long chain alkenone patterns in the baltic sea an ocean freshwater transition two different patterns of long chain alkenones are found in surficial sediments of the baltic sea which is the largest brackish water body on earth one pattern occurs in surficial sediments from the western baltic sea where surface water salinitiy is in excess of 7 7 psu it corresponds to the pattern produced by the marine coccolithophorid emiliania huxleyi with a suite of c37 di to tetra unsaturated methyl ketones and c38 di and tri unsaturated methyl and ethyl ketones a second pattern resembling that found in lake sediments in lacking c38 methyl ketones and having distinctly higher c37 4 methyl ketone concentrations dominates in surficial sediments of the eastern and northern baltic sea where salinities are lower than 7 7 psu correspondence of sea surface temperature sst estimates from the u37 and u379 indices using marine calibrations with mean sst in the euphotic zone from july august the main haptophyte growth season is poor thus these indices are not applicable as sedimentary thermometers in surficial sediments of the baltic sea the different patterns may either reflect the salinity dependent occurrence of specific alkenone producers or changes in the alkenone biosynthesis due to physiological stress caused by salinity variations furthermore advection of saline and oxygenated north sea water may transport marine algal material characterized by a marine e huxleyi like alkenone pattern into the western baltic sea thus covering the signature of the local alkenone producers with a baltic sea pattern copyright 2000 elsevier science ltd

the metal oxide fraction of pelagic sediment in the equatorial north pacific ocean a source of metals in ferromanganese nodules abstract pelagic sediment recovered at domes site a in the equatorial north pacific 151 w 9 15 n consists of a surface homogeneous layer approximately 10 cm thick overlying a strongly mottled layer that is lighter in color the radiolarian composition of both units is quaternary in areas where this sediment was only a few centimeters thick the underlying sediment was early tertiary clay mineralogy and major oxide composition of the two quaternary sediments are uniform their similarity to continental shale suggests that the sediment has a terrigenous source clay mineralogy and major oxide composition of the tertiary sediment also are uniform although they differ markedly from the quarternary sediment in contrast to the major oxides concentrations of mn co cu and ni soluble in hydroxylamine hydrochlorideacetic acid are strongly different in the surface and subsurface quaternary sediment mn and ni exhibit pronounced depletions in the subsurface sediment ni slightly more than mn cu is also depleted in the subsurface sediment but less than mn it is also depleted in the subsurface tertiary sediment whereas the mn concentration remains high concentration of co relative to mn increases into the subsurface quaternary sediment to a constant co mn ratio of 3 10 2 the trivalent ree the ree exclusive of ce and fe exhibit little down core variation distribution of elements in these sediments is closely related to their concentration in associated surface ferromanganese nodules the nodules are of two distinct types those from the area where the quaternary sediment is relatively thick have mno2 as the dominant manganese mineral the ratios of ni mn cu mn and fe mn in these nodules approximate the corresponding ratios of the soluble fraction of surface sediment todorokite is the dominant mineral of nodules recovered from areas where the quaternary sediment is thin relatively high cu mn ni mn and low fe mn ratios of these nodules mirror differences between the soluble fraction of surface and subsurface quaternary sediment these compositional trends of sediment and nodules at domes site a reflect a diagenetic origin for the todorokite nodules and a predominantly hydrogenous origin for the mno2 nodules

metal diagenesis in oxic marine sediments the metal nutrient relationships observed for nickel and cadmium in the deep ocean are continued at the interface between seawater and oxidizing pore water this continuum results in pore water concentrations of these metals which are only slightly greater than near bottom seawater levels manganese concentrations in these oxidizing pore waters are also extremely low less than three times bottom water in contrast release in the boundary layer produces a maximum of dissolved copper which is 10 40 times ambient seawater assuming these pore waters are at steady state flux estimates based on these measurements suggest that the manganese in todorokite rich nodules of the central equatorial pacific was not supplied by upward diffusion through pore waters below the interface most nodular nickel is precipitated with manganese while nodular copper is supplied by diffusion

late and postglacial sea level change and paleoenvironments in the oder estuary southern baltic sea abstract knowledge of sea level change in the southern baltic sea region is important for understanding the variations in late pleistocene and holocene sea level change across northern europe these variations are a consequence of the response of the earth s crust to the deglaciation of fennoscandia and of the water added to the oceans from the melting of all pleistocene ice sheets the sedimentological and geochemical composition of five sediment cores from the lagoonal oder estuary offers new observational evidence for sea level change and coastal development in the southern baltic sea region the combined use of several geochemical proxies organic carbon nitrogen calcium carbonate and biogenic opal contents corg s and corg n ratios 13c values of organic matter and 15n values is a new approach for the study area the chemical evidence of this multiproxy approach allows clear identification of several stages in the development of the lagoonal environment postglacial lake stages with sandy sedimentation during the older dryas and the allerod stades lacustrine phases with high autochthonous productivity during the atlantic stade terrestrial stages with peat formation at the beginning of the subboreal stade sedimentation as a result of marine transgression and brackish sedimentation after the formation of sand spits and barrier islands during the subatlantic stade the stages are the result of regional sea level change owing to complex shoreline development they support the tentative sea level curve proposed nearly 20 years ago for the region in addition changes in oder river input in response to climate conditions is monitored whereas high terrigenous input of organic matter from the oder river occurred during periods of humid climate during the allerod atlantic and subatlantic stades oder river discharge decreased with drier and cooler climate conditions during the subboreal stade furthermore the geochemical evidence points to local anomalies such as the significance of river input and additional sulfate supply into the oder lagoon for the composition of the sediments overall the results provide a framework for future studies which would allow for a more detailed comparison with other similar environments

origin of phosphatic stromatolites in the upper cretaceous condensed sequence of the polish jura chain abstract the turonian stromatolite bearing condensed sequence in the polish jura chain the european epicontinental basin provides good insight into the environment of formation of cretaceous phosphatic stromatolites owing to their purely phosphatic development and negligible post depositional alteration the sequence developed as a result of slow pelagic sedimentation and microbial mat phosphatization on a submarine swell surrounded by local basins with non condensed carbonate deposition diagenesis of organic matter and dissolution of biogenic apatite were the major sources of reactive phosphorus for the microbial mat phosphatization stromatolite growth occurred due to pulses of amorphous or poorly ordered calcium phosphate precipitation followed by crystallization of carbonate fluorapatite cfa the phosphogenic environment left an imprint on the isotopic composition of limestone carbon and lattice bound carbon and sulphur in cfa and on the light rare earth element lree distribution in cfa the 13c of the stromatolite bearing sequence shows a negative excursion 1 to 3 standing in marked contrast to positive carbon values of the surrounding basinal carbonate most of the 34s values of cfa 20 to 21 fit the value range of the coeval seawater sulphate and the lree distribution shows a well defined seawater pattern this geochemical signature is indicative of intense diagenesis of organic matter at the seafloor pelagic carbonate dissolution and prolonged exposure of the deposited phosphate towards the water column the enhanced deposition and diagenesis of organic phosphorus in the stromatolitic environment reflects elevated levels of the epicontinental basin nutrification related to sea level rises and the associated oceanographic and geochemical changes

provenance of pliocene sediments and paleoenvironmental changes in the southern north sea region using samarium neodymium sm nd provenance ages and clay mineralogy abstract an 800 m thick sedimentary succession from the late pliocene north sea has been investigated on the provenance of the sediments and on changes of the source regions related to transport processes and climate changes the lower zanclean to piacenzian part of the succession from 1250 to 1050 m depth and the middle early gelasian part from 1100 to 700 m depth belong to one distributory system with at least two contributing source areas provenance ages calculated on basis of sm nd content indicate one old archean and one young

physicochemical and biological influences on sedimentary fabric formation in a salinity and oxygen restricted semi enclosed sea gotland deep baltic sea two ca 8000 year long sediment cores from the gotland deep the central sub basin of the baltic sea were studied by means of digital images x radiographs and scanning electron microscopy energy dispersive x ray mineralogical analysis to gain understanding of the physicochemical and biological influences on sedimentary fabric formation in modern and ancient seas with a high flux of organic carbon and associated oxygen stress and depauperate ichnofauna four lithofacies were recognized i sharply laminated mud ii biodeformed mud iii burrow mottled mud and iv sedimentation event bed the sharply laminated and burrow mottled facies dominate the cores as alternating long intervals whereas the biodeformed and sedimentation event facies occur as thin interbeds within the sharply laminated intervals the sharply laminated mud comprises alternating diatom rich and lithic laminae with occasional mn carbonate laminae lamination discontinuity horizons within the laminites where the regular lamination is overlain sharply by gently inclined lamination challenge the traditional view of mud accumulation by settling from suspension but indicate localized accumulation by particle trapping microbial mats and potentially by the rapid lateral accretion of mud from bedload transport the biodeformed interbeds record brief few years to few decades oxic dysoxic conditions that punctuated the anoxic background conditions and permitted sediment surface grazing and feeding by a very immature benthic community restricted to the surface mixed tier the likely biodeformers were meiofauna and nectobenthic pioneers passively imported with currents the sedimentation event interbeds are distal mud turbidites deposited from turbidity currents probably triggered by severe storms on the adjacent coastal areas the turbidite preservation was favoured by the anoxic background conditions the long burrow mottled intervals are characterized by intensely bioturbated fabrics with discrete planolites rare arenicolites polykladichnus and very rare lockeia trace fossils as well as bivalve biodeformational structures which represent shallowly penetrating endobenthic feeding and grazing strategies and permanent dwellings these burrowed intervals represent longer periods several years to few centuries of oxic dysoxic conditions that permitted maturation in the benthos by means of larval settling of opportunistic worm like macrofauna and bivalves resulting in the development of a transition tier these observations imply more dynamic and oxic depositional conditions in gotland deep than previously thought comparison to previous zoobenthic studies in the area allowed discussion of the benthic dynamics and the identification of probable biodeforming and trace producing species implications for current biofacies and trace fossil models are discussed

the benthic cycle of copper evidence from sediment trap experiments in the eastern tropical north pacific ocean abstract the benthic fluxes of 24 elements and components are calculated from sediment trap fluxes and sediment accumulation rates at manop sites h and m in the eastern tropical north pacific ocean in this paper we focus our discussion on our data for copper benthic flux estimates for copper are 0 7 and 1 4 nmol cm 2 yr at h and m respectively these results compare well with estimates from another trap deployment in the galapagos and modeling of pprewater and water column concentration data by other authors partitioning of near bottom cu flux indicates that the two sites receive similar amounts of primary cu flux flux from upper water column and resuspended cu flux only the site located on the east pacific rise site m shows any input of hydrothermal cu at site m 35 of the near bottom flux is due to some source other than primary resuspended or hydrothermal flux we speculate that dissolved cu from the sediments is readsorbed onto particles near the bottom at this site sequential leaching of trap material indicates that the flux of cu associated with organic matter using an operational definition ranges from 56 to 84 of the trap material this fraction of the total cu increases with depth in the water column probably through scavenging

terrestrial organic matter in surface sediments of the baltic sea northwest europe as determined by cuo oxidation abstract we studied the distribution and composition of terrestrial organic matter in sediments of the baltic sea northwest europe to this end surface sediments from all basins of the baltic sea were analyzed for their lignin oxidation product yields and compositions after cuo oxidation lignin oxidation product yields depend on the concentration of organic carbon and range from 0 4 to 10 2 mg g 1 total organic carbon toc on the basis of an average of 13 mg g 1 toc in two river sediments we estimate that the upper limit of terrestrial organic matter in baltic sea sediments is 30 of toc the contribution of terrestrial organic matter differed between the individual basins depending on the distance from runoff discharge areas and on the area occupied by each submarine catchment lignin composition showed a relative decrease of angiosperm tissue from the southwest to the northeast reflecting the shift from temperate to boreal vegetation type the gotland and the bornholm seas which have no significant river input were characterized by high relative contributions of nonwoody strongly altered material the source may either be a mixture of pollen and peat being eroded from geologically older strata at the seafloor or laterally advected material from the other basins however the pronounced compositional differences between the basins indicated that interbasin transport of terrestrial organic matter is less important than direct river input although river signals can only be traced at a few places in the baltic sea

the inorganic geochemistry of cretaceous black shales dsdp leg 41 in comparison to modern upwelling sediments from the gulf of california

oxygen isotope variations in phosphate of biogenic apatites ii phosphorite rocks abstract phosphorites from sedimentary sequences ranging in age from archaean to recent were analysed for 18 o in both the po 4 18 o p and co 3 18 o c in the apatite lattice the oxygen isotope record is considerably better preserved in phosphates than in either carbonates or cherts the use of the longinelli and nuti 8 temperature equation yields temperatures for recent phosphorites that are in good agreement with those measured in the field the 18 o p values of ancient phosphorites decrease with increasing age these changes with time are not likely to be due to post depositional exchange changes in 18 o values of seawater and variations of temperature with time can account for the 18 o p time trend but the latter explanation is preferred in ancient phosphorites 18 o c in structurally bound carbonate in apatite is not a reliable geochemical indicator

early diagenesis of organic matter in peru continental margin sediments phosphorite precipitation abstract pore water chemistry total dissolved co 2 nh 4 no 3 no 2 po 4 si oh 4 ca mg fe mn so 4 h 2 s and f and titration alkalinity solid phase chemistry c org p org c tot n tot f si opal and s ii and sediment characteristics porosity dry bulk density and formation factors were determined on a centimeter scale spacing in the upper 20 40 cm of sediments under intense upwelling areas on the peru continental shelf these data demonstrate that carbonate fluorapatite cfa is precipitating from pore waters in the upper few centimeters of a gelatinous mud with high organic carbon content up to 20 c org very high porosity 0 96 ml cm 3 and very low dry bulk density 3 dissolved phosphate concentrations at the sediment water interface range from 20 to 100 m orders of magnitude higher than bottom water concentrations and much higher than predicted from regeneration of organic matter the mechanism of this interfacial phosphate release is unclear but is apparently uncoupled from carbon and nitrogen metabolism and thus may be linked either to dissolution of fish debris or to the presence of a microbial mat in surficial sediments fluoride is incorporated into cfa by diffusion from the overlying seawater and carbonate ions are provided from pore water alkalinity magnesium concentrations in this reaction zone are not significantly different from those of seawater suggesting that magnesium depletion is not a necessary prerequisite for cfa precipitation the environment of precipitation is interface linked rather than driven by organic diagenesis of phosphorus deeper in the sediment most of the cores display a wide range of diagenetic characteristics below the immediate interfacial region but almost all show the precipitation signature near the interface this interface linked early diagenetic porewater environment for the precipitation of cfa explains many of the geochemical characteristics of phosphorites and provides a testable model to compare the modern phosphogenic analog with ancient phosphorite deposits two of the cores display very high solid phase phosphorus and fluoride contents reflecting the presence of apparently modern pelletal apatites

accumulation and biological mixing of peru margin sediments abstract rates of sediment accumulation and biological particle mixing in eight cores from the peru shelf have been estimated by application of uranium series disequilibrium techniques and radiocarbon dating activities of 210pb 226ra 234th and 238u have been determined in closely spaced intervals in each sediment core biological particle mixing coefficients were determined via a two box advection diffusion steady state mixing model based on the distribution profiles of excess 210pb and in some cases excess 234th activities the sedimentation rates estimated were in the order of a few millimeters yr except for cores enriched in phosphatic components which displayed rates a few orders of magnitude slower bioturbation was significant in most cores studied with the exception of one core collected from within the middle of the oxygen minimum zone estimated biological mixing coefficients were in the order of 100 101 cm2 yr 1 for the surface mixed layer and 10 1 100 cm2 yr 1 for the layer below sediment slumping appears to have affected the 210pb distribution of two or three of our cores

reappraisal of anoxia and organic richness with emphasis on cretaceous of north atlantic accumulation of anoxic sediments in the north atlantic during barremian through turonian time early to middle cretaceous was controlled mainly by local conditions although global climatic and oceanographic factors played a supporting role evidence does not support the popular hypothesis developed over the past few years of global or oceanwide anoxia data which contradict this hypothesis are based on 1 a reevaluation of criteria for identifying sediments that accumulated in anoxic water 2 a critical reappraisal of reported worldwide occurrences of anoxic sediments of these ages and 3 an examination of the spatial and temporal distribution of anoxic sediments in the north atlantic and elsewhere a model is proposed in which the earliest anoxic sediments of cretaceous age in the north atlantic were deposited in deep restricted basins by middle cenomanian time about 97 m y ago sluggish circulation had led to a gradual expansion of the oxygen minimum layer permitting deposition of anoxic sediment in nonbasinal settings as well expansion of the oxygen minimum layer caused the calcite compensation depth to rise promoting oxidation of organic carbon and causing contraction of the oxygen minimum layer development of anoxia was thus self damping anoxia effectively disappeared by early senonian time 88 m y ago when improved circulation created oceans more like those of the present some evidence indicates that enhanced biologic productivity and upwelling may have been local factors in fostering anoxia but the early and middle cretaceous were generally not highly productive times

trace metals in metalliferous sediments manop site m interfacial pore water profiles we present data showing enrichments of metals mn cu v cr cd and ni and dissolved organic matter dom in surficial pore waters depths 1 cm at a metalliferous sediment site in the pacific we also present a model of metal release during particulate organic carbon poc oxidation and opal dissolution at the sediment seawater interface a comparison of measured interfacial metal concentrations with those predicted from the model suggest that cd ni and cr are released during oxidation of poc at the sediment seawater interface however for v cu and mn additional source s and or processes are required to account for the measured interfacial concentrations for cu recycling via interfacial remineralization and release to bottom waters with subsequent scavenging out of bottom waters by particulates probably provides the major additional source for v we suggest that in addition to some contribution from a benthic flux bottom water scavenging scenario complexation with dom at the interface serves as a trap to accumulate v released from particulates in the zone of oxygen reduction for manganese we suggest that most of the interfacial pore water content is produced from reduction of sedimentary mn iv by reactions with dom at the sediment seawater interface the calculated benthic flux of manganese as a result of this reaction may account for a large fraction of the particulate manganese rain that is apparently not preserved in the sediment at this site

the contrasting biogeochemistry of iron and manganese in the pacific ocean abstract vertical and horizontal distributions of dissolved and suspended particulate fe and mn and vertical fluxes of these metals obtained with sediment traps were determined throughout the pacific ocean in general dissolved fe is low in surface and deep waters 0 1 to 0 7 nmol kg with maxima associated with the intermediate depth oxygen minimum zone 2 0 to 6 6 nmol kg vertical distributions of dissolved mn are similar to previous reports exhibiting a surface maximum a subsurface minimum a mn maximum layer coincident with the oxygen minimum zone and lowest values in deep waters near shore removal processes are more intense for dissolved fe than for dissolved mn dissolved mn in the surface mixed layer remains elevated much farther offshore than dissolved fe elevated near surface dissolved mn concentrations occur in the north pacific equatorial current suggesting transport from the eastern boundary near surface mixed layer dissolved mn concentrations are higher in the north pacific gyre reflecting enhanced northern hemisphere aeolian sources residence time estimates for the settling of refractory paniculate fe and mn from the upper water column are 62 220 days fe and 105 235 days mn in contrast residence times for the scavenging of dissolved fe and mn are 2 13 years fe and 3 74 years mn scavenging residence times for dissolved mn based on horizontal mixing in the surface mixed layer of the northeast pacific are 0 4 years nearshore to 19 years 1000 km offshore there is no evidence for in situ fe redox dissolution within sub oxic waters in the eastern tropical north pacific dissolved fe appeared to be controlled by dissolution from sub oxic sediments with oxidative scavenging in the water column or upper sediment layers however in situ mn dissolution within the oxygen minimum zone was evident

organic carbon oxidation and benthic nitrogen and silica dynamics in san clemente basin a continental borderland site organic carbon oxidation rates in san clemente basin were determined by benthic chamber experiments using the bottom lander along with studies of pore water chemistry non steady state diagenetic models are developed for interpreting concentration time data from the benthic chamber experiments o2 no3 and so42 are all important oxidants for organic carbon at our study site regenerated fixed nitrogen was consumed by no3 reduction there is a flux of no3 into the sediments and the benthic flux of nh4 is undetectable the total rate at which fixed nitrogen is removed from the oceans at this site is about twice the flux of pon to the sea floor sio2 fluxes calculated from interfacial pore water gradients are in satisfactory agreement with those determined using the lander most silica dissolution must therefore occur within the sediments although interstitial profiles show that little dissolution occurs below 1 cm depth

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

clay mineral assemblages in the western baltic sea recent distribution and relation to sedimentary units abstract surface samples and nine cores from the western baltic sea and marginal water bodies were investigated for clay mineral composition the clay mineral assemblages of recent sediments are rather homogeneous variations result mainly from the erosion of different glacial source deposits high percentages of illite and low kaolinite chlorite and quartz feldspar ratios are characteristic for this glacial source advection of kaolinite rich suspensions from the north sea is believed to account for higher kaolinite chlorite ratios in the mecklenburg bight a contribution of the rivers trave and oder to the western baltic sea is indicated by increased smectite values in marginal water bodies they correspond to increased kaolinite chlorite and quartz feldspar ratios in the main basins the river signal is diluted beyond recognition cores from the arkona bornholm and gotland basins penetrate through post littorina muds and sediments of the ancylus lake yoldia sea into late glacial sediments of the baltic ice lake clay mineral assemblages are characterized by an increase in kaolinite chlorite ratios from late glacial to holocene sediments with a distinct shift at each facies change this allows the distinction and core to core correlation of main lithological units with kaolinite chlorite ratios kaolinite enrichment of holocene muds corresponds to a brackish marine facies and may reflect influx of kaolinite rich suspensions from the north sea cores from the lagoon of the oderhaff show fluctuations in the contributions of the two main sediment sources river suspension and glacial deposits during the late glacial and postglacial sequence lacustrine sediments which were deposited prior to 5500 years b p are characterized by smectite kaolinite and quartz from the drainage area of the oder river erosion of coastal and offshore glacial boulder clays with the littorina transgression supplied a marine component rich in illite chlorite and feldspars to the brackish muds of the oderhaff

a mid holocene geochemical record of saline inflow to the gotland deep baltic sea the formation of mn enrichments in gotland deep sediments has been linked to the occurrence of periodic inflows of saline water from the north sea in turn these saline inflow events are very strongly linked to variation in north atlantic atmospheric conditions here sedimentary mn concentrations in mid holocene sediments are measured with a 0 5 mm sampling resolution using scanning electron microscope techniques as the sedimentation rate in core 20001 5 was estimated to be approximately 0 5 1 mm per year examining the variation in mn enrichments may potentially provide an annual record of variation in saline inflow and by extension north atlantic climate on interannual timescales there are many processes that can affect mn cycling in the gotland deep when considered together these processes could potentially act to remove or significantly weaken the transmission of the primary saline inflow signal to the measured geochemical record producing an effectively random mn record analysis of the mn rec

geochemistry of the mississippian delle phosphatic event eastern great basin u s a abstract the middle mississippian delle phosphatic event marks a significant change in depositional conditions in the devonian mississippian antler foreland basin of north america stratigraphic and petrographic studies show that deposition of delle event rocks ended a long period of open marine carbonate sedimentation when facies shifted to phosphorites cherts fine grained siliciclastics and lime mudstones from highly productive waters that may have been episodically anoxic this drastic change in lithology is reflected in the chemistry of the two suites of rocks 18o values of the delle event lime mudstones and phosphatized wackestones packstones affected by the delle event are 3 5o oo lighter than underlying and overlying open marine wackestones packstones sr concentrations of delle event lime mudstones and open marine wackestone packstone facies are low suggesting that both of these lithologies have undergone similar postdiagenetic alteration the uniform sr concentrations and variable 18o data suggest that either the younger delle event rocks were exposed to meteoric water during diagenesis or that the relatively light 18o values represent a primary brackish water depositional signal either interpretation is consistent with sedimentological evidence of the delle event occurring in a predominantly shallow water setting 13c values of delle event lime mudstones are also anomalously light indicating a high input of organic carbon during their formation mn concentrations of the delle event lime mudstones and stratigraphic equivalents are highly variable suggesting fluctuating oxygen concentrations during their deposition and diagenesis rare earth element data from phosphorites and cherts of the delle event indicate oxic to suboxic depositional conditions

the behaviour of the rare earth elements during mixing of river and sea waters rare earth element concentrations have been measured in organic rich luce river water and coastal sea water concentrations e g 350 1850 pmol kg nd in the water of luce and 45 350 pmol kg nd in luce bay are related to the presence of particles with 30 60 of the ree associated with 0 4 0 7 m particles and to riverine fe concentrations ree fractionation occurs in the river water the submicrometre river water is heavy ree enriched whereas the coarser fraction has a more shale like ree pattern laboratory experiments show that the ree in organic rich river waters are chiefly associated with feorganic matter colloids which flocculate during estuarine mixing preferential removal of heavy ree 95 relative to light ree 60 occurs but no ce anomaly is developed in contrast no ree removal occurs during estuarine mixing with organic poor river water

carbon isotopic composition and lattice bound carbonate of peru chile margin phosphorites new light stable carbonate carbon isotope and lattice bound co2 data from quaternary peru chile margin phosphatic nodules crusts and pelletal grains and from associated dolomicritic concretions are presented which provide constraints on the timing and mechanisms of growth of these phases in organic carbon rich sediments comparison of 13c values from carbonate fluorapatite cfa nodules and pelletal grains 4 8 to 0 0 and 2 9 to 1 0 pdb respectively with pore water total dissolved 13c values from these sediments suggests early authigenic cfa precipitation from pore waters within a few centimeters of the sediment water interface in association with suboxic to perhaps anoxic microbial degradation of organic matter in contrast the dolomicritic cores of nodules recovered from about 12 s display both strongly negative to positive 13c values 10 8 to 6 1 characteristic of formation deeper in the sediments in association with methanogenic and perhaps sulfate reduction microbial processes the amount of structural carbonate in cfa suggests that carbonate substitution generally increases as 13c in cfa decreases a probable consequence of increasing carbonate and accompanying charge balancing substitutions in the cfa lattice in response to increasing pore water carbonate ion concentrations with depth below the sediment water interface in one buried upward growing nodule decreasing cfa 13c and increasing structural co2 also correspond to decreasing cfa growth rates these data suggest that in addition to other constraints such as pore water phosphorus and fluoride availability the lower limit of cfa precipitation in suboxic to anoxic sediments may be controlled by lattice poisoning due to excessive dissolved carbonate ion concentrations in organic rich peru chile margin sediments this depth threshold appears to be at approximately 5 10 cm below the sediment water interface where maximum cfa co2 contents of about 6 wt occur in less organic rich settings greater depths of precipitation of cfa may be anticipated below this relatively shallow depth of cfa precipitation on the peru shelf high pore water alkalinity and associated elevated total dissolved carbon and carbonate ion concentration apparently favor the precipitation of authigenic carbonates

southwestern baltic sea a sink for suspended matter from the north sea clay mineral analyses of 300 surface sediment samples in the skagerrak kattegatt and the southwestern baltic sea have yielded qualitative evidence of considerable advective transport of suspended fine grained terrigenous matter from the north sea to the baltic sea the transport is related to periodic near bottom saltwater inflows whereas the outflow of less saline surface water carries little suspended matter of baltic origin although there are not enough data at this stage for exact budgeting it is evident that this process contributes considerably to the sedimentation in the southwestern baltic sea and has probably done so during the past 6 k y it has been neglected so far hence the southwestern baltic sea is believed to be a final sink for fine grained north sea material this fact is corroborated by a compilation of sediment thickness data in the major basins of the baltic sea which shows that the shallow southwestern basins accumulate more holocene mud than the eastern and central basins the external terrigenous matter also has far reaching implications concerning the assessment of organic and inorganic pollutants which are bound to fine grained clayey material the baltic sea can no longer be regarded as a closed sedimentary system and pollution assessment and control must be considered with a wider perspective

geochemical diagenetic trends during phosphorite formation economic implications the case of the negev campanian phosphorites southern israel research on the upper campanian upper cretaceous negev phosphorites mishash formation based on microprobe analyses fourier transform infrared spectroscopy wet chemistry microtextural scanning electron microscopy studies and mineralogical analyses together with quantified rates of sedimentation and p accumulation enables the chemistry of these rocks to be better constrained across the negev area and allows their suitability for the manufacture of p fertilizers to be better determined two phosphorite facies are differentiated i a pristine phosphorite facies of low p content more typical of basinal sections and ii a reworked granular phosphorite facies commonly enriched in p found predominantly near palaeo highs and forming most of the economic phosphates the distribution of f p2o5 co2 f u iv cd zn and other trace metals mo ni cr cu v and y rare earth elements concentration ce and eu anomalies and heavy rare earth elements enrichment are controlled by these two facies f p2o5 in carbonate fluorapatite is much lower 0 090 to 0 107 in the pristine than in the reworked facies 0 107 to 0 120 in addition the lower f p2o5 in the pristine facies is coupled with i higher cd zn mo ni cr cu and v concentrations ii a considerably reduced 10 u iv fraction of total u iii lower rare earth elements p2o5 and y p2o5 ratios iv less negative ce and eu anomalies and lower heavy rare earth elements lu la enrichment v an increase in fe rich smectites in the clay fraction and vi presence of oh in the carbonate fluorapatite structure sedimentary reworking of previously formed pristine phosphate together with its redeposition near structural highs in more oxic bottom conditions results in considerable diagenetic changes in the chemistry of the phosphorites making them more suitable for economic exploitation the results presented here provide geochemical criteria for identifying pristine phosphate in other phosphorite sequences and may help to better locate phosphate strata chemically suitable for the phosphate industry elsewhere

varve microfabric record of seasonal sedimentation and bottom flow modulated mud deposition in the coastal northern baltic sea abstract eutrophication induced hypoxia has resulted in preservation of laminated sedimentary fabric in coastal areas of the northern baltic sea these laminites offer a potential technique for dating recently deposited organic rich muds but their formation mechanisms have been inadequately understood in this study microfabric of the modern laminated sediments in the coastal gulf of finland and archipelago sea was investigated through x radiography and scanning electron microscopy of samples embedded in epoxy resin the sedimentary fabric comprises rhythmic biogenic and lithogenic lamina successions reflecting seasonal changes in the composition of accumulating material the diatom rich biogenic lamina succession is formed during the vernal phytoplankton bloom through rapid sedimentation of aggregates composed of intact diatom frustules and minor proportions of clay rich lithic material that are enclosed in a sticky matrix of amorphous phytodetritus analogous to the formation of the marine snow accumulation of the lithogenic lamina succession results from decline in primary production towards late summer enhanced recycling of organic carbon due to grazing by zooplankton and intensified resuspension of lithic rich terrigenous material concomitantly with increased cyclonic activity towards late autumn and winter the inclusion of silt grains and isolated diatoms and faecal pellets in the lithogenic laminae attests to lateral transport and deposition from near bottom flows contradicting the generally accepted view that laminated sediments accumulate by suspension settling under quiescent conditions only accumulation rates inferred from 137 cs dating are consistent with the biogenic lithogenic lamina succession couplet thickness supporting the interpretation that the couplets reflect an annual cycle of deposition the results indicate that these modern laminated sediments provide a high resolution archive for assessing recent human induced environmental changes as well as a robust tool for evaluating the lateral expansion of seafloor oxygen deficiency due to anthropogenic eutrophication in the area during the past decades

geochemistry of a tertiary sedimentary phosphate deposit baja california sur mexico abstract the san gregorio formation in baja california sur a phosphate enriched sedimentary unit of late oligocene to early miocene age has been analyzed in two areas la purisima and san hilario for its chemical composition major oxides cu cd cr co v and rare earth elements ree and isotopic composition 18 o and 13 c a detrital and a marine component were determined from major oxides the detrital component consists of an unaltered volcanic ash fraction and a terrigenous clay silt fraction the marine component which accumulated initially as biogenic and hydrogenous material is now present as opal a opal ct caco 3 organic matter and an authigenic phosphate fraction mostly pelletal and composed of the carbonate fluorapatite mineral francolite the minor elements have been partitioned into these components by assuming a constant composition for the two detrital fractions the composition of the marine component of minor elements can then be interpreted by assuming that the stoichiometry of the original accumulating organic matter was equal to that of modern plankton the cu and cd contents in the marine component of all rocks require that the seawater derived fractions of these two metals were supplied to the seafloor solely by organic matter enrichments of cr and v at both sites required an additional marine input on the basis of their geochemistry in the modern ocean cr and v could have precipitated or been adsorbed onto settling particles from an o 2 minimum zone in which the o 2 content was low enough to promote denitrification rather than oxygen respiration an enrichment of the ree now within the apatite fraction resulted from their adsorption onto particulates also in the o 2 minimum zone and to the dissolution and alteration of biogenic phases predominantly silica within the sediment co and fe 2 o 3 show no enrichment above a detrital contribution the 18 o values of apatites from the la purisima site are heavier than those of apatites from the san hilario site whereas the 13 c values show the opposite trend one possible interpretation of these variations is that 18 o reflects seawater values and 13 c sediment pore water values this interpretation suggests that upwelling rates and primary productivity within the water column were greater at la purisima an interpretation that is corroborated by a greater abundance of apatite measured in outcrop at la purisima the ce anomalies of the phosphate enriched samples also differ between the two sites indicating that they also recorded water masses similar to the 18 o values

rare earth elements in foraminifera tests abstract the concentrations of nine rare earth elements ree la ce nd sm eu gd dy er and yb have been determined in mixed species assemblages of foraminifera tests taken from atlantic ocean sediment core tops reductive cleaning techniques have revealed that ree are present in three phases in foraminifera tests collected from sea floor sediments ree included in the foraminiferal calcite matrix termed lattice ree ree associated with an authigenic femn rich phase adsorbed onto the surface of the test following the death of the organism termed coating ree and ree associated with alumino silicate detritus termed detrital ree which commonly infills the test chambers after burial in the sediment the concentrations of ree in the nondetrital lattice plus coating and lattice phases have been measured in this study approximately 90 of the ree measured in the non detrital phase reside in the coating phase the remainder being present in the lattice phase these data have been used to investigate the relationship between the distribution of dissolved ree in the ocean and in the coating and lattice phases in addition to the ree the concentrations of mn fe cu al and po4 have been measured as an aid to characterisation of the various phases

anomalous geochemical signals from phosphatic middle cambrian rocks in the southern georgina basin australia middle cambrian rocks of the georgina basin contain both phosphatic and organic rich sediments the former often occurring as commercially viable phosphate deposits and the latter as minor oil shale occurrences both kinds of rocks occur in the hay river formation penetrated by bureau of mineral resources bmr stratigraphic corehole tobermory 14 detailed sampling and analysis of this core has been undertaken to assess the chemostratigraphy of the hay river formation to examine the possible use as a palaeoceanographic tool of changes in 13c values of carbonates and kerogens and to gain an understanding of phosphate deposition in this part of the basin the upper hay river formation was deposited in a normal marine environment characterized by oxic bottom conditions it contains several episodes of significant trace metal enrichment which appear to indicate periodic replacement of the water body the lower hay river formation however was deposited in an abnormal marine environment low in sulphate and mo and enriched in p its carbonate phase has positive 13c values 1 1 5 0 enriched over the accepted cambrian marine carbonate value of 0 57 0 17 0 the very low sulphate concentration mo depletion and spiking of carbonate 18o values suggests there was an influx of deeper ocean water of sufficient volume to maintain prolonged stable anoxic bottom waters these data support a previous suggestion that phosphogenesis in the georgina basin was related to oceanic anoxic events

mesogenetic dissolution of the middle ordovician limestone in the tahe oilfield of tarim basin nw china abstract the mesogenetic dissolution is well developed in the middle ordovician yijianfang formation o2yj limestone and the dissolution pores are very important for petroleum accumulation in the south slope area of the tahe oilfield which lies in the north of the tarim basin northwestern china mottled dotted or laminar dissolution can be observed in the o2yj limestone under microscope the grains lime matrix and all stages of calcite cements including oil inclusion bearing blocky calcite cements can all be found dissolved ubiquitously the stylolites in the limestone were enlarged and rounded because of dissolution some dolomite rhombs precipitated along stylolites in burial environment were found dissolved as well the dissolution of the blocky calcite cements and dolomite rhombs and the enlarging of stylolites demonstrate that the dissolution took place in the mesogenetic environment concentration of trace elements including rees of the eroded part of the o2yj limestone is intermediate between that of the uneroded part and that of the underlying lower ordovician limestone hydrocarbon source rocks both 13cpdb and 18opdb values of the eroded part are less than those of the uneroded part respectively the geochemical characteristics indicate that the eroding fluids are hydrocarbon bearing fluids coming from the underlying hydrocarbon source rocks

paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite abstract rare earth element concentrations in biogenic apatite of conodonts fish debris and inarticulate brachiopods were determined in over 200 samples from cambrian to modern sediments tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory interexperiment or interspecies related variations clearly show that no resolvable fractionation of ree occurs incorporation of ree in biogenic apatite of recent fish debris occurs near the sediment water interface soon after deposition and reflects characteristics of seawater the original ree signature apparently survives subsequent burial and diagenesis cerium variations in fish debris from modern environments are controlled by redox potential ce is fractionated by co precipitation with metallic oxides under oxidizing conditions this fractionation produces a negative ce anomaly ce anom in seawater that is reflected in the sedimented fish debris conversely no fractionation of ce occurs under reducing conditions resulting in ce concentrations that are normal to enriched in anoxic seawater and fish debris deposited under local or basinwide anoxic conditions extrapolation of observations of the redox control of ce anom in modern oceans to fossil apatite indicates that anoxic conditions were prevalent in lower paleozoic and lower triassic oceans whereas in the upper paleozoic the world ocean was generally oxidizing

rare earth elemental concentrations in some pacific northwest rivers abstract soluble rare earth element ree concentrations have been measured for five pacific northwest rivers columbia fraser klamath rogue and sacramento using radiochemical neutron activation analysis the relative abundances of the ree in river water resemble the ree abundance pattern in average sedimentary type rocks the la material balance in the oceans is discussed

pore waters of the central pacific ocean nutrient results interstitial waters from the manop siliceous and calcareous ooze sites in the central pacific ocean were recovered by shipboard squeezing and centrifuging techniques and an in situ harpoon sampler the pore waters were analyzed for nutrients carbonate system species mn 2 ca 2 total alkaline earth metals and dissolved oxygen siliceous ooze site only in calcareous sediments the co 2 alkalinity po 4 3 and ca 2 results obtained from shipboard techniques are significantly different than those recovered in situ the other species measured as well as all of the data from the siliceous ooze site reveal no significant dependence on the method used to sample the pore water the relative changes in o 2 no 3 mn 2 alkalinity and co 2 indicate that respiration using o 2 no 3 and mno 2 as electron acceptors is the dominant reaction affecting the pore water species we develop a model which simulates the fate of pore water oxygen and nitrate and particulate organic carbon in sediments this model includes the effects of pore water diffusion oxygen and nitrate respiration sediment accumulation sediment mixing and changes in sediment porosity we observe that factor of 2 variations in the rates of sediment mixing and accumulation have only a minor effect on the pore water profiles the major factor controlling the pore water profiles is the flux of organic carbon across the sediment water interface we conclude that the large intra site variability observed in the interstitial water nitrate profiles is probably caused by small scale variations in the flux of organic material

oxygen isotope variations in phosphate of biogenic apatites i fish bone apatite rechecking the rules of the game abstract the major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone and teeth building organisms are alive and the record is nearly perfectly preserved after death fish from seven water bodies of different temperatures 3 23 c and different 18 o values 16 to 3 of the water were analysed the 18 o values of the analysed po 4 vary from 6 to 25 the system passed the following tests a the temperatures deduced from isotopic analyses of the sequence of fish from lake baikal are in good agreement with the temperatures measured in the thermally stratified lake b the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish but only by temperature and water composition isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates

clay mineral and heavy metal distributions in the northeastern north sea abstract clay mineralogy and heavy metal distribution of surface sediments of the northeastern north sea have been analysed in order to show the origin and transport pathways of fine grained sediments the distribution patterns of clay minerals largely reflect regional current patterns fine material enriched in smectite derived mostly from the german bight sector in the south is transported by the jutland current parallel to the west coast of denmark into the skagerrak where a decreasing proportion of smectite indicates the increasing influence of the central and northern north sea currents illite and chlorite have identical distribution patterns in the northeastern north sea which suggests a common origin for both clay minerals this origin is located in pleistocene relict sediments of the northern north sea rather than in a contribution from the north atlantic zinc cadmium copper and lead in surface sediments of the north sea when compared to background values are significantly enriched sediments of the inner german bight are in comparison with other north sea sediments highly polluted a zone of high heavy metal contents zn cd and cu is found along the german and danish coasts comparable to the smectite distribution indicating the transport of fine grained polluted sediments to the north further to the north these sediments are diluted by less polluted sediments finally in the skagerrak and the norwegian trench a relatively low stage of pollution is reached

relation between sedimentation rate and burial of organic phosphorus and organic carbon in marine sediments organic carbon and organic phosphorus concentrations in marine sediment cores with known sedimentation rates were determined and collected from the literature with the exception of organic rich sediments from upwelling areas organic phosphorus concentrations in marine sediments do not correlate linearly with organic carbon concentrations the c p ratios of organic matter buried in marine sediments vary systematically with sedimentation rate over the range studied 0 0001 to 2 5 cm y low c p ratios 200 atomic occur in sediments with sedimentation rates both less than 0 002 cm y and greater than 1 cm y higher c p ratios up to 600 are found at intermediate sedimentation rates a simple steady state model is developed for the early diagenesis of organic carbon and organic phosphorus in marine sediments the processes included are sediment burial pore water diffusion and bacterial decomposition of organic matter by oxic respiration and sulfate reduction preferential regeneration of phosphorus relative to carbon is assumed to take place during oxic respiration the modeling shows that both organic matter preservation and the degree of elemental fractionation between phosphorus and carbon depend strongly on the overall sedimentation rate very high sedimentation rates coastal deltaic environment result in a good preservation of deposited organic matter with an initial c p ratio close to the redfield value at very slow sedimentation rates pelagic environment the oxidation of the sedimentary organic matter is nearly complete and produces a low c p residual organic material this residual organic matter may represent either refractory detrital organic compounds enriched in phosphorus or in situ synthesized low c p bacterial remains the high c p ratios at intermediate sedimentation rates slope and shelf environment reflect the preferential regeneration of phosphorus during the incomplete decomposition of the metabolizable organic matter

uranium series and ams 14c studies of modern phosphatic pellets from peru shelf muds recent sediments and separated phosphate pellets 125 500 m in diameter from the peru shelf have been analyzed for uranium decay series isotopes and 14c in order to determine age relationships and mineralization rates uranium series ages of pellets separated from one box core are significantly higher than ams radiocarbon ages determined for the same pellets these differences appear to be a consequence of mixing of an older generation of pellets with ones which are more recently formed postdepositional adsorption of reactive elements such as thorium and protactinium onto pellet surfaces may also contribute to the observed discordancy with radiocarbon ages sediment radiocarbon and 210pb sediment results as well as some trends in the uranium series data suggest that high concentrations of phosphate pellets have accumulated in some peru shelf sediments without extensive reworking individual pellets apparently form very quickly on time scales of a few years estimated authigenic uptake rates of phosphorus into pellets ranges from 0 5 to 9 40 mol p cm 2 yr 1 somewhat higher than rates measured for nodules from the same area this is consistent with observations that pelletal morphologies predominate over nodular forms within ancient phosphorite deposits

seawater as the source of minor elements in black shales phosphorites and other sedimentary rocks many of the minor elements in seawater today have a concentration depth profile similar to that of the biologically essential nutrients no 3 and po3 4 they show a relative depletion in the photic zone and enrichment in the deep ocean the difference between their surface and deep ocean values normalized to the change in po3 4 approaches the average of measured minor element p ratios in marine plankton although individual analyses of the latter show extreme scatter for a variety of reasons despite this scatter in the minor element analyses of plankton agreement between the two sets of data shows unequivocally that an important marine flux of many minor elements through the ocean is in the form of biogenic matter with a composition approaching that of plankton this interpretation is further supported by sediment studies particularly of sediments which accumulate in shelf slope environments where biological productivity in the photic zone is exceptionally high and organic carbon contents of the underlying sediment elevated the interelement relations observed for some of these sediments approach the average values of plankton these same interelement relations are observed in many marine sedimentary rocks such as metalliferous black shales and phosphorites rocks which have a high content of marine fractions e g organic matter apatite biogenic silica and carbonates many previous studies of the geochemistry of these rocks have concluded that local hydrothermal activity and or seawater with an elemental content different from that of the modern ocean was required to account for their minor element contents however the similarity in several of the minor element ratios in many of these formations to minor element ratios in modern plankton demonstrates that these sedimentary rocks accumulated in environments whose marine chemistry was virtually identical to that seen on continental shelf slopes or in marginal seas of the ocean today the accumulation of the marine fraction of minor elements on these ancient sea floors was determined largely by the accumulation of organic matter settling from the photic zone and with a composition of average plankton a second marine fraction of minor elements in these rocks accumulated through precipitation and adsorption from seawater the suite of elements in this fraction reflects redox conditions in the bottom water as determined by bacterial respiration for example high mn high cr v and high mo concentrations above those which can be attributed to the accumulation of planktonic matter characterize accumulation under bottom water oxidizing denitrifying and sulfate reducing conditions respectively

structure of the frontal part of the andean convergent margin a multichannel seismic reflection record across the central peru margin and trench was improved by processing 24 rather than the 12 channels previously processed and by thorough migrating to reject the strong diffractions that obscured weaker primary reflections the increased resolution clarifies the structure of the 15 km wide frontal accretionary complex and the adjacent truncated continental framework against which the trench sediment was imbricated resolved are individual thrust slices and packets adjacent to the trench axis subducting sediment filled graben in the ocean crust beneath the lower slope and a tertiary stratigraphic section of the upper slope yaquina basin which is cut by normal faults the resolution in this multichannel record provides criteria for reinterpreting single channel data off chile with increased confidence the previously proposed truncation of the south american continent along much of the peru chile trench is confirmed and the development of an accretionary complex in front of the truncated continental crust appears to vary with the amount of sediment seen in the trench axis the andean margin frontal structure is similar to that off central america the aleutian trench and the japan trench which suggests common truncation as well as accretion at the front of convergent margins

composition of clays along the continental shelf off israel contribution of the nile versus local sources the eastern mediterranean sedimentary regime is dominated by sediment transport from the nile river and its delta but recent studies have also suggested a certain contribution of clay fraction from streams to the continental shelf and slope off israel in the present study we focused on clay fraction deposition along the inner 40 1000 m water depth shelf of israel in order to substantiate and quantify its different sources for this purpose detailed xrd mineralogical determinations as well as chemical compositions of the clay 2 m fraction of marine and continental sediments were used the clay mineral composition of israeli stream sediments is variable with no distinct spatial or temporal trend but within a limited assemblage this clay assemblage is made up of illite smectite is phases 70 90 kaolinite 5 25 and illite 10 and is similar to that of the nile however it is clearly distinguished by the type of the is phases which are derived mainly from mesozoic outcrops and recent sediments soils and are less expandable than those of the nile which are derived mainly from weathered basalt the nile derived component is depleted in the marine clay fraction along the israel coast evidenced by a decrease of is expandability and the fe2o3 al2o3 ratio and an increase in the k2o al2o3 mgo al2o3 and cao al2o3 ratios the depletion is well pronounced north of tel aviv where the largest coastal plain stream flows to the sea a northward increase of carbonates in the clay fraction and particularly of the bioskeletal component is indicated by the ratios of mgo and sr to cao the contribution of the local streams to the shallow shelf marine clay fraction is estimated to be about 50 a minor contribution of desert dust is identified by the relative increase in kaolinite in the marine sediments south of tel aviv

miocene phosphate accumulation in the cuyama basin southern california abstract middle and upper miocene phosphatic strata in the cuyama basin of southern california contain approximately 6 4 10 9 metric tons 2 1 10 14 mol of phosphorus p that accumulated in slope and shelf strata at rates between 0 9 and 3 8 mol p cm 2 year 1 from 15 5 to 10 8 ma an estimated 63 of all phosphorus lies in a single third order sequence deposited between 14 8 and 13 ma the main impetus for this brief phosphogenic event was a 200 m relative sea level rise that resulted from strike slip faulting immediately east of the basin minor element and petrologic analyses suggest the overall increase in phosphorus accumulation correlates with less reducing conditions in the shallowly buried marine sediments on the slope and the expansion of phosphogenesis to the outer shelf both events were probably related to landward shifts of the pacific oxygen minimum zone and coastal upwelling centers during the relative sea level rise whereas these tectonic events were apparently local the phosphatic deposits of the cuyama basin clearly demonstrate that tectonism can strongly influence phosphate accumulation rates in marginal marine environments

miocene phosphorites from the murray ridge northwestern arabian sea abstract phosphorites from the murray ridge nw arabian sea comprise nodules bioclasts and bone fragments the nodules are made up of a homogeneous light colored phosphate nucleus consisting of rivulariacean filamentous cyanobacteria and a thin dark grey colored phosphate cortex showing abundant microbial filaments and microborings the bioclasts comprise of 14 14 5 ma old planktonic foraminifers accepted as the time of deposition spherical to ovoid shaped apatite microparticles resembling fossil bacteria are distinct components in the bioclasts bone fragments exhibit apatite fillings the nodules and bone fragments consist entirely of carbonate fluorapatite cfa with low al k and th concentrations suggesting absence of continental detritus shale normalized ree patterns of the samples support a seawater derived composition the highly uniform initial nd values of 4 8 to 5 1 are interpreted as the seawater value at the onset of phosphatization 14 ma ago in contrast 87sr 86sr ratios show a large range of 0 709055 to 0 709124 corresponding to unusually young stratigraphic ages of 1 to 3 ma the data are interpreted as evidence for post depositional sr exchange of the recrystallizing phosphorites with fluids isotopically not much different from modern seawater it is concluded that the phosphorites formed under oxic shallow water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of cfa during early diagenesis at the sediment water interface on different substrates

uranium oxidation state and related variations in geochemistry of phosphorites from the negev southern israel abstract study of the u iv fraction in mishash phosphorites of the negev reveals an apparently paradoxical trend the u iv fraction is very low less than 10 in the pristine organic rich laminated phosphorites while this proportion considerably increases up to 60 in the recycled mechanically reworked granular phosphorites which deposited under more oxidizing conditions this u iv trend seems to differ from that reported in other phosphate sequences elsewhere and is also quite unexpected in view of the sediment patterns and the specific formational conditions of the two phosphorite facies in addition a lower u iv in the analyzed granular phosphorites is coupled with a lower rare earth elements ree p 2 o 5 and y p 2 o 5 ratio a higher cd and zn concentration less negative ce ce ce and eu eu eu anomalies a lower hree dy er enrichment and a lower f p 2 o 5 and higher co 2 f ratio in francolites this u iv trend in the two negev phosphorite facies may be explained by varying time spans of apatite growth changes in sediment burial rates and principally different residence times of the phosphate fraction in the suboxic apatite forming diagenetic zone near the sediment water interface the associated varying concentrations of rees y cd and zn in phosphorites and of f and co 2 in francolites in the two granular phosphorite facies are apparently collectively regulated by the same sedimentary dynamics during phosphate deposition it is presumed that the u iv trend observed in the negev phosphorites could be detected in other phosphate sequences as well if pristine phosphorites are carefully identified and selectively analyzed

microfabric study of diatomaceous and lithogenic deposition in laminated sediments from the gotland deep baltic sea the deep basins of the baltic sea are commonly anoxic and finely laminated diatomaceous sediments have been deposited at intervals throughout the last 8000 yr the origin and composition of individual laminae in gotland deep sediments have often proved difficult to characterise using traditional micropalaeontological and sedimentological studies here we present a scanning electron microscope study in which lamina down to 30 m in thickness with distinct mineralogical or micropalaeontological composition have been identified and described depositional laminae sequences in the form of couplets triplets and quadruplets of diatomaceous and lithogenic laminae are observed with an average thickness of approximately 700 m diagenetic ca rhodochrosite laminae also occur within these depositional sequences examination of the diatom assemblages suggests that these bundles of laminae represent annual deposits or varves varves are relatively uncommon and typically occur in small intervals of two to five varves which are interrupted by more diffusely laminated and homogenous sediments the origin of these more massive sediments probably relates to periodic re oxygenation of the basin on inter annual time scales and destruction of varves by bioturbation

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

trace and rare earth elemental variation in arabian sea sediments through a transect across the oxygen minimum zone we have determined the calcium carbonate caco3 organic carbon coorg trace element and rare earth element ree composition of surface sediments collected from a transect on the central western continental shelf and slope of india in the eastern arabian sea the transect samples across the oxygen minimum zone omz allows us to compare the relative abundances of trace elements and rees in the sediments beneath and beyond the omz shale normalized ree patterns lan ybn ratios and eu eu anamolies indicate that the sediments in the study area are either derived from the adjoining archaean land masses or from distal indus source sediment deposited in the omz have high u values from 3 6 to 8 1 ppm with their uexcess of that can be supplied by continental particles values ranging between 82 91 of the total u indicating that the u may be precipitated as u 4 in the reducing conditions of omz sediments deposited beneath the intense omz 0 2 ml l and away from the omz 1 2 ml l show slight negative ce anomalies with no significant differences between these two sets of sediments the ce ceshale values are poorly related to u and corg which are indicators of suboxic bottom waters normative calculations suggest that two sources namely terrestrial and seawater terrestrial seawater contribute to the total cc anomaly of the sediments the cc anomaly values of the calculated seawater derived component are similar to the anomalies reported for other coastal waters and the oxygenated surface waters of the arabian sea and do not show any correspondence to the lowered redox state of the overlying water probably due to the redirection of dissolved ce into the oxic deeper water this data on recently deposited sediments from a known oxygen poor environment suggest that the ce cesh in high sedimentation areas of continental margin environments may not be a good paleoredox proxy u th ratios above 1 25 noticed in omz are in accordance with the earlier usage of this ratio for identifying reducing environment of ancient sediments

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

investigation of authigenic and diagenetic processes by chemical leaching of pelagic sediments from the cape verde abyssal plain abstract detailed geochemical data are presented from a 13 m long sediment core taken in 4830 m water depth in an oligotrophic environment on the cape verde abyssal plain eastern atlantic ocean a complex intercalation of calcareous oozes and marly clays is interpreted in the light of 230th excess activity data and coccolith stratigraphy as representing slow 0 3 0 6 cm ka 1 continuous accumulation throughout the pleistocene twenty bulk sediment subsamples were analyzed for major and trace element composition and a further four subsamples were subjected to chemical leaching the data base is used to calculate the composition of the lithogenous and biogenous end members and to identify authigenic vs residual components a selective chemical extraction procedure leads to the recognition of an exchangeable carbonate fraction ecf an easily reducible fraction erf an acid soluble fraction asf and a residual fraction rf erf and asf consist of mineral coatings enriched in mn and fe respectively the comparison of these results with those obtained from mathematical leaching yields useful information on pre and post depositional processes affecting sediment particles during their residence in the ocean system

intense pyrite formation under low sulfate conditions in the achterwasser lagoon sw baltic sea in comparison to similar low sulfate coastal environments with anoxic sulfidic sediments the achterwasser lagoon which is part of the oder estuary in the sw baltic sea reveals unexpectedly high pyrite concentrations of up to 7 5 wt pyrite occurs mainly as framboidal grains variable in size with diameters between 1 and 20 m pyritization is not uniform down to the investigated sediment depth of 50 cm the consumption of reactive fe is most efficient in the upper 20 cm of the sediment column leading to degrees of pyritization dop as high as 80 to 95 sediment accumulation in the achterwasser takes place in high productivity waters the content of organic carbon reaches values of up to 10 wt indicating that pyrite formation is not limited by the availability of organic matter although dissolved sulfate concentration is relatively low 2 mmol l in the achterwasser the presence of h2s in the pore water suggests that sulfate is unlikely to limit pyrite authigenesis the lack of free fe ii in the pore waters combined with the possibility of a very efficient transformation of fe monosulfides to pyrite near the sediment water interface suggests that pyrite formation is rather controlled by i the availability of reactive fe which limits the fes formation and by ii the availability of an oxidant which limits the transformation of fes into pyrite the ultimate source for reactive fe is the river oder which provides a high portion of reactive fe 65 of the total fe in the form of suspended particulate matter the surficial sediments of the achterwasser are reduced but are subject to oxidation from the overlying water by resuspension oxidation of the sediments produces sulfur species with oxidation states intermediate between sulfide and sulfate e g thiosulfate and polysulfides which transform fes to fes2 at a significant rate this process of fes recycling is suggested to be responsible for the formation of pyrite in high concentrations near the sediment surface with dop values between 80 and 95 even under low sulfate conditions a postdepositional sulfidization takes place in the deeper part of the sediment column at 22 cm depth where the downward diffusion of h2s is balanced by the upward migration of fe ii the vertical fluctuation of the diffusion front intensifies the pyritization of sediments we suggest that the processes described may occur preferentially in shallow water lagoons with average net sedimentation rates close to zero such environments are prone to surficial sediment resuspension initiating oxidation of fe sulfides near the sediment water interface subsequent fes2 formation as well as postdepositional sulfidization leads to a major pyrite spike at depth within the sediment profile

development of anoxia during the holocene fresh brackish water transition in the baltic sea one of the most pronounced environmental changes during the holocene baltic sea history was the transition from the freshwater ancylus lake to the brackish water litorina sea the establishment of

cerium a chemical tracer for paleo oceanic redox conditions abstract the ce anomalies found in marine carbonates provide a sensitive indicator for the study of paleo oceanic redox conditions the dependency of cce the observed ce concentration and cepo04 the activity of the cepo4 complex to the po2 ph and pco2 of seawater can be used for deciphering some aspects of the paleo ocean chemistry and is log c ce log cepo 0 4 13 2 0 25 log p o 2 3 0 ph 1 95 0 25 log p o 2 1 50 log p co 2 1 50 log ca the ph which is related to pco2 and po2 are major factors for controlling the ce concentration in seawater therefore ce anomalies ceas ce observed ce interpolated between la and pr or nd serve as indicators for ph or pco2 or po2 changes nearly uniform ce abundances found in pacific 5000 m water columns piepgras and jacobsen 1988 and the ceas in ichthyoliths can be explained using this model a general cea shift in sediments from d s d p holes 525a 530a b 516 516f suggest that the entire south atlantic water redox condition changed from reducing to oxidizing at 56 my in the north atlantic the galicia margin samples show a redox change between 132 148 my indicating active surface currents between the atlantic ocean and the shallow sea off the iberian peninsula the carbonate samples from d s d p hole 316 in the central pacific yielded an average cea of 0 15 0 01 which is 2 3 the ceas observed in deep pacific seawater by piepgras and jacobsen 1988 the relative enrichment of ce in these samples is ascribed to coprecipitation of ce oh 4 onto fe mn o coatings the striking similarities in the trace element profiles of ree sc hf th and ceas and the low u abundances 0 08 ppm in many marine carbonates indicate insignificant ce redox and trace elemental concentration changes for the pacific ocean over the past 95 my no significant ce redox change occurred in the pacific ocean within k t boundary one 240 my china limestone deposited under oxic sedimentary conditions yielded a cea of 0 53 calculations indicate a pco2 of 1 9 present value prevailed over the 240 my tethyan ocean u th ratios and low u concentrations are diagnostic indicators for obtaining reliable ceas in marine carbonates and perhaps for biogenic apatites and conodonts as well

sedimentation history of the northern north sea margin during the last 150 ka the norwegian channel ice stream ncis is one the defining features of the fennoscandian icesheet still little is known of the detailed dynamics of this ice stream in relation to regional changes in ice cover paleoceanographic and climatic changes sedimentological data from core md99 2283 in combination with seismic data allow a detailed chronological reconstruction of the outbuilding of the margin and the ice extent in southern scandinavia through the last 150 ka an integrated stratigraphy of the margin is presented and compared to the glacial history changes in the regional ice cover are reflected in the accumulation rates the clay mineralogy the coarse chalk fraction and the number of ird 2 mm in core md99 2283 while the sedimentation on the north sea fan as derived from seismic data provides direct evidence for the glacial activity at the shelf edge tentative evidence was found for two early weichselian glacial advances in southern scandinavia and possibly scotland at around 110 and 80 ka bp from 42 cal ka bp the ice cover expanded in southern fennoscandia and led to increased deposition on the margin and the occurrence of local melt water outbursts significantly increased accumulation rates coarse chalk local meltwater output and smectite occur during the ice expansion in the north sea from around 34 cal ka bp the main outbuilding phase of the nsf during the last glacial cycle occurred after 30 cal ka bp from around 24 cal ka bp the ncis became highly active and advanced at least three times prior to the final retreat from the shelf edge around 19 0 cal ka bp

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

the cenomanian turonian oceanic anoxic event i stratigraphy and distribution of organic carbon rich beds and the marine δ13c excursion marine strata deposited during late cenomanian and early turonian time display lithological faunal and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient at or very close to the cenomanian turonian boundary between 90 5 and 91 5ma ago oxygen deficiencies were particularly marked over a period of 1ma this short lived episode of oceanic oxygen deficiency has been termed the cenomanian turonian oceanic anoxic event oae the widespread distribution of anoxic sediments deposited synchronously during such a short lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the cenomanian turonian oxygen minimum zone related to feedback between sea level rise and regional palaeoceanography the palaeoceanography of the cenomanian turonian oae is discussed in detail in a companion paper by arthur et al 1987 from authors

rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments abstract analyses have been made of ree contents of a well characterized suite of deep sea 4000 m principally todorokite bearing ferromanganese nodules and associated sediments from the pacific ocean ree in nodules and their sediments are closely related nodules with the largest positive ce anomalies are found on sediments with the smallest negative ce anomalies in contrast nodules with the highest contents of other rare earths 3 ree are found on sediments with the lowest 3 ree contents and vice versa 143 nd 144 nd ratios in the nodules 0 51244 point to an original seawater source but an identical ratio for sediments in combination with the ree patterns suggests that diagenetic reactions may transfer elements into the nodules analysis of biogenic phases shows that the direct contribution of plankton and carbonate and siliceous skeletal materials to ree contents of nodules and sediments is negligible inter element relationships and leaching tests suggest that ree contents are controlled by a p rich phase with a ree pattern similar to that for biogenous apatite and an fe rich phase with a pattern the mirror image of that for sea water it is proposed that 3 ree concentrations are controlled by the surface chemistry of these phases during diagenetic reactions which vary with sediment accumulation rate processes which favour the enrichment of transition metals in equatorial pacific nodules favour the depletion of 3 ree in nodules and enrichment of 3 ree in associated sediments in contrast ce appears to be added both to nodules and sediments directly from seawater and is not involved in diagenetic reactions

early diagenetic stabilization of trace elements in reptile bone remains as an indicator of maastrichtian late paleocene climatic changes evidence from the naran bulak locality the gobi desert south mongolia abstract maastrichtian dinosaur bone remains from the naran bulak locality the gobi desert with well preserved bone textural features are enriched in some trace elements primarily in ree these features of vertebrate fossils were formed during diagenesis following rapid burial in mudflow sediments and prior to postfossilization epigenetic changes trace elements are mainly concentrated in diagenetic apatite their contents in the bones correlate with that in their enclosing sediments for both maxima and minima fossil and sediment compositions were established under the influence of paleoclimate they are correlated with long term climatic changes with the aridity maximum at the k t boundary climatic changes were recorded via the change of salinity of waters interacting with the buried vertebrate remains

cobalt manganese and iron near the hawaiian islands a potential concentrating mechanism for cobalt within a cyclonic eddy and implications for the hybrid type trace metals abstract the vertical distributions of cobalt iron and manganese in the water column were studied during the e flux program e flux ii and iii which focused on the biogeochemistry of cold core cyclonic eddies that form in the lee of the hawaiian islands during e flux ii january 2005 and e flux iii march 2005 17 stations were sampled for cobalt n 147 all of which demonstrated nutrient like depletion in surface waters during e flux iii two depth profiles collected from within a mesoscale cold core eddy cyclone opal revealed small distinct maxima in cobalt at 100 m depth and a larger inventory of cobalt within the eddy we hypothesize that this was due to a cobalt concentrating effect within the eddy where upwelled cobalt was subsequently associated with sinking particulate organic carbon poc via biological activity and was released at a depth coincident with nearly complete poc remineralization benitez nelson c bidigare r r dickey t d landry m r leonard c l brown s l nencioli f rii y m maiti k becker j w bibby t s black w cai w j carlson c a chen f kuwahara v s mahaffey c mcandrew p m quay p d rappe m s selph k e simmons m p yang e j 2007 mesoscale eddies drive increased silica export in the subtropical pacific ocean science 316 1017 1020 there is also evidence for the formation of a correlation between cobalt and soluble reactive phosphorus during e flux iii relative to the e flux ii cruise that we suggest is due to increased productivity implying a minimum threshold of primary production below which cobalt phosphate coupling does not occur dissolved iron was measured in e flux ii and found in somewhat elevated concentrations 0 5 nm in surface waters relative to the iron depleted waters of the surrounding pacific fitzwater s e coale k h gordon m r johnson k s ondrusek m e 1996 iron deficiency and phytoplankton growth in the equatorial pacific deep sea research ii 43 4 6 995 1015 possibly due to island effects associated with the iron rich volcanic soil from the hawaiian islands and or anthropogenic inputs distinct depth maxima in total dissolved cobalt were observed at 400 600 m depth suggestive of the release of metals from the shelf area of comparable depth that surrounds these islands

rare earth element patterns of the central indian basin sediments related to their lithology rare earth element ree concentrations have been determined in terrigenous siliceous nodule barren and nodule bearing calcareous and red clay from the central indian basin the bulk distribution of ree and in particular the relative cerium fractionation in these surface sediments has been studied in relation to bottom water conditions ree fractionations within a single depositional environment are found to be characteristic for each sediment type with flat shale normalized patterns associated with terrigenous sediments positive ce anomalies with siliceous sediments negative ce and positive eu anomalies with calcareous sediments and lree depleted patterns with pelagic red clays there is no relation of any ree fractionation to bottom water redox conditions our results indicate that the ree signatures in marine sediments are not only related to depositional setting but also to the lithological variations and surficial diagenetic processes therefore these further constraints on understanding ree behaviour indicate that ree fractionations for paleotectonic and paleoredox reconstructions should be used with caution

isotope geochemistry of oxygen and carbon in phosphate and carbonate of phosphorite francolite oxygen isotope ratios in phosphate delta sup 18 o sub p were determined in 219 samples of phosphoritic rocks from all major phosphogenic provinces of the world ranging in age from lower proterozoic to recent in 58 samples oxygen was analyzed in the two oxygen lattice sites of francolite both in phosphate and in structural carbonate delta sup 18 o sub c delta sup 13 c was also analyzed in the latter and in coexisting calcite for 10 of them both delta sup 18 o sub p and delta sup 18 o sub c decrease sharply from the recent to the cretaceous and decrease with a gentler slope to the precambrian the nature of the time variation is elucidated by means of a delta sup 18 o sub p vs delta sup 18 o sub c plot which suggests that a the main cause of the time trends is the increase in temperature between recent and the cretaceous b the pre cretaceous trend is overprinted by both low temperature nonequilibrium exchange between sup 18 o depleted water and the rocks and higher temperature exchange between phosphate and carbonate c the observed trend cannot be explained by sup 18 o depleted cretaceous and paleozoic oceans the calcite coexisting with apatite in phosphatic rocks is similar in both delta sup 18 o and delta sup 13 c to the structural carbonatemore of the apatite even though phosphate may exchange its oxygen with environmental water to a greater extent than the authors originally claimed it is probably still a very good isotopic recorder of sedimentary environments less

distribution of rare earth and some trace elements in tertiary phosphorites from the senegal basin and their weathering products abstract the distribution of rare earth and some trace elements is studied in the eocene phosphate deposits of farim saliquinhe lam lam and n diendouri ouali diala from the mauritania senegal guinea basin the depth of weathering varies between the three deposits the strong weathering of lam lam is marked by the leaching of apatites ca phosphate and the appearance of epigenetic crandallites al ca phosphate in the void spaces that have resulted from leaching of apatites and then of crandallites ferruginous and kaolinitic fillings are epigenised in millisites al ca phosphate all the studied phosphates have high ree ba and sr abundances and present shale normalized patterns with a negative ce anomaly of variable intensity clay minerals of sediments smectites and of weathered rocks kaolinites are characterized by low ree and high v zn cu cr sc and zr abundances they have no ce anomaly the comparison of the ree patterns and of the trace element abundances lead to three important conclusions at first the genesis of al ca phosphates is marked by specific leaching of heavy ree relative to the light ones then millisites have a ree abundance and a ce anomaly less pronounced than those of apatites and crandallites they show also v zn cu cr sc and zr abundances like clay minerals these facts can be related to their epigenetic formation from clay minerals last but not least the negative ce anomaly of epigenetic crandallites follows the same trend as in apatites therefore this anomaly cannot constitute a proof of the primary character for apatites if such variations should be related to the paleogeographic setting of studied deposits they must be considered with prudence

salinity changes in the central baltic sea nw europe over the last 10000 years we attempt a reconstruction of salinity levels of the central baltic sea based on diatom assemblages the isotopic composition of organic matter and sedimentological expression of anoxia over the last 10 000 years we use the data to investigate the dependence of salinity levels on climate evolution and isostasy changes in salinity of surface and deep waters were most pronounced from 8400 to approximately 5000 cal bp density stratification between salty deep and fresher surface waters caused the frequent development of anoxic conditions and deposition of laminated sediments on large parts of the sea floor in the central baltic sea and dramatic changes in organic carbon accumulation rates from 5000 to 3100 cal bp the salinity of the basin decreased oxygenation of deep sea floors was improved and fertility of the sea surface was significantly reduced this is reflected by low accumulation rates of organic carbon in bioturbated sediments since 2800 cal bp salinity rose again and anoxic periods were more common even though the major steps in environmental evolution in the baltic sea coincide with known patterns of climatic change of the north atlantic realm over the last 10 000 years we find no conclusive evidence for synchronous changes or linear responses on submillennial timescales however we note that major variations in our salinity records agree with temporal patterns of reconstructed summer warmth and winter precipitation in southern scandinavia both types of record suggest that climate in the mid holocene was far from stable our data also confirm that climate evolution over the late holocene had significant impact on environmental conditions in the baltic sea

clay mineral stratigraphy during the last 2 4ma at iodp exp 323 site u1343 in the bering sea abstract the clay mineral composition at iodp exp 323 site u1343 in the bering sea was analyzed so as to unravel their provenance over glacial interglacial cycles for the last 2 4 ma smectite was negatively correlated with the sum of illite and chlorite therefore their ratio s i c was used as an indicator of clay mineral composition changes in general the s i c ratio was rather similar for glacial and interglacial periods during most of the last 2 4 ma in addition these results overlap with those of surface sediments in the modern east aleutian basin which suggests that smectite rich clay particles are delivered from the aleutians by the northward bering slope current bsc rather than from rivers in western alaska however some clay mineral compositions of the glacial periods after the mid pleistocene transition mpt 1 25 0 7 ma were characterized by low illite and relatively high smectite during this period extensive ice rafting might have transported the smectite rich clay particles to site u1343 from the glacial shelf off alaska and or from glacial rivers from that area

paleomagnetism of cretaceous and eocene strata san miguel island california borderland and the northward translation of baja california the history of poleward motion of the baja california peninsula is a subject of continuing geologic investigations including paleomagnetic studies during the past decade geologic correlations seem not to necessitate northward movement while paleomagnetic data suggest movement of 1000 km or more we have made paleomagnetic measurements on cretaceous and eocene sedimentary rocks of san miguel island california which are western lithofacies of rocks cropping out on the baja peninsula a total of 97 drill cores taken from upper cretaceous turbidites though weakly magnetized were found to clean best in response to thermal demagnetization revealing a characteristic remanence the characteristic magnetization has an inclination 43 9 declination of 24 0 and an 95 of 3 9 this direction is 19 shallower and rotated 50 clockwise from the expected direction for the present site position and corresponds to a paleolatitude of 26 n a total of 117 drill cores of middle eocene rocks revealed characteristic magnetizations in response to either alternating field or thermal demagnetizations some samples suffer from a secondary thermal magnetization from early miocene volcanic activity requiring a thermal cleaning that incompletely removes the overprint a mean direction of magnetization can be derived from the intersection of planes fitted to the paths of demagnetization the characteristic magnetization for the eocene rocks has an inclination of 31 9 a declination of 71 0 and an 95 of 3 8 this direction is 19 shallower and rotated 79 clockwise from the expected eocene direction for this site and corresponds to a latitude of 17 n these paleomagnetic data in combination with recently published data from the baja peninsula and peninsular ranges of southern california indicate motion trajectories that mimic the north american craton for the period cretaceous to late eocene time during the oligocene the baja peninsula and adjoining regions to the west moved northward relative to the craton arriving at a pre gulf of california position not later than earliest miocene time a comparison of the northward motion of the baja peninsula with that of the santa lucia orocopia allochthon shows that both areas underwent rapid poleward translations but these motions occurred at different times

sulfidization of lacustrine glacial clay upon holocene marine transgression arkona basin baltic sea abstract towards the end of the last deglaciation more than 13 500 years ago the southern baltic sea was a freshwater lake the baltic ice lake for several thousand years during which iron rich organic poor clay was deposited the modern brackish marine stage started about 8600 years ago with the deposition of organic rich mud which is today characterized by high rates of sulfate reduction and high concentrations of free sulfide we studied the iron sulfur diagenesis in gravity cores from the arkona basin sw baltic sea to track the progressing sulfidization front in the buried ice lake sediment the geochemical zonation was unusual as the sulfate concentration dropped steeply by two thirds below which it increased again due to a deep sulfate reservoir the reservoir had been established during the early holocene marine period as sulfate and other seawater ions diffused down into the lake sediment for several thousand years sulfur isotope analyses confirmed its origin as seawater sulfate while its oxygen isotope composition indicated a microbially catalyzed equilibration with ambient interstitial water decoupled from net sulfate reduction today hydrogen sulfide diffuses from the marine mud down into the lake sediment where a black band with high magnetic susceptibility and high iron monosulfide greigite and elemental sulfur content shows progressing sulfidization of the large pool of solid phase reactive iron dissolved iron from the deep ice lake sediment diffuses up to the sulfide front and provides a small supplement to the solid fe iii pool as a sulfide sink pyrite formation at the sulfidization front may involve surface bound zero valent sulfur while above the front polysulfides are in equilibrium with the system hydrogen sulfide polysulfide rhombic sulfur and may not be important for further pyrite formation the holocene iron sulfur diagenesis observed in the arkona basin represents an important transitional state for post glacial transgressions with organic rich marine sediment overlying lacustrine clay such as in other areas of the baltic sea or in the black sea