climate and environment of a pliocene warm world the pliocene epoch 5 33 2 58 million years ago ma was a generally warmer and wetter interval with atmospheric co2 concentrations at or slightly above modern levels this paper provides an overview of pliocene vegetation sea surface temperatures and climate modelling outcomes most prominent changes in pliocene biome distribution compared to today include a northwards shift of temperate and boreal vegetation zones in response to a warmer and wetter climate as well as an expansion of tropical savannas and forests at the expense of deserts faunal analysis techniques and modelling experiments using the hadley centre climate model identified significantly higher pliocene sea surface temperatures at mid and high latitudes of the northern hemisphere with cooling or unchanged sea surface temperatures at low latitudes global mean annual surface temperatures mat are estimated to have been 2 to 3 c higher during the piacenzian 3 6 2 58 ma than today with a reduced equator to pole gradient the marine realm during the pliocene was characterised by a reconfiguration of ocean gateways particularly the narrowing of the indonesian seaway and closure of the central american isthmus which produced essentially a modern pattern of ocean circulation in the southern ocean a warm early pliocene gave way to late piacenzian cooling proxy data indicate a reduced east to west sea surface temperature gradient in the tropical pacific during the pliocene warmth the pliocene is one of the most intensively studied geological intervals of the pre quaternary no other warm period in the geological past yields such a unique combination of near modern atmospheric co2 concentrations palaeogeography and palaeobiology however this paper also identifies data gaps and shortcomings in the reconstruction of pliocene environments using proxy data and climate models on which future research should focus

late quaternary history of the marmara sea and black sea from high resolution seismic and gravity core studies abstract lithologic and multi proxy paleoenvironmental data from 21 dated cores have been used to define three allostratigraphic units allounits within the late quaternary successions of the marmara sea and black sea allounits are bounded by unconformities and their correlative conformities in both regions allounit a extends from the seafloor downward to a 12 11 ka sequence boundary which is a major shelf crossing unconformity in water depths less than 100 110 m in deep basins of the marmara sea the lower part of allounit a designated subunit a2 is a laminated sapropel m1 on the shelf subunit a2 consists of backstepping delta lobes and early transgressive barrier islands and sand sheets allounit b has only been recovered in marmara sea cores collected at water depths greater than 90 m and represents basinal or prodeltaic deposition during the 23 12 ka late pleistocene lowstand during the last glacial maximum the shelves surrounding the marmara sea were subaerially exposed and deltas of allounit b accumulated along the present day shelf edge following the post glacial rise of global sea level to 75 m at 12 ka the marmara sea quickly became inundated and thereafter rose in synchroneity with the mediterranean by 10 ka the black sea rose to start spilling into the marmara sea leading to establishment of a brackish water lid that has persisted to the modern day the strongest black sea outflow began at 10 ka and persisted to 6 ka promoting the accumulation of sapropel m1 in the deep marmara sea and progradation of an overflow delta just south of the exit from the bosphorus strait allounit c is a laminated sapropel m2 in basinal cores dated at 30 23 ka like m1 it is believed that m2 accumulated during a period of increased brackish water input into the marmara sea mainly from the black sea in the black sea wave erosion kept the shelf stripped of unconsolidated sediments during the falling sea level associated with the last glaciation and subsequent early stages of the post glacial holocene transgression this erosion created a major unconformity shelf edge deltas of allounit b received their sediment during the last lowstand from small rivers that likely coalesced into a single system toward the shelf edge at modern water depths of 100 to 110 m these deltas were active until 11 10 5 ka subsequently sea level in the black sea rose to 40 m by 10 ka and a set of backstepping barrier islands developed on the shelf as part of the associated transgressive systems tract once water level reached 40 m continued sea level rise stalled until 9 ka as the black sea began to spill across the bosphorus strait into the marmara sea

similarities among the plio pleistocene terrestrial aeolian dust deposits in the world and in hungary abstract the widely distributed plio pleistocene aeolian dust deposits are one of the most important terrestrial archives of past climate and environmental changes the alternation of loess and palaeosol layers is regarded as evidence of the cyclic nature of pleistocene climate changes the loess succession is underlain by aeolian red clay which has been formed under warm humid climates according to the studies of red clay loess palaeosol sequences from china central asia alaska south america and central europe the mineral dust deposition has shown similar patterns since the pliocene the typical loess of the last one million years reflects glacial interglacial conditions whereas the old loess palaeosol sequences could be the product of shorter arid humid climate cycles the similarity of the sedimentary structures could be caused by the similar global climate conditions controlled by orbital forcing the investigated sections from hungary central europe have been affected by local and regional geomorphological and climate factors even so they can be correlated fairly well with the major global climate changes the hungarian aeolian dust deposits consist of three main groups of sedimentary formations 1 pliocene early pleistocene aeolian red clays 2 the oldest loess palaeosol sequences formed from the almost continuous early pleistocene dustfall and 3 the typical glacial interglacial loess deposits of the last one million years without remarkable dust deposition in the warmer periods

regional variations in provenance and abundance of ice rafted clasts in arctic ocean sediments implications for the configuration of late quaternary oceanic and atmospheric circulation in the arctic abstract the composition and distribution of ice rafted glacial erratics in late quaternary sediments define the major current systems of the arctic ocean and identify two distinct continental sources for the erratics in the southern amerasia basin up to 70 of the erratics are dolostones and limestones the amerasia suite that originated in the carbonate rich paleozoic terranes of the canadian arctic islands these clasts reached the arctic ocean in glaciers and were ice rafted to the core sites in the clockwise beaufort gyre the concentration of erratics decreases northward by 98 along the trend of the gyre from southeastern canada basin to makarov basin the concentration of erratics then triples across the makarov basin flank of lomonosov ridge and siltstone sandstone and siliceous clasts become dominant in cores from the ridge and the eurasia basin the eurasia suite the bedrock source for the siltstone and sandstone clasts is uncertain but bedrock distribution and the distribution of glaciation in northern eurasia suggest the taymyr peninsula kara sea regions the pattern of clast distribution in the arctic ocean sediments and the sharp northward decrease in concentration of clasts of canadian arctic island provenance in the amerasia basin support the conclusion that the modern circulation pattern of the arctic ocean with the beaufort gyre dominant in the amerasia basin and the transpolar drift dominant in the eurasia basin has controlled both sea ice and glacial iceberg drift in the arctic ocean during interglacial intervals since at least the late pleistocene the abruptness of the change in both clast composition and concentration on the makarov basin flank of lomonosov ridge also suggests that the boundary between the beaufort gyre and the transpolar drift has been relatively stable during interglacials since that time because the beaufort gyre is wind driven our data in conjunction with the westerly directed orientation of sand dunes that formed during the last glacial maximum on the north slope of alaska suggests that atmospheric circulation in the western arctic during late quaternary was similar to that of the present

quaternary ice transport in the canadian arctic and extent of late wisconsinan glaciation in the queen elizabeth islands most of the ice rafted debris in channels off the queen elizabeth islands nunavut is of local origin particularly in the inner part of the archipelago but samples from the arctic shelf contain as much as 40 grains from sources as far away as 2000 km including the siberian shelves particle transport by drifting sea ice from distant shelves is an important process on the arctic continental shelf of the queen elizabeth islands in the interior of the queen elizabeth islands and in the viscount melville and lancaster sounds particle transport is limited to distances of approximately 200 km mixing is more common among grains of coarse silt to fine sand than in the 250 m fraction but even the latter contains debris from sources far apart during the late wisconsinan the northern southern and eastern queen elizabeth islands were covered by glaciers flowing radially from ice centers on the islands into the inter island channels queens channel was completely filled by ice and a glacier lobe moved

ephemeral formation of perennial sea ice in the arctic ocean during the middle eocene arctic sea ice is a key component of the modern climate system marine sediment analyses suggest that perennial sea ice in the arctic ocean first formed transiently about 44 million years ago

sediments in arctic sea ice implications for entrainment transport and release despite the arctic sea ice cover s recognized sensitivity to environmental change the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood sea ice sediment inclusions were studied in the central arctic ocean during the arctic 91 expedition and in the laptev sea east siberian arctic region expedition 1992 results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central arctic ocean this study documents the regional distribution and composition of particle laden ice investigates and evaluates processes by which sediment is incorporated into the ice cover and identifies transport paths and probable depositional centers for the released sediment in april 1992 sea ice in the laptev sea was relatively clean the sediment occasionally observed was distributed diffusely over the entire ice column forming turbid ice observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment in the central arctic ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes the surface sediment accumulation in central arctic multi year sea ice exceeds by far the amounts observed in first year ice from the laptev sea in april 1992 sea ice sediments are generally fine grained although coarse sediments and stones up to 5 cm in diameter are observed component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles the biogenous components namely shells of pelecypods and benthic foraminiferal tests point to a shallow benthic marine source area apparently sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing clay mineralogy of ice rafted sediments provides information on potential source areas a smectite maximum in sea ice sediment samples repeatedly occurred between 81 n and 83 n along the arctic 91 transect indicating a rather stable and narrow smectite rich ice drift stream of the transpolar drift the smectite concentrations are comparable to those found in both laptev sea shelf sediments and anchor ice sediments pointing to this sea as a potential source area for sea ice sediments in the central arctic ocean sea ice clay mineralogy is significantly different from deep sea clay mineral distribution patterns the contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms

modern dirty sea ice characteristics and sources the role of anchor ice extensive dirty ice patches with up to 7 kg m 2 sediment concentrations in layers of up to 10 cm thickness were encountered in 2005 and 2007 in numerous areas across the central arctic the fe grai

sources and dispersal patterns of clay minerals in surface sediments from the continental shelf areas off alaska the three mineral suites were recognized in the gulf of alaska the glaciomarine sediments of fjords and the eastern shelf consist typically of the primary phyllosilicates micas and chlorites derived locally from argillite graywacke and metavolcanics under conditions of mild chemical weathering more glycol expandable clay minerals gecm in the north gulf substantiate clay supply to that region primarily from the yakataga and poul creek formations and to a lesser extent from the copper river the northern gulf clay mineral suite is transported to central prince william sound and northeast kodiak shelf by the alaska coastal current in the western gulf clay minerals adjacent to the alaska peninsula are derived principally from the susitna river via cook inlet whereas those of the outer shelf presumably have their provenance in kodiak island and the katmai ash submarine deposit in the southeast bering sea a progressive northwestward decrease in gecm from 65 to 11 is caused by a gradually decreased sediment export from the alaska peninsula and the aleutians with a possible minor increase in illite from the kuskokwin river the yukon river is the predominant clay source for the north bering sea as signified by an abrupt increase in that area of gecm 20 to 35 and of kaolinite chlorite ratios clay mineralogy indicates that the central chukchi sea is the major repository of the yukon clays suggesting that clay mineral stratigraphic studies have implications for interpretation of the quaternary paleogeography of beringia in the beaufort sea nearshore influence of different fluvial inputs and their dispersals by currents are sharply defined the lack of a definite pattern to the distribution of clay minerals in the outer continental shelf may be due to haphazard transport of clays by ice rafting and or reworking and redistribution of sediments resulting from ice gouging of the sea substrate movement of sediment to the west in the alaskan portion of the inner shelf of beaufort sea is evident an apparent seaward increase in illite gecm ratio in the colville delta is tentatively ascribed to regeneration of degraded illite micas by k fixation in saline waters an isolated area of sediment rich in expandable clay minerals in the central beaufort shelf presumably is relict

sea ice transport of riverine particles from the laptev sea to fram strait based on clay mineral studies the aim of this study was to identify pathways and processes of modern sediment transport from the siberian hinterland to the laptev sea and further to the arctic ocean clay mineral analyses were performed on riverine suspended particulate material spm surface sediments of the laptev sea shelf and sea ice sediments sis material collected during seven expeditions was included in this study clay mineral assemblages are used to decipher the distribution of riverine sediments on the shallow laptev sea shelf the entrainment of fine particles into newly forming ice and the transport of sis from the laptev sea towards the ablation areas a cluster analysis of our data set shows that the clay mineral assemblages of laptev sea shelf sediments and sis are controlled mainly by the input of riverine spm supplied by the khatanga lena and yana rivers whereas the western shelf clay mineral province is characterized by enhanced smectite concentrations supplied by the khatanga river the eastern laptev sea is dominated by illite discharged through the lena and yana rivers the sis smectite concentration serves as an indicator for sediment source areas on the circum arctic shelves subsequently the transpolar drift can be distinguished into a siberian branch fed from the eastern kara sea and the western laptev sea and a polar branch originating from the eastern laptev sea

the evolution of pco2 ice volume and climate during the middle miocene abstract the middle miocene climatic optimum 17 15 ma mco is a period of global warmth and relatively high co2 and is thought to be associated with a significant retreat of the antarctic ice sheet ais we present here a new planktic foraminiferal 11b record from 16 6 to 11 8 ma from two deep ocean sites currently in equilibrium with the atmosphere with respect to co2 these new data demonstrate that the evolution of global climate during the middle miocene as reflected by changes in the cyrosphere was well correlated to variations in the concentration of atmospheric co2 what is more within our sampling resolution 1 sample per 300 kyr there is no evidence of hysteresis in the response of ice volume to co2 forcing during the middle miocene contrary to what is understood about the antarctic ice sheet from ice sheet modelling studies in agreement with previous data we show that absolute levels of co2 during the mco were relatively modest 350 400 ppm and levels either side of the mco are similar or lower than the pre industrial 200 260 ppm these new data imply the presence of either a very dynamic ais at relatively low co2 during the middle miocene or the advance and retreat of significant northern hemisphere ice recent drilling on the antarctic margin and shore based studies indicate significant retreat and advance beyond the modern limits of the ais did occur during the middle miocene but the complete loss of the ais was unlikely consequently it seems that ice volume and climate variations during the middle miocene probably involved a more dynamic ais than the modern but also some component of land based ice in the northern hemisphere

evidence from the mesta half graben sw bulgaria for the late eocene beginning of aegean extension in the central balkan peninsula abstract the ene tilted mesta half graben contains a 3 km thick section of priabonian late eocene to oligocene sedimentary and volcanic rocks that rest unconformably on basement metamorphic rocks along its west side basal strata dip 50 60 e and dip at progressively lower angles upward indicating synrotational deposition the southern part of the half graben contains nested volcanic caldera complexes formed during the deposition of the middle part of the sedimentary sequence which have been rotated by about half the total rotation of the sedimentary succession the half graben is bounded on the east by a fault that steepens from more deeply exposed structural levels in the south 8 18 w to shallower exposed structural levels in the north 70 w and together with the rotation of paleogene strata during deposition indicate the mesta half graben is underlain by a listric detachment fault the mesta detachment subhorizontal middle miocene strata that unconformably overlie tilted paleogene strata yield an upper age limit to the extension west and northwest of the mesta half graben are many other nnw trending ne tilted paleogene half grabens which we suggest are part of an important extended area in sw bulgaria and eastern macedonia that lies above one or more west dipping detachment faults and date the beginning of aegean extension in the southern balkan region as at least as old as priabonian the mesta detachment is oblique to the trend of a contemporaneous paleogene magmatic arc in the southern balkans and the origin of the detachment is probably related to gravitationally induced spreading of thickened hot arc crust and hellenic trench roll back

is ice rafted sediment in a north pole marine record evidence for perennial sea ice cover ice rafted sediments of eurasian and north american origin are found consistently in the upper part 13ma bp to present of the arctic coring expedition acex ocean core from the lomonosov ridge

new insights on arctic quaternary climate variability from palaeo records and numerical modelling terrestrial and marine geological archives in the arctic contain information on environmental change through quaternary interglacial glacial cycles the arctic palaeoclimate and its extremes apex scientific network aims to better understand the magnitude and frequency of past arctic climate variability with focus on the extreme versus the normal conditions of the climate system one important motivation for studying the amplitude of past natural environmental changes in the arctic is to better understand the role of this region in a global perspective and provide base line conditions against which to explore potential future changes in arctic climate under scenarios of global warming in this review we identify several areas that are distinct to the present programme and highlight some recent advances presented in this special issue concerning arctic palaeo records and natural variability including spatial and temporal variability of the greenland ice sheet arctic ocean sediment stratigraphy past ice shelves and marginal marine ice sheets and the cenozoic history of arctic ocean sea ice in general and holocene oscillations in sea ice concentrations in particular the combined sea ice data suggest that the seasonal arctic sea ice cover was strongly reduced during most of the early holocene and there appear to have been periods of ice free summers in the central arctic ocean this has important consequences for our understanding of the recent trend of declining sea ice and calls for further research on causal links between arctic climate and sea ice

pliocene palaeoceanography of the arctic ocean and subarctic seas the pliocene is important in the geological evolution of the high northern latitudes it marks the transition from restricted local to extensive regional scale glaciations on the circum arctic continents between 3 6 and 2 4 ma since the arctic ocean is an almost land locked basin tectonic activity and sea level fluctuations controlled the geometry of ocean gateways and continental drainage systems and exerted a major influence on the formation of continental ice sheets the distribution of river run off and the circulation and water mass characteristics in the arctic ocean the effect of a water mass exchange restricted to the bering and fram straits on the oceanography is unknown but modelling experiments suggest that this must have influenced the atlantic meridional overturning circulation cold conditions associated with perennial sea ice cover might have prevailed in the central arctic ocean throughout the pliocene whereas colder periods alternated with warmer seasonally ice free periods in the marginal areas the most pronounced oceanographic change occurred in the mid pliocene when the circulation through the bering strait reversed and low salinity waters increasingly flowed from the north pacific into the arctic ocean the excess freshwater supply might have facilitated sea ice formation and contributed to a decrease in the atlantic overturning circulation

orbital scale variations and timescales from the arctic ocean we investigate geochemical measurements from the arctic coring expedition to derive sedimentation rates for selected intervals in the early and middle eocene this analysis is performed by quantifying cyclical variations in physical property data and elemental concentrations derived with an x ray fluorescence xrf core scanner our results show that physical properties and xrf derived elemental concentrations are coherent and correlated to each other changes in elemental concentrations occur on depth scales from decimeters to meters and correspond to varying contributions of detrital minerals and biogenic silica we confirm and refine sedimentation rates of the order of 10 to 25 m ma 1 these rates were obtained independently through biostratigraphic and magnetostratigraphic methods we observe a strong imprint of astronomically sourced cycles particularly through climatic precession this observation allows us to test recently proposed theoretical calculations of insolation

controls on the genesis of some high fluoride groundwaters in india india has an increasing incidence of fluorosis dental and skeletal with some 62 million people at risk high fluoride groundwaters are present especially in the hard rock areas south of the ganges valley and in the arid north western part of the country the phenomenon is related to groundwater with residual alkalinity ca2 hco3 fluoride concentrations are governed by adsorption equilibria and by fluorite solubility evapotranspiration leads to a precipitation of calcite a lowering of ca activity and increase in na ca ratios and this allows an increase in f levels in southern india mg seems to be controlled by dolomite while sepiolite and palygorskite are mg sinks in rajasthan but may then release f under alkaline conditions the latter two minerals are probably also important sources and sinks for f in the hydroxy positions the increase in the extent of sodic soils as a result of irrigation is a contributing factor to the increasing incidence of fluorosis remedial measures including addition of gypsum and rainwater harvesting are needed even in areas where the sodicity does not cause structural problems in the soil

holocene and late glacial palaeoceanography and palaeolimnology of the black sea changing sediment provenance and basin hydrography over the past 20 000 years abstract the elemental geochemistry of late pleistocene and holocene sediments of the black sea recovered in box cores from the basin margins and a 5 m gravity core from the central abyssal region of the basin identifies two terrigenous sediment sources over the last 20 kyrs one source region includes anatolia and the southern caucasus the second region is the area drained by rivers entering the black sea from eastern europe alkali metal al and heavy light rare earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early holocene lacustrine phase of the basin the shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral hosted trace elements ti and zr the geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase when high salinity mediterranean water entered the basin beginning 9 3 kyrs bp bottom water that had been oxic throughout the lake phase became anoxic at approximately 8 4 kyrs bp as recorded by the accumulation from the water column of several redox sensitive trace metals mo re u the accumulation of organic carbon and several trace nutrients cd cu ni zn increased sharply ca 0 4 kyrs later at 8 0 kyrs bp reflecting an increase of primary productivity its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages during this profound environmental change from the lacustrine to the marine phase the accumulation rate of the lithogenous sediment fraction decreased as much as 10 fold in response to the rise of the water level in the basin from a low stand ca 9 3 ka to its current level

influence of brine formation on arctic ocean circulation over the past 15 million years the early oceanographic history of the arctic ocean is important in regulating and responding to climatic changes however constraints on its oceanographic history preceding the quaternary the past 1 8 myr have become available only recently because of the difficulties associated with obtaining continuous sediment records in such a hostile setting here we use the neodymium isotope compositions of two sediment cores recovered near the north pole to reconstruct over the past approx15 myr the sources contributing to arctic intermediate water a water mass found today at depths of 200 to 1 500 m we interpret high neodymium ratios for the period between 15 and 2 myr ago and for the glacial periods thereafter as indicative of weathering input from the siberian putoranan basalts into the arctic ocean arctic intermediate water was then derived from brine formation in the eurasian shelf regions with only a limited contribution of intermediate water from the north atlantic in contrast the modern circulation pattern with relatively high contributions of north atlantic intermediate water and negligible input from brine formation exhibits low neodymium isotope ratios and is typical for the interglacial periods of the past 2 myr we suggest that changes in climatic conditions and the tectonic setting were responsible for switches between these two modes

central arctic surface ocean environment during the past 80 000 years stable oxygen and carbon isotope and sedimentological paleontological investigations supported by accelerator mass spectrometry 14 c datings were carried out on cores from north of 85 degrees n in the eastern central arctic ocean significant changes in accumulation rates provenance of ice rafted debris ird and planktic productivity over the past 80 000 years are documented during peak glacials i e oxygen isotope stages 4 and 2 the arctic ocean was covered by sea ice with decreased seasonal variation limiting planktic productivity and bulk sedimentation rates in early stage 3 and during termination i major deglaciations of the circum arctic regions caused lowered salinities and poor oxygenation of central arctic surface waters a meltwater spike and an associated ird peak dated to similar to 14 12 14 c ka can be traced over the southern eurasian basin of the arctic ocean this event was associated with the early and rapid deglaciation of the marine based barents sea ice sheet a separate termination ib meltwater event is most conspicuous in the central arctic and is associated with characteristic dolomitic carbonate ird this lithology suggests an origin of glacial ice from northern canada and northern greenland where lower paleozoic platform carbonates crop extensively out

is the central arctic ocean a sediment starved basin abstract numerous short sediment cores have been retrieved from the central arctic ocean many of which have been assigned sedimentation rates on the order of mm ka implying that the arctic basin was starved of sediments during plio pleistocene times a review of both shorter term sedimentation rates through analysis of available sediment core data and longer term sedimentation rates through estimates of total sediment thickness and bedrock age suggests that cm ka scale rates are pervasive in the central arctic ocean this is not surprising considering the physiographic setting of the arctic ocean being a small land locked basin since its initial opening during early cretaceous times we thus conclude that the central arctic ocean has not been a sediment starved basin either during plio pleistocene times or during pre pliocene times rigorous chronstratigraphic analysis permits correlation of sediment cores over a distance of 2600 km from the northwestern amerasia basin to the northwestern eurasia basin via the lomonosov ridge using paleomagnetic biostratigraphic and cyclostratigraphic data

variable eocene miocene sedimentation processes and bottom water redox conditions in the central arctic ocean iodp expedition 302 abstract in 2004 integrated ocean drilling program expedition 302 arctic coring expedition acex to the lomonosov ridge drilled the first central arctic ocean sediment record reaching the uppermost cretaceous 430 m composite depth while the neogene part of the record is characterized by grayish yellowish siliciclastic material the paleogene part is dominated by biosiliceous black shale type sediments the lithological transition between paleogene and neogene deposits was initially interpreted as a single sedimentological unconformity hiatus of 26 ma duration separating eocene from miocene strata more recently however continuous sedimentation on lomonosov ridge throughout the cenozoic was proclaimed questioning the existence of a hiatus in this context we studied the elemental and mineralogical sediment composition around the paleogene neogene transition at high resolution to reconstruct variations in the depositional regime e g wave current activity detrital provenance and bottom water redox conditions already below the hiatus mineralogical and geochemical proxies imply drastic changes in sediment provenance and or weathering intensity in the hinterland and point to the existence of another earlier gap in the sediment record the sediments directly overlying the hiatus the zebra interval are characterized by pronounced and abrupt compositional changes that suggest repeated erosion and re deposition of material regarding redox conditions euxinic bottom waters prevailed at the eocene lomonosov ridge and became even more severe directly before the hiatus with detrital sedimentation rates decreasing authigenic trace metals were highly enriched in the sediment this continuous authigenic trace metal enrichment under persistent euxinia implies that the arctic trace metal pool was renewed continuously by water mass exchange with the world ocean so the eocene arctic ocean was not fully restricted above the hiatus extreme positive ce anomalies are clear signs of a periodically well oxygenated water column but redox conditions were highly variable during deposition of the zebra interval significant mn enrichments only occur above the zebra interval documenting the miocene establishment of stable oxic conditions in the arctic ocean in summary extreme and abrupt changes in geochemistry and mineralogy across the studied sediment section do not suggest continuous sedimentation at the lomonosov ridge around the eocene miocene transition but imply repeated periods of very low sedimentation rates and or erosion

a key source area and constraints on entrainment for basin scale sediment transport by arctic sea ice combining field measurements remote sensing and numerical modelling a key site for ice entrainment and basinwide dispersal of sediments by sea ice has been identified near the new siberian islands the total ice bound sediment export of 18 5 x 10 6 t for an entrainment event documented in 1994 95 is of the same order of magnitude as annual sediment supply to the deep sea sector of the eurasian arctic and the greenland sea satellite imagery and ancillary data indicate that ice advection from this source may play an important role in sedimentation downstream in the transpolar drift

a global synthesis of the marine and terrestrial evidence for glaciation during the pliocene epoch abstract the pliocene climate is globally warm and characterised by high atmospheric carbon dioxide concentrations yet the terrestrial and marine scientific communities have gathered considerable evidence for substantial glaciation events in both the northern and southern hemisphere prior to the quaternary evidence on land is fragmentary but marine records of glaciation present a more complete history of pliocene glaciation here we present a global compilation of the terrestrial and marine glacial evidence for the pliocene and demonstrate four glaciation events that can be identified in the southern and or northern hemisphere prior to the latest pliocene intensification of northern hemisphere glaciation there are two globally recognisable glacial events in the early pliocene c 4 9 4 8 ma and c 4 0 ma one event around the early late pliocene transition c 3 6 ma and one event during marine isotope stage m2 c 3 3 ma long term climate cooling decreasing carbon dioxide concentrations in the atmosphere and high climate sensitivity in the pliocene probably facilitated each glaciation event however the mechanisms behind the early pliocene glacial events are unclear the global glaciation at c 3 3 ma may be caused by changes in ocean gateways whereas the decline in carbon dioxide concentrations is important for the latest pliocene intensification of northern hemisphere glaciation

modern river discharge and pathways of supplied material in the eurasian arctic ocean evidence from mineral assemblages and major and minor element distribution clay mineral heavy mineral and elemental distributions in sediments from the arctic ocean and the adjacent laptev and kara seas can be attributed to the geology of the hinterland and the transport of terrigenous material by rivers onto the shelves kara sea sediments are characterized by increased contents of smectite and elevated ni al ti al and cr al ratios in the western laptev sea sediments are enriched in smectite and clinopyroxene and increased in ti al cr al and ca al ratios the composition of the sediments reflects suspended matter input from the large trap basalt of the putoran mountains the eastern laptev sea sediments display increased illite and amphibole contents as well as a chemical composition similar to average shale this composition is due to the discharge from the lena and yana rivers which drain a large catchment area consisting of sedimentary mesozoic and paleozoic rocks material from the eastern laptev sea is transported by ocean currents and sediment laden sea ice along the transpolar drift into the central arctic ocean this is indicated by similar values of ti al cr al rb al and k al ratios as well as increased concentrations of amphibole and illite determined in sediments from the lomonosov ridge a minor input from the beaufort sea into the central arctic ocean is suggested from increased ca al ratios and increased contents of opaque minerals

a statistical approach to source determination of lithic and fe oxide grains an example from the alpha ridge arctic ocean abstract discriminant function analysis dfa of microprobe data on 12 elements in nine fe oxide mineral types was used to match each fe oxide grain from an arctic ocean core to similarly analyzed grains in probable source areas for ice rafted detritus this approach to provenance allows us to determine the proportion of multiple sources with a high degree of statistical probability counts of microscopically identified dropstones 250 m from centimeter thick samples of the core and from source area samples provide a direct link to the sediment source multiple types of dfa e g direct vs stepwise on the dropstone data provide slightly different sources for many samples from the core this is due to multiple sources for each core sample and provides a more accurate picture of ources than one dfa procedure alone most of the lithic grains were derived from the northwestern queen elizabeth islands centered around ellef ringnes island and from the vicinity of victoria and banks islands whereas the microprobe data from individual fe oxide grains led to these same source areas they always showed that several sources contributed to each centimeter thick core sample significant input from both the dominant source areas to the same intervals in the core indicates that the ice sheets or ice caps covering these different areas coexisted during several pre wisconsin glaciations

hydrogeochemical evolution of groundwaters with excess fluoride concentrations from dashtestan south of iran hydrogeochemical investigations were carried out in the dashtestan the eastern part of borazjan with a focus on fluoride content the study area is underlain by a complex geology that is dominated by three lithological units namely marl alluvial sediments and carbonate rocks to assess the major geochemical factors controlling the fluoride enrichment in water 37 groundwater and 12 surface water samples were collected from the three lithological units fluoride concentrations ranged up to 3 mg l and average concentrations varied from 1 12 in carbonate aquifers to 1 73 in alluvial aquifers to 1 82 mg l in marl aquifers to study the influence of rocks and soils on groundwater quality an additional 41 soil and rock samples were also taken and analyzed for fluoride the order of average fluoride content in both rocks and soils is marl alluvial sediments limestone which confirms that marl is a likely source of fluoride

isotopic analysis of permo carboniferous talchir sediments from east central india signature of glacial melt water lakes abstract presence of calcareous nodules in the upper part of the talchir sedimentary sequence permo carboniferous in gondwana sediments of east central india offers a chance to delineate the environment of deposition and the regional palaeo climate carbon and oxygen isotopic compositions of the carbonate cement in these early diagenetic nodules indicate that this phase of talchir sedimentation took place in lakes formed by glacial melt water the estimated mean 18o of the meteoric water is about 22 5 close to the expected composition at the 70 s palaeo latitude of this area majority of the nodules have highly depleted carbon isotope ratios indicating significant contribution from biogenic carbon dioxide since the lower part of the talchir formation is characterized by glacier derived materials conglomerates and diamictites the presence of biotic signature in the upper part indicates a climatic change from the cold glacier regime to a warm period

pleistocene environmental dynamics recorded in the loess of the middle and lower danube basin abstract the substantial loess deposits of the middle and lower danube basin in southeastern europe represent one of the thickest and most comprehensive terrestrial palaeoenvironmental records on the continent yet are also the least well understood environmental conditions over the last million years have resulted in relatively continuous deposits uninterrupted by glaciation and tundra conditions which nevertheless reflect oscillations between relatively warm humid interglacial and cold dry glacial intervals this relative environmental stability may have proven important for hominins migrating into and through the region the loess stratigraphy comprises distinct loess paleosol sequences reflecting glacial interglacial phases which can be quantified for intensity using environmental magnetism and geochemistry these phases are emphasised by variations in vegetation and malacofauna which respond to climatic change the loess deposits demonstrate broadly similar sedimentological characteristics across the basin danubian loess deposits initiated in response to the tectonic formation of the pannonian basin retreat of the large palaeolakes and increased sediment supply from the danube the period from 1 ma 500 ka mis 27 13 was characterised by alternating loess deposition and pedogenesis during glacial and interglacial periods respectively in response to relatively humid forested conditions this period represents the opening of the danube corridor and provides the backdrop for initial hominin arrival into europe after 500 ka and particularly after mis 9 loess accumulation rates increased in response to relatively more steppic arid environments mis 9 and 13 15 were the most humid phases of the last 600 ky the mis 5 interglacial period was the warmest and relatively most humid period preceding the holocene and was followed by substantially increased loess accumulation during mis 4 which may be linked to north atlantic circulation the complexity of the mis 3 interstadial paleosol suggests that conditions were not uniformly warm and wet during this time mis 3 corresponds with the first arrival of anatomically modern humans to europe the last glacial maximum and younger dryas of mis 2 were characterised by substantially increased loess accumulation indicating cold steppe environments most likely influenced by the north atlantic although conditions were sufficiently mild that the region acted as a refugium for thermophilic biota as may also have been the case for most of the pleistocene glacial cycles the holocene soil represents relatively wamer and more humid conditions corresponding to the current interglacial

thermohaline circulation in the arctic mediterranean seas the renewal of the deep north atlantic by the various overflows of the greenland scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north the arctic ocean and the greenland iceland and norwegian seas collectively called the arctic mediterranean the traditional site of deep ventilation for these basins is the greenland sea but a growing body of evidence also points to the arctic ocean as a major source of deep water this deep water is relatively warm and saline and it appears to be a mixture of dense brine enriched shelf water with intermediate strata in the arctic ocean the deep water exits the arctic ocean along the greenland slope to mix with the greenland sea deep water conversely very cold low salinity deep water from the greenland sea enters the arctic ocean west of spitsbergen within the arctic ocean the lomonosov ridge excludes the greenland sea deep water from the canadian basin leaving the latter warm saline and rich in silica in general the entire deep water sphere of the arctic mediterranean is constrained by the greenland scotland ridges to circulate internally therefore it is certain of the intermediate waters formed in the greenland and iceland seas which ventilate the north atlantic these waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface induced signals into the deep north atlantic

geochemical appraisal of fluoride contamination of groundwater in the nayagarh district of orissa india the occurrence of high concentrations of fluoride in groundwater 1 5 mg l in the villages of singhpur and sagaragan in the nayagarh district of orissa and its relation with the fluoride rich hot spring water 10 mg l located nearby have been studied the composition of the hot spring water is very comparable to the other thermal waters of the world thermodynamic considerations show that more than 65 of the groundwater and hot spring water samples are oversaturated with calcite and only four samples are oversaturated with fluorite fluoride concentration shows a positive relation to sodium bicarbonate and ph and a negative relation to calcium and magnesium in fluoride rich groundwater and hot spring water principal component analysis shows that the fluoride rich groundwater was produced due to a mixing of hot spring water with the surrounding groundwater studies of the saturation index of fluorite with log electrical conductivity also indicate mixing of hot spring water with the surrounding groundwater the spatial distribution of fluoride in groundwater follows the topography of the area

plate tectonic evolution of the mediterranean middle east region abstract an interpretive model for the mesozoic cenozoic plate tectonic evolution of the mediterranean and adjacent areas is illustrated by a series of paleoposition maps at selected intervals between the late triassic and recent this interval witnessed an important period of tensional development during the triassic and jurassic that fragmented pangea after its late paleozoic consolidation a number of oceanic areas evolved through jurassic time all of which have since been consumed during the alpine orogeny during the cretaceous and tertiary sea floor spreading geometry in the north and south atlantic resulted in convergence between africa and eurasia that controlled the evolution of the mediterranean and adjacent middle east areas from the late mesozoic to recent the interpretation departs from several previous ones in the following respects 1 1 the eastern mediterranean and adjacent middle east area are interpreted to have developed as two seaways with an intervening continental sliver derived from africa that now comprises central turkey and west iran these seaways persisted from the late triassic to late cretaceous by which time they were largely consumed by northward subduction 2 2 spreading that produced the present eastern mediterranean sea developed during the late cretaceous driving the tripolitza eratosthenes iskenderun continental fragments northward from africa to collision with central turkey as the preceding southern arm of the mesozoic tethys sea floor was entirely consumed initial block faulting in this zone occurred during the jurassic and early cretaceous but without subsidence reaching clearly bathyal depths until the cenomanian turonian this differs from the timing of events in the ionian sequence of the pindic nappe of crete which shows a change from shallow carbonate shelf in the triassic to deep basin in the liassic to the north of equivalent platform facies of the tripolitza nappe 3 3 moesia and rhodope are concluded to have been a single plate until a rifting event that started during the late jurassic the balkan mountains are interpreted to represent an alpine inversion of this mesozoic rift system that extended west from the black sea basin 4 4 the eastern carpathian microcontinental sliver is concluded as continuing southward as the serbo macedonian massif that separates rhodope from the vardar zone rather than as rhodope itself 5 5 the scutari pec lineament is considered as representing a major discontinuity between the apulia pannonian plate and adjacent greece and turkey ophiolites to the northwest of this lineament originated in a single oceanic area the vardar zone ophiolites to the southeast of this lineament evolved from two oceanic areas those of interior greece and northern anatolia and the associated ankara melange relating to the vardar zone the former north arm of tethys and the pindos southern anatolia zagros oman ophiolites relating to a former south arm of mesozoic tethys 6 6 based on the history of development of various elements of the alpine system there is a strong suggestion that important dextral movement took place along a major strike slip fault system reaching from the middle east to the central alps between late cretaceous and middle eocene times

high fluoride in groundwater of an industrialized area of eastern india odisha inferences from geochemical and isotopic investigation an assessment of fluoride distribution in groundwater of an industrialized area talchir odisha india was carried out to understand the potential sources and processes this study is significant as the water resources are being endangered by the mining and other industrial activities in this region high concentration of fluoride 4 4 mg l was observed in groundwater of this area which was attributed mainly to mining activities additional source for high fluoride is the basement granitic rock containing fluoride bearing minerals like amphibole biotite and fluorite the dominant chemical types are found to be na ca hco3 na mg hco3 ca mg hco3 and ca na hco3 the groundwater facies variation was found in accordance with the local lithology there was no marked difference in the fluoride concentration of groundwaters between near and far off mining zone geochemical modeling indicated precipitation of calcite and dolomite as the driving force for the release of fluoride from the formation in addition to the precipitation of calcite and dolomite evapotranspiration also contributes to high fluoride in groundwater environmental stable isotopes inferred that there was no clear isotopic distinction between high and low fluoride groundwater and the groundwater was found to be evaporated environmental tritium data suggested that the groundwater was modern and fluoride enrichment was facilitated by long residence time of groundwater statistical methods also corroborate the geochemical and isotopic inferences the study highlights that natural geogenic source is the main cause for high fluoride in groundwater refuting earlier theories that attribute mining activities as the only source for high fluoride in this region

genesis of high f groundwaters southern india abstract high f groundwaters are common in the dry parts of the indian peninsula constituting a serious health problem the f originates mainly from hydroxypositions in biotite and hornblende and is concentrated through evapotranspiration in soil and groundwater exhibiting residual alkalinity such waters are common in areas with generally alkaline soils along the flow paths of the water from hilltops to valley bottoms calcite dolomite and fluorite seem to precipitate in that order a practical solution to the health problem may be to locate drinking water wells in upslope positions

prompt transgression and gradual salinisation of the black sea during the early holocene constrained by amino acid racemization and radiocarbon dating abstract the restricted environment of the black sea is particularly sensitive to climatic and oceanographic fluctuations owing to its connection with the mediterranean sea via the narrow bosphorus strait the exact mechanism and timing of the most recent connection between these water bodies is controversial with debate on the post glacial history of the black sea being dependent on radiocarbon dating for numerical ages here we present new 23 accelerator mass spectrometer ams radiocarbon ages on peat and bivalve molluscs supported by the first amino acid racemization aar dating of bivalve molluscs n 66 in the black sea these data indicate infilling of the black sea during the early holocene from an initial depth 107 m below sea level and 72 m below that of the bosphorus sill these data combined with a review of previous radiocarbon ages has enabled a unique perspective on the post glacial black sea a sea level curve based on conventional and ams radiocarbon ages on peat and ams based ages on dreissena sp shells indicate the water level in the earlier lake phase continued until the early holocene to be lower than the bosphorus sill after the younger dryas ended however the absence of ams dated mollusc ages from the shelves of this basin older than the younger dryas is suggestive of sub aerial exposure of the shelves and comparatively lower water levels when the younger dryas began thus post glacial outflow from the black sea occurred through a lowered or open bosphorus seaway basin wide radiocarbon ages on peat indicate a prompt increase in water level from that of the pre existing and unconnected palaeo lake during the earliest holocene 9600 9200 cal a bp mass colonisation of the black sea by mediterranean taxa did not occur until salinity had risen sufficiently a process which took 1000 a or more from the initial transgressive event this gradual change in salinity contrasts with the prompt transgression which would have taken 400 a to occur

paleoenvironmental implications of cenozoic sediments from the central arctic ocean iodp expedition 302 using inorganic geochemistry 1 integrated ocean drilling program iodp expedition 302 arctic coring expedition acex recovered a unique sediment record from the central arctic ocean revealing that this region underwent major environmental fluctuations since the late cretaceous major and trace element composition of 1 300 samples were determined using x ray fluorescence xrf the results show significant compositional variability of the sediments with depth that can be attributed to changes in a provenance and pathways of detrital material b paleoenvironmental conditions and depositional processes and c diagenetic overprint of the primary record in addition to existing lithological units we introduce new geochemical units for a more process related approach interpreting the acex record in detail via the geochemical signature of siberian flood basalts we are able to reconstruct the discontinuous rifting and deepening of the central lomonosov ridge during the paleogene accompanied by changing current regimes and the onset of sea ice eocene biosiliceous sedimentation took place in a relatively shallow setting under predominantly anoxic bottom water conditions causing a positive anoxia productivity feedback although water column stratification was repeatedly interrupted by ventilation events anoxic to sulfidic conditions were even more extreme after biosilica production ceased and significant amounts of pyrite were deposited on the lomonosov ridge especially in organic matter rich paleogene deposits diagenetic processes obscured the paleoenvironmental signals fundamental environmental changes occurred in the middle eocene but geochemical and micropaleontological proxies point not to the identical sediment depth after approximately 26 ma of non deposition or erosion the middle miocene record shows the transition to dominantly oxic bottom water conditions although suboxic diagenesis seemingly affected these deposits

coupling of co2 and ice sheet stability over major climate transitions of the last 20 million years the co2 content of the atmosphere has varied cyclically between 180 and 280 ppmv over the last 800 000 years closely coupled with temperature and sea level for earlier periods in earth s history pco2 is much less certain and the relationship between pco2 and climate remains poorly constrained we use boron calcium ratios in foraminifera to estimate pco2 during major climate transitions of the last 20 million years myr during the middle miocene when temperatures were 3 to 6 c

ice events along the east siberian continental margin during the last two glaciations evidence from clay minerals abstract a large ice sheet or ice shelf may have developed repeatedly along the east siberian continental margin since the middle pleistocene in combination with ice rafted debris major elements and foraminifera clay mineral records from four gravity sediment cores are used to trace ice events along the east siberian continental margin during the last two glaciations the clay mineral assemblages show a strong link to the extent of the east siberian ice sheet esis rather than the ice shelf or icebergs sourced from the canadian arctic during the last two glaciations illite rich sediment from east siberia was transported mainly toward the deep basin whereas kaolinite rich sediment from the canadian arctic was mostly blocked from the east siberian continental margin we speculate that during marine isotope stage 2 mis2 the southern mendeleev ridge chukchi basin and chukchi rise may have been covered by an esis extended ice shelf however the chukchi plateau and northwind ridge were dominated by a laurentide sourced ice shelf during mis4 the esis may have undergone a marked expansion with an extended ice shelf occupying all of the chukchi plateau and northwind ridge thereby restricting iceberg discharge from other ice sheets

biochronology and paleoceanography of late pleistocene and holocene calcareous nannofossil abundances across the arctic basin biochronology and paleoceanography of late pleistocene and holocene calcareous nannofossils across the arctic basin

cenozoic ice rafting history of the central arctic ocean terrigenous sands on the lomonosov ridge the cenozoic ice rafted debris ird history of the central arctic is reconstructed utilizing the terrigenous coarse sand fraction in iodp 302 cores from 0 to 273 meters composite depth this holocene middle eocene quantitative record of terrigenous sand accumulation on the lomonosov ridge along with qualitative information on grain texture and composition confirms the interpretation that ice initiation sea ice and glacial ice occurred 46 ma in the arctic and provides a long term pattern of arctic ice expansion and decay since the middle eocene ird mass accumulation rates range from 0 to 0 13 g cm2 ka in the middle eocene and from 0 to 0 36 g cm2 ka in the neogene ird mass accumulation rate mar maxima in the miocene and pliocene cooccur with either glacial initiation or intensification in the sub arctic the 46 25 ma ird onset in the central arctic slightly precedes the earliest evidence of ice in the antarctic and compares in timing with a 1000 ppm decrease in atmospheric concentrations of co2 the decline of pco2 in the middle eocene may have driven both poles across the temperature threshold that enabled the nucleation of glaciers on land and partial freezing of the surface arctic ocean especially during times of low insolation

further evidence of abrupt holocene drowning of the black sea shelf a 1999 survey of the black sea continental shelf off the north central turkish seaport of sinop using a side scan sonar small remotely operated vehicles and a series of dredge lowerings located inspected and sampled an exposed high energy paleoshoreline at a depth of 155 m radiocarbon dating of mollusk shells collected from this ancient beach revealed that the marine flooding of the black sea took place between 7460 and 6820 yr b p all ages are reported in radiocarbon years not calendar years without correction for reservoir age or dendro calibration changing it from a lacustrine to marine environment this relic surface remained in contact with the bottom waters of the black sea for a long period of time before being draped by a thin layer of sapropel mud wood samples recovered from this same location were very well preserved and yielded dates as old as 3580 yr b p q 2000 elsevier science b v all rights reserved

sources of sediment found in sea ice from the western arctic ocean new insights into processes of entrainment and drift patterns 1 the geochemical fingerprint of entrained fe oxide mineral grains in arctic ocean sea ice is used to determine precise sources of this sediment this approach substantiates the importance of the laptev sea as a source of sea ice and even the presence of russian ice in the beaufort sea off alaska fe oxide grains from the laptev sea were found in floes in the beaufort sea chukchi borderland and central arctic ocean demonstrating the importance of sea ice in distributing itself throughout the arctic ocean and the potential of transporting sediment from russian rivers to north american shelves banks island shelf is the most important source of sediment sampled from ice floes in the beaufort sea northern chukchi sea and chukchi borderland area although most of the entrained sediment fits the criteria for suspension freezing in shallow water the presence of winter polynyas with offshore winds and not the size of shallow areas appears to be the critical factor for sea ice entrainment seven of the 18 ice floes sampled contained fe oxide grains from more than one source area the two most common sources that are found in the same ice floes are banks island and the laptev sea multiple sources in ice floes suggest that either mingling of fragmented ice floes occurs or that a source area containing grains from both these sources has yet to be located the addition of fine sand sized windblown sediment is not thought to be significant

organic carbon carbonate and clay mineral distributions in eastern central arctic ocean surface sediments abstract results from a detailed sedimentological investigation of surface sediments from the eastern arctic ocean indicate that the distribution of different types of sediment facies is controlled by different environmental processes such as sea ice distribution terrigenous sediment supply oceanic currents and surface water productivity in comparison to other open ocean environments total organic carbon contents are high with maximum values in some deep basin areas as well as west and north of svalbard in general the organic carbon fraction is dominated by terrigenous material as indicated by low hydrogen index values and high c n ratios probably transported by currents and or sea ice from the eurasian shelf areas the amount of marine organic carbon is of secondary importance reflecting the low productivity environment described for the modern ice covered arctic ocean in the area north of svalbard some higher amounts of marine organic matter may indicate increased surface water productivity controlled by the inflow of the warm westspitsbergen current wsc into the arctic ocean and reduced sea ice cover this influence of the wsc is also supported by the high content of biogenic carbonate recorded in the yermak plateau area the clay mineral distribution gives information about different source areas and transport mechanisms illite the dominant clay mineral in the eastern central arctic ocean sediments reaches maximum values in the morris jesup rise area and around svalbard indicating north greenland and svalbard to be most probable source areas kaolinite reaches maximum values in the nansen basin east of svalbard and in the barents sea possible source areas are mesozoic sediments in the barents sea and franz josef land in contrast to the high smectite values determined in sea ice samples smectite contents are generally very low in the underlying surface sediments suggesting that the supply by sea ice is not the dominant mechanism for clay accumulation in the studied area of the modern central arctic ocean

provenance analysis of central arctic ocean sediments implications for circum arctic ice sheet dynamics and ocean circulation during late pleistocene abstract mineralogical and geochemical data generated from the well referred shallow core 96 12 1pc on the lomonosov ridge central arctic ocean was used to evaluate ice transport from the circum arctic sources and variability in sediment drainage and provenance changes in this study heavy minerals in central arctic sediments were used to determine those most prominent provenance areas and their changes related to the late pleistocene history of glaciations in the arctic provenance changes were then used to infer variations in the paleoceanographic environment of the central arctic ocean such as variations in the distribution of sea ice icebergs controlled by the arctic ocean circulation four critical end members including victoria and banks islands the putorana plateau the anabar shield and the verkhoyansk fold belt were identified from the amerasian and eurasian source areas and their proportional contributions were estimated in relation to late pleistocene ice sheet dynamics and ocean circulation the results show changes in transport pathways and source areas within two examined transitions mis6 5 and mis4 3 the main source for material during mis6 5 transition was amerasian margin due to the high dolomite content in the studied section of sediments inferring strong beaufort gyre bg and transpolar drift tpd transport for this material ird material during late the mis6 to 5 deglacial event was from terrigenous input through from the mackenzie route banks victoria islands then transported as far as the lomonosov ridge area the transition mis4 3 in comparison with mis6 5 shows a clear shift in source areas reflected in a different mineralogical composition of sediments supplied from the eurasian margin such as the anabar shield the putorana plateau and the verkhoyansk fold belt during active decay of the barents kara ice sheet presumable associated with an ice dammed lake outburst then triggered by a strong tpd over the central arctic these two studied deglaciations suggest that contributions of different circum arctic sediment sources are related to interaction between ice sheet decay sea ice production and circulation

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

the early miocene onset of a ventilated circulation regime in the arctic ocean deep water formation in the northern north atlantic ocean and the arctic ocean is a key driver of the global thermohaline circulation and hence also of global climate1 deciphering the history of the circulation regime in the arctic ocean has long been prevented by the lack of data from cores of cenozoic sediments from the arctic s deep sea floor similarly the timing of the opening of a connection between the northern north atlantic and the arctic ocean permitting deep water exchange has been poorly constrained this situation changed when the first drill cores were recovered from the central arctic ocean2 here we use these cores to show that the transition from poorly oxygenated to fully oxygenated ventilated conditions in the arctic ocean occurred during the later part of early miocene times we attribute this pronounced change in ventilation regime to the opening of the fram strait a palaeo geographic and palaeo bathymetric reconstruction of the arctic ocean together with a physical oceanographic analysis of the evolving strait and sill conditions in the fram strait suggests that the arctic ocean went from an oxygen poor lake stage to a transitional estuarine sea phase with variable ventilation and finally to the fully ventilated ocean phase 17 5 myr ago the timing of this palaeo oceanographic change coincides with the onset of the middle miocene climatic optimum3 although it remains unclear if there is a causal relationship between these two events

compositional trends through the holocene mud succession of the southwestern black sea shelf implications for sedimentary provenance and water level history abstract cores mar02 45 and mar05 03 were raised from 68 69 m water depth on the sw black sea shelf and indicate transgression and submergence beneath several tens of metres of water before 11 0 cal ka those who postulate a black sea lowstand below 100 m until the approximately 9 1 cal ka reconnection with the world ocean have suggested that sites like mar02 45 and mar05 03 must have been located in perched lakes on what is now the modern shelf however the silt and clay fraction mineralogy of samples from mar02 45 provides no evidence for a shift in provenance at 9 1 cal ka with earlier input from local rivers and later input from a broader region sedimentary abundances of sc fe co ce la th and y also show no significant downcore trends these elements likely reside in aluminosilicate mineral grains shed from terrestrial sources so negligible downcore variation suggests long term continuity in the composition of the detrital supply more critically the volume of pre 9 1 cal ka sediment around the mar02 45 and mar05 03 sites is 25 times the expected yield from local rivers over a 5000 year period so other more substantial sources are required the predominant silt size of the recovered sediments the configuration of late holocene currents in the western black sea and analogies with dispersal systems elsewhere suggest that the bulk of the fine grained muds at these sites likely came from the danube and kamchiya drainage basins where thick deposits of unconsolidated pleistocene loess have been strongly dissected to reach core sites on the sw black sea shelf this material must have been advected from the danube and kamchiya deltas by unobstructed marine currents only thin event beds tempestites of fine sand and silt in the lower part of cores mar02 45 and mar05 03 are interpreted to have a local source in the strandja mountains of thrace comparison of the palynology of surface samples from the danube delta and its associated coastal lagoons with the pre 9 1 cal ka sediments of core mar02 45 confirms that the hypothesis of deposition in a perched ancient lake is untenable

seismic stratigraphy of late quaternary deposits from the southwestern black sea shelf evidence for non catastrophic variations in sea level during the last 10 000 yr abstract detailed interpretation of single channel seismic reflection and huntec deep tow boomer and sparker profiles demonstrates that the southwestern black sea shelf formed by a protracted shelf edge progradation since the miocene pliocene five seismic stratigraphic units are recognized unit 1 represents the last phase of the progradational history and was deposited during the last glacial lowstand and holocene it is divided into four subunits subunit 1a is interpreted as a lowstand systems tract 1b and 1c are interpreted as a transgressive systems tract and subunit 1d is interpreted as a highstand systems tract the lowstand systems tract deposits consist of overlapping and seaward prograding shelf edge wedges deposited during the lowstand and the subsequent initial rise of sea level these shelf edge wedges are best developed along the westernmost and easternmost segments of the study area off the mouths of rivers the transgressive systems tract deposits consist of a set of shingled shore parallel back stepping parasequences deposited during a phase of relatively rapid sea level rise and include a number of prograded sediment bodies including barrier islands beach deposits and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features a number of radiocarbon dates from gravity cores show that the sedimentary architecture of unit 1 contain a detailed sedimentary record for the post glacial sea level rise along the southwestern black sea shelf these data do not support the catastrophic refilling of the black sea by waters from the mediterranean sea at 7 1 ka postulated by ryan pitman major shimkus maskalenko jones dimitrov gorur sakinc yuce mar geol 138 1997 119 126 ryan pitman touchstone book 1999 319 pp and ballard coleman rosenberg mar geol 170 2000 253 261

imprint of late pleistocene continental processes visible in ice rafted grains from the central arctic ocean abstract ice rafted quartz sand grains of sediment samples representing marine isotope stages mis 3 and 4 from the lomonosov ridge arctic ocean are here analysed with a scanning electron microscope sem to characterise processes in the sediment source area the microtextural characteristics of the grains were observed and their microtexture frequencies calculated specific sets of microtextures were identified and classified group i iii using principal component analysis pca and cluster analysis the statistically analysed microtextural data were used to identify signals of continental processes that operated during the late pleistocene mis 4 to mis 3 in the eurasian arctic the microtextures of group i generally formed as a result of prolonged fluvial alluvial or aeolian transport the glacial microtextures of groups ii and iii indicate subglacial conditions and transport based on the data two principal components seem to characterise late pleistocene continental environmental conditions glacial and non glacial there is a signal of non glacial continental processes in the ice rafted grains at around 62 64 and 67 ka ago a signal of subglacial processes was observed in the grains at around 26 34 42 and 45 ka and concurrent with non glacial at around 62 and 64 ka ago we suggest that these signals in mis 4 sediments are related to deglaciation with an increased supply of glacial sediment to the arctic ocean whereas during mis 3 they were probably related more to iceberg calving from the oscillating barents kara ice sheet

late glacial holocene clay minerals elucidating glacial history in the sw barents sea abstract detailed investigations of the distribution of clay minerals of late glacial holocene sediments from the sw barents sea provide important new information about the provenance and transport paths of the sediments this information leads to better understanding of the onset of the last deglaciation and subsequent advances retreats of the barents sea and fennoscandian ice sheets the results show interaction and changes in the fennoscandian ice sheet and bjornoyrenna ice stream during the last deglaciation high illite content and maximum kaolinite content 18 700 cal yr b p indicate glacial erosion from both the fennoscandian ice sheet and bjornoyrenna ice stream lgm ii the occurrence of a c reniforme dominated benthic foraminiferal assemblage 18 700 cal yr b p indicates that the northern most cores site in ingoydjupet had already been deglaciated and was probably situated in a glacier distal environment in addition smectite content reaching its highest level concurrent with the presence of neogloboquadrina pachyderma sin dominated planktic foraminifera can be related to the strengthening of the atlantic current the inflow of the atlantic water may have triggered deglaciation of the fennoscandian ice sheet bolling interstadial a rapid increase in illite content reflecting strong melting of the fennoscandian ice sheet 15 000 cal yr b p indicates the onset of deglaciation in a core closer to the continent decrease of illite and ird content together with the deposition of laminated sediments during the older dryas stadial 15 000 14 000 cal yr b p indicates colder conditions and formation of at least seasonal sea ice in addition increased kaolinite content indicates increased glacial erosion of the bjornoyrenna ice stream the highest values of illite content and increased ird content 14 000 13 000 cal yr b p can be related to strong melting of the fennoscandian ice sheet a slight indication of the younger dryas cold period is given by the decrease in illite and ird contents all clay contents are more stable during holocene compared to lgm and the last deglaciation

was the black sea catastrophically flooded in the early holocene abstract a catastrophic flooding of the black sea basin was proposed to have occurred during its reconnection to the ocean in the early holocene possible cultural consequences of the flood include the migration of neolithic farmers from around the black sea towards central europe as well as the creation of flood myths stratigraphic and paleo geomorphologic information from danube delta aided by radiocarbon ages on articulated mollusks constrain the level in the black sea before the marine reconnection to ca 30 m below the present sea level rather than 80 m or lower if the flood occurred at all the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed

variations in the age of arctic sea ice and summer sea ice extent 1 three of the past six summers have exhibited record low sea ice extent on the arctic ocean these minima may have been dynamically induced by changes in the surface winds based on results of a simple model that keeps track of the age of ice as it moves about on the arctic ocean we show that the areal coverage of thick multi year ice decreased precipitously during 1989 1990 when the arctic oscillation was in an extreme high index state and has remained low since that time under these conditions younger thinner ice anomalies recirculate back to the alaskan coast more quickly decreasing the time that new ice has to ridge and thicken before returning for another melt season during the 2002 and 2003 summers this anomalously younger thinner ice was advected into alaskan coastal waters where extensive melting was observed even though temperatures were locally colder than normal the age of sea ice explains more than half of the variance in summer sea ice extent

beryllium isotopes in central arctic ocean sediments over the past 12 3 million years stratigraphic and paleoclimatic implications the upper 200 m of the sediments recovered during iodp leg 302 the arctic coring expedition acex to the lomonosov ridge in the central arctic ocean consist almost exclusively of detrital material the scarcity of biostratigraphic markers severely complicates the establishment of a reliable chronostratigraphic framework for these sediments which contain the first continuous record of the neogene environmental and climatic evolution of the arctic region here we present profiles of cosmogenic 10be together with the seawater derived fraction of stable 9be obtained from the acex cores the down core decrease of 10be 9be provides an average sedimentation rate of 14 5 1 m ma for the uppermost 151 m of the acex record and allows the establishment of a chronostratigraphy for the past 12 3 ma the age corrected 10be concentrations and 10be 9be ratios suggest the existence of an essentially continuous sea ice cover over the past 12 3 ma

alternating southern and northern hemisphere climate response to astronomical forcing during the past 35 m y earth s climate has undergone different intervals of gradual change as well as abrupt shifts between climate states here we aim to characterize the corresponding changes in climate response to astronomical forcing in the icehouse portion of the cenozoic from the latest eocene to the present as a tool we use a 35 m y long 18 o benthic record compiled from different high resolution benthic isotope records spliced together what we refer to as a megasplice we analyze the climate response to astronomical forcing during four 800 k y long time windows during the mid miocene climatic optimum ca 15 5 ma global climate variability was mainly dependent on southern hemisphere summer insolation amplified by a dynamic antarctic ice sheet 2 5 m y later relatively warm global climate states occurred during maxima in both southern hemisphere and northern hemisphere summer insolation at that point the antarctic ice sheet grew too big to pulse on the beat of precession and the southern hemisphere lost its overwhelming influence on the global climate state likewise we juxtapose response regimes of the miocene ca 19 ma and oligocene ca 25 5 ma warming periods despite the similarity in 18 o benthic values and variability we find different responses to precession forcing while miocene warmth occurs during summer insolation maxima in both hemispheres oligocene global warmth is consistently triggered when earth reaches perihelion in the northern hemisphere summer this pattern is in accordance with previously published paleoclimate modeling results and suggests an amplifying role for northern hemisphere sea ice

middle to late pleistocene arctic paleoceanographic changes based on sedimentary records from mendeleev ridge and makarov basin abstract three sediment cores from the makarov basin and mendeleev ridge off the siberian margin were analyzed for a number of litho bio and magnetostratigraphic proxies correlation to previously studied arctic records from mendeleev to lomonosov ridges enables paleoceanographic reconstructions for the middle to late pleistocene estimated 0 8 ma on orbital time scales cyclic changes in lithology corroborated by multiple stratigraphic constraints were tuned to global climate variations based on the manganese content that increases during interglacials while calcium and zircon were used as proxies for the laurentide and eurasian ice sheet inputs the combined evaluation of glacial and interglacial proxy variabilities provides a coherent picture of the western arctic ocean development in the pleistocene we suggest that major cyclic changes were driven by summer processes such as sea ice retreat and enhanced biological production vs suppressed ice melt in warmer and colder summers respectively a potential link to low latitudes via atmospheric moisture and heat transport is indicated by similarities in the western arctic ocean and east asian monsoon records long term cooling is signified by biogenic proxies related to sea ice expansion over the western arctic ocean with step changes at mis 11 and 7 0 4 and 0 2 0 3 ma this transition also features better fossil preservation indicating less corrosive oxidative bottom waters probably resulting from a decrease in organic export production and or weakening of bottom water ventilation under perennial sea ice the latter was possibly enhanced by atmospheric cooling and increased meltwater fluxes with the growth of circum arctic ice sheets

significance of clay mineral assemblages in the antarctic ocean abstract typical examples from different morphological and geological settings in the antarctic ocean are reviewed in order to discuss the value of clay mineral assemblages for reconstructing the glacial history of antarctica the paleoceanographic history of the antarctic ocean and the sedimentary processes at the antarctic continental margin the significance of clay minerals for paleoenvironmental reconstructions strongly varies with both the position of the sites under investigation and the age of the sediments in late mesozoic to paleogene sediments clay mineral assemblages are sensitive tools for reconstructing climatic conditions for example the shift from smectite dominated assemblages to illite and chlorite dominated assemblages in the earliest oligocene clearly documents the transition from chemical weathering conditions under a warm and humid climate to physical weathering under cooler conditions submarine elevations such as maud rise and kerguelen plateau give the best record for direct paleoclimatic and paleoceanographic studies at the proximal sites of the continental slope and shelf as well as in the deep sea the paleoclimatic information normally is masked by a variety of processes resulting in sediment redistribution at those sites in contrast the clay mineral assemblages bear a wealth of information on different sedimentary processes after the establishment of a continental east antarctic ice sheet physical weathering prevailed variations in the clay mineral records predominantly reflect the influence of different sediment sources resulting from different glacial hydrographic or gravitational transport processes because these sedimentation processes are generally linked to climatic variations the clay mineral assemblages in most of the neogene and quaternary sediments provide indirect paleoclimatic information the processes are best documented in the clay mineral composition in those areas where changes in source regions with distinct petrographic differences are expected and where distances from the source region are low

comparing sea ice sediment load with beaufort sea shelf deposits is entrainment selective abstract modern dispersal of sea ice rafted debris ird is important for the arctic ocean sediment budget from sources to sinks sediment entrainment occurs mainly through the action of small ice crystals frazil attaching to sedimentary particles in shallow water a mechanism that could be selective the principal source for entrainment of ird by suspension freezing into the beaufort gyre western arctic ocean is the adjacent shallow 250 m lithology and carbon and carbonate content of ird in the beaufort gyre were compared to sediments from the probable source surface in order to determine whether preferential entrainment occurs with any of these sediment parameters ird is generally much finer grained than the source surface showing that silt and clay size particles are preferentially entrained by frazil ice although anchor ice can locally incorporate very high percentages of sand and coarser clasts the coarsest ird is also the most poorly sorted the clay mineralogy of the 2 m ird fraction is very similar to that of the source surface indicating no selective entrainment within the clay fraction the lithology of sand in ird also matches that of the source surface although the number of coarse grains is too small 100 in most samples for a statistically meaningful count the average organic carbon content of ird is three times higher than that of the source surface but we attribute this to summer algal growth on ice floes rather than to selective entrainment a relatively low carbonate content in ird may be because much of the carbonate in the source is of silt size while about 50 of the ird measured is clay size the low carbonate content may also reflect solution under acidic summer conditions on sea ice selective export of silt and clay size particles by ice rafting from the shallow shelf with time should lead to the formation of a slightly coarser lag even though some of the dirty ice drops its sediment load in the entrainment area further mineralogical and lithological analysis on ird promises to become a useful tool for the study of sediment dispersal paths by drift ice in the arctic today and in the past and also for the study of sources of anthropogenic pollutants found in sea ice

hydrogeochemical study in the main ethiopian rift new insights to the source and enrichment mechanism of fluoride the central main ethiopian rift suffers a severe water quality problem characterized by an anomalously high fluoride f content that causes an endemic fluorosis disease the current study conducted in the ziway shala lakes basin indicates that the f content exceeds the permissible limit for drinking prescribed by the world health organization who 1 5 mg l in many important wells up to 20 mg l with even more extreme f concentration in hot springs and alkaline lakes up to 97 and 384 mg l respectively the groundwater and surface water from the highlands typically characterized by low total dissolved solids tds and ca mg hco3 hydrochemical facies do not show high f content the subsequent interaction of these waters with the various rocks of the rift valley induces a general increase of the tds and a variation of the chemical signature towards na hco3 compositions with a parallel enrichment of f the interacting matrixes are mainly rhyolites consisting of volcanic glass and only rare f bearing accessory minerals such as alkali amphibole comparing the abundance and the composition of the glassy groundmass with other mineral phases it appears that the former stores most of the total f budget this glassy material is extremely reactive and its weathering products i e fluvio volcano lacustrine sediments further concentrate the fluoride the interaction of these weathered reworked volcanic products with water and carbon dioxide at high ph causes the release of fluoride into the interacting water this mainly occurs by a process of base exchange softening with the neo formed clay minerals i e ca mg uptake by the aquifer matrix with release of na into the groundwater this is plausibly the main enrichment mechanism that explains the high f content of the local groundwater as evidenced by positive correlation between f ph and na and inverse correlation between f and ca mg saturation indices si have been calculated using phreeqc 2 for the different water groups highlighting that the studied waters are undersaturated in fluorite in these conditions fluoride cannot precipitate as caf2 and so mobilizes freely without forming other complexes these results have important implications for the development of new exploitation strategies and accurate planning of new drilling sites

the fluoride in the groundwater of guarani aquifer system the origin associated with black shales of parana basin this work presents petrological and geochemical results of the black shales interval from permian and devonian strata of the parana basin brazil and its relationships with fluoride of groundwater from guarani aquifer system the guarani aquifer located in south brazil uruguay paraguay and argentine presents contents of fluoride higher than the brazilian accepted potability limits several hypotheses have been presented for the origin of the fluoride in the groundwater of the guarani aquifer microcrystalline fluorite was registered in black shales of ponta grossa and irati formations from parana basin the results shown in this work suggest that fluoride present in groundwater of guarani aquifer can be originated in deeper groundwater that circulates in ponta grossa and irati formations the interaction of the groundwater coming from deeper black shales with the groundwater bearing aquifer guarani system occurs through regional fragile structures faults and fractures that constitute excellent hydraulic connectors between the two sedimentary packages the microcrystalline fluorite registered in ponta grossa and irati formations can be dissolved promoting fluoride enrichment in groundwater of these black shales and guarani aquifer system

mid to late pleistocene ice drift in the western arctic ocean evidence for a different circulation in the past the provenance of ice rafted debris ird in four arctic sediment cores implies that icebergs from the northwestern laurentide ice sheets drifted across the western arctic ocean along the 180 0 meridian toward fram strait during mid to late pleistocene deglaciations within the last 700 000 years this iceberg drift was different from the present day beaufort gyre circulation and resembled a dislocated transpolar drift tpd sea ice mainly followed the iceberg trajectories but also frequently drifted from the russian shelves eastward into the amerasian basin

paleogene record of elemental concentrations in sediments from the arctic ocean obtained by xrf analyses we present a high resolution x ray fluorescence xrf core scanner record for the expanded middle eocene section from integrated ocean drilling program iodp expedition 302 acex drilled on the lomonosov ridge central arctic ocean the division of the middle eocene into two units subunit 1 6 and unit 2 is seen in the cyclical behavior of the elements as well as the changing interelemental correlations and their relationship to physical property measurements of bulk sediment al ti and k strongly correlate throughout the record while the behavior of fe mn and si is more complex utilizing sediment geochemistry calibration to ground truth the xrf data we suggest the middle eocene arctic ocean was predominately euxinic although periodic oxygenation of bottom waters must have occurred during unit 2 49 7 45 4 ma initially the sediments are rich in biogenic silica unit 2 but there is a pronounced shift to terrigenous dominated sediment accumulation in subunit 1 6 we report changes in the elemental concentrations of these elements and investigate the relationship between fe content and pyrite additionally we explore the potential change in paleoenvironmental conditions across the unit boundary

introduction to special section on cenozoic paleoceanography of the central arctic ocean 1 in late summer 2004 the integrated ocean drilling program iodp conducted one of the most transformational missions in the almost 40 year history of scientific ocean drilling the arctic coring expedition acex backman et al 2006 moran et al 2006a this technically challenging expedition moran et al 2006b to the lomonosov ridge near 88 n recovered the first long term cenozoic sediment record from the arctic ocean extending previous records from 1 5 ma to an unprecedented 56 ma glimpses of the breadth of this transformation were seen during the acex cruise when the massulae from freshwater ferns azolla were found in 49 ma old sediments brinkhuis et al 2006 and the presence of apectodinium augustum confirmed that the paleocene eocene thermal maximum petm 55 ma was unexpectedly recovered sluijs et al 2006 2 soon after the expedition when the cores were opened and analyzed ice rafted debris was found in surprisingly old 46 ma sediments moran et al 2006a these middle eocene sediments are characterized also by their high organic carbon content stein et al 2006 the exciting early results attracted other investigators that expanded the scientific investigating team to more than 40 people analyses were extended to include studies that revealed surprisingly high arctic ocean surface water temperatures sluijs et al 2006 and an amplified hydrological system pagani et al 2006 during the petm initial analyses revealed an extensive hiatus encompassing about 26 million years that occurred below a short interval showing starkly alternating black and white layers that is now dubbed the zebra interval thus the time interval from the late early miocene 18 ma to the middle middle eocene 44 ma is missing although the hiatus is a lost window in time for the arctic paleoclimate record it spawned other studies that integrated the regional tectonic history with acex results revealing a major oceanographic reorganization at 17 5 ma ventilation of the arctic ocean to the north atlantic through the fram strait jakobsson et al 2007 in terms of ventilation and water mass history neogene neodymium isotope data reveal that arctic intermediate waters originate from brine formation on eurasian shelf areas between 15 and 2 ma and during glacial periods throughout pleistocene times haley et al 2008a they conclude that this mode of arctic circulation differs markedly from today s situation showing relatively high contributions of north atlantic intermediate water and minor input from brine formation 3 in this special section the transformation continues results from the large acex scientific family include a robust age model detailed analyses of the middle eocene that document a unique brackish water environment sea ice and iceberg history reconstructions as well as the provenance of ice rafted debris from the eocene to present evolution of depositional environments times of isolation and connection to the global ocean geochemical analyses of the organic carbon rich sediments and unique applications of high resolution proxies and cyclostratigraphy highlights from this special section are presented here

quaternary dinoflagellate cysts in the arctic ocean potential and limitations for stratigraphy and paleoenvironmental reconstructions abstract the arctic ocean is a siliciclastic depositional environment which lacks any rock forming biogenic calcareous and siliceous components during large parts of its quaternary history these hemipelagic sediments are nevertheless suitable for the study of organic walled microfossils of which the fossil remains of dinoflagellates dinoflagellate cysts are the most important group dinoflagellate cysts have become an important tool in paleoceanography of the high northern latitudes but their potential for quaternary biostratigraphy has remained largely unexplored dinoflagellate cysts are the dominant marine palynomorph group which is more continuously present in the marginal seas e g barents sea bering sea than in the arctic ocean itself throughout the quaternary most species have long stratigraphic ranges are temporary absent and show abundance variations on glacial interglacial timescales of the more than 30 taxa recorded only habibacysta tectata and filisphaera filifera became extinct in the pleistocene the highest persistent occurrence of h tectata at ca 2 0 ma and the top of f filifera acme at ca 1 8 ma can be used for supra regional stratigraphic correlation between the arctic ocean and adjacent basins these events corroborate a slow sedimentation rate model for the quaternary section on the central lomonosov ridge but a combination of different methods will have to be applied to provide a detailed chronostratigraphy the occurrence of cysts of phototrophic dinoflagellates in certain stratigraphic intervals on lomonosov ridge supports published evidence of episodic opening of the multiyear arctic sea ice cover during the quaternary probably related to a stronger inflow of atlantic water this contradicts the hypothesis of a permanently ice covered central arctic ocean in the quaternary

fluoride enrichment in aquifers of the thar desert controlling factors and its geochemical modelling the groundwater is the only source of drinking water in the jaisalmer district of rajasthan india the study area is a part of the thar desert it has low and scattered population and no industries hence the possibility of anthropogenic input of fluoride is almost negligible thus the enrichment of fluoride is only possible due to geochemical processes taking place in the groundwater of the region a total of 100 groundwater samples 34 samples from jaisalmer and 66 samples from the pokharan administrative blocks were collected it was observed that the concentration of fluoride ranged from 0 08 mg l to 4 56 mg l in the groundwater of jaisalmer and from 0 56 mg l to 6 60 mg l in the samples of the pokharan block the alkaline condition average ph 7 7 0 22 and 8 01 0 25 in jaisalmer and the pokharan administrative block respectively in the region favours fluorite dissolution ion exchange dissolution of calcite semi arid climate alkaline conditions and weathering are responsible for fluoride enrichment in the groundwater of the study area copyright 2012 john wiley sons ltd

anchor ice seabed freezing and sediment dynamics in shallow arctic seas diving investigations confirm previous circumstantial evidence of seafloor freezing and anchor ice accretion during freeze up storms in the alaskan beaufort sea these related bottom types were found to be continuous from shore to 2 m depth and spotty to 4 5 m depth spotty anchor ice occurred as pillow shaped crystal aggregates on buried slabs of frozen sand surrounded by unfrozen sand considerations of required conditions for ice bonding and anchor ice growth allows regional extrapolation and suggests the possibility of anchor ice growth out to 20 m depth the estimated maximum depth of supercooling during fall storms anchor ice and seabed freezing apparently do not develop during a calm freeze up because of the abrupt growth of anchor ice during a freezing storm and its release soon after formation of a surface ice cover this ice type has not been documented before the concretelike nature of frozen bottom where present should prohibit sediment transport by any conceivable wave or current regime during the freezing storm but elsewhere particularly where the bonded crust is broken by grounded ice anchor ice lifts coarse material off the bottom and incorporates it into the ice canopy thereby leading to significant ice rafting of shallow shelf sediment and likely sediment loss to the deep sea

a shift in heavy and clay mineral provenance indicates a middle miocene onset of a perennial sea ice cover in the arctic ocean during the arctic coring expedition acex a 428 m thick sequence of upper cretaceous to quaternary sediments was penetrated the mineralogical composition of the upper 300 m of this sequence is presented here for the first time heavy and clay mineral associations indicate a major and consistent shift in provenance from the barents kara western laptev sea region characterized by presence of common clinopyroxene to the eastern laptev east siberian seas in the upper part of the section characterized by common hornblende amphibole sea ice originating from the latter source region must have survived at least one summer melt cycle in order to reach the acex drill site if considering modern sea ice trajectories and velocities this shift in mineral assemblages probably represents the onset of a perennial sea ice cover in the arctic ocean which occurred at about 13 ma thus suggesting a coeval freeze in the arctic and antarctic regions

spatial and temporal arctic ocean depositional regimes a key to the evolution of ice drift and current patterns sediment physical properties measured in cores from all the major ridges and plateaus in the central arctic ocean were studied in order to analyze the spatial and temporal consistency of sediment d

geochemical studies to delineate topsoil contamination around an ash pond of a coal based thermal power plant in india in the present study an attempt was made to delineate soil contamination around the ash pond of a coal based thermal power plant the topsoil in the study area was found to be contaminated to varying degrees from ash disposal the soil drawn from various profiles was largely contaminated by ash fall out predominantly in the prevalent wind direction pb zn cu ni co mn cr v and ba were found to be enriched in the topsoil around the ash pond with respect to the crust as well as the background while mn v cr co and ni were enriched compared to their maximum permissible concentrations prescribed for agricultural soils these observations have been further strengthened from the contamination index map and lognormal distribution pattern of the elements as a consequence of this contamination many of the important physicochemical properties of topsoil in the direction of the wind have been modified significantly

corrigendum to a gradual drowning of the southwestern black sea shelf evidence for a progressive rather than abrupt holocene reconnection with the eastern mediterranean sea through the marmara sea gateway quaternary international 167 168 2007 19 34 on page 24 in table 1 several species identi cations listed are incorrect we attribute this to our limited experience prior to 2006 withbrackish to fresh water molluscs of the black sea and caspian sea well illustrated recent articles orlova et al 2005 gelembiuk et al 2006 wesselingh 2007 internet sites e g www gastropods com and helpful advice from william ryan columbia university haveallowed us to correct the errors for six shells with radiocarbon laboratory numbers to 11438 to 11439 to 11440 to 11441 to 11007and to 11443 the revised shell identi cations respectively are the bivalves monodacna pontica didacna praetrigonoides didacna spp dreissena rostiformis d rostiformis and the gastropod theodoxus spp in the description of unit c on pages 25 and 26 references to par vicardium exiguum and dreissena polymorpha should be replaced by monodacna pontica didacna spp dreissena polymorpha andd rostiformis references

eemian and holocene sea surface conditions in the southern black sea organic walled dinoflagellate cyst record from core 22 gc3 in order to compare the sea surface conditions in the black sea during the holocene and eemian sapropelic parts of marine core 22 gc3 42 13 53 n 36 29 55 e 838 m water depth were studied for organic walled dinoflagellate cyst content the record shows a change from freshwater brackish assemblages pyxidinopsis psilata spiniferites cruciformis and caspidinium rugosum to more marine assemblages lingulodinium machaerophorum and spiniferites ramosus complex during each interglacial due to the inflow of saline mediterranean water the lacustrine marine transitions in 22 gc3 occurred at 8 3 cal kyr bp during the early holocene and 128 kyr bp during the early eemian slightly later compared to the onset of interglacial conditions on the adjacent land dinoflagellate cyst assemblages reveal higher sea surface salinity 28 30 e g spiniferites pachydermus bitectatodinium tepikiense and spiniferites mirabilis around 126 5 121 kyr bp in comparison to the holocene 15 20 as well as relatively high sea surface temperature e g tuberculodinium vancampoae s pachydermus and s mirabilis especially at 127 6 125 3 kyr bp establishment of high sea surface salinity during the eemian correlates very well with reconstructed relatively high global sea level and is explained as a combined effect of increased mediterranean supply and high temperatures at the beginning of the last interglacial the observed changes in the dinocyst record highlight the importance of nutrients for the composition of the eemian and holocene dinocyst assemblages

plio pleistocene trends in ice rafted debris on the lomonosov ridge although more than 700 sediment cores exist from the arctic ocean the plio pleistocene evolution of the basin and its marginal seas remains virtually unknown this is largely due the shallow penetration of most of these records and difficulties associated with deriving chronologies for the recovered material the integrated ocean drilling program s iodp expedition 302 arctic coring expedition acex recovered 197 m of neogene quaternary sediment from the circumpolar regions of the lomonosov ridge as detailed analyses of this material emerge research is beginning to formulate a long term picture of paleoceanographic changes in the central arctic ocean this paper reviews the acex plio pleistocene age model identifies uncertainties and addresses ways in which these may be eliminated within the established stratigraphic framework a notable reduction in the abundance of ice rafted debris ird occurs in the early part of the pleistocene and persists until marine isotope stage 6 mis 6 therefore while global oceanographic proxies indicate the gradual growth of terrestrial ice sheets during this time ird delivery to the central arctic ocean remained comparatively low and stable within the resolution of existing data the pleistocene reduction in ird is synchronous with predicted changes in both the inflow of north atlantic and pacific waters which in modern times are known to exert a strong influence on sea ice stability

changes in sediment source areas to the amerasia basin arctic ocean over the past 5 5 million years based on radiogenic isotopes sr nd pb of detritus from ferromanganese crusts abstract ferromanganese femn crusts provide a useful paleoenvironmental archive for studying the poorly understood climatic oceanographic and geologic evolution of the arctic ocean this study is based on the identification and temporal reconstruction of sources and inferred transport pathways of terrigenous material in femn crusts collected from several sites across the amerasia basin samples from the alpha ridge ar mendeleev ridge mr and chukchi borderland cb have similar chemical compositions and high detrital contents sr nd and pb isotopic compositions of the terrigenous detritus extracted from the femn crust layers show spatial and temporal variability due to the variable proportions of inputs from the north american and east siberian margins and local submarine outcrops the temporal resolution is restricted by macroscopic crust layers which represent times of significant changes in the depositional environment and are used to study first order environmental changes during the period of ca 4 4 to 3 8 myr ago detritus in the mr area was derived mostly from the laptev sea then until about 1 3 myr ago femn crusts from mr received a higher volcanic component sourced from the east siberian sea with mixing of detritus from the okhotsk chukotka volcanic belt ocvb area and possibly weathering of local mr outcrops which is mostly high arctic large igneous province halip rocks the period from about 1 3 myr ago to the present reflects enhanced contributions of detritus from the canadian shield approximately equal to the east siberian contribution for the mr area cb crusts show three main periods of distinct detrital input during the period ca 5 5 5 0 myr ago cb detritus was sourced from local submarine outcrops of the jurassic cretaceous halip rocks and possibly from northeast siberia including ocvb rocks while during the period from about 5 0 to 3 6 myr ago the cb femn crusts had a much greater input of detritus from the north american margin after 3 6 myr ago the cb detritus shows a mixed composition predominantly sourced from north america with some material transported from the bering sea and smaller contributions from northeast siberia the ar crust was influenced mostly by detritus sourced from the canadian shield this study shows that femn crusts from the arctic ocean are a useful tool and archive for climate reconstruction and depositional history of this polar region

palaeoclimate the sea ice thickens little is known about the presence of high latitude sea ice before 2 6 million years ago a reanalysis of marine sediments from the arctic ocean indicates an intermittent presence of perennial sea ice as early as 44 million years ago

a 20 million year record of planktic foraminiferal b ca ratios systematics and uncertainties in pco2 reconstructions we use new and published data representing a 20 million long record to discuss the systematics of interpreting planktic foraminiferal b ca ratios b ca based reconstructions of seawater carbonate chemistry and atmospheric pco 2 assume that the incorporation of boron into foraminiferal tests can be empirically described by an apparent partition coefficient k d b ca caco 3 b oh 4 hco 3 seawater hemming and hanson 1992 it has also been proposed that there is a species specific relationship between k d and temperature yu et al 2007 as we discuss although these relationships may be robust there remain significant uncertainties over the controls on boron incorporation into foraminifera it is difficult to be certain that the empirically defined correlation between temperature and k d is not simply a result of covariance of temperature and other hydrographic variables in the ocean including carbonate system parameters there is also some evidence that k d may be affected by solution hco 3 co 2 3 ratios i e ph or by co 2 3 in addition the theoretical basis for the definition of kd and for a temperature control on k d is of debate we also discuss the sensitivity of pco 2 reconstructions to different k d temperature calibrations and seawater b ca if a k d temperature calibration is estimated using ice core pco 2 values between 0 and 200 ka b ca ratios can be used to reasonably approximate atmospheric pco 2 between 200 and 800 ka however the absolute values of pco 2 calculated are sensitive to the choice of k d temperature relationship for older time periods the absolute values of pco 2 are also dependent on the evolution of seawater b concentrations however we find that over the last 20 ma reconstructed changes in declining pco 2 across the mid pleistocene transition pliocene glacial intensification and the middle miocene climate transition are supported by the b ca record even if a constant coretop k d is used or different k d temperature calibrations and models of seawater b evolution are applied to the data the inferred influence of temperature on k d from coretop data therefore cannot itself explain the structure of a published pco 2 reconstruction tripati et al 2009 we conclude the raw b ca data supports a coupling between pco 2 and climate over the past 20 ma finally we explore possible implications of b ca based pco 2 estimates for the interpretation of other marine pco 2 proxies

arctic ocean deep sea record of northern eurasian ice sheet history the sediment composition of deep sea cores from the central arctic ocean the fram strait and the yermak plateau was analyzed for several parameters to reconstruct the history of marine paleoenvironment and terrestrial glaciation in the last 200 000 years layers with high amounts of coarse terrigenous ice rafted debris ird and often high contents of smectite were deposited during extensive glaciations in northern eurasia when ice sheets reached the northern continental margins of the barents and kara seas and discharged icebergs into the arctic ocean intercalated layers with relatively low ird and smectite contents but abundant planktic foraminifers in the coarse fraction were deposited during periods of atlantic water inflow to the arctic ocean and seasonally open waters leads in a sea ice cover with only few icebergs in the arctic ocean high ird contents in the sediments reflect the presence of ice sheets on the kara and barents seas shelves and the hinterland during the entire oxygen isotope stage 6 ca 190 130 ka in substage 5b ca 90 80 ka at the stage boundary 5 4 around 75 ka and in late stage 4 early stage 3 ca 65 50 ka these results are in excellent correlation with those from recent field work in northern scandinavia european russia siberia and on the shelves relatively low amounts of ird in central arctic ocean sediments from the late weichselian glacial maximum ca 24 18 ka correlate well with the recent reconstruction of a very limited eastern ice sheet extension during this time oxygen and carbon isotope records of planktic foraminifers from the analyzed sediment cores show a number of prominent excursions which can be interpreted as evidence for freshwater events in the arctic ocean the synchroneity of freshwater events and ird input suggests a common source strongest events were associated with deglaciations of the barents and kara seas after the ice sheets had blocked the outflow of large rivers for several millennia the outflow of freshwater from large ice dammed lakes occurred at ca 130 80 75 and 52 ka freshwater events in the central arctic ocean during the last deglaciation ca 18 ka were relatively small compared to the previous events this indicates that during most of the late weichselian glacial maximum a river outflow from northern siberia to the arctic ocean was possible atlantic water inflow to the arctic ocean and seasonally open waters in the ice leads occurred during the interglacials ofoxygen isotope stage 1 and substage 5e during several interstadials stage 3 substages 5a and 5c and to a lesser degree within stadials and glacials stages 2 4 and 6 with the exception ofthe interglacials these periods were times ofstrong ice growth on the continents as revealed by terrestrial data the coincidence suggests that open waters in the arctic ocean and the nordic seas were an important moisture source in addition to more southerly sources which fostered the growth of ice sheets on northern eurasia

major ion signatures for identification of geochemical reactions responsible for release of fluoride from geogenic sources to groundwater and associated risk in vaniyar river basin dharmapuri district tamil nadu india fluoride is a common constituent in most of the rocks and the release of fluoride into groundwater is the major problem in several parts of the world the present study was carried out with the objective of identifying sources and mechanism of release of fluoride from the rocks and its impact on human health in vaniyar river basin dharmapuri district tamil nadu groundwater samples were collected from 44 wells once in 2 months from june 2011 to august 2014 and analyzed for major cations and anions using an ion chromatograph the possible reasons for the increased concentration of fluoride in groundwater of the area were investigated by taking into account of the agricultural practises and the major rock types in the area the observed order of the dominance of cations in groundwater in the study area is na ca2 mg2 k and that of anions is cl hco3 so42 co3 f the fluoride concentration in groundwater of this region ranges from 0 15 to 6 14 mg l out of 569 samples analysed fluoride concentration exceeded the maximum permissible limit of the drinking water standards of bis 1 5 mg l in 396 samples many people living in this area are suffering from dental and skeletal fluorosis due to prolonged use of fluoride rich groundwater for drinking concentration of fluoride in groundwater is relatively low in wells located in charnockite region whereas the concentration of fluoride in groundwater is high in the deep wells in regions comprising of epidote hornblende biotite gneiss the major source of fluoride in groundwater in the area is due to leaching of fluoride bearing minerals fluoride ions from biotite and hornblende minerals leach into the groundwater and contribute high fluoride concentration in this region the concentration of fluoride in groundwater increases when the water level is deep indicating higher release of fluoride from greater depth the geochemical reactions that control the release of fluoride from fluoride bearing minerals such as biotite and hornblende into groundwater were identified removal of high concentration of fluoride from drinking water is necessary in this region and measures should be taken to supply water after removal of fluoride for the betterment of the livelihood in the area

late cenozoic sedimentary environments in the amundsen basin arctic ocean analyses of sediment cores recovered on the arctic 91 cruise with rv polarstern to the amundsen basin and lomonosov ridge identify four main sedimentary facies and associated depositional sedimentary processes these include 1 homogenous mud facies interpreted as hemipelagic deposits most abundant in the central parts of the amundsen basin 2 fining upward cycle facies interpreted as fine grained distal turbidite deposits present in all amundsen basin cores but most abundant laterally in the basin 3 massive diamicton facies found in the north pole core and 4 laminated diamicton facies abundant in the upper parts of lomonosov ridge cores both diamictons are heavily influenced by ice rafted debris and the massive diamicton may result from redeposition of laminated diamicton downslope from the lomonosov ridge the lomonosov ridge core exhibits a sedimentation rate of 29 mm ka while the sedimentation rates of turbidite rich sediments of the amundsen basin may be up to 10 times as high clay minerals show that the eastern kara sea and the laptev sea is the source area for most of the sediments while some clay mineral zones may have their source in northern greenland or the barents sea shelf

entrainment and export of laptev sea ice sediments siberian arctic sea ice sediments sis sediments rafted by ice and shelf surface deposits from the siberian laptev sea were analyzed to study turbulent entrainment processes this study focused on the silt and clay fractions on average representing 63 4 and 30 4 total 93 7 of the bulk sis respectively generally the sis contains 50 more silt than the shelf deposits while the clay percentages in both sample groups are similar sand sized particles are less abundant in sis than in bottom sediment although sis is clearly enriched in silt no evidence was found for preferential ice entrainment of any silt subfraction coarse medium fine statistical tests of sis and shelf silt parameters and the similar clay mineral compositions of both sample groups provide evidence for entrainment of laptev bottom deposits into newly forming ice the entrainment is related to the mechanism known as suspension freezing accordingly coarser clasts sand and plant debris may be lifted upward by buoyant anchor ice while coarse silt particles are supposed to be transported to the surface by rising frazil aggregates additionally turbulent interaction of convergent langmuir circulation and near surface frazil ice streaks is proposed to support ice entrainment of the finest particles 6 4 phi 12 m entrainment and export of sis from the laptev sea were assessed for ten individual flaw leads extended narrow polynyas separating fast and drifting ice using particle concentrations in ice samples and new ice formation rates the results show that roughly 20 mt of sis can be annually exported from the laptev sea by lead ice only thus formation and export of sediment laden lead ice may play a major geological role in siberian arctic shelf erosion and coastal retreat

a holocene record of changing arctic ocean ice drift analogous to the effects of the arctic oscillation 1 the arctic oscillation ao controls the configuration of the transpolar drift tpd if thicker ice from the beaufort gyre were exported the volume of fresh water sea ice in the nordic seas would significantly increase decreasing the formation of north atlantic deep water this would cool large parts of the northern hemisphere and affect global climate therefore in order to understand how the global climate system functions it is imperative to know how the tpd changed over the last millennium or more the provenance of grains in a sediment core located near the confluence of the tpd and the beaufort gyre provides a direct proxy for changes in seaice drift owing to these circulation systems the core has more than 200 cm of holocene sediment with intervals dominated by grains from the russian shelves alternating with intervals of abundant grains from north american sources grains matched to russian shelves indicate that the tpd was shifted toward north america similar to what occurs during a more positive phase of the ao this condition alternated with intervals where few grains matched to russian sources presumably because the tpd was restricted to the russian half of the arctic far from the core site during the last 1300 years increased influx of russian grains occurred approximately every 50 150 years this fluctuation might represent the long term oscillation of the ao which modulates the same tpd shift today