ago coincides with the initiation of the northern hemisphere glaciation

detrital and early diagenetic processes in late pleistocene and holocene sediments from the sw galicia bank inferred from high resolution enviromagnetic and geochemical records abstract u channel based high resolution magnetic and geochemical measurements supported by scanning electron microscopy x ray diffraction and fluorescence and grain size analyses of discrete samples were carried out on six sediment cores recovered from the sw flank of the galicia bank at the prestige s wreck area five magnetochemical facies reflecting the different sedimentary environments i e hemipelagic contouritic turbiditic sediment provenances and early diagenetic redoxomorphic processes i e mn peaks are defined on the basis of a cluster analysis the records showed climatically forced detrital signatures of regional importance associated with continental slope sedimentary processes the chronostratigraphy and correlation of the cores is based on 20 14 c ams dating recognition of heinrich like events h1 to h3 and well documented holocene climatic features from a geochemical and enviromagnetic perspective the late pleistocene to holocene evolution of the area shows two different sedimentation contexts mis 2 is dominated by down slope depositional processes the highest sedimentation rates 9 1 cm ky were achieved during this interval the major turbidite activity is recorded between 31 000 yr bp and 13 500 yr bp successive arrivals of ird h1 to h3 are also identified during this period in contrast holocene sedimentation was dominated by a mixture of pelagic hemipelagic and along slope depositional processes and presented considerable lower sedimentation rates 3 cm ky bottom currents intensification at 7000 yr bp and 4500 yr bp coinciding with late holocene warm events are also recognised during this stage

thorium and uranium isotopes in a manganese nodule from the peru basin determined by alpha spectrometry and thermal ionization mass spectrometry tims are manganese supply and growth related to climate thorium and uranium isotopes were measured in a diagenetic manganese nodule from the peru basin applying alpha and thermal ionization mass spectrometry tims alpha counting of 62 samples was carried out with a depth resolution of 0 4 mm to gain a high resolution230thexcess profile in addition 17 samples were measured with tims to obtain precise isotope concentrations and isotope ratios we got values of 0 06 0 59 ppb 230th 0 43 1 40 ppm 232th 0 09 0 49 ppb 234u and 1 66 8 24 ppm 238u the uranium activity ratio in the uppermost samples 1 6 mm and in two further sections in the nodule at 12 5 1 0 mm and 27 3 33 5 mm comes close to the present ocean water value of 1 144 0 004 in two other sections of the nodule this ratio is significantly higher probably reflecting incorporation of diagenetic uranium the upper 25 mm section of the mn nodule shows a relatively smooth exponential decrease in the230thexcess concentration tims the slope of the best fit yields a growth rate of 110 mm ma up to 24 5 mm depth the section from 25 to 30 3 mm depth shows constant230thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule from 33 to 50 mm depth the growth rate is approximately 60 mm ma two layers in the nodule with distinct laminations 11 15 and 28 33 mm depth probably formed during the transition from isotopic stage 8 to 7 and in stage 5e respectively the mn fe ratio shows higher values during interglacials 5 and 7 and lower ones during glacials 4 and 6 a comparison of our data with data from adjacent sediment cores suggests a a variable supply of hydrothermal mn to sediments and mn nodules of the peru basin or b suboxic conditions at the water sediment interface during periods with lower mn fe ratios

accumulation rates of th 230 pa 231 and some transition metals on the bermuda rise abstract measurements of 238u 234u 230th 232th 231pa mn fe co ni cu and zn were made on 23 samples from core gpc 5 a 29 m giant piston core from a water depth of 4583 m on the northeastern bermuda rise 33 41 2 n 57 36 9 w this area is characterized by rapid deposition of sediment transported by abyssal currents unsupported 230th and 231pa are present throughout the core but because of large variations in the sedimentation rate show marked departures from exponential decay with depth the trend with depth of the 231 pa ex 230 th ex ratio is consistent with the average accumulation rate of 36 cm 1000 y reported earlier on the basis of radiocarbon dating and caco3 stratigraphy when expressed on a carbonate free basis concentrations of mn co ni cu zn 230thex and 231paex all show cyclic variations positively correlated with those of caco3 the correlations can be explained by a model in which all of these constituents including caco3 are supplied to the sediments from the water column at a constant rate concentration variations are controlled mainly by varying inputs of terrigenous detritus with low inputs occurring during interglacials and high inputs during glacials relationships between the metal and 230thex concentrations permit estimates of the rates at which the metals are removed to the sediment by scavenging from the water column the results in g cm2 1000 y are 4300 1100 for mn 46 16 for ni and 76 26 for cu these rates are somewhat larger than ocean wide averages estimated by other methods and the absolute rate of 230th accumulation in gpc 5 averages about nine times higher than production in the overlying water column this part of the bermuda rise and similar bottom current deposits may act as important accumulators of elements scavenged from seawater

tracers of ocean paleoproductivity and paleochemistry an introduction new developments in ocean paleoproductivity and paleochemistry have involved the application of tracers that record seawater composition that document sedimentary fluxes and that may be used to infer oceanic processes these include the use of cd ca and ba ca ratios in benthic foraminifera rare earth element patterns of chemical sediments uranium series nuclides in carbonate sediments and studies of the origins of chemical fluxes and anomalies in sedimentary profiles

environmental controls on mid ocean ridge hydrothermal fluxes abstract high temperature hydrothermal fluxes at mid ocean ridges are thought to be an important component of oceanic biogeochemical cycles however little consideration has been given to how these fluxes vary as a consequence of changing environmental conditions over earth history here we consider how changes in sea level and ocean chemistry are likely to have impacted on axis high temperature hydrothermal fluxes focusing on phanerozoic conditions changes in sea level lead to changes in hydrostatic pressure near the base of hydrothermal systems where both peak fluid rock reaction temperatures and phase separation occur in general higher global sea level will lead to higher peak temperatures of fluid rock reaction additionally phase separation at higher pressure tends to lead to formation of a more cl rich vapor that constitutes a larger mass fraction of the system these combined factors may serve to significantly modify hydrothermal fluxes even for sea level changes on the scale of 100 m changes in ocean chemistry can also affect axial hydrothermal fluxes in several ways seawater sulfate contents control the amount of anhydrite that forms which has both physical porosity filling and chemical effects the most important aspect of ocean chemistry in controlling the composition of high temperature vent fluids may be ocean salinity if evaporite formation and dissolution has changed ocean salinity substantially over the phanerozoic hydrothermal fluxes could have been greatly modified ocean chemistry also plays a large role in controlling processes operating in hydrothermal plumes and hence the net flux of elements into and out of the ocean associated with hydrothermal systems we conclude that there is a need for substantial further work to quantify the effects of sea level and ocean chemistry on high temperature hydrothermal fluxes including the development of more robust models that integrate field laboratory and theoretical observations

relative paleointensity rpi and age control in quaternary sediment drifts off the antarctic peninsula abstract lack of foraminiferal carbonate in marine sediments deposited at high latitudes results in traditional oxygen isotope stratigraphy not playing a central role in quaternary age control for a large portion of the globe this limitation has affected the interpretation of quaternary sediment drifts off the antarctic peninsula in a region critical for documenting past instability of the west antarctic ice sheet wais and antarctic peninsula ice sheet apis here we use piston cores recovered from these sediment drifts in 2015 during cruise jr298 of the rrs james clark ross to test the usefulness for age control of relative paleointensity rpi data augmented by scant 18o data thermomagnetic and magnetic hysteresis data as well as isothermal remanent magnetization irm acquisition curves indicate the presence of prevalent magnetite and subordinate oxidized magnetite maghemite in the cored sediments the magnetite is likely detrital maghemite is an authigenic mineral associated with surface oxidation of magnetite grains which occurs preferentially in the oxic zone of the uppermost sediments and buried oxic zones deposited during prior interglacial climate stages low concentrations of labile organic matter apparently led to arrested pore water sulfate reduction explaining oxic zone burial and downcore survival of the reactive maghemite coatings at some sites maghemitization has a debilitating effect on rpi proxies whereas at other sites maghemite is less evident and rpi proxies can be adequately matched to the rpi reference template published rpi data at odp site 1101 located on drift 4 can be adequately correlated to contemporary rpi templates probably as a result of disappearance dissolution of maghemite at sediment depths 10 m

changes in fe oxidation rate in hydrothermal plumes as a potential driver of enhanced hydrothermal input to near ridge sediments during glacial terminations j t c and l a c were supported by the natural sciences and engineering research council of canada

holocene sea level determination relative to the australian continent u th tims and 14c ams dating of coral cores from the abrolhos islands u th tims and 14 c ams measurements are presented from two coral cores from the easter group of the houtman abrolhos islands between 28 s and 29 s on the western continental margin of australia the u th measurements on the morley core from morley island cover a depth interval from 0 2 m above present sea level to 24 4 m below present sea level and comprise eleven samples the ages vary between 6320 50 a at 0 2 m above sea level and 9809 95 a at 24 4 m below sea level all errors are 2 the mean growth rate is 7 1 0 9 m ka the 14 c dates of selected morley core corals show that the 14 c ages are 1000 a younger than their corresponding u th ages which agrees with previous results the main purpose of our 14 c measurements is to be able to compare them precisely with other coral cores where no u th measurements are available the u th measurements of the suomi core from suomi island cover a depth interval from 0 05 m to 14 2 m below present sea level and consist of four samples the ages vary between 4671 40 a at 0 05 m below sea level and 7102 82 a at 14 2 m below sea level with a mean growth rate of 5 8 0 2 m ka the growth history of both cores is explained by a simple model in which the growth rates of the morley core can be interpreted as reflecting local rates of sea level rise whereas the suomi core is interpreted as reflecting lateral growth during the past 6000 a our results indicate that sea level relative to the western margins of the australian continent was about 24 m lower than present at about 9800 a b p 14 c gives a date of 8500 a b p sea level then rose and reached a highstand slightly higher than the present position at about 6300 a b p 14c date 5500 a this highstand declined but was still higher than present at 4600 a b p this is in agreement with previous observations along the australian coastal margins and with observations from the huon peninsula papua new guinea our results are very similar to theoretical numerical models which take into consideration water loading and isostatic compensation and viscous mantle flow in contrast coral cores from barbados show that corals with a 14 c age of 5500 a b p are some 10 m b p s l we interpret the difference between the barbados core and the morley core as resulting from additional flooding of barbados by water redistribution due to changes in the earth s geoid but not reflecting global sea level rise or major addition of melt waters over the past 6000 a the difference in the geoid at barbados between 6000 a b p and the present will require a refinement in the geophysical models precise 230 th tims measurements on continental coasts will be required to provide an adequate data base for modelling deformation flow of mantle material and sea level height

the role of vertical chemical fractionation in controlling late quaternary atmospheric carbon dioxide the 30 decrease in atmospheric carbon dioxide during glacial maxima must be driven by some change in the chemical circulation of the ocean here a new model for late quaternary co2 variability is presented which resolves some problems occurring in previous models including the timing of carbon dioxide response and changes in the oxygen content of the deep ocean the primary driving factor in this model is a rearrangement of chemical distributions in the ocean whereby labile nutrients and metabolic co2 are concentrated in deep waters rather than in intermediate waters as observed in the modern ocean this new bottom heavy chemical structure does not affect atmospheric carbon dioxide directly instead co2 induced acidity lowers the deep ocean carbonate ion concentration and temporarily increases carbonate dissolution rates oceanic alkalinity then rises until the deep ocean carbonate ion is restored to its steady state value the resulting increase in oceanic alkalinity draws co2 out of the atmosphere into the ocean alkalinity and atmospheric co2 lag several thousand years behind the change in oceanic chemical structure this delayed response is determined by the limited rate of continental weathering and deep ocean carbonate dissolution relative to the oceanic alkalinity inventory it is proposed that characteristic deglacial and preglacial states of the ocean are leading factors driving glacial interglacial climate changes this concept reinterprets the carbon isotope contrast between surface water and deep waters 13c p b as due to a shift of light metabolic carbon from intermediate waters into deep waters the process is illustrated here by a simple equilibrium five box ocean model the observed intermediate depth nutrient depletion is not sufficient in itself to determine which of several possible mechanisms are operating and some mechanisms are not as effective in changing atmospheric co2 as others the largest response is seen from deepening the regeneration cycle of organic carbon the least response is seen from converting north atlantic deep water into intermediate water

re examination of berlinite alpo4 from the cioclovina cave romania berlinite is a mineral indicative of high temperature formation and therefore it would not be expected to be present in a sedimentary environment in this study we review the characteristics of a berlinite bearing deposit and present a single crystal structure investigation based on x ray data the refinement converged at r 1 f 0 0276 wr 2 f 2 0 0657 for 677 reflections 2 mo k 70 and 31 variables in space group p 3 1 21 a 4 9458 10 c 10 9526 20 a v 232 0 a 3 z 3 alpo 4 the average t o bond distances within the two crystallographically unique t o 4 tetrahedra are 1 734 and 1 526 a respectively from the scattering power at these t sites and the stereochemistry the presence of an alo 4 tetrahedron linked to a po 4 tetrahedron is established consequently the sample from cioclovina cave is verified as alpo 4 modification berlinite reconfirming the first description of this mineral from a sedimentary occurrence which underwent an obvious natural heating process

transport of10be and9be in the ocean beryllium isotopes 10be and9be have been measured in suspended particles of 1 mm size collected by mid water sediment traps deployed in the eastern pacific at manop sites h 6 32 n 92 50 w water depth 3600 m and m 8 50 n 104 00 w 3100 m for comparison surface sediments from box cores taken from the two sites were also studied the concentrations of10be and9be in sediment trap particles are about an order of magnitude smaller than those in the bottom sediments which contain about 8 109 and 6 1016 atoms g 1 of10be and9be respectively the sediment trap samples collected from 50 m off the bottom showed significant 26 63 contributions from resuspended bottom sediments the10be 9be ratio in trap samples varies from 3 to 20 10 8 the variation may partly result from varied proportion of authigenic detrital material the fluxes of both isotopes exhibit a very strong seasonality the fluxes of10be into the traps at about 1500 m are estimated as 9 105 and 4 105 atoms cm 2 a 1 at sites h and m respectively these values are to be compared with the fluxes into the sediments of 4 5 105 atoms cm 2 a 1 at both locations good correlations exist between10be 9be and27al indicating that the primary carrier phase s for the beryllium isotopes in the water column may be aluminosilicates

anatomy of heinrich layer 1 and its role in the last deglaciation this research used data acquired at the xrf core scanner lab at the marum center for marine environmental sciences university of bremen germany this research used samples provided by the international ocean discovery program iodp funding for this research was provided by the uk natural environmental research council nerc to hodell the nerc radiocarbon facility supported two radiocarbon dates and wally broecker generously supported the remainder with funding from the comer family foundation research by rodriguez tovar and dorador was financed by project cgl2015 66835 p b m acknowledges support from the csic ramon y cajal postdoctoral programme ryc 2013 14073 j f e would like to acknowledge funding under erc advanced grant 320750 nanopaleomagnetism

high resolution 230thex stratigraphy of sediments from high latitude areas norwegian sea fram strait abstract we present data on the average sedimentation rates ranging from 1 6 cm kyr to 3 cm kyr for the last 300 000 years based on 18o analyses of foraminifera in a core from the norwegian sea and 230thex measurements in cores from the norwegian sea and the fram strait arctic ocean furthermore we relate 230thex variations downcore to the various oxygen isotope stages this correlation is tentatively interpreted as being a result of the paleoceanographic and paleoclimatic control of bioproductivity it is shown that based on the average sedimentation rates and characteristic 230thex variations carbonate poor sediment cores from northern latitudes can be correlated

particle size distribution analysis of sand sized particles by laser diffraction an experimental investigation of instrument sensitivity and the effects of particle shape laser diffraction is now widely used for particle size distribution analysis of sediments and soils the technique can be very precise and offers advantages of speed and cost over many other methods when used to analyse mixtures of sand silt and clay this study presents the results of an experimental investigation that examined the sensitivity of the beckman coulter ls230 instrument to mixtures of different grain populations and differences in particle shape the instrument was found to have high sensitivity to coarse particles in a finer matrix detection threshold 1 2 but much lower sensitivity to finer particles in a coarser mixture detection threshold 12 17 experiments using near spherical ballotini showed that laser analysis provides very similar values to dry sieving for the mean median and mode but for a range of natural sand samples values for the mean median and mode were offset by 8 21 with an average of ca 15 compared with sieving analysis using a beckman coulter rapidvue instrument which provides both size and shape information provided support for the hypothesis that the differences between laser analysis and sieving are partly attributable to the effects of particle shape however an additional factor is the way in which the laser software interprets the optical diffraction data the software predicts a high degree of log normality in the size distribution such that highly skewed truncated or bimodal samples are poorly represented experiments using sieved fractions of ballotini indicated that even with near perfectly spherical particles the particle size distribution predicted by the laser software includes a relatively large percentage of particles outside the sieve class limits

sedimentary manganese metallogenesis in response to the evolution of the earth system abstract the concentration of manganese in solution and its precipitation in inorganic systems are primarily redox controlled guided by several earth processes most of which were tectonically induced the early archean atmosphere hydrosphere system was extremely o2 deficient thus the very high mantle heat flux producing superplumes severe outgassing and high temperature hydrothermal activity introduced substantial mn2 in anoxic oceans but prevented its precipitation during the late archean centered at ca 2 75 ga the introduction of photosystem ii and decrease of the oxygen sinks led to a limited buildup of surface o2 content locally initiating modest deposition of manganese in shallow basin margin oxygenated niches e g deposits in india and brazil rapid burial of organic matter decline of reduced gases from a progressively oxygenated mantle and a net increase in photosynthetic oxygen marked the archean proterozoic transition concurrently a massive drawdown of atmospheric co2 owing to increased weathering rates on the tectonically expanded freeboard of the assembled supercontinents caused paleoproterozoic glaciations 2 45 2 22 ga the spectacular sedimentary manganese deposits at ca 2 4 ga of transvaal supergroup south africa were formed by oxidation of hydrothermally derived mn2 transferred from a stratified ocean to the continental shelf by transgression episodes of increased burial rate of organic matter during ca 2 4 and 2 06 ga are correlatable to ocean stratification and further rise of oxygen in the atmosphere black shale hosted mn carbonate deposits in the birimian sequence ca 2 3 2 0 ga west africa its equivalents in south america and those in the francevillian sequence ca 2 2 2 1 ga gabon are correlatable to this period tectonically forced doming up attenuation and substantial increase in freeboard areas prompted increased silicate weathering and atmospheric co2 drawdown causing glaciation on the neoproterozoic rodinia supercontinent tectonic rifting and mantle outgassing led to deglaciation dissolved mn2 and fe2 concentrated earlier in highly saline stagnant seawater below the ice cover were exported to shallow shelves by transgression during deglaciation during the sturtian glacial interglacial event ca 750 700 ma interstratified mn oxide and bif deposits of damara sequence namibia was formed the varangian marinoan ca 600 ma cryogenic event produced mn oxide and bif deposits at urucum jacadigo group brazil the datangpo interglacial sequence south china liantuo nantuo varangian event contains black shale hosted mn carbonate deposits the early paleozoic witnessed several glacioeustatic sea level changes producing small mn carbonate deposits of tiantaishan early cambrian and taojiang mid ordovician in black shale sequences china and the major mn oxide carbonate deposits of karadzhal type central kazakhstan late devonian the mesozoic period of intense plate movements and volcanism produced greenhouse climate and stratified oceans during the early jurassic oae organic rich sediments host many mn carbonate deposits in europe e g urkut hungary in black shale sequences the late jurassic giant mn carbonate deposit at molango mexico was also genetically related to sea level change mn carbonates were always derived from mn oxyhydroxides during early diagenesis large mn oxide deposits of cretaceous age at groote eylandt australia and imini tasdremt morocco were also formed during transgression regression in greenhouse climate the early oligocene giant mn oxide carbonate deposit of chiatura georgia and nikopol ukraine were developed in a similar situation thereafter manganese sedimentation was entirely shifted to the deep seafloor and since ca 15 ma b p was climatically controlled glaciation deglaciation assisted by oxygenated polar bottom currents aabw nadw the changes in climate and the sea level were mainly tectonically forced

major and trace element variations of the sediments at odp site 1144 south china sea during the last 230 ka and their paleoclimate implications abstract we present here the major and trace element data of the sediments at odp site 1144 of the last 230 ka with time resolution about 1 5 kyr to investigate their relations to the climate changes estimated from tio2 and cao contents over 70 in weight of the sediments are terrestrial materials and caco3 abundance ranges between 7 and 19 the variation patterns of some of the major elements such as al fe k mg and mn and some of the trace elements such as the alkali elements such as rb and cs the alkali earth elements such as ba and most transition metals such as sc v co cr zn well match that of the oxygen isotopes of the planktonic foraminifer after normalized with ti with higher values during interglacial periods and lower values during glacial periods whilst the na abundance exhibits inverse variation patterns with lower values during interglacial periods and higher values during glacial periods however most refractory elements such as y zr nb hf ta rees th and u do not show such patterns these agree well with the behaviors of these elements during chemical weathering therefore the changes of chemical weathering intensity in south china the source area of these sediments may account for such variation patterns during interglacials wet and warm climate might occur at south china which resulted in stronger chemical weathering and dry climate might occur during glacials which resulted in weaker chemical weathering such paleoclimate interpretation agrees with those from other paleoclimate proxies such as pollen records indicating that change of the east asian monsoon especially change of the winter monsoon is the key for such paleoclimate variation patterns

ultimate removal mechanisms of elements from the ocean abstract the surface complex formation model can adequately explain the observed partitioning of most of the elements between seawater and pelagic clays and between river water and river suspended particles the adsorption of elements on the hydrous oxide surface of iron oxide manganese oxide and clay minerals is the most important ultimate removal mechanism of most of the elements from the ocean

sea level changes and carbonate platform evolution of the xisha islands south china sea since the early miocene abstract analyses of the biogeochemical branched and isoprenoid tetraether bit index and elemental geochemistry from well xk1 provide insight into the development of the xisha islands carbonate platform in the south china sea scs since the early miocene bit is the ratio of branched glycerol dialkyl glycerol tetraethers bgdgts to isoprenoid glycerol dialkyl glycerol tetraethers igdgts which are derived from meteoric and marine environments respectively bit serves as a novel proxy for tracking sea level changes the bit curve of well xk1 is characterized by low high low high alternating stages indicating the superposition of sea level changes on carbonate platform evolution in the scs following the rapid expansion of the scs in the early stages of the early miocene biogenic reefs began to form and bit oscillated intensely the scs started to regress after its initial expansion during the middle miocene at which time global sea level was also falling significantly the combination of both tectonic activity and eustatic variation has resulted in the deposition of strata with reef beach facies which are characterized by high bit values relative sea level reached its lowest point in the late stages of the middle miocene 11 6 ma subsequent sea level rise between the late miocene and pliocene induced a negative shift in bit and lagoonal facies formed under optimal warm marine conditions periodic exposure caused the reefs of the xisha islands to suffer from erosion during the pleistocene which is consistent with a second elevation in the bit index however modern trends show increasing regional water depths again major and trace element curves na si p b ga mo zn as well as the associated ratios na2o k2o na2o sio2 b ga ti sr zr sr al sr th u accurately record sea level variations several significant discontinuities correlate with sea level shifts and provide important details about the geomorphology sedimentation patterns and diagenesis types on the scs carbonate platform the agreement between organic and inorganic geochemical data demonstrates that our reconstructions of scs sea level changes and modes of carbonate platform development are robust our findings also demonstrate that carbonate evolution in the xisha islands was shaped by relative sea level changes implying that sea level fluctuations in the scs were controlled by global eustatic factors in addition to regional tectonic subsidence

sedimentary facies of glacial interglacial cycles in the norwegian sea during the last 350 ka sediment fluxes were highest in the norwegian sea during late glacial early deglacial periods i e at oxygen isotope transition 43 below transition 65 at various levels within stage 6 and below stage 9 dark diamictons deposited at these times reflect intense iceberg rafting in surface waters fed by surges along the front of the marine based parts of the continental ice sheets in the southeastern sector of the norwegian sea the high organic carbon content 0 5 1 3 in these layers reflects input from erosion of terrigenious matter rich sediments outcropping on the shelves partial oxidation of organic matter and decreased deep water renewal may explain the strong carbonate dissolution observed during these periods interglacial environments were strongly variable throughout the last 350 ka circulation patterns of stage 5e best resemble modern conditions while stage 7 and 9 sediments record a much weaker norwegian current

mid holocene indian summer monsoon variability off the andaman islands bay of bengal abstract a sediment core retrieved from the andamans forearc basin afb near landfall island north andaman provides a record of sediment provenance and climate change during the mid to late holocene radiocarbon ages ranging from 6078 to 1658 indicate that the core represents the interval from 6500 bp to the present grain size variation indicates a cyclic variation of wetter and drier conditions corresponding to changes in intensity of the indian summer monsoon ism which was at greatest intensity near 6400 5300 and 3300 3000 bp geochemical parameters including abundance of caco3 end and 18o in globigerinoides ruber are consistent with a long term trend from cooler wetter conditions to the warmer drier conditions at present chemical weathering intensity which lags behind climate changes on land shows a pulse of highly weathered sediment deposited at about 4000 bp during the short duration pulses of intense monsoon activity sandy sediment was supplied from the andaman islands the irrawaddy salween and sittang rivers of myanmar are the secondary sediment sources for the study area