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

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

the palaeontology and dating of the weybourne crag an important marker horizon in the early pleistocene of the southern north sea basin abstract in the north sea basin the marine bivalve macoma balthica first appears within the early pleistocene weybourne crag which forms an important biostratigraphical datum here we review the fossil assemblages from sites of this age prompted by new discoveries from sidestrand norfolk uk the molluscan assemblages from this horizon are dominated by intertidal species with some colder deeper water taxa and a few temperate non marine species a high boreal low arctic marine environment with reduced salinities is indicated an extensive assemblage of small mammals dominated by voles includes two species mimomys hordijki and ungaromys dehmi previously unknown from the british pleistocene the assemblage can be assigned to tesakov s mammal biozone mnr1 mn17 middle villafranchian which according to current estimates corresponds to a date of 2 2 2 1 ma mis 84 79 it matches another assemblage from 61 m to 65 m in the zuurland 2 borehole in the netherlands and is similar to that from the dutch tiglian type site at tegelen although this has more temperate elements a late tiglian age is consistent with the co occurrence of the marine bivalves macoma balthica mya arenaria and the freshwater gastropod viviparus glacialis in the zuurland 2 borehole and in a north sea borehole bgs 52 02 472 a macoma balthica mya arenaria concurrent range zone is defined for this assemblage which can be traced across the north sea basin amino acid dating provides strong independent support for these correlations and indicates that the baventian cold stage post dates the bramertonian norwich crag it also confirms that early pleistocene molluscan assemblages with m balthica are younger than those without it the correlation of this marine marker horizon with mammal biozone mnr1 provides a secure link between continental and marine sequences during the early pleistocene it also provides a basis for dating events in the pre glacial fluvial drainage history and linking it to the east european mammal zonation

calabrian eopleistocene micromammal assemblages from the lacustrine and fluvial deposits of the southern trans urals and chronological position of some regional stratigraphic units abstract in the southern trans urals the quaternary deposits dated back to the early pleistocene 2 58 0 77 ma are scarce incomplete and often severely eroded data scarcity is a major challenge for accurate geological correlation and for integration of regional data into continent wide stratigraphic frameworks we provide a review of stratotypes and type localities for regional stratigraphic subdivisions of the eopleistocene the units correlated with the calabrian stage of the western european stratigraphical timescale 1 8 0 77 ma with particular focus on small mammals and their biochronological significance subdivisions of the eopleistocene which have been officially accepted in russia include three regional chronostratigraphic units horizons starting from uvel ka to chumlyak and sarykul we show that the calabrian deposits are characterized in the southern trans urals by sequential changes in the evolutionary level of micromammal assemblages that could be directly correlated with the mammal based biochronological zones mqr of russia vangengeim and tesakov 2008 tesakov and titov 2013 within the interval from mqr 10 to mqr 8 analysis of micromammal assemblages reveals incongruent positioning of the officially accepted uvel ka chumlyak and sarykul horizons in the regional stratigraphic chart the revealed incongruences appear to be a result of the difficulty to delineate chronostratigraphic units using the highly eroded and reworked sediments of fluvial origin the complete cycles of alternating fluvial lacustrine sedimentation and subaerial exposure provide the most reliable sections to establish the chronostratigraphic units of the calabrian stage of the early pleistocene in the southern trans urals the position of chumlyak and sarykul horizons in the regional stratigraphic chart of the southern trans urals is proposed to be changed the validity of the uvel ka formation as a chronostratigraphic unit should be further verified with a particular focus on faunal proxies mollusks ostracods and small mammals

deposition of sapropel s1 sediments in oxic pelagic and anoxic brine environments in the eastern mediterranean differences in diagenesis and preservation sediments from a boxcore in the previously anoxic brine filled poseidon basin eastern mediterranean have been studied and compared to sediments deposited in a normal eastern mediterranean environment the boxcore can be divided into three main sedimentary intervals based on ams radiocarbon ages foraminiferal and geochemical zonations from the base of the core upwards these are 1 12 3 31 2 cm organic rich sediments redeposited from within the brine 2 6 6 12 3 cm sediment containing a cold foraminifera fauna redeposited from above the brine into the basin while the brine was still present 3 0 6 6 cm oxic pelagic sediment accumulated since the reoxygenation of poseidon basin which occurred1800 yrs bp near the base of the latter unit a mn oxide peak has formed and it marks the present boundary between oxic and suboxic environments a progressive downward oxidation front which is usually found in normal sapropel s1 sediments has never formed in poseidon basin sediments this has resulted in the preservation of the relationship between organic carbon and organic related trace elements e g se in the organic rich sediments of poseidon basin whereas such a relationship has been obliterated in normal sapropel s1 sediments on the basis of the carbonate content as well as the sr ca ratio preservation of carbonates appears to be better in the brine sapropel sediments of bc15 than it is in normal sapropel s1 sediments the high opal content of bc15 shows that biogenic opal is also much better preserved the overall lower corg ba ratio in bc15 suggests a better preservation of barite relative to that of organic carbon in shallow brine sediments but is as yet inconclusive for the organic carbon preservation potential of brine relative to normal unoxidised sediments 1999 elsevier science b v all rights reserved

benthic foraminiferal response to variations in surface water productivity and oxygenation in the northern arabian sea abstract a benthic foraminiferal record of 120 000 year obtained from the base of the oxygen minimum zone omz at a site in the northern arabian sea was studied quantitative benthic foraminiferal data were compared with palaeoproductivity indices corg and globigerina bulloides and indices for bottom water oxygen concentration pteropod preservation index mo al v al and mn al the benthic foraminiferal record revealed two distinct assemblages that show variations in the precession frequency band a high diversity low equitability assemblage proliferates in isotopic stages 1 4 and 5 and has been interpreted to reflect relatively oxygenated bottom water conditions this assemblage shows a strong covariance with minima in summer monsoon productivity a low diversity low equitability fauna typically with a few species showing high dominances is considered to reflect low bottom water oxygen conditions related to eutrophic surface water conditions dominating species in this assemblage are bolivinids buliminids and globobuliminids this assemblage dominates during precession driven maxima in summer surface water productivity and also during isotopic stages 2 and 3 we suggest that an intensified and colder glacial winter ne monsoon led to increased winter production which superimposed on the precession driven changes in surface water productivity resulted in overall poorly oxygenated bottom water during glacial stages 2 and 3 a promising proxy for tracing winter productivity in the northern arabian sea is the planktonic foraminifer globigerina falconensis the benthic foraminiferal species rotaliatinopsis seminvoluta in particular is prolific under glacial conditions

post depositional migration of elements during diagenesis in brown clay and turbidite sequences in the north east atlantic abstract two cores from a ne atlantic pelagic clay area of low accumulation rate each contain a single turbidite with different age thickness and composition diagenesis following introduction of exotic turbidite material into the pelagic clay sequence has resulted in distinctive colour changes the diagenetic process is thought to be driven by bacterially mediated organic oxidation and compositional differences in the turbidites and clays allow examination of the effects on metal concentrations of this process in one core a long turbidite section emplaced 330 000 years ago is overlain by clay organic oxidation has apparently proceeded from the turbidite top downwards and has maintained a u concentration peak below the oxidation front marked by a colour change the u source is believed to be u initially associated with the organic matter in the oxidised section of the turbidite vanadium and cu behave similarly but upward migration of the redox sensitive metals mn and ni is also seen in the second core an 8 cm turbidite section was emplaced about 170 000 years ago in a clay column in this case organic consumption now appears complete but evidence for diagenetic effects is found in a 16 cm compositional alteration halo of the underlying pelagic clay fe ii has been enriched and the hydrogenous component of mn co ni and cu removed from the pelagic clay to form the halo

authigenic sulfide and carbonate mineral formation in holocene sediments of the baltic sea formation of authigenic sulfides and carbonates in holocene 14c dated sediments is interpreted based on analyses of cations fes s fes2 s corg and sulfur isotopes mineral distribution was studied in thin sections and mineral morphology with sem eds the sediments were deposited in the gotland deep baltic sea during freshwater and brackish stages calcium rich rhodochrosite mnco3 occurs in concentrations up to 17 dw in brackish water sediments and are mainly confined to 0 02 0 5 mm thick laminae the frequency with which these laminae occur suggests that they formed with a periodicity of one to a few years and their purity suggests that formation took place in a few weeks we propose that these carbonate laminae resulted from oxic water inflow to the euxinic basin mn ii dissolved in the water column was rapidly oxidized and large amounts of mn oxides reached the sediment reduction of these mn oxides in a high alkalinity environment facilitated rhodochrosite precipitation at the sediment surface pyrite in the brackish water sediments formed at or above the sediment water interface in an iron limited environment due to alternating oxic and euxinic conditions fes was oxidized resulting in a high fes2 sfes s ratio median 170 formation of iron sulfides in the freshwater sediments occurred below the sediment water interface in a sulfate limited environment as a result of the rapid exhaustion of reactive iron in the brackish water sediments excess h2s diffused downwards to pyritize the uppermost part of the underlying freshwater sediments

middle and late quaternary depositional sequences and cycles in the eastern mediterranean although most of the quaternary sediments of the eastern mediterranean appear reworked extensive areas of hemipelagic sediments occur mainly in the central part of the basin mediterranean ridge the most obvious character of these muddy sediments is the numerous changes in colour they result from the organic carbon content as well as from concentration and chemical form of metallic elements mn fe cu zn the succession of coloured layers is arranged into sequences developed between two sharp contacts a complete sequence involves five lithofacies from an oxidized layer at the base to a reduced sapropel at the top and displays progressive internal changes of colour from ochre beige greyish beige grey and black layers several sequence variants top truncated base truncated recurrent are identified these sequences are a consequence of changes in oceanographic conditions i e from oxidizing to reduced environments resulting in different organic and mineral contents based on detailed studies of quaternary sediments collected by coring a synthesized standard succession representative of the ordered sequences in the eastern mediterranean is proposed from about 650 000 yr as deduced from the calculated rate of sedimentation of 1 7 mm 1000yr 1 this succession appears modulated by cyclic events large scale periods 200 000 yr of reduced and oxidized sequences correlate with major alternate phases of flooding and reduced flow of the nile river during the quaternary subsequent sequences of shorter time scale 20 000 50 000 yr results from two factors heaviest monsoons leading to an increase of the influx of the nile river and global climatic changes eurasian ice sheet meltwater these two factors act synchronously or independently along the studied time span these interplaying factors result in periodic stages of increasingly restricted conditions in the basin and explain the complexity of the eastern mediterranean succession at least since 650 000 yr ago

the behaviour of manganese in atlantic carbonate sediments abstract manganese porewater and solid phase data are considered from two different atlantic carbonate sediments both with good geochemical characterisation the first case is a continuously accumulated alternating pelagic marl carbonate ooze where there is a correlation in post oxic conditions between mn ii porewater levels and an acetate leachable mn fraction of the sediment this leachable mn appears to have an association with calcite and in this example the leached residue mn content approximates to that of shale in the second case a very recent compositionally homogeneous calcareous turbidite is underlain by mn oxyhydroxide at the former sediment surface which is now acting as a source of mn ii by reduction sorption of mn by the turbidite sediment and shale like leached residue mn levels in anoxic conditions are again observed as mn ii diffuses towards present oxic conditions although no unique equilibrium is achieved similar older buried turbidites have concentration decreases in solid phase mn content preserved from bottom to top as relict evidence that this process has occurred in these turbidites 54 64 of the total mn is leachable by the acetate method and therefore presumed to be sorbed by calcite the oldest example has persisted for 125 kyr it is suggested that the slow breakdown of metastable mn oxyhydroxide and sorption of mn ii to calcite surfaces are important controls on the behaviour of mn in pelagic carbonates in mildly reducing conditions where accumulation fluctuations occur these processes act together with accumulation to limit overall mn migration and to prevent the large mn enrichments seen near the sediment surface in more reducing environments

late pleistocene variability of arabian sea summer monsoon winds and continental aridity eolian records from the lithogenic component of deep sea sediments the modern indian ocean summer monsoon is driven by differential heating between the asian continent and the indian ocean to the south this differential heating produces a strong pressure gradient which drives southwest monsoon winds during june july and august satellite and meteorological observations aerosol measurements sediment trap studies and mineralogical studies indicate an atmospheric mode of transport for modern lithogenic sediments in the northwest arabian sea analyses of lithogenic grain size and mass accumulation rate mar records from the owen ridge indicate that eolian transport has been the primary mode of transport for the past 370 kyr visual inspection shows that the mar record is positively correlated with global ice volume as indicated by the marine 18o record in contrast the grain size record varies at a much higher frequency showing little correlation to either the mar or the 18o records spectral analyses confirm these relationships indicating that the lithogenic grain size and mar records are coherent only over the precession band whereby the grain size leads the mar by 124 8 kyr we conclude that an eolian transport mechanism is the only mechanism that allows for this phase difference and at the same time is supported by comparison of the grain size and mar with independent eolian records we use lithogenic grain size as a paleoclimatic indicator of summer monsoon wind strength and lithogenic mar as a paleoclimatic indicator of source area aridity these interpretations are supported by comparison of the lithogenic records to independent indicators of wind strength globigerina bulloides upwelling record and aridity a loess record from central china such comparisons indicate high coherence and zero phase relationships our work supports the findings of previous studies which have documented the link between monsoon strength and the earth s axial precession cycles both the lithogenic mar and the grain size records have high coherency with precessional insolation maximum lithogenic mar source area aridity is in phase with 18o global ice volume and leads maximum precessional insolation by 88 6 kyr we attribute this lead to the influence of glacial conditions on the aridity and therefore the deflation potential of the source areas maximum lithogenic grain size summer monsoon wind strength lags maximum precession by 148 9 kyr we attribute this lag both to the influence of global and or local ice volume and to the availability of latent heat from the southern hemisphere indian ocean the two of which combine to determine the strength of the indian ocean monsoon

a luminescence dating study of loess deposits from the beglitsa section in the sea of azov russia abstract the loess palaeosol deposits at the beglitsa section in the east european plain play an important role in the understanding of climate and environmental changes in eurasia however the absence of absolute geochronology has restricted the interpretation of the loess sedimentation process and its relevance to palaeoenvironmental change in this paper a detailed chronology was obtained from the beglitsa section using a quartz optically stimulated luminescence osl dating technique in the southern area of the east european plain grains with a diameter of 38 63 m extracted from 8 samples and a single aliquot regenerative dose sar protocol were applied for equivalent dose de determination the results showed that the osl ages are generally in agreement with the field observed stratigraphic order and no age inversions were apparent compared with magnetic susceptibility and previously published radiocarbon ages the osl dating results showed great potential to provide a reliable chronology sequence for loess sediments in the sea of azov with a span ranging from 5 4 0 4 to 203 8 18 0 ka deposition of the azov loess may have begun during the penultimate glaciation based on a comparative analysis of the stratigraphic composite the sedimentary thickness differences between sections around the azov region were likely affected by the local topography and the location

the reset project constructing a european tephra lattice for refined synchronisation of environmental and archaeological events during the last c 100 ka this paper introduces the aims and scope of the reset project response of humans to abrupt environmental transitions a programme of research funded by the natural environment research council uk between 2008 and 2013 it also provides the context and rationale for papers included in a special volume of quaternary science reviews that report some of the project s findings reset examined the chronological and correlation methods employed to establish causal links between the timing of abrupt environmental transitions aets on the one hand and of human dispersal and development on the other with a focus on the middle and upper palaeolithic periods the period of interest is the last glacial cycle and the early holocene c 100 8 ka during which time a number of pronounced aets occurred a long running topic of debate is the degree to which human history in europe and the mediterranean region during the palaeolithic was shaped by these aets but this has proved difficult to assess because of poor dating control in an attempt to move the science forward reset examined the potential that tephra isochrons and in particular non visible ash layers cryptotephras might offer for synchronising palaeo records with a greater degree of finesse new tephrostratigraphical data generated by the project augment previously established tephra frameworks for the region and underpin a more evolved tephra lattice that links palaeo records between greenland the european mainland sub marine sequences in the mediterranean and north africa the paper also outlines the significance of other contributions to this special volume collectively these illustrate how the lattice was constructed how it links with cognate tephra research in europe and elsewhere and how the evidence of tephra isochrons is beginning to challenge long held views about the impacts of environmental change on humans during the palaeolithic

temporal variability in the northern arabian sea oxygen minimum zone omz during the last 225 000 years the northern arabian sea is one of the few regions in the open ocean where thermocline water is severely depleted in oxygen the intensity of this oxygen minimum zone omz has been reconstructed over the past 225 000 years using proxies for surface water productivity water column denitrification winter mixing and the aragonite compensation depth acd changes in omz intensity occurred on orbital and suborbital timescales lowest o2 levels correlate with productivity maxima and shallow winter mixing precession related productivity maxima lag early summer insolation maxima by 6 kyr which we attribute to a prolonged summer monsoon season related to higher insolation at the end of the summer periods with a weakened or even non existent omz are characterized by low productivity conditions and deep winter mixing attributed to strong and cold winter monsoonal winds the timing of deep winter mixing events corresponds with that of periods of climatic cooling in the north atlantic region

vertex manganese transport through oxygen minima abstract manganese transport through a well developed oxygen minimum was studied off central mexico 18 n 108 w in october november 1981 as part of the vertex vertical transport and exchange research program refractory leachable and dissolved mn fractions associated with particulates caught in traps set at eight depths 120 1950 m were analyzed particles entering the oxygen minimum had relatively large mn loads however as the particulates sank further into the minimum total mn fluxes steadily decreased from 190 nmol m 2 day 1 at 120 m to 36 nmol m 2 day 1 at 400 m manganese fluxes then steadily increased in the remaining 800 1950 m reaching rates of up to 230 nmol m 2 day 1 at 1950 m manganese concentrations were also measured in the water column dissolved mn levels 1 were consistently observed within the 150 600 m depth interval in contrast suspended particulate leachable mn amounts were especially low at those depths and never exceeded 0 04 nmol kg 1 the combined water column and particle trap data clearly indicate that mn is released from particles as they sink through the oxygen minimum rate of change estimates based on trap flux data yield regeneration rates of up to 0 44 nmol kg 1 yr 1 in the upper oxygen minimum 120 200 m however only 30 of the dissolved mn in the oxygen minimum appears to be from sinking particulate regeneration the other 70 probably results from continental slope release horizontal transport processes dissolved mn scavenges back onto particles as oxygen levels begin to increase with depth scavenging rates ranging from 0 03 to 0 09 nmol kg 1 yr 1 were observed at depths from 700 to 1950 m these scavenging rates result in mn residence times of 16 19 years and scavenging rate constants on the order of 0 057 yr 1 manganese removal via scavenging on sinking particles below the oxygen minimum is balanced by mn released along continental boundaries and transported horizontally via advective diffusive processes manganese appears to be very weakly associated with particulates nevertheless the amounts of mn involved with sinking biogenic particles are large and the resulting fluxes are on the same order of magnitude as those necessary to explain the excess mn accumulating on the sea floor the overall behavior of mn observed in this and other studies strongly suggests some type of equilibrium occurring between dissolved and particulate phases this equilibrium appears to shift in direct or indirect response to dissolved oxygen levels

manganese and iron in indian ocean waters abstract the first vertical profiles of dissolved mn and fe for the nw indian ocean are reported the area is characterized by seasonal upwelling and a broad oxygen minimum zone in intermediate waters the dissolved fe profile exhibits a maximum 5 1 nm in the oxygen minimum zone with low values both in surface waters 0 3 nm and deep waters around 1 nm mn concentrations in the surface waters are elevated 2 0 4 3 nm and decrease rapidly in an offshore direction below the first 25 m concentrations decrease dramatically 0 5 1 3 nm indicating removal by oxidation and particle scavenging further down various mn maxima are observed which can be related to hydrographic features sigma 1 1 intermediate water originating from the red sea lost its dissolved o2 while flowing northward along the omani coast and exhibits a strong mn maximum 4 6 6 5 nm coincident with the deep o2 minimum 2 2 at the two inshore stations in the gulf of oman this is overlain by relatively modest mn maxima 2 7 nm related to arabian gulf overflow water 3 3 finally the strong mn maxima 4 4 5 6 nm in the oxygen minimum zone at the two offshore stations are related to yet another watermass below these various maxima concentrations decrease gradually to values as low as 90 pm at 2000 meters depth towards the seafloor concentrations increase again leading to a modest bottom water maximum 0 7 1 5 nm the overall vertical distributions of mn and fe are strikingly similar also in actual concentrations to those previously reported for the eastern equatorial pacific an area also characterized by an extensive o2 minimum zone

modification and complete removal of eastern mediterranean sapropels by postdepositional oxidation sapropels unusually dark organic rich sediment layers whose origin is controversial are widespread in the eastern mediterranean the upper surfaces of these layers appear sharp and show little evidence of bioturbation it has been suggested that postdepositional oxidation may have removed the dark coloration from the upper part of the original layer so that the top of the visible layer now lies somewhat below the original position of the sapropel top such a diagenetic alteration has considerable implications for the interpretation of the sedimentary record where the tops of dark layers are usually correlated with the cessation of sapropel formation geochemical data demonstrate that all visual evidence of a thin example of the most recent eastern mediterranean sapropel has been removed from the sedimentary record by oxidation processes such a process may have thinned all sapropel units by several centimetres the most recent period of sapropel formation probably ended as recently as 5 ka cf cited values between 6 0 and 7 6 ka

distribution of various extracted phosphorus compounds in the interbedded turbiditic pelagic sediments of the madeira abyssal plain eastern north atlantic abstract a sequential extraction scheme was used to differentiate different p fractions in the interbedded turbiditic pelagic sediments of the madeira abyssal plain these fractions were carbonate associated exchangeable phosphate pex iron and aluminium associated phosphate poh calcium associated phosphate apatite phcl organic phosphorus porg and remaining phosphorus pr the pex forms a minor fraction of the total sedimentary phosphorus ptot whereas for most samples phcl represents near 80 of the ptot the amount of p in most fractions appears to be determined by the composition and provenance of the various turbidites the relatively high pex and the moderately high apatite p phcl for the sediment of turbidite e organicrich turbidite provenance group may point to a source area that is possibly upwelling related on the other hand the high phcl for the sediments of the turbidites b g n o p corresponds nicely to their volcanic and near coastal provenance area in contrast to this major impact of inherited p only a small contribution comes from p that is associated to post depositional re allocation of fe poh this results in a poh concentration that is slightly higher in the upper post depositionally oxidized layer of a turbidite than it is in the lower still un oxidized layer of the same turbidite in addition this postdepositional oxidation of the upper layer of a turbidite may also result in enhanced fe and p levels in the overlying pelagic interval the c p molar ratio for organic matter in these sediments is much higher than that reported for more recent sediments and for average marine plankton 1200 versus 500 and 106 respectively which may be caused by postdepositional differential decomposition of organic matter

early pleistocene tiglian sites in the netherlands a revised view on the significance for quaternary stratigraphy abstract the tiglian a b and c form the main subdivision of the early pleistocene tiglian stage in northwest european chronostratigraphy since the 1960 s we re evaluated the sedimentary context and new and legacy pollen assemblages of the classic type localities of these tiglian pollen zones in the dutch german border area and roer valley graben following recalculation of new upland pollen sums we found that the three fold subdivision of the tiglian stage is too simplistic and lacks a sound stratigraphic basis the tiglian a is only found locally and cannot be positively identified in the rvg the tiglian b in the tegelen maalbeek area is not unique since similar occurrences are present at other depths in the rvg sedimentary and pollen analysis suggests tiglian c as defined in the tegelen maalbeek type area could have been deposited in a very short amount of time although this does contradict mammal data the t b c cycle preserved in the type area likely represent a single example of multiple similar early pleistocene climate cycles the sediments of the so called cool or cold phase of pollen zone t c 4c in the stratotype of the tiglian c substage are interpreted as having formed during the onset of crevassing and therefore its significance as a regional climate indicator is discussed we conclude that the extrapolation of the tiglian pollen zones into chronostratigraphical substages is questioned and it is concluded that the chronostratigraphical subdivision of the early pleistocene based on palynological characteristics and palaeobotanical analyses requires reconsideration based on independent dating and land sea record integration

lateglacial and holocene vegetation and climatic change on auckland island subantarctic new zealand auckland island is a small uninhabited subantarctic island south c 51 s of the new zealand mainland it is the southernmost outpost of tall forest in the southwest pacific pollen analysis of two closely adjacent peat cores near tree line documents climate change and forest dynamics during the lateglacial and holocene after the retreat of glaciers before 15 000 14c yr bp mountain tundra communities dominated on mineral soils under a cooler c 3 c lower climate than now by 11 000 14c yr bp a transition to chionochloa14c yr bp shrub grassland became dominant forest tree species metrosideros umbellata dracophyllum longifolium and raukaua simplex spread slowly from 10 000 14c yr bp but did not form tall forest until 5500 4000 14c yr bp despite southern ocean temperatures being warmer in the early holocene we suggest that warm cloudy low radiation environments inhibited forest growth during the early holocene in this intensely oceanic setting through promoting saturated soils and reducing net

amino acid geochronology of the type cromerian of west runton norfolk uk aminostratigraphic studies of continental deposits in the uk have hitherto relied almost exclusively on data from the aragonitic shells of non marine molluscs for dating pleistocene sequences this is usually based on the d l value of a single amino acid d alloisoleucine l isoleucine a i in the total shell proteins two genera of freshwater gastropods valvata and bithynia are used to explore the value of using multiple amino acids from the intra crystalline fraction which should be more protected from the effects of diagenesis than the inter crystalline component results are compared from both the aragonitic shells and opercula composed of calcite a more stable form of calcium carbonate in order to put the amino acid data from the west runton freshwater bed into perspective statistical analyses are used to compare them with results from the hoxnian mis 11 site at clacton on sea essex twelve protein decomposition indicators revealed that the results from the shells were not as clear cut as those from the opercula five indicators from the valvata shell suggest that west runton is older than clacton at a 95 significance level but two actually suggested a younger age seven indicators show that the bithynia shells from west runton are older than congeneric shells from clacton in marked contrast all 12 indicators isolated from the opercula demonstrate that west runton is significantly older than clacton the data are also compared with results from waverley wood an important archaeological site in the english midlands falling within the cromerian complex contrary to earlier interpretations the new amino acid data from bithynia opercula indicate that west runton is older than waverley wood a relationship now consistent with the available biostratigraphy

a chronological framework for the british quaternary based on bithynia opercula the british quaternary spanning roughly the past 2 6 million years is unmatched for the biodiversity and abundance of its fossil localities and its record of climatic contrasts however with all but the most recent deposits beyond radiocarbon range and with no readily datable volcanic rocks it has been difficult to get accurate dates for many british pleistocene deposits penkman et al have developed new analytical methods based on the intra crystalline proteins of stable biominerals in the opercula shell closure of the freshwater gastropod bithynia common in quaternary deposits they obtain confident assignments for various strata to global marine isotope stages securely placing britain s rich record of faunal and archaeological change into a broader context marine and ice core records show that the earth has experienced a succession of glacials and interglacials during the quaternary last 2 6 million years although it is often difficult to correlate fragmentary terrestrial records with specific cycles aminostratigraphy is a method potentially able to link terrestrial sequences to the marine isotope stages mis of the deep sea record1 2 we have used new methods of extraction and analysis of amino acids preserved within the calcitic opercula of the freshwater gastropod bithynia to provide the most comprehensive data set for the british pleistocene based on a single dating technique a total of 470 opercula from 74 sites spanning the entire quaternary are ranked in order of relative age based on the extent of protein degradation using aspartic acid asparagine asx glutamic acid glutamine glx serine ser alanine ala and valine val this new aminostratigraphy is consistent with the stratigraphical relationships of stratotypes sites with independent geochronology biostratigraphy and terrace stratigraphy3 4 5 6 the method corroborates the existence of four interglacial stages between the anglian mis 12 and the holocene in the terrestrial succession it establishes human occupation of britain in most interglacial stages after mis 15 but supports the notion of human absence during the last interglacial mis 5e 7 suspicions that the treeless optimum of the upton warren interstadial at isleworth pre dates mis 3 are confirmed this new aminostratigraphy provides a robust framework against which climatic biostratigraphical and archaeological models can be tested

sedimentary geochemistry of manganese implications for the environment of formation of manganiferous black shales the sedimentary geochemistry of manganese is dominated by the redox control of its speciation higher oxidation states mn super 3 and super 4 occurring as insoluble oxyhydroxides in well oxygenated environments and the lower oxidation state mn super 2 being much more soluble in oxygen deficient settings its geochemical behavior is therefore quite different in oxic and anoxic environments and where oxic and anoxic conditions are juxtaposed mn is recycled between the two environments in modern marine sediments mn is present above its crustal abundance as an oxyhydroxide in all slowly accumulating pelagic sediments of the deep ocean and in surficial deposits of continental margin environments diagenetic recycling of mn in the latter causes surficial deposits to have larger mn enrichments than in many pelagic sediments bottom sediments of permanently anoxic basins show no enrichments and have mn concentrations that are controlled solely by the aluminosilicate fraction manganese carbonates kutnohorite and calcic rhodochrosite are found only in anoxic sediments accumulating beneath surface oxic horizons and therefore under oxygenated bottom waters in many nearshore environments such enrichments are due to delivery of mn by burial of surface oxyhydroxides into the subsurface anoxic environment where they are dissolved pore water mn levels can reach saturation with respect to a mixed mn ca carbonate phase in such sediments the diagenetic origin for these phases is shown by their carbon isotope compositions which typically indicate a carbon source from decomposing organic matter the presence of mn carbonates therefore signifies that the host sediment must have accumulated under oxygenated bottom waters on the basis of this information it is proposed that in contrast to several current explanations for the formation of mn carbonates kutnohorite and rhodochrosite in ancient organic rich shales limestone and marl sequences and in many mn ore deposits the occurrence of these mineral phases indicates that the sediments originally accumulated beneath oxygenated bottom waters by analogy with the present mn carbonates could not have formed in the bottom waters of anoxic basins these diagenetic phases however did form where mn was supplied at a high rate namely by the burial of oxyhydroxide enriched surface sediments to a subsurface anoxic environment this situation could only have occurred under oxygenated bottom waters the presence of mn carbonates in ancient black shales and in some carbonate rich rocks lends strong support to the notion that these rocks did not necessarily form in anoxic basins but owe their carbon richness to a high supply of organic matter to sediments deposited under oxygenated bottom waters probably in continental margin settings

can sediment geochemistry record changes in coastal upwelling palaeoproductivity evidence from northwest africa and the arabian sea abstract the causes and consequences of organic carbon c org burial in sediments underlying regions of coastal upwelling are of profound importance to studies of palaeoceanography and palaeoclimatology alike the primary control on coastal upwelling wind stress and resulting ekman transport is linked intimately to variation in the earth s insolation record via a variety of feedback mechanisms in comparison the nutrients required to sustain productivity and the factors affecting the c org content of the sediment are related to variation in global glacial boundary conditions using a variety of geochemical indicators it is apparent that the record of upwelling off northwest africa driven by the northeast trade winds is characterized by arid glacial conditions and high wind stress sustaining elevated euphotic zone productivity the resulting c org accumulation record reflects higher palaeoproductivity during glacial episodes in contrast the arabian sea upwelling is seasonal faunal and geochemical ba al u th ratios indicators suggest strong interglacial 23 ka cyclicity in the southwest monsoon the c org record is spatially and temporally consistent but in disagreement with other palaeoproductivity indicators these results point to the decoupling of surface ocean productivity in areas of coastal upwelling from deep ocean circulation and nutrient supply this result has important consequences for driving atmospheric p co 2 changes on timescales less than that of oceanic mixing further applications of geochemical tracers to areas of coastal upwelling such as northwest africa and peru are needed urgently

manganese flux from continental margin sediments in a transect through the oxygen minimum the flux of manganese from continental margin sediments to the ocean was measured with a free vehicle benthic flux chamber in a transect across the continental shelf and upper slope of the california margin the highest fluxes were observed on the shallow continental shelf manganese flux decreased linearly with bottom water oxygen concentration and the lowest fluxes occurred in the oxygen minimum zone at a depth of 600 to 1000 meters although the flux of manganese from continental shelf sediments can account for the elevated concentrations observed in shallow coastal waters the flux from sediments that intersect the oxygen minimum cannot produce the subsurface concentration maximum of dissolved manganese that is observed in the pacific ocean

geochemical evidence for anoxic deep water in the arabian sea during the last glaciation various paleoceanographic studies have indicated that the deep ocean was probably depleted in dissolved oxygen during the last glacial period approximately 18 kyr b p delta sup 18 o stage 2 compared to present time however direct evidence of low oxygen content in the deep waters has been lacking here the authors report geochemical evidence of near anoxic conditions in the deep arabian sea during the entire last glacial cycle delta sup 18 o stages 2 3 and 4 anoxia is inferred from the concomitant enrichment of organic carbon and authigenic uranium in the glacial sections of a core from the deep eastern arabian sea the anoxic conditions during the last glacial period probably caused by a change in deep water circulation evidently enhanced preservation of organic matter and simultaneous removal of uranium from seawater 57 refs 3 figs 2 tabs

manganese scavenging and oxidation at hydrothermal vents and in vent plumes abstract hydrothermal vents provide a major source of dissolved mn ii to the oceans where concentrations range from 5 mm within the 350 c hot smokers to just above ambient seawater concentration in far field vent plumes the mn ii rich environments within warm vents and vent plumes provide a suitable habitat for mn ii oxidizing bacteria in order to compare rates of scavenging and oxidation of mn ii proximally within vent fields

late cenozoic sequences of mammalian sites in eurasia an updated correlation abstract a review of the geochronological sequence of late cenozoic mammalian sites in eurasia covering the time span from the vallesian up to the toringian is given an updated correlation chart of mammalian localities in eastern europe and asia with the chronology of the neogene and the magnetic polarity time scale is presented some new data on the phylogeny evolution distribution and biochronology of voles and lemmings in eurasia are briefly discussed

plio pleistocene geological record and small mammal faunas eastern shore of the azov sea southern european russia the shoreline of the taganrog gulf of the azov sea at the mouth of don river provides a series of extended upper pliocene and quaternary sections that have been actively studied in the last century this extraglacial region had a complex sedimentary history combining subaerial aggradation with marine fluvial and deltaic sedimentation the well exposed stratigraphical sequence and abundant palaeontological record continuously attract geologists and highlight the region as one of international importance for the addressing of numerous problems of late pliocene and quaternary stratigraphy and palaeogeography fossil mammalian faunas of the region include important eurasian biostratigraphical markers such as stenocranius ex gr hintoni gregaloides lagurini spp and mimomys savini for many years fossil remains of mammals provide decisive clues to the geological history of the region recent geological studies of reference sections have provided data on small mammals palaeomagnetism and palaeogeographical reconstructions in the northeastern part of the azovian region mammalian assemblages indicate the presence of the late pliocene late early pleistocene middle pleistocene and late pleistocene levels and in addition provide a clear biostratigraphical context for the early middle pleistocene transition

aminostratigraphical test of the east european mammal zonation for the late neogene and quaternary abstract an aminostratigraphical study was undertaken to provide an independent test of the veracity of the east european mammal zonation this important biostratigraphical scheme was originally defined from reference sites in the azov black sea region of southern russia but is now widely used to correlate late neogene and quaternary sediments across much of europe and western asia as well as yielding a series of mammal assemblages these reference sites which range in age from the late pliocene piacenzian ca 3 0 ma to late pleistocene 0 1 ma also contain calcitic opercula of two genera bithynia and parafossarulus of freshwater gastropod snails that are suitable for amino acid dating the intra crystalline protein decomposition icpd of four amino acids aspartic acid alanine valine and glutamic acid was analysed from the opercula of these two genera which showed similar patterns of protein degradation allowing both to be used for aminostratigraphy the icpd data are consistent with the relative ages inferred from the mammal biostratigraphy and also with stratigraphical hiatuses interpreted from the fossil record the temporal resolution provided by icpd data from opercula is amino acid dependent and declines in samples older than 2 ma the high variability of icpd between opercula samples at some sites suggests reworking anomalously high levels of icpd in samples from the early pleistocene site of tizdar may be due to geothermal heating from local mud volcanism this study provides the first large scale application of icpd based aminostratigraphy for the quaternary of continental europe and highlights its importance in testing regional stratigraphic schemes for the late pliocene and the pleistocene

eastern european rodent rodentia mammalia faunas from the early middle pleistocene transition abstract the rodent faunas from nine sites on the russian plain and taman peninsula corresponding to the early middle pleistocene transition have been analyzed these localities are situated in the dnieper don dniester and danube drainage basins and in the northern regions of the black and azov seas seven of the sites are associated with the upper part of matuyama reversed polarity chron and located between the beginning of jaramillo event and the brunhes matuyama boundary one of the sites was recovered from the chauda marine deposits of the black sea and referred to the very beginning of brunhes epoch the species composition of the rodent fauna sequence has been established the faunas referred to the jaramillo event 1 1 1 0 ma contain the advanced mimomys steppe lemmings prolagurus pannonicus and lagurodon arankae and allophaiomys pliocaenicus faunas were recovered from korotoyak ostrogozhsk suite roksolany zapadnye kairy and ushkalka localities the more advanced rodent faunas of the morozovian assemblage port katon site include also the first representatives of terricola karai dubina and shamin localities have been found below the brunhes matuyama boundary 0 85 ma including the first representatives of microtus microtus ex gr oeconomus and microtus arvalinus the pitymys like voles microtus stenocranius hintoni steppe lemming p pannonicus and yellow steppe lemming eolagurus argyropuloi compose the core of these faunas the litvin locality located in the deposits of the chauda transgression of the black sea and corresponding to the very beginning of the middle pleistocene contains a rodent fauna closely resembling the shamin one it yielded the remains of mimomys savini advanced a pliocaenicus p pannonicus microtus stenocranius hintoni microtus ex gr oeconomus and mcirotus arvalinus thus numerous data permit elucidation of the history of rodent faunas of the russian plain during early middle pleistocene transitions and reveal the definitive stages in their evolution

processes controlling the distribution and cycling of manganese in the oxygen minimum zone of the arabian sea abstract vertical and horizontal distributions of dissolved and particulate manganese were investigated in the arabian sea northwestern indian ocean during the 1995 spring intermonsoon period march april us jgofs process cruise 2 tn045 the region is characterized by an intense basin wide oxygen minimum zone omz that strongly influences the manganese distribution in the omz two distinct dissolved mn d mn maxima were observed at depths of 200 300 m and 600 m respectively the latter peak displayed concentration maxima of approximately 6 nanomolar and was largely confined to stations north of 19 n latitude stations n2 n7 this mid depth maximum was associated with the low oxygen core of the omz o 2 saager et al 1989 geochimica et cosmochimica acta 53 2259 2267 this signal was largely absent at stations along the southern transect likely due to oxidative scavenging of d mn to the suspended particulate phase mid depth particulate mn maxima at some southern stations stations s4 s11 appear to be remnants of this feature the upper d mn maximum 200 300 m depth was more widely distributed than the 600 m peak with d mn concentrations of 3 to as high as 8 nm at most stations east of about 62 e longitude the signal was everywhere correlated with the secondary nitrite maximum at stations within the main denitrification zone delineated by naqvi 1991 nepheloid layers presumably bacterial also were associated with this depth interval particulate mn profiles displayed corresponding concentration minima and low mn al and reactive refractory mn ratios for this same depth interval suggesting reductive dissolution of mn oxyhydroxides these observations imply that in situ microbially mediated processes may be the predominant source of d mn in the upper omz while horizontal advection is more important deeper in the water column

quaternary time scales for the pontocaspian domain interbasinal connectivity and faunal evolution the pontocaspian black sea caspian sea region has a very dynamic history of basin development and biotic evolution the region is the remnant of a once vast paratethys sea it contains some of the best eurasian geological records of tectonic climatic and paleoenvironmental change the pliocene quaternary co evolution of the black sea caspian sea is dominated by major changes in water lake and sea levels resulting in a pulsating system of connected and isolated basins understanding the history of the region including the drivers of lake level and faunal evolution is hampered by indistinct stratigraphic nomenclature and contradicting time constraints for regional sedimentary successions in this paper we review and update the late pliocene to quaternary stratigraphic framework of the pontocaspian domain focusing on the black sea basin caspian basin marmara sea and the terrestrial environments surrounding these large mostly endorheic lake sea systems

formation and solid solution behavior of ca rhodochrosites in marine muds of the baltic deeps authigenic ca rhodochrosites are found in organic rich sediments in the deep anoxic basins of the baltic sea rhodochrosite formation is apparently the result of organic matter degradation the rhodochrosite contains 10 to 40 mol caco3 and 2 to 5 mol mgco3 as determined by microprobe the composition of the carbonates at a given depth varies by about 5 mol mnco3 sem revealed the rhodochrosite to be present as globular aggregates consisting of microcrystallites dissolution features such as cavities within the aggregates are frequently observed and indicate that extensive recrystallization takes place pore waters are greatly supersaturated with respect to both rhodochrosite and calcite rhodochrosite is only found in sediments where pore waters show the highest degree of supersaturation due to ion exchange ca2 diffuses from the underlying freshwater clays this results in increasing aca2 amn2 ratios in the pore waters from the sediment surface downward in response to this the maximum caco3mnco3 ratio also increases with depth the composition of rhodochrosite which forms under these conditions may be determined by both the porewater aca2 amn2 and precipitation kinetics however if their composition is controlled solely by the aca2 amn2 in solution their behavior can be described by a regular solid solution model

the early pleistocene site of kermek in western ciscaucasia southern russia stratigraphy biotic record and lithic industry preliminary results abstract the discovery of the early pleistocene sites of bogatyri sinyaya balka and rodniki 1 on the taman peninsula in western ciscaucasia led to the recognition of a distinctive tamanian industry with a time range of 1 6 1 2 ma and with characteristics that are transitional between oldowan and acheulean archaic acheulean the site of kermek was discovered by v e shchelinsky in 2008 during investigation of the older lower pleistocene sediments exposed in the coastal cliff of the sea of azov in the vicinity of previously studied sites in this paper we present preliminary data from a multidisciplinary study of the early pleistocene site of kermek situated near to the sites of bogatyri sinyaya balka and rodniki 1 but which is significantly older this site is connected with a well studied early pleistocene late kujalnikian fluviatile shallow marine sequence these reverse magnetized deposits are characterized by freshwater and brackish water mollusks with dreissena theodori and by a small mammal fauna with allophaiomys deucalion and are dated to the latest gelasian or early calabrian ca 2 1 1 8 ma the lithic industry from the site can be attributed to the classic oldowan but with distinctive local features that include indications of advanced technologies such as the manufacture of large flakes and picks in this respect this industry is assumed to have been a genetic precursor of the later early pleistocene tamanian industry which has a well pronounced acheulean component

manganese carbonate overgrowths on foraminifera tests below the zone where manganese is remobilized as mn2 aq reductively cleaned foraminifera in deep sea sediments have much higher mnca than those in core tops and sediment traps mnca ranges from less than 20 10 6 in and above the mno2 maximum to as high as 700 10 6 in reducing panama basin sediments the most plausible explanation for this enrichment is that the tests are coated with mn carbonate overgrowths these coatings can account for a significant proportion of the mn in reduced deep sea sediments uptake of manganous ion by carbonate may explain the absence of mn nodules in areas of high carbonate accumulation extreme degrees of overgrowth can alter foram trace element values but this artifact can be avoided by avoiding foraminifera with high mn ca

the geochemistry of manganese carbonate in panama basin sediments abstract the mn distribution in panama basin area sediments and interstitial waters is discussed striking surficial mn enrichments produced by a well known diagenetic recycling process characterize the sediments of the region thermodynamic solubility calculations indicate that in at least one core interstitial waters approach saturation with respect to mnco3 a mixed carbonate phase of composition mn48 ca47 mg5 co3 was recovered from an ash band in the same core the association of this material with the coarse volcaniclastic debris is thought to result from facile manganous carbonate precipitation in sediment horizons of coarser mean grain size since sulphate reduction in the upper two metres of panama basin sediments is fairly minor little increase in alkalinity is observed and it is postulated that significant production of carbonate alkalinity is not a prerequisite for manganous carbonate generation in hemipelagic sediments a more important factor appears to be the availability of mn oxides for solution during early diagenesis stable c isotopic analyses indicate that little c of organic origin is used in the precipitation reaction in either panama basin or loch fyne scotland sediments

manganese uptake during calcite precipitation from seawater conditions leading to the formation of a pseudokutnahorite manganoan magnesian calcite overgrowths were precipitated from artificial seawater at 25 c on pure calcite seeds using a constant disequilibrium technique the composition of the overgrowths and more specifically their mn mg na and sr content was determined as a function of the precipitation rate and mn2 concentration in the parent solution x ray diffraction patterns indicate that the overgrowths produced were one phase multicomponent solid solutions and contained up to 40 mole mnco3 the amount of mn coprecipitated with calcite decreased with increasing precipitation rate thus overgrowths are not in exchange equilibrium with the solutions from which they precipitated a kinetic model is proposed which adequately describes the composition of the overgrowths in terms of the relative precipitation rate of an 8 10 mole magnesian calcite and a pseudokutnahorite from seawater the possible existence of a pseudokutnahorite in marine sediments and its implications are discussed the concentration of mg in the overgrowths decreased with increasing mnco3 content but their mg ca ratio remained nearly constant strontium and na incorporation was strongly dependent on the number of available nonlattices sites

a 225 kyr record of dust supply paleoproductivity and the oxygen minimum zone from the murray ridge northern arabian sea abstract analysis of a 15 m long sediment core recovered from the murray ridge northern arabian sea reveals a 225 000 year record of climate induced variations in surface water productivity mid water ventilation and dust input in the northern arabian sea productivity and dust input records closely resemble those from the owen ridge and oman margin also the phase lag of 10 kyr between maximum productivity and precession minimum is in phase with the summer monsoon upwelling record from the owen ridge and the oman margin this implies that the productivity variations in the northern arabian sea during the last 225 kyr are primarily controlled by changes in the indian ocean summer monsoon the winter monsoon obviously played a minor role in the productivity history of the northern arabian sea another result from this study is that the mg al record from the murray ridge nicely documents the post glacial flooding of the persian gulf which is the main glacial source for dolomite dust in this region finally it is concluded that the intensity of the omz co varies with surface water productivity being weak during periods of reduced summer monsoon especially during glacial periods

an aminostratigraphy for the british quaternary based on bithynia opercula aminostratigraphies of quaternary non marine deposits in europe have been previously based on the racemization of a single amino acid in aragonitic shells from land and freshwater molluscs the value of analysing multiple amino acids from the opercula of the freshwater gastropod bithynia which are composed of calcite has been demonstrated the protocol used for the isolation of intra crystalline proteins from shells has been applied to these calcitic opercula which have been shown to more closely approximate a closed system for indigenous protein residues original amino acids are even preserved in bithyniid opercula from the eocene showing persistence of indigenous organics for over 30 million years geochronological data from opercula are superior to those from shells in two respects first in showing less natural variability and second in the far better preservation of the intra crystalline proteins possibly resulting from the greater stability of calcite these features allow greater temporal resolution and an extension of the dating range beyond the early middle pleistocene here we provide full details of the analyses for 480 samples from 100 horizons 75 sites ranging from late pliocene to modern these show that the dating technique is applicable to the entire quaternary data are provided from all the stratotypes from british stages to have yielded opercula which are shown to be clearly separable using this revised method further checks on the data are provided by reference to other type sites for different stages including some not formally defined additional tests are provided by sites with independent geochronology or which can be associated with a terrace stratigraphy or biostratigraphy this new aminostratigraphy for the non marine quaternary deposits of southern britain provides a framework for understanding the regional geological and archaeological record comparison with reference to sites yielding independent geochronology in combination with other lines of evidence allows tentative correlation with the marine oxygen isotope record

sea surface temperatures and the history of monsoon upwelling in the northwest arabian sea during the last 500 000 years abstract arabian sea sediments record changes in the upwelling system off arabia which is driven by the monsoon circulation system over the nw indian ocean in accordance with climate models and differing from other large upwelling areas of the tropical ocean a 500 000 yr record of productivity at odp site 723 shows consistently stronger upwelling during interglaciations than during glaciations sea surface temperatures ssts reconstructed from the alkenone unsaturation index uk 37 are high up to 27 c during interglaciations and low 22 24 c during glaciations indicating a glacial interglacial temperature change of 3 c in spite of the dampening effect of enhanced or weakened upwelling the increased productivity is attributed to stronger monsoon winds during interglacial times relative to glacial times whereas the difference in ssts must be unrelated to upwelling and to the summer monsoon intensity the winter ne monsoon was more effective in cooling the arabian sea during glaciations then it is now

micromammals from the 1995 mammoth excavation at west runton norfolk uk morphometric data biostratigraphy and taxonomic reappraisal abstract in this paper the small mammals recovered from sediments associated with the west runton elephant have been analysed and compared with sites in other parts of europe major taxonomical problems are indicated and we suggest ways of utilising such morphological complexity to refine biostratigraphical and chronostratigraphic attributions the micromammal assemblage from the west runton elephant site so far totals 16 species from the west runton freshwater bed wrfb there are strong similarities with the arvicolid spectrum of basal layer h8 in the kon prusy c 718 profile czech republic which accumulated under cooler conditions preceding the thermal maximum of an early middle pleistocene interglacial rare steppic indicators e g cricetus at west runton also imply a somewhat cooler and more continental climate than the present day but overall the fauna is fully temperate in character west runton shares several stratigraphically significant small mammal taxa with voigtstedt central germany and morphometric comparisons suggest that voigtstedt may be slightly younger than west runton the presence of mimomys savini with a latest occurrence in the early part of marine isotope stage mis 15 together with the palaeomagnetic evidence suggests the wrfb may have been emplaced during the early part of mis 17 however given the complexity of the marine isotope curve during the early part of the brunhes chron and differences between global and regional climatic evolution it is difficult to assign the normally magnetised wrfb to a particular marine isotope stage mis

manganese geochemistry near high temperature vents in the mid atlantic ridge rift valley in july 1985 the first high temperature hydrothermal vents ever discovered on the mar were found at 26 n tag a transponder navigated survey of a 4 8 km area was begun when on board measurements of manganese revealed concentrated hydrothermal plumes in the water column comparable in size and intensity to those found over geothermal fields on the epr these plumes also possess anomalously high light scattering properties and anomalously warm potential temperatures using relay transponder navigation with a rosette ctd system it was possible to sample bottom waters with temperature anomalies of several decidegrees samples collected near vent orifices possessed silica anomalies of up to 17 m and dissolved manganese anomalies as large as 360 nmol kg these manganese and silica anomalies are linearly related and predict amn si ratio of 20 mmol mol for these mar vent fluids a value essentially identical to that measured in 350 c fluid from the epr at 21 n the distribution of temperature anomalies in the water column over this area requires the presence of more than one active vent site a rough estimate of the convective heat loss from this section of the mar based on z profiles is 1 2 108 cal s which is similar to the heat loss estimated for the vent field on the epr at 21 n

benthic foraminifera as proxies of organic matter flux and bottom water oxygenation a case history from the northern arabian sea abstract benthic foraminifera have been quantified in two sediment cores from a topographic high murray ridge in the northern arabian sea one core is from a station within the present day oxygen minimum zone omz the other from a station below the omz changes in the intensity of the omz linked to monsoonal climate variability had a strong impact on benthic foraminiferal composition and accumulation rates at the shallower omz station 920 m an intensification of the omz resulted in lower diversities and high dominances of low oxygen tolerant species the deeper station 1470 m was far less affected though at least once during the last 225 000 years the benthic faunal composition and accumulation rates show evidence for a deepening of the base of the omz to a level close to or even below 1470 m we suggest that percentages of miliolids can be used for rapid reconstruction of periods of increased ventilation in the northern arabian sea and are a promising proxy for tracing changes in bottom and pore water oxygenation in general omz conditions are characterised by high abundances of deep infaunal species and increased burial efficiency of organic matter the proportion of deep infaunal species appears to be a measure for the anoxic burial efficiency of organic matter and not a direct measure for the arriving flux at the seabed results furthermore show that benthic foraminiferal accumulation rates cannot be used as a proxy for surface water productivity under the prevalence of severe dysoxia