late quaternary sapropel sediments in the eastern mediterranean sea faunal variations and chronology distinctive planktonic foraminiferal assemblages which characterize particular late quaternary sapropel layers in deep basin sediments from the eastern mediterranean sea have been identified using cluster analysis three distinct clusters allow for identification and intercore correlation of the nine sapropels deposited during the last 250 000 yr cluster 1 representing sapropel layers s1 and s9 exhibits low abundances of neogloboquadrina dutertrei and high abundances of globigerinoides ruber cluster 2 which groups s3 s5 and s7 contains high abundances of g ruber n dutertrei and globigerina bulloides and cluster 3 which includes samples from s4 s6 and s8 is marked by extremely abundant n dutertrei and g bulloides and rare g ruber analysis of sedimentation rates in 14 cores reveals the following approximate ages for the sapropel layers s2 52 000 yr b p s3 81 000 78 000 yr b p s4 100 000 98 000 yr b p and s5 125 000 116 000 yr b p as previously suggested sedimentation rates on the mediterranean ridge were determined to be relatively constant during the last 127 000 yr in contrast basin sedimentation rates have fluctuated markedly from lower rates during interglacial stage 5 to higher rates during the last glacial episode these glacial interglacial differences are most pronounced in the northern ionian basin because of increased terrigenous sediment deposition during glacial episodes unusually high biogenic sedimentation rates occurred in an arc south of crete during the deposition of sapropel s5 probably due to higher productivity in this region

modeling phosphorus cycling and carbon burial during cretaceous oceanic anoxic events article i nfo in the greenhouse world of the cretaceous there were episodes of oxygen depletion in the deep ocean associated with enhanced organic carbon burial in sediments black shale formation in this study we use a box model of the oceanic phosphorus p organic carbon orgc and oxygen cycles to explore the hypothesis that variations in marine p availability control deep ocean oxygen depletion anoxia and the formation of black shales under cretaceous ocean conditions we find that for the cretaceous ocean with large continental shelves slow oceanic overturning and high sea surface temperatures oceanic anoxic events oaes can be triggered by enhanced p supply from land and that the system is particularly sensitive to oceanic mixing in our baseline scenario the deep sea becomes completely anoxic while the shelves attain only partial anoxia sedimentary burial differs between the shelves and open ocean while organic carbon burial is enhanced in both regions deep sea reactive p burial decreases dramatically under anoxia but not on the shelves where oxygen depletion is not complete furthermore our model results imply that oaes can be sustained by p recycling from sediments under low oxygen conditions ultimately however the feedbacks which result in the accumulation of atmospheric oxygen terminate the anoxic event atmospheric oxygen is modulated by land processes such as forest fires and oxidative weathering which limit the rise of atmospheric o2 our model findings are corroborated by p burial data from the geological record for oae2 approximately 94 myr bp through a sensitivity analysis we identify two necessary criteria for oaes low mixing of surface and deep waters poor ocean ventilation and enhanced sedimentary p recycling under low oxygen conditions when these criteria are met ocean anoxia is a robust result to a mild increase of continental supply of phosphorus under a wide range of environmental conditions

spatial productivity variations during formation of sapropels s5 and s6 in the mediterranean sea evidence from ba contents abstract we investigated five time equivalent core sections 180 110 kyr bp from the balearic sea menorca rise the easternmost levantine basin and southwest south and southeast of crete to reconstruct spatial patterns of productivity during deposition of sapropels s5 and s6 in the mediterranean sea our indicators are ba total organic carbon and carbonate contents we found no indications of ba remobilization within the investigated core intervals and used the accumulation rate of biogenic ba to compute paleoproductivity maximum surface water productivity up to 350 g c m2 yr was found during deposition of s5 isotope stage 5e but pronounced spatial variability is evident coeval sediment intervals in the balearic sea show very little productivity change suggesting that chemical and biological environments in the eastern and western mediterranean basins were decoupled in this interval we interpret the spatial variability as the result of two different modes of nutrient delivery to the photic zone river derived nutrient input and shoaling of the pycnocline nutricline to the photic zone the productivity increase during the formation of s6 was moderate compared to s5 and had a less marked spatial variability within the study area of the eastern mediterranean sea given that s6 formed during a glacial interval glacial boundary conditions such as high wind stress and or cooler surface water temperatures apparently favored lateral and vertical mixing and prevented the development of the spatial gradients within the eastern mediterranean sea ems observed for s5 a non sapropel sediment interval with elevated ba content and depleted 18o 16o ratios in planktonic foraminifer calcite was detected between s6 and s5 that corresponds to the weak northern hemisphere insolation maximum at 150 kyr at this time productivity apparently increased up to five times over surrounding intervals but abundant benthic fauna show that the deep water remained oxic following our interpretation the interval denotes a failed sapropel when a weaker monsoon did not force the ems into permanent stratification the comparison of interglacial and glacial sapropels illustrates the relevance of climatic boundary conditions in the northern catchment in determining the facies and spatial variability of sapropels within the ems

carbon to phosphorus ratios in sediments implications for nutrient cycling defining the transformations of phosphorus p in sediments is critical to assessing the geochemical behavior of sedimentary p and the behavior of reactive p preactive poxide associated pauthigenic porganic relative to organic carbon corganic this study includes the determination of p components and corganic concentrations on samples from sites in the california current region ocean drilling program odp leg 167 sites 1010 1011 1012 1014 1016 and 1021 in the benguela current region odp leg 175 sites 1082 1084 and 1085 and on blake nose in the western atlantic odp leg 17 1b sites 1050 and 1052 sample depths range up to 650 m and ages range up to 65 ma our data demonstrate the transformation of labile forms of p porganic and poxide associated to pauthigenic throughout the sediment column in all redox states and at all sedimentation rates investigated until a substantial portion of reactive p is in the authigenic form 80 c p organic ratios are always greater than or equal to the redfield ratio in all of the sediments we studied sediments with corganic concentrations 2 wt have corganic preactive ratios less than the redfield ratio and corganic preactive ratios increase linearly with corganic consistent with degradation of corganic with age in general corganic preactive ratios for sediments with corganic concentrations 2 wt from a variety of redox states and sedimentation rates center around the redfield ratio although some ratios are as high as 3 times the redfield ratio however corganic preactive ratios up to 400 do not approach the high ratios observed for c p organic ratios up to 4500 because of the efficient transfer of labile forms of p to pauthigenic corganic preactive ratios better describe the geochemical behavior of sedimentary p

geochemical and paleomagnetic evidence for the occurrence of missing sapropels in eastern mediterranean sediments the cyclic occurrence of sapropels appears to be associated with maxima in the 65 n summer insolation target curve studies of the most recent sapropel have revealed extensive oxidation of organic matter or even the complete removal of this unit geochemical and magnetic signals allow for the detection of such a missing sapropel in older sediments these signals are altered by ongoing diagenetic processes an important parameter to reveal missing sapropels is ba elevated concentrations of ba are always found in visible sapropels and even after oxidation of part of the sapropel the initial ba profile remains visible we use this tool to trace down missing sapropels in kc01b a 37 m kullenberg core from the calabrian ridge eastern mediterranean at least 8 of 11 sampled intervals around insolation maxima contain evidence of a completely oxidized sapropel ba trace metal distributions and magnetic parameters are similar to those observed around visible sapropels

trace elemental derived paleoceanographic and paleoclimatic conditions for pleistocene eastern mediterranean sapropels abstract eastern mediterranean sediments are characterized by cyclic deposition of organic rich sediments known as sapropels enhanced primary productivity combined with bottom water oxygen depletion are thought to be the main drivers for sapropel deposition we selected sapropel layers from a suite of odp leg 160 cores and applied a set of geochemical proxies to determine paleo productivity variations redox conditions of the water column during deposition and provenance of detrital material high sedimentary ba al and corg contents indicate enhanced primary production whereas the sedimentary la lu ratio points to an enhanced contribution from a north african riverine source during sapropel formation these features are especially pronounced on sapropels s5 and s7 deposited during a particularly warm climatic interval this indicates a more intense north african drainage weathering and consequently run off for those sapropels that have the most enhanced expression of productivity too correspondingly the latter has also resulted in bottom water redox conditions that have been more severe during these sapropels than during others deepwater formation from adriatic and aegean areas thought to be mainly controlled by sustained cooling of preconditioned surface waters triggers the onset of bottomwater ventilation thus sapropel duration our data therefore suggest that the intensity of sapropel formation is determined by the north african monsoonal system whereas their duration is directed by northern borderlands climatic conditions

carbon and phosphorus burial associated with modern phosphorite formation phosphorite formation plays a significant but poorly constrained role in the marine c and p cycles this report concerns a site of modern phosphorite formation on the upper continental slope off southern baja california mexico sta 6 380 m water depth 23 41 n 111 05 w at this site a series of six narrow 1 3 cm partially indurated phosphorite layers have formed authigenically during the last 15 000 years within a surficial section of slowly but steadily accumulating 3 8 10 3 cm year 1 organic rich mud a poorly oxygenated benthic environment has prevailed at the study site since approximately 8100 year b p probably helping to produce and preserve the pristine phosphorite layers the mean p burial flux 1 1 mol cm 2 year 1 recorded by these deposits agrees closely with the downward diffusive p flux 1 3 mol cm 2 year 1 attributed to active francolite growth such a coincidence implies that the phosphorite layers could have formed entirely under present conditions however a much larger upward diffusive p flux 4 2 mol cm 2 year 1 directed out of the sediment limits the efficiency of ongoing phosphorite formation and the most recently deposited sediment does not contain enough labile p to maintain the overall p regeneration rate indefinitely attendant burial fluxes of inorganic and especially organic c 7 7 and 6 6 mol cm 2 year 1 respectively do not accord with a depositional model of coastal upwelling suggesting that an alternative mechanism possibly fe redox cycling controls porewater p concentrations and hence phosphorite formation a comparison with previously published p burial fluxes for a wide variety of other modern marine settings reveals that phosphorite formation in general does not disproportionately affect the global p burial flux from these data we tentatively estimate a minimum global p burial flux of approximately 70 109 mol year 1 with almost 80 occurring on continental margins

climate controlled multidecadal variability in north african dust transport to the mediterranean high resolution laser ablation inductively coupled plasma mass spectroscopy scanning of resin embedded laminated sediments is used to detail variability in the composition and magnitude of recent eolian dust deposition in the eastern mediterranean the composition of dust accumulating in the anoxic atalante basin varies in response to the strength of the summer blocking mode of mediterranean climate dust sources located upwind on the westerly airflow are favored during phases of weaker blocking hence stronger summer westerlies this mode is in turn correlated to the pronounced multidecadal oscillation in mediterranean sea surface temperature related to the atlantic multidecadal oscillation suggesting that coupled ocean atmosphere dynamics control the large scale transport of dust in the region variable precipitation in dust source regions may also exert an influence on the relative flux of dust from each source and hence the net composition of dust deposited in the basin persistent oscillations in the composition of deeper sediments indicate that the basin offers a high potential archive for reconstruction of climate controlled variability in dust transport prior to the instrumental era

modes of sapropel formation in the eastern mediterranean some constraints based on pyrite properties abstract pyrite formation within and directly below sapropels in the eastern mediterranean was governed by the relative rates of sulphide production and fe liberation and supply to the organic rich layers at times of relatively high so2 4 reduction sulphide could diffuse downward from the sapropel and formed pyrite in underlying sediments the sources of fe for pyrite formation comprised detrital fe and diagenetically liberated fe ii from sapropel underlying sediments in organic rich sapropels input of fe from the water column via fe sulphide formation in the water may have been important as well rapid pyrite formation at high saturation levels resulted in the formation of framboidal pyrite within the sapropels whereas below the sapropels slow euhedral pyrite formation at low saturation levels occurred 34s values of pyrite are 33 to 50 below the sapropels 34s is lower than within the sapropels as a result of increased sulphide re oxidation at times of relatively high sulphide production and concentration when sulphide could escape from the sediment the percentage of initially formed sulphide that was re oxidized was estimated from organic carbon fluxes and burial efficiencies in the sediment it ranges from 34 to 80 varying significantly between sapropels increased palaeoproductivity as well as enhanced preservation contributed to magnified accumulation of organic matter in sapropels

biological productivity during sapropel s5 formation in the eastern mediterranean sea evidence from stable isotopes of nitrogen and carbon we determined 15n 14n ratios in modern surface and sapropel s5 sediments of the mediterranean sea to clarify differences in the nutrient regime associated with sapropel formation in the modern situation high 15n of unused nitrate 15 20 remaining in the surface waters during the winter phytoplankton bloom evidences p limitation of biological production in winter 15n of surface sediments decrease towards the east of the basin 5 to 2 5 this is a consequence of either eastward increasing nitrogen fixation during the summer months or of particulate matter being supplied predominantly by the p limited winter bloom very low 1 1 15n values in sapropel s 5 from four locations require a very light source of nutrient n assimilated at a minimum of ten times the modern export flux because the isochronous records show no spatial gradient in 15n we exclude both ekman type upwelling and direct riverine discharge as likely sources of nutrients our data are consistent with an anti estuarine thermohaline circulation in the upper 500m during s5 time allowing for the trapping of nutrients in the eastern basin the most likely scenario for s5 is that phosphorus release from a relatively shallow redox boundary resulted in an imbalanced supply of n p 16 1 to the photic zone the result was a slow assimilation of carbon during summer stratification and extensive n2 fixation providing the majority of the export flux from a n limited system

timing and hydrological conditions of sapropel events in the eastern mediterranean as evident from speleothems soreq cave israel this paper explores the connection between the timing of sapropel events in the eastern mediterranean sea and the time of low 18o events in speleothems of the soreq cave israel a new well dated 18o and 13c profile of the soreq cave speleothems for the last 140 kyr reveals five prominent low 18o events dated at 124 to 119 kyr with the main peak at 122 kyr event v 108 to 100 kyr with peaks at 107 and 102 kyr event iv 85 to 79 kyr with peak at 80 kyr event iii 55 to 52 kyr with a peak at 54 kyr event ii and 8 5 to 7 kyr with peaks at 8 5 and 7 kyr event i these events are characteristic of period of enhanced rainfall in the eastern mediterranean area particularly so for events v and i where the marked decrease in 18o and the correspondingly marked increase in 13c indicate very wet conditions the chronology of the low 18o events v iv iii and i match the ages estimated for the formation of sapropels s5 s4 s3 and s1 which are also associated with high hydrological activity thus it is suggested that the low 18o events in the soreq cave speleothems constrain the maximum duration of the sapropel formation pollen data from the sapropel layers and the isotopic pattern of the speleothems indicate that sapropels s5 and s1 were deposited during very wet periods when there were major decrease in the sea surface salinity coupled with frost free winters and drought free summers sapropels s4 and s3 were formed during periods of increased precipitation but ones in which the general climate was mediterranean semi arid

sedimentary organic carbon to phosphorus ratios as a redox proxy in quaternary records from the mediterranean abstract in this study organic carbon to organic phosphorus c org p org and total phosphorus c org p tot ratios as bottom water redox proxies are explored for two eastern mediterranean sediment records extending back 600 700 kyrs cores kc19c 19 6 m long 2750 m water depth and kc01b 37 0 m long 3643 m water depth contain numerous organic rich layers sapropels throughout the two cores variations found in the c org p ratios correspond to those for other redox proxies such as total s contents and v al ratios accordingly these are interpreted as variations in bottom water oxygenation and inter sapropel redox variability in core kc19c the original c org p signals seem to have been preserved despite intense post depositional sulfidization high resolution p fractionation data of sapropel s5 from a third core ps25pc 3304 m water depth showing high and relatively stable c org p org ratios indicate that sapropel s5 at this deep location was deposited under permanently reducing conditions while p regeneration from organic matter was intense net p burial increased in the sapropel due to enhanced burial of inorganic calcium phosphate likely biogenic ca p sediment p contents and c org p tot ratios in s5 are variable reflecting short term changes in marine conditions productivity redox and sediment chemistry the c org p org and c org p tot ratios thus provide valuable insight into paleoceanographic conditions and pathways of p cycling for mediterranean sediment records extending back at least 600 700 kyrs

phosphate regeneration from sediments of the peru continental margin by dissolution of fish debris generally oxidative regeneration of phosphate from anoxic sediments is by microbially mediated sulfate reduction processes stoichiometric modelling of such reactions takes into consideration varying proportions of decomposable organically bound p to account for the ratios among nutrients in depth concentration profiles of near surface sediments new results of interstitial water composition from sediments underlying the water masses influenced by coastal upwelling of the eastern boundary current system off peru indicate that dissolution of phosphatic fish debris represents a mechanism for remineralization of phosphate comparable to or larger in magnitude than that by oxidative regeneration of organically bound p dissolved interstitial phosphate from fish debris is revealed by an excess amount of phosphate over that predicted from a simple stoichiometric oxidative regeneration model and by anomalously high dissolved interstitial fluoride concentrations phosphate flux estimates based on diffusion from the sediment suggest that this mechanism may generate up to 10 of the nutrient pool in the waters of the peru undercurrent partitioning of p among the two sources reveals further that fish debris phosphate is about four times more important than organically bound p in nutrient generation from sediments of the peru continental margin not only does this mechanism of regeneration affect the nutrient cycling but may also control widespread phosphorite formation in this area

sedimentary corg p ratios paleocean ventilation and phanerozoic atmospheric po2 the corg p ratios of organic rich facies tocn1 exhibit considerable variation through the phanerozoic from b10 1 in the permian phosphoria formation to n1000 1 in some devonian black shales relative to the composition of phytoplankton c p 106 1 which provide the bulk of organic c and p to organic rich marine sediments the range of phanerozoic sedimentary corg p ratios largely reflects the influence of benthic redox conditions on diagenetic pathways of c and p remobilization enhanced preservationoforganiccatlowerredoxpotentials combinedwithenhancedsedimentaryretentionofremineralizedorganicpathigher redox potentials results in a strong relationship between benthic redox conditions and sedimentary corg p ratios the strong secular coherence of the phanerozoic corg p record i e limited variation within narrow time slices suggests that these ratios are controlled primarily by factors influencing benthic redox conditions on a global scale such as atmospheric po2 inversion and scaling of the phanerozoic corg p record yields a new atmospheric po2 model that has strong similarities to existing models based on elemental and isotopic mass balances yet differs in some potentially significant respects in particular the new model suggests that atmospheric po2 wasmarkedlylowerduringtheearlytomiddlepaleozoicthanpreviouslyinferred duringmostofthedevonian atmospherico2levels mayhavebeensufficientlylow b13 astopreventthesustainedcombustionofplantmaterial thisfeatureofthemodelmayaccount for ananomalous gapinthefossilcharcoalrecordduringthedevonian theredox dependentburialofpintheoceanresults inpositive and negative feedback mechanisms that tend to stabilize atmospheric oxygen concentrations on geologic timescales temporal variations in the burial of p relative to c suggest that the strength of these feedback mechanisms varied over the phanerozoic 2007 elsevier b v all rights reserved

aegean sea as driver of hydrographic and ecological changes in the eastern mediterranean the eastern mediterranean is undergoing a long term increase in net evaporation which may have preconditioned the profound changes that occurred in its deep sea ventilation over the past two decades we test the sensitivity of aegean convective deep water formation to forcing in the opposite sense based on a last interglacial episode of enhanced freshwater injection into the eastern mediterranean we find that aegean subsurface ventilation collapsed completely within 40 20 yr promoting euxinic conditions hostile to aerobic life that expanded toward the photic layer within 650 250 yr similar conditions extended throughout the eastern mediterranean 300 120 yr later these findings emphasize the exceptional sensitivity of aegean deep water formation to climate forcing driving large scale hydrographic adjustments throughout the eastern mediterranean and beyond

bottom water anoxia inoceramid colonization and benthopelagic coupling during black shale deposition on demerara rise late cretaceous western tropical north atlantic 1 the bulk rock geochemistry and inoceramid isotopic composition from cenomanian to santonian finely laminated organic rich black shales recovered during ocean drilling program leg 207 on demerara rise western tropical north atlantic suggest persistent anoxic free h2s conditions within the sediments and short term variations within a narrow range of anoxic to episodically dysoxic bottom waters over a 15 ma time interval in addition to being organic rich the 50 90 m thick sections examined exhibit substantial bulk rock enrichments of si p ba cu mo ni and zn relative to world average shale these observations point to high organic burial fluxes likely driven by high primary production rates which led to the establishment of intensely sulfidic pore waters and possibly bottom waters as well as to the enrichments of cr mo u and v in the sediments at the same time the irregular presence of benthic inoceramids and foraminifera in this facies demonstrates that the benthic environment could not have been continuously anoxic the 13c and 15n values of the inoceramid shell organics provide no evidence of chemosymbiosis and are consistent with pelagic rain as being a significant food source demerara rise inoceramids also exhibit well defined regularly spaced growth lines that are tracked by 13c and 18o variations in shell carbonate that cannot be simply explained by diagenesis instead productivity variations in surface waters may have paced the growth of the shells during brief oxygenation events suitable for benthic inoceramid settlement these inferences imply tight benthopelagic coupling and more dynamic benthic conditions than generally portrayed during black shale deposition by invoking different temporal scales for geochemical and paleontological data this study resolves recent contradictory conclusions e g sulfidic sedimentary conditions versus dysoxic to suboxic benthic waters drawn from studies of either sediment geochemistry or fossil distributions alone on demerara rise this variability may be relevant for discussions of black shales in general

active post depositional oxidation of the most recent sapropel s1 in sediments of the eastern mediterranean sea abstract over a wide area of the eastern mediterranean basin two mn rich layers have been observed above the most recent sapropel s1 one immediately above the sapropel top and one a few centimetres closer to the sediment surface different mechanisms have been proposed to explain the occurrence of these two mn peaks either both peaks have a diagenetic origin in which case the upper mn peak is actively forming or the lower peak is actively forming and the upper peak has a different formation mechanism high resolution porewater including a gel sampler used for the first time in marine sediments and solid phase data are now used to demonstrate that the oxidation front is located at the level of the lower mn peak which therefore is presently being formed a barium organic carbon relationship is used to calculate the initial organic carbon profile of the s1 sapropel the palaeoproductivity profiles generated by this method demonstrate that the original sapropel unit was bounded by the upper mn peak this implies that the interval between the two mn peaks where a low organic carbon content is now observed was originally part of the sapropel the initially deposited organic carbon has been oxidised by a progressive downwards moving oxidation front the penetration depth of this oxidation front i e the distance between the two mn peaks is mainly determined by the organic carbon content the sediment accumulation rate and the bioturbation depth the upper mn peak appears to have formed as a result of either mn precipitation upon oxygenation of previously anoxic eastern mediterranean deep water or preservation of a surficial mn peak at the end of the high productivity episode in either case the upper mn peak marks the end of sapropel formation as indicated by the ba profiles this means that formation of the s1 sapropel ceased more recently than is indicated by radiocarbon dating of the visible top of s1

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

mo total organic carbon covariation in modern anoxic marine environments implications for analysis of paleoredox and paleohydrographic conditions 1 sedimentary molybdenum mo s has been widely used as a proxy for benthic redox potential owing to its generally strong enrichment in organic rich marine facies deposited under oxygen depleted conditions a detailed analysis of mo s total organic carbon toc covariation in modern anoxic marine environments and its relationship to ambient water chemistry suggests that 1 mo s while useful in distinguishing oxic from anoxic facies is not related in a simple manner to dissolved sulfide concentrations within euxinic environments and 2 patterns of mo s toc covariation can provide information about paleohydrographic conditions especially the degree of restriction of the subchemoclinal water mass and temporal changes thereof related to deepwater renewal these inferences are based on data from four anoxic silled basins the black sea framvaren fjord cariaco basin and saanich inlet and one upwelling zone the namibian shelf representing a spectrum of aqueous chemical conditions related to water mass restriction in the silled basin environments increasing restriction is correlated with a systematic decrease in mo s toc ratios from 45 5 for saanich inlet to 4 5 1 for the black sea this variation reflects control of mo s by mo aq which becomes depleted in stagnant basins through removal to the sediment without adequate resupply by deepwater renewal the basin reservoir effect the temporal dynamics of this process are revealed by high resolution chemostratigraphic data from framvaren fjord and cariaco basin sediment cores which exhibit long term trends toward lower mo s toc ratios following development of water column stratification and deepwater anoxia mo burial fluxes peak in weakly sulfidic environments such as saanich inlet owing to a combination of greater mo aq availability and enhanced mo transport to the sediment water interface via fe mn redox cycling and are lower in strongly sulfidic environments such as the black sea and framvaren fjord these observations demonstrate that at timescales associated with deepwater renewal in anoxic silled basins decreased sedimentary mo concentrations and burial fluxes are associated with lower benthic redox potentials i e more sulfidic conditions these conclusions apply only to anoxic marine environments exhibiting some degree of water mass restriction e g silled basins and are not valid for low oxygen facies in open marine settings such as continent margin upwelling systems

enhanced regeneration of phosphorus during formation of the most recent eastern mediterranean sapropel s1 phosphorus regeneration and burial fluxes during and after formation of the most recent sapropel s1 were determined for two deep basin low sedimentation sites in the eastern mediterranean sea organic c p ratios and burial fluxes indicate enhanced regeneration of p relative to c during deposition of sapropel s1 this is largely due to the enhanced release of p from organic matter during sulfate reduction release of p from fe bound p also increased but this was only a relatively minor source of dissolved p pore water hpo4 concentrations remained too low for carbonate fluorapatite formation an increased burial of biogenic ca p i e fish debris was observed for one site estimated benthic fluxes of p during sapropel formation were elevated relative to the present day 900 to 2800 vs 70 to 120 mol m 2 yr 1 the present day sedimentary p cycle in the deep basin sediments is characterized by two major zones of reaction 1 the zone near the sediment water interface where substantial release of hpo4 from organic matter takes place and 2 the oxidation front at the top of the s1 where upward diffusing hpo4 from below the sapropel is sorbed to fe oxides the efficiency of aerobic organisms in retaining p is reflected in the low organic c p ratios in the oxidized part of the sapropel burial efficiencies for reactive p were significantly lower during s1 times compared with the present day 7 to 15 vs 64 to 77 budget calculations for the eastern mediterranean sea demonstrate that the weakening of the antiestuarine circulation and the enhanced regeneration of p both contributed to a significant increase in deep water hpo 4 concentrations during sapropel s1 times provided that sufficient vertical mixing occurred enhanced regeneration of p at the seafloor may have played a key role in maintaining increased productivity during sapropel s1 formation copyright 2002 elsevier science ltd

sediment carbon nitrogen and phosphorus cycling in an anoxic fjord effingham inlet british columbia sediment geochemistry as well as benthic exchange of nutrients was investigated in effingham inlet a fjord located on the west coast of vancouver island in barkley sound the effect of bottom water oxygenation on sediment carbon nitrogen and phosphorus cycling was compared at sites overlain by oxic and anoxic bottom waters the sites separated by only 3 kilometers were similar in terms of key diagenetic parameters including mass accumulation rate and bulk sediment organic carbon content thus allowing a focus on diagenetic effects attributable to depositional oxygen availability benthic flux chamber incubations sulfate reduction rate measurements measurements of solid phase and pore water chemical profiles were compared for the sites these comparisons reveal that diagenetic processes in the site overlain by oxic waters act to retain more phosphorus in the sediment relative to the anoxic site differences in phosphorus benthic fluxes and burial between the two sites most likely result from differences in organic matter cycling under aerobic versus anaerobic conditions and are not strongly influenced by cycling of p associated with metal oxide phases

phosphorus cycling from the margin to abyssal depths in the proto atlantic during oceanic anoxic event 2 abstract phosphorus p burial during the cenomanian turonian oceanic anoxic event oae 2 93 55 ma was studied using sediment records from four sites in the proto atlantic ocean the sites represent a variety of depositional settings from the continental margin and slope to the abyssal plain strong links between changing marine conditions during oae 2 and p cycling were observed in black shale sections on the continental margin and slope sedimentary p contents and p mars increased around the onset of oae 2 which may reflect enhanced productivity and p burial partly in the form of biogenic apatite fish debris during the main stage of oae 2 phosphorus was efficiently regenerated from the sediment resulting in p depleted sediments and high organic c corg total p ratios the increased availability of dissolved p may have helped to sustain high productivity during oae 2 the termination of oae 2 was associated with a strong recovery of p burial efficiency in the sediment sedimentary records from the two deep sites do not reveal such close links between different stages of oae 2 and the characteristics of p cycling here oae 2 was a period with maximum deposition of relatively thin black shale intervals that alternate with more oxic deep sea sediments the black shale layers record enhanced p regeneration from organic matter and in some cases p enrichment relative to the oxic sediments detailed chemical p fractionation was performed on sediment from all sites but the results were found to mostly reflect diagenesis and sample handling artifacts in these ancient sediments total p concentrations and the corg total p ratio appear to be the most robust indicators of p cycling and regeneration

pitfalls of normalization of marine geochemical data using a common divisor abstract normalization of trace element contents of sediment through division by the content of an immobile element usually aluminum is common practice in marine geochemical studies this might appear to be a simple way of correcting for dilution by sedimentary phases barren of a particular trace element for instance carbonates or silica and for comparison with its content in a standard clay or shale the purpose of this paper is to revive the awareness of the pitfalls of this practice by giving numerical examples of the often unexpected results of normalization taking a statistical perspective it is first shown that uncorrelated variables acquire spurious correlations when normalized but normalization can also increase decrease change sign of or even blur the correlations between unmodified variables next a number of realistic scenarios are worked out to show that the correlations between normalized element contents still suffer from the closure effect only in a few simple cases it is possible to extract from the normalized data realistic estimates of trace element contents in distinct sedimentary phases such as organic matter this is ascertained from data on copper contents in sediment from the black sea and arabian sea when the coefficient of variation i e standard deviation divided by the mean of the aluminum data is relatively low and much lower than for the original values of the trace elements comparisons of correlations can equally well or even better be made on the basis of the unmodified values then the comparison of trace element data with their values for standard shales is discussed the inherent problem is that the composition of the commonly used standard shale and consequently the reference values of normalized elements are not necessarily representative of the local or regional sediments in the study area also this method falls short of identifying the processes responsible for enrichment or diminution in trace element contents finally consideration is given to some aspects of a proper use of al normalization

a synthetic pollen record of the eastern mediterranean sapropels of the last 1 ma implications for the time scale and formation of sapropels abstract the quaternary climate of southern europe south italy and greece is investigated by pollen analysis of the sapropels which were deposited in the deep eastern mediterranean sea during the last 1 million year ma the time scale of core kc01b in the ionian sea has been established by tuning its oxygen isotopic record to the ice volume model of imbrie and imbrie 1980 for the last 250 000 year 250 ka the previous pollen studies and astronomical tuning have been confirmed sapropels were deposited under a large range of mediterranean climates fully interglacial fully glacial and intermediary as revealed mainly by the balance between the respective pollen abundances of oak quercus and sage brush artemisia the high value of the oak reveals the warm and wet climate of an interglacial and the high value of the sage brush the dry and cold climate of a glacial whereas the mediterranean climate is directly related to the variation of the high latitude ice sheets the deposition of sapropels is not so in contrast with the wide climatic range sapropels were deposited only when summer insolation in the low latitudes reached its highest peaks however between 250 ka and 1 ma that stable pattern is not yet established only six sapropels are observed many expected ones do not appear even as ghosts signalled by peaks of barium abundance that remain after the post deposition oxidation of organic matter the pattern of sapropel formation in stable and direct relationship to highest insolation does not seem to apply for five of those sapropels neither climate extremes are observed they mainly formed during intermediary types of mediterranean climate in contrast one sapropel and one ghost relates to a relatively low peak of insolation and its climate is of a unique composite type not seen later this might suggest an unsuspected more complex pattern linking the formation of mediterranean sapropels to the astronomical configuration

geochemical and micropaleontological characterisation of a mediterranean sapropel s5 a case study from core ban89gc09 south of crete several geochemical and micropaleontological proxies were studied in a well developed sapropel s5 from a core collected south of crete to investigate the causes and the mechanisms of its deposition to reconstruct the paleoenvironmental and paleoceanographical conditions at time of its formation and to detect the roles played by productivity and anoxia the geochemical proxies are also used to unravel the sediment provenance and therefore to help tracing water circulation patterns and freshwater sources the multiproxy approach reveals that the sapropel layer has high internal variability and five different depositional phases can be identified four within the visible sapropel layer an increase in temperature and the development of a deep chlorophyll maximum characterise the onset of the sapropel phase 1 with enhanced productivity being favoured by local riverine input not clearly ascribable to nile river freshwater discharge and by the shoaling of the pycnocline nutricline surface water stratification and productivity develop together with strong seafloor dysoxia anoxia phase 2 is characterised by lower stratification slightly lower temperature and or higher seasonal contrast and still high productivity phase 3 records high productivity high temperature and high stratification probably more sustained by the nile input a sudden partial re oxygenation takes place at the end of this phase changing the main features of the sapropel in the fourth phase productivity starts to decrease water stratification seems to be partially broken down and sediment oxygenation increases a transitional phase phase 5 occurs between the end of the visible sapropel and the normal pelagic post sapropel sedimentation where productivity is still high and oxygenation improves compared to the visible sapropel layer the massive occurrence of polysphaeridium zoharyi cyst of a red tide forming dinoflagellate also characterises this phase the geochemical proxies indicate that pre sapropel and post sapropel sediments are quite different from each other and the provenance shifts from a more mixed to a more markedly southern origin of sediments

calcareous nannofossils and the origin of eastern mediterranean sapropels a quantitative analysis of calcareous nannofossil assemblages was carried out with an optical microscope on four deep sea cores raised from the eastern mediterranean and selected to form a nw se transect a total of 748 samples were studied including a very detailed analysis of sapropels s5 and s6 in two out of the four cores this paper is restricted to the discussion of the results obtained on florisphaera profunda which provided important insights on the mechanisms of sapropel formation an intricated and unravelled puzzle for the scientists of the last decades on the basis of abundance variations of f profunda the only species of calcareous nannoplankton which inhabits the lower part of the photic zone i suggest that sapropel formation was triggered by increased primary production either confined to a deep chlorophyll maximum dcm a concept previously introduced by rohling and gieskes 1989 or extended to a thicker layer of the photic zone when increased primary production was confined to the dcm sapropel s3 s4 s5 s7 and s1 this latter only in the eastern part of the basin the abundance of f profunda was enhanced greatly with respect to all other species living in the higher part of the photic zone on the contrary when the increased primary production was extended to a thicker layer of the photic zone glacial sapropels s6 and s8 the production of most nannoplankton species was favored decreasing the relative proportion of f profunda

a dynamic concept for eastern mediterranean circulation and oxygenation during sapropel formation we propose that intermittent bottom water ventilation occurred throughout periods of sapropel deposition and that the recently reported sapropel interruptions represent centennial scale episodes of enhanced frequency intensity of that process in essence the modern high frequency variability in deep water formation affected by climatic variability over the northern basins on seasonal to longer time scales prevailed also at times of sapropel deposition although the overall ventilation state was much reduced this concept is supported by detailed multiple species isotope records for three aegean cores the presence of abundant globorotalia truncatulinoides within especially sapropels s7 and s8 in the western levantine basin observations of three rapid benthic repopulations within sapropel s6 in the deep western levantine basin a report of continuous benthic presence through sapropel s1 at intermediate deep locations offshore libya and further supporting information from the literature in the aegean records concomitant abundance of low oxygen tolerant benthic foraminifera and presence of the more oxyphilic benthic foraminifer uvigerina mediterranea with surface similar 13c values indicate repeated deep water re oxygenation events throughout the deposition of s1 the observations of a continuous benthic presence through s1 offshore from libya imply that no persistent anoxia developed at mid depth levels in that region which is far removed from direct deep ventilation influences the abundance of deep mesopelagic g truncatulinoides through several sapropels from the western levantine basin also suggests the presence of bio available oxygen at many hundreds of meters of depth moreover the rapid intermittent benthic repopulations within sapropels from the deep eastern mediterranean imply that bottom water anoxia was spatially restricted and or of a highly intermittent nature the short time scales of these repopulation events are incompatible with titration of an extensively anoxic water column and subsequent re establishment of water column anoxia we suggest that where anoxic azoic conditions were present they most likely were restricted to a veneer at the sediment water interface the extent of such an anoxic blanket depends on the balance between advective oxygen supply into the deep sea and biological and chemical oxygen demand the demand functions imply a decoupling of oxygenation from water mass advection allowing export production and corg posting rates to the sea floor to delimit the extent of the anoxic blanket in both space and time low productivity regions would develop no anoxic blanket allowing for the observed persistence of deep dwelling planktonic and bottom dwelling benthic faunas

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

neogene sapropels in the mediterranean a review for 50 years the existence of sapropels organic carbon rich sediments deposited within plio pleistocene sediments of the mediterranean sea has been known initially research concentrated on material recovered in relatively short gravity piston cores taken from the eastern basins where sequences were found to be well developed preserved and had extensive spatial coverage in the main previous studies concentrated upon establishing a workable stratigraphy spatial correlation of individual layers and determining the probable depositional mechanisms however despite a plethora of research papers some issues still remain unresolved this is in part due to a lack of agreement between investigators sampling and analytical short comings restricted sample size and the fact that in many instances like was not being compared with like recently the limit of sapropels in the western basin has been further extended as a result the palaeoceanographic palaeoclimate models which had previously been developed for deposition of sapropels in the eastern basin have been modified most recently strong links have been established between astronomical cyclicity and sapropel formation this review paper provides a summary of sapropel research to date and ongoing sapropel research in the mediterranean some of which appears in this thematic issue of marine geology it is fitting that this thematic issue of marine geology be dedicated to the memory of colette vergnaud grazzini and rob kidd who in many ways helped to initiate the resurgence in sapropel studies in the 1970s in the mediterranean perhaps in 50 more years we will know all of the answers 1999 elsevier science b v all rights reserved

a sediment nutrient oxygen feedback responsible for productivity variations in late miocene sapropel sequences of the western mediterranean abstract cyclic sediments observed throughout the mediterranean during the late miocene have been related to precessional forcing of ocean stratification individual couplets typically 2 m thick sequences of sapropels and diatom rich marls can be reliably traced from western spain to crete and were formed in restricted marginal basins micropaleontological evidence indicates paradoxically that the organic carbon rich sapropels were formed under low productivity conditions marked by surface water stratification and deep anoxia whereas the diatom rich marls were formed under high productivity conditions marked by upwelling here we present geochemical evidence mainly from detailed phosphorus determinations and paleo redox proxies indicating that a sediment nutrient oxygen feedback herein dubbed the sno effect is in part responsible for driving the observed productivity variations during stratification anoxic conditions in these basins cause the release of the limiting nutrient phosphorus from reducible oxide phases in the sediments basin stagnation causes the buildup of phosphorus below the photic zone subsequent overturn driven by precessionally driven winds injects phosphorus rich bottom waters into the photic zone the biotic response to this overturn is high productivity in marls directly overlying the sapropels culminating in diatom mat formation exhaustion of the stored excess phosphorus results in lower productivity marls which grade back into sapropels due to lower wind stresses and the return of stagnant basin conditions these findings indicate that the sno effect may in part be responsible for precessional scale productivity variations observed in parts of the mediterranean and perhaps present in other restricted ocean basins like the miocene monterey formation and the modern santa barbara basin

authigenic apatite formation and burial in sediments from non upwelling continental margin environments abstract evidence for precipitation of authigenic carbonate fluorapatite cfa in long island sound and mississippi delta sediments suggests that formation of cfa is not restricted to environments of active coastal upwelling we present porewater data suggestive of cfa formation in both these areas application of a sequential leaching procedure designed specifically to separate authigenic carbonate fluorapatite from other phosphorus containing phases including detrital apatite of igneous or metamorphic origin provides strong supporting evidence for authigenic apatite formation in these sediments the size of the authigenic apatite reservoir increases with depth indicating continued formation of cfa during early diagenesis this depth increase is mirrored by a decrease in solid phase organic p at both sites suggesting that cfa is forming at the expense of organic p mass balance considerations application of diagenetic models to interstitial water nutrient data and the saturation state of the interstitial water are consistent with this interpretation diagenetic redistribution of phosphorus among the different solid phase reservoirs is observed at both sites and results in near perfect retention of p by these sediments over the depth intervals sampled formation of cfa in continental margins which do not conform to the classically defined regions of phosphorite formation renders cfa a quantitatively more important sink than has previously been recognized including this reservoir as a newly identified sink for reactive p in the ocean the residence time of p in the modern ocean must be revised downward the implication for ancient oceans of cfa formation in continental margin sediments other than phosphorites is that phosphorite formation may be less a representation of episodicity in removal of reactive p from the oceans than of localized concentration of cfa in phosphatic sediments by secondary physical processes

origin and diagenesis of polyphosphate in lake sediments a 31pߚnmr study polyphosphate poly p was detected with the use of 31 p nuclear magnetic resonance nmr spectroscopy in sediments from a large variety of lakes with different trophic state and morphometry in the top 0 5 cm of sediment poly p was 1 5 to 11 4 of total p nonreactive phosphorus nrp in the naoh fraction often classified as organically bound phosphate was up to 46 inorganic poly p in some surface sediments the poly p content equalled the iron fixed phosphorus determined by chemical phosphorus fractionation sediments were probably supplied with poly p by sedimentation because there were substantial amounts of poly p in plankton and settling seston as demonstrated with sediments of lake petersdorf benthic organisms can also contribute to the formation of poly p up to 0 11 mg p g dry weight 21 under favorable aerobic conditions poly p is more rapidly transformed into single orthophosphate during diagenesis than other inorganic and organic p species the transformation of organic p compounds and poly p can contribute significantly to the release of p during diagenesis and should be considered along with the reductive dissolution of p sorbed to iron oxihydroxides

a novel chemical method to quantify fish debris in marine sediments burial of fish bones which consist primarily of hydroxyapatite has been recognized as a mechanism to remove reactive phosphorus from the oceans in this study a new method is presented which differentiates p associated with biogenous apatite pfish from other p fractions the method consisting of a sequential chemical extraction with 2 m nh4cl has been successfully tested on standard materials it enables us for the first time to quantify fish debris in sediment records and to assess their importance for the marine phosphorus cycle the nh4cl extraction has been applied to sediment samples from the arabian sea preservation of fish debris is significantly higher in sediments located above 1 200 m water depth than it is for deeper sediments the distribution of pfish contents in surface sediments is predominantly governed by the extent of fish debris regeneration which is related to differences in water depth and sedimentation rates in addition a good correlation between high sedimentary pfish contents and low oxygen bottom water concentrations suggests that the presence of the intense oxygen minimum zone may account for the enhanced preservation of fish debris in continental slope sediments

trace element behavior and redox facies in core shales of upper pennsylvanian kansas type cyclothems the black shale submember of core shales of pennsylvanian kansas type cyclothems is highly enriched in redox sensitive trace elements tes relative to the overlying gray shale submember as well as to many other modern and ancient organic rich deposits controls on trace element behavior in the black shale can be inferred from trace element enrichment factors efs relative to gray shale and the relationship of tes to total organic carbon toc most tes conformed to one of two patterns 1 mo u v zn and pb exhibited moderate efs and strong covariation with toc in samples having 10 wt toc and 2 cu ni cr and co exhibited low efs and moderate to strong covariation with toc in all samples these patterns are inferred to represent different responses to benthic redox conditions the first pattern is characteristic of tes of strong euxinic affinity i e those taken up in solid solution by fe sulfide or involved in other reactions catalyzed by free h2s and resident mainly in authigenic phases whereas the second pattern is characteristic of tes of weak euxinic affinity i e those not strongly influenced by the presence of free h2s and resident mainly in the organic carbon or detrital fractions of the sediment these inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples euxinic conditions were considered to have existed if at least two of four redox indicator trace elements mo u v zn showed euxinic levels of enrichment and nonsulfidic anoxic conditions were inferred otherwise the validity of the procedure is indicated by 1 agreement among all four redox indicators for a large majority of samples 69 of 185 2 among samples yielding a mixed redox signal a systematic sequence of te enrichment v zn mo u and 3 for tes of weak euxinic affinity reduced variance among samples representing each redox facies sequential enrichment may be a response to differential redox thresholds for accumulation e g v or postdepositional remobilization of trace elements e g u and may provide a basis for finer assessment of redox conditions in low oxygen paleoenvironments than permitted by simple classification schemes the multiproxy procedure for redox facies analysis developed in this study is likely to be more reliable than widely used single proxy indicators based on trace elements e g mo authigenic u or v v ni or c s fe systematics e g s toc or dop d 2004 elsevier b v all rights reserved

the geochemistry of redox sensitive trace metals in sediments abstract we analyzed the redox sensitive elements v mo u re and cd in surface sediments from the northwest african margin the u s northwest margin and the arabian sea to determine their response under a range of redox conditions where oxygen penetrates 1 cm or less into the sediments mo and v diffuse to the overlying water as mn is reduced and remobilized authigenic enrichments of u re and cd are evident under these redox conditions with the onset of sulfate reduction all of the metals accumulate authigenically with re being by far the most enriched general trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes oxic reducing where oxygen penetrates 1 cm and anoxic conditions using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations we calculate the area of sediments below 1000 m water depth in which oxygen penetration is 1 cm to be 4 of the ocean floor we conclude that sediments where oxygen penetrates 1 cm release mn v and mo to seawater at rates of 140 260 60 150 and 5 10 of their respective riverine fluxes using the authigenic metal concentrations and accumulation rates from this work and other literature these sediments are sinks for re cd and u with burial fluxes of 70 140 30 80 and 20 40 respectively of their dissolved riverine inputs we modeled the sensitivity of the response of seawater re cd and v concentrations to changes in the area of reducing sediments where oxygen penetrates 1 cm our analysis suggests a negligible change in seawater re concentration whereas seawater concentrations of cd and v could have decreased and increased respectively by 5 10 over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10 20 if the area increased by a factor of 3 the concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of cd ca and v ca ratios observed in foraminifera shells over the last 40 kyr this implies that the area of reducing sediments in the ocean deeper than 1000 m 4 has not been greater than twice the present value in the recent past

water column dynamics during the last interglacial anoxic event in the mediterranean sapropel s5 1 marine organic rich sediments are important for long term carbon sequestration and as a source of fossil hydrocarbons but the processes underlying their formation remain elusive we present a multiproxy analysis of a relatively recent well preserved mediterranean organic rich deposit known as sapropel s5 which formed 124 119 thousand years ago ka b p where b p references year 1950 combining planktonic foraminiferal abundance records with stable isotope and organic biomarker data we reconcile the apparently contradicting coexistence of deep dwelling foraminiferal faunas with green sulphur bacteria that indicate photic zone euxinia s5 started with a rapid freshwater induced increase of density stratification that inhibited vertical mixing and deepwater ventilation through the first 900 years anoxic to euxinic deepwater conditions developed and extended up to roughly 200 m water depth then followed a 4100 year period of variability in the depth intensity of winter mixing with a roughly 1400 year periodicity coincident with fluctuations in water column stability s5 terminated with a marked decrease in density stratification and consequently renewed convective overturn

benthic phosphorus regeneration net primary production and ocean anoxia a model of the coupled marine biogeochemical cycles of carbon and phosphorus we examine the relationships between ocean ventilation primary production water column anoxia and benthic regeneration of phosphorus using a mass balance model of the coupled marine biogeochemical cycles of carbon c and phosphorus p the elemental cycles are coupled via the redfield c p ratio of marine phytoplankton and the c p ratio of organic matter preserved in marine sediments the model assumes that on geologic timescales net primary production in the oceans is limited by the upwelling of dissolved phosphorus to the photic zone the model incorporates the dependence on bottom water oxygenation of the regeneration of nutrient phosphorus from particulate matter deposited at the water sediment interface evidence from marine and lacustrine settings modern and ancient demonstrates that sedimentary burial of phosphorus associated with organic matter and ferric oxyhydroxides decreases when bottom water anoxia dysoxia expands steady state simulations show that a reduction in the rate of thermohaline circulation or a decrease of the oxygen content of downwelling water masses intensifies water column anoxia dysoxia and at the same time increases surface water productivity the first effect reflects the declining supply of oxygen to the deeper parts of the ocean the second effect is caused by the enhanced benthic regeneration of phosphorus from organic matter and ferric oxyhydroxides sedimentary burial of organic carbon and authigenic calcium phosphate mineral francolite on the other hand is promoted by reduced ocean ventilation according to the model global scale anoxia dysoxia leads to a more efficient recycling of reactive phosphorus within the ocean system consequently higher rates of primary production and organic carbon burial can be achieved even when the continental supply of reactive phosphorus to the oceans remains unchanged

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

revised tuning of ocean drilling program site 964 and kc01b mediterranean and implications for the δ18o tephra calcareous nannofossil and geomagnetic reversal chronologies of the past 1 1 myr 1 high resolution color reflectance records of kc01 and kc01b calabrian ridge ionian sea are presented and compared with a modified spliced high resolution color reflectance record of ocean drilling program odp site 964 this comparison revealed that kc01b is characterized by intensive deformation between 27 and 28 5 m piston depth and that some sapropels are tectonically reduced in thickness moreover the piston coring has caused considerable stretching in the top of kc01 and kc01b using a new splice of odp site 964 as guide previous astronomical tuned timescales of kc01b and odp site 964 were evaluated this evaluation resulted in a new sapropel based astronomical timescale for the last 1 1 myr the new timescale implies a much more uniform change in sedimentation rate for the ionian sea cores two prominent excursions to lighter values in the 18o record of the planktonic foraminiferal species globigerinoides ruber occur during marine isotopic stages 12 and 16 applying the new timescale these shifts correspond with maxima in obliquity and are punctuated by minima in the precession cycle they are absent in global ice volume records and are interpreted as reflecting a summer low salinity surface water lens that floats on top of extremely saline intermediate and deep waters at times of the very low sea levels during these glacial periods all biostratigraphic and magnetostratigraphic events found in kc01b and odp site 964 were re dated according to the new timescale and the ages of 33 tephra layers were reviewed the new ages for the calabrian ridge 2 and 3 magnetic events in the brunhes are concordant with minima in the global sint800 composite record derived from worldwide deep sea records of relative paleointensity and have been attributed to the big lost and la palma excursions respectively

influence of water column anoxia on the burial and preservation of carbon and phosphorus in marine shales abstract organic p and organic c concentrations were measured in several well characterized phanerozoic marine shale sequences with the primary focus being the camp run member of the devonian mississippian new albany shale sequences were selected with close spatial association of bioturbated and laminated sediments which reflect deposition from oxic and anoxic waters respectively average organic c p mole ratios calculated from the data are 150 for bioturbated shales and 3900 for the laminated shales of the new albany differences in the extent and mechanisms of early diagenesis related to the oxygenation of waters at the sediment water interface can account for the c p ratios of buried organic matter low c p ratios of bioturbated sediments are attributed to 1 1 the increased ability of bacteria to store p in well oxygenated environments which leads to the production of low c p ratio bacterial biomass and 2 2 the extensive oxidation of sedimentary organic matter resulting in the formation of residual organic phases with low c p ratios high organic c p ratios of laminated sediments are explained by a combination of 1 1 the limited ability of bacteria to store p under anoxic conditions 2 2 extensive p regeneration from sedimentary organic matter 3 3 enhanced c preservation relative to the bioturbated shales it is also shown that relative to organic c laminated shales are not as effective a p sink as are bioturbated shales this provides a mechanism in anoxic environments for burying large quantities of organic matter without simultaneously sequestering the p needed to sustain further productivity

geochemical evidence for high resolution variations during deposition of the holocene s1 sapropel on the cretan ridge eastern mediterranean abstract major and minor element distributions and solid phase phosphorus contents were measured in a sediment core from the cretan ridge that contains the holocene s1 sapropel micro xrf ultra high resolution analysis reveals multiple mn peaks in the oxidized upper portion of the sapropel which implies either a non steady state upward remobilization of mn or not constant downward diffusion of bottom water oxygen sequential extraction allowed the identification of different phosphorus phases detrital phosphorus increases in the sapropel layer suggesting enhanced delivery from land during sapropel deposition higher organic carbon to organic phosphorus ratios in the sapropel indicate enhanced regeneration of phosphorus relative to carbon under low oxygen conditions fourier analysis on the ultra high resolution xrf data reveals frequencies that are provisionally assigned to millennial to decennial solar cycles although these cycles have been reported from several continental and marine archives they have never been documented from sapropel s1 in the eastern mediterranean

surface deformation in houston texas using gps abstract surface deformation in the houston area has been quantified by using a variety of methods including lidar insar extensometers drilling to approximately 100 m and ground penetrating radar in this paper we report on gps data acquired during the period between 1995 and 2005 that found evidence of ongoing subsidence up to 56 mm year in northwestern houston and of possible horizontal surface movement towards the gulf of mexico up to 6 mm year we describe the methods of data processing used in the study and speculate on the possibility that the active elevation of salt domes mainly at the south and east of the city may indirectly influence other surface movements including fault movements and subsidence over areas 1 km 2 making use of our observations and analysis could help in natural hazard mitigation in the houston area and possibly also indicate approaches to surface subsidence study that might be used in other urban areas

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

pliocene holocene evolution of depositional conditions in the eastern mediterranean role of anoxia vs productivity at time of sapropel deposition a multiproxy geochemical study of nine sapropel layers from odp hole 964a odp leg 160 in the eastern mediterranean spanning the pliocene holocene time interval provides new insights into the evolution of sapropel deposition paleoenvironmental proxies were used for reconstruction of productivity ba derived from marine barite oxygen conditions trace metal ratios and sedimentary regime clay minerals detrital elements these proxies reveal a significant increase in river runoff relative to decreasing aeolian input during sapropel deposition over the whole time interval ba excess supports the argument that a significant increase in export productivity is the main triggering mechanism for sapropel deposition although preservation also played an important role furthermore major differences exist in depositional conditions including both oxygenation and productivity since the pliocene productivity fluctuated substantially and was higher during the pliocene and pleistocene than during the holocene at the same time decreasing oxygen availability parallels the enhanced productivity dysoxic to anoxic conditions appear to coincide with marine productivity maxima thus suggesting that oxygen depletion may be linked to greater consumption rather than restricted circulation this correspondence supports the hypothesis that productivity fluctuations resulting from climate oscillations were the main cause of enhanced organic matter contents and also a main controlling factor for reduced oxygen availability

evidence for enhanced phosphorus regeneration from marine sediments overlain by oxygen depleted waters phosphorus regeneration and burial fluxes determined from in situ benthic flux chamber and solid phase measurements at sites on the californian continental margin peruvian continental slope north carolina continental slope and from the santa monica basin california are reported comparison of these sites indicates that o2 depleted bottomwaters enhance p regeneration from sediments diminishing overall phosphorus burial efficiency based on these observations a positive feedback linking ocean anoxia enhanced benthic phosphorus regeneration and marine productivity is proposed on shorter timescales these results also suggest that o2 depletion in coastal regions caused by eutrophication may enhance p regeneration from sediments thereby providing additional p necessary for increased biological productivity

late quaternary sedimentation in the tyro and kretheus basins southeast of crete abstract this paper summarizes micropaleontologic foraminifera calcareous nannoplankton radiolaria pteropods and pollen grains and sedimentologic piston core data from the eastern mediterranean tyro and kretheus basins 14 c datings indicate a holocene age for the tyro basin cores the latter show anoxic bottom conditions throughout while the kretheus basin core indicates anoxic conditions prior to 3000 years ago and oxic conditions after that time resedimentation through slumps turbidity currents and from suspension resulted in high sediment accumulation rates in both basins reworking in the tyro basin predominantly originated from the basin flanks while the presence of common to abundant metamorphic clastics in the kretheus basin points to a more distant source the minoan eruption of santorini ca 3350 yrs b p which is supposed to have caused a gigantic tsunami is linked to the presence of turbidites and a thick homogenite in the tyro basin the same event may be responsible for the initiation of oxic conditions in the kretheus basin