oceanography in the kattegat and skagerrak over the past 8000 years in the kattegat between sweden and denmark a large number of cores containing holocene seafloor deposits were investigated stratigraphically sedimentological biostratigraphical and chronostratigraphical variables were especially emphasized palynological and foraminiferal analyses indicate several changes in the oceanographic circulation system in the skagerrak kattegat during the holocene radiocarbon datings and pollen analyses suggest that these changes occurred at 8000 4000 2000 between 1000 and 500 and 300 years b p compilation of stratigraphical data from the region suggests that at about 8000 years b p the english channel opened and the southern jutland current was formed this had a major influence on the skagerrak but only a marginal effect can be traced in the kattegat the major components of the present circulation system in the kattegat skagerrak were established about 4000 years b p and the subsequent changes in the circulation pattern and the inflow outflow system that developed at approximately 2000 500 and 300 years b p are variants of these

controls on mo isotope fractionations in a mn rich anoxic marine sediment gullmar fjord sweden abstract molybdenum isotopes have emerged as an important tool for determining the spatial extent of past ocean redox conditions however our understanding of mo cycling and associated isotopic fractionations in modern and ancient continental margin sediments is limited restricting attempts to fully utilize the potential of mo isotopes this is particularly the case with regard to the relative significance of mo isotope fractionations associated with biogeochemical mn and fe oxide cycling under conditions of low dissolved sulfide to rectify this we have investigated sediments from gullmar fjord sweden which contain high concentrations of mn oxides and exhibit a strong redox zonation between mn and fe reduction a combination of dissolved and particulate mo isotope measurements with porewater and solid phase mn and fe characterization reveals that the main influence on porewater 98 mo compositions is exerted by adsorption and desorption processes during reductive dissolution of both mn and fe oxyhydr oxide minerals in areas enriched in mn oxides distinctively low solid phase 98 mo values are observed 1 0 and 0 4 which occur due to the large mo isotope fractionation associated with mo adsorption to mn oxides however where mn oxide concentrations are lower authigenic 98 mo is largely controlled by fe oxyhydr oxide minerals resulting in more positive 98 mo isotopic compositions 0 5 and 2 our results suggest that for modern anoxic marine sediments where deposition occurs beneath an oxic to suboxic water column 98 mo is dominantly controlled by the relative availability of mn and fe oxides and the production of dissolved sulfide

oceanographic conditions in the deepest parts of the kattegat scandinavia revealed through recent benthic foraminifera and hydrography the kattegat has since the 1980s been subject to extensive investigations focusing on various aspects of the marine environment the most important reasons for this concentration of work are marine eutrophication periodically occurring oxygen deficiency in the bottom water and subsequent benthic mortality in this study a previously not discussed sill area separating two deep areas in the kattegat has been identified in the contexts of periodically occurring oxygen deficiency in the southern kattegat it is most relevant to study the environmental conditions in this area hydrographic data from the area inside and outside the sill area suggest that the deep water on both sides of the sill do communicate no evidence for stagnation in the deep area inside the sill was found in addition to hydrography data benthic foraminifera has been used as environmental tracers two characteristic benthic foraminiferal faunas have been defined one representing water depths exceeding 80 m and one representing shallower depths these faunas occur on both sides of the sill area two investigated deep depressions within the deep area inside the sill the alkor depth 138 m and poseidon depth 150 m are marked by a fauna that is identical with that in the so called kattegat trench this suggests that the depressions are not more stagnant if stagnant at all than the surrounding kattegat trench and the djupa rannan trench located outside the sill area the information generated in this study is essential for the understanding of the processes resulting in oxygen deficiency in the deep water of the southern kattegat

aeolian abrasion and modes of fine particle production from natural red dune sands an experimental study a series of experiments was conducted to determine the potential for aeolian abrasion of natural dune sands to produce fine particles 125 m by 1 the release of resident fines 2 spalling chipping and breakage of particles and 3 the removal of grain surface coatings parent samples were obtained from the surfaces of four active continental dunes and abraded using a glass test tube chamber for up to 120h the fine particles produced by this abrasion process were trapped at varying time intervals and subject to detailed particle size analyses using a coulter multisizer the abrasion of untreated parent samples produced fine particles in one of two main size classes 50 m but when the parent sample was sieved to exclude particles 250 m relatively more material in the range 10 50 m was produced for unsieved parent samples the size range associated with the dominant mode varied according to the length of the abrasion time the coarsest mode 63 m was dominant during the first 16 h of abrasion then became less significant and is thought to be associated with the release of resident fines into suspension the finest mode 10 m was absent or very weak during the first 16h of abrasion then became more significant and in some instances dominated the distribution as abrasion continued removal of grain surface coatings is the main source of fine material 10 m and this may be a significant source of fine material in areas where sands are dominated by subrounded and rounded particles by comparison with previous studies of aeolian particle abrasion these natural dune sands produced very low quantities of fine material by weight but their spatial extent makes them potentially a significant source of dust sized particles at the global scale

sources of non glacial loess size quartz silt and the origins of desert loess abstract descriptions of peridesertic loess deposits and possible non glacial origins for silt size quartz are reviewed including direct release from weathered bedrock results from salt and frost weathering experiments are presented and methods by which sufficient energy can be imparted to sand size grains to release silt size fragments are identified these fragments may then be entrained by aeolian or fluvial action results from fluvial comminution experiments indicate that high energy mixed sediment fluvial systems may be very effective in generating quartz silt purely aeolian attrition is also seen as a major source of silt size and finer material results from aeolian abrasion experiments performed using crushed quartz sand are complemented by trials using sands from deeply weathered granite and pannonian sands from hungary field and laboratory observations are therefore seen to argue for the existence of deposits that can be classified as desert loess

seasonal study of d18o and d13c in living stained benthic foraminifera from two swedish fjords in a previous 16 month seasonal study on living stained benthic foraminifera from two fjords on the swedish west coast it was reported that foraminifera proliferated in response to phytodetritus input the strongest response came from the opportunistic species stainforthia fusiformis in this study our objective was to find out if that phytodetritus input resulted in a change in the carbon isotopic composition of the foraminiferal tests we also wanted to examine if variations in salinity and temperature due to seasonality or deep water exchanges were reflected in the 18o values from s fusiformis that were obtained from the havstens fjord 20 m and the gullmar fjord 119 m during the 16 month study we developed a time series of 18o and 13c after the spring blooms in the havstens and the gullmar fjord decreases of about 0 2 to 0 3 in the foraminiferal 13c values were noted in the gullmar fjord after the autumn blooms decreases of the same order were also noted comparing the havstens and the gullmar fjord we found a 1 difference in both 13c and 18o we attribute this to hydrographic differences between the two fjords using calculated values of 18o together with the measured ones we noticed that s fusiformis in the gullmar fjord seems to calcify close to equilibrium with respect to the oxygen isotopes during autumn water temperatures were relatively high in the havstens fjord and foraminiferal abundance in the fjord was also high after a phytodetritus input but the measured 18o values do not reflect these higher temperatures this apparently contradictory combination of results might be explained by a varying 18o composition of the water during the year which counterbalances the temperature effect

the benthic foraminiferal record of the medieval warm period and the recent warming in the gullmar fjord swedish west coast a high resolution study of benthic foraminiferal assemblages was performed on a ca eight metre long sediment core from gullmar fjord on the west coast of sweden the results of pb 210 and ams c 14 datings show that the record includes the two warmest climatic episodes of the last 1500 years the medieval warm period mwp and the recent warming of the 20th century both periods are known to be anomalously warm and associated with positive nao winter indices benthic foraminiferal successions of both periods are compared in order to find faunal similarities and common denominators corresponding to past climate changes during the mwp adercotryma glomerata cassidulina laevigata and nonionella iridea dominated the assemblages judging from dominance of species sensitive to hypoxia and the highest faunal diversity for the last ca 2400 years the foraminiferal record of the mwp suggests an absence of severe low oxygen events at the same time faunas and delta c 13 values both point to high primary productivity and or increased input of terrestrial organic carbon into the fjord system during the medieval warm period comparison of the mwp and recent warming revealed different trends in the faunal record the thin shelled foraminifer n iridea was characteristic of the mwp but became absent during the second half of the 20th century the recent skagerrak kattegat fauna was rare or absent during the mwp but established in gullmar fjord at the end of the little ice age or in the early 1900s also there are striking differences in the faunal diversity and absolute abundances of foraminifera between both periods changes in primary productivity higher precipitation resulting in intensified land runoff different oxygen regimes or even changes in the fjord s trophic status are discussed as possible causes of these faunal differences c 2011 elsevier b v all rights reserved less

the impact process in aeolian saltation two dimensional simulations a critical event in the trajectory of a sand grain saltating in air is its interaction with the surface we examine the phenomenon of grain bed impacts in two dimensions using a combination of dynamical computer simulations analytical models and physical reasoning the results indicate that the grain bed collisions can be treated as two body collisions with the bed particle assuming an effective mass greater than its true mass also the presence of geometrical surface irregularities has a strong bearing on the interaction between saltating and surface grain populations as well as on the formation of small scale bedforms

multiple dust sources in the sahara desert the importance of sand dunes 1 we determine the current sources of dust in the sahara desert using quantitative correlation between the number of days with dust storms nds derived from remote sensing data of high temporal resolution with the distribution of the soil types and geomorphic units during 2006 8 the source of over 90 of the nds was found to be sand dunes leptosols calcisols arenosols and rock debris in contrast to previous studies only few dust storms originated from playas and dry lake beds land erodibility was estimated by regressing the nds to the number of days with high speed wind events and was found to be high for sand dunes clay and fine silt grains and aggregates are scarce in sand dunes which most likely produce dust particles through aeolian abrasion of sand grains thus saltating sand grains impacting clay aggregates on playa surfaces cannot be the sole process for generating dust in the sahara

a common opportunistic foraminiferal species as an indicator of rapidly changing conditions in a range of environments abstract long term biological and environmental time series several decades to centuries are essential for distinguishing between anthropogenically and naturally induced environmental change as well as for monitoring environmental change over time irrespective of the causes since such long time series are virtually non existent for most areas other methods have to be explored which can provide the best possible analogues numerous investigations have shown that benthic foraminifera meiofaunal protists which leave a fossil record in most marine sediments are well suited for this purpose a prerequisite for performing sound interpretations is an optimal understanding of their biology and ecology stainforthia fusiformis williamson is one of the most common benthic foraminiferal species in nw european waters and living stained populations have been recorded in all clastic soft bottom intertidal to outer shelf and slope areas with sediments consisting of at least some fines 4 28 its predominance in ephemerally dysoxic anoxic areas has caused it to be used as a proxy for severe oxygen depletion a strong dominance even 90 of this species is however also reported from well oxygenated coastal and shelf settings and consequently high abundance of this species occurs in habitats with very different environmental characteristics a closer examination of these areas suggests that they can be roughly grouped into three categories 1 beneath hydrographic frontal areas 2 physically disturbed areas of sediment and 3 ephemerally dysoxic anoxic basins the main characteristic feature that these highly different environments have in common is that they experience rapidly changing conditions it is concluded that the opportunistic life strategy of s fusiformis makes it highly adapted to cope with environmental stress and that this rather than tolerance to a particular environmental parameter causes it to predominate in areas subject to rapidly changing environmental conditions

source regions and formation of the loess sediments on the high mountain regions of northwestern china loess on the high mountains of northwestern china is largely controlled by the topographic features distributed mainly on the northern slopes of the tianshan and kunlun mountains as well as in the ili valley between the northern and central tianshan ranges loess distributed in different regions has different ages with the oldest early pleistocene loess occurring in the ili valley geochemical mineralogical and granulometric analyses demonstrate that the loess in the three different regions has different provenance the loess on the northern tianshan and kunlun mountains is mainly derived from the junggar and taklimakan deserts respectively whereas the loess in the ili valley is derived mainly from the sary ishikotrau desert located in the republic of kazakhstan however these deserts serve mostly as holding areas for the silts rather than original source regions the production of the silt sized particles is mainly associated with glacial abrasion and tectonic induced rock denudation thus the loess in the studied regions can be described as mountainous loess rather than simply glacial loess or desert loess it is unlikely that the mechanisms of loess formation are the same in different regions given their dependence on specific geomorphological conditions and associated processes

silt production as a function of climate and lithology under simulated comminution production of the silt sized particles composing loess represents a critical step in its ultimate formation but the volume and rate of production in different settings remain underdetermined this study addresses the influence of climate and source lithology on silt formation by subjecting natural alluvial fluvial sand from systems characterized by varying climatic setting to simulated comminution bulk samples from comparable transport distances were collected from a hot arid california desert alluvial system hot humid puerto rico fluvial system and cold humid norway proglacial fluvial system and sieved to isolate the coarse very coarse sand fraction for experimental milling source rocks in all three systems consist of granitoids with some contributions from foliated coarse grained metamorphic rocks gneissic and schistose in norway results indicate that contributions from coarse grained foliated lithologies impart a negligible effect on rate of silt production from the sand starting material climatic setting imparts no significant difference on sand durability but influences clay production at later stages of comminution for the puerto rico sample presumably owing to the effects of deep chemical weathering prior to physical transport comminution and silt production in all experiments exhibit exponential decay wherein rapid initial rates diminish with time this is interpreted to reflect the effects of the dynamic milling conditions particle size and distribution and slurry viscosity as well as particle strength with the latter including both relative strengths of different minerals in general and the influences of lattice defects and microfractures in quartz in particular empirical observations reveal that silt fractions of the natural alluvial fluvial samples collected at comparable transport distances 5 7 km in the respective systems exhibit significant differences bulk sediment samples from the norwegian proglacial system contain substantially more silt 3 10 times than either of the other two localities implying a significant difference in the natural processes operating to generate silt in these different field settings we suggest this difference reflects the efficacy of glacial grinding in silt production

transport direction of peoria loess in nebraska and implications for loess sources on the central great plains abstract in the midwestern united states large rivers draining the laurentide ice sheet lis were the most important sources of peoria loess deposited during the last glaciation loess deposition near those rivers may have responded primarily to ice sheet dynamics rather than direct effects of climatic change in contrast it has been proposed that thick peoria loess on the central great plains was derived mainly from unglaciated landscapes northwest of the main loess deposits in this study transport directions inferred from more than 600 measurements of peoria loess thickness in nebraska are used to test the hypothesis that much of the peoria loess on the great plains is nonglaciogenic a strong northwest to southeast thickness trend indicates that most peoria loess in nebraska was transported from one or more unglaciated northwestern source areas rather than from glacially influenced river floodplains the missouri river draining the lis the platte river draining alpine glaciers and the elkhorn river unglaciated basin were secondary sources their contribution is not detectable beyond a distance of 40 60 km peoria loess deposition on the central great plains was largely a direct response to climatic change in the unglaciated source region

stable oxygen and carbon isotope information on the establishment of a new opportunistic foraminiferal fauna in a swedish skagerrak fjord basin in 1979 1980 significant faunal changes reported fromrecent coastal environments which are not directly influenced by urban and industrial impact are rarely seen in gullmar fjord on the swedish west coast a significant foraminiferal fauna change occurred in connectionwith severe low oxygen conditions that evolved in thewinter of 1979 1980 a foraminiferal fauna marked by common skagerrak kattegat species which had previously characterised the deep fjord basin was replaced by the opportunistic low oxygen tolerant species stainforthia fusiformis williamsson to study this phenomenon further we performed stable oxygen and carbon isotope analyses on the indicator species itself s fusiformis both on specimens from sediment cores representing approximately the last 85 years and on living stained individuals taken from a transect across the deep fjord basin our purpose was to detail how and why s fusiformis came to dominate the fauna the oxygen isotope results suggest that salinities and temperatures in the deep basin have been relatively constant over the last c 85 years while the carbon isotopes show a significant change towards more negative values in association with the faunal shift of 1979 1980 the combined results from both the cores and the surface sediments suggest that s fusiformis did not inhabit the deep basin until 1980 before then almost all specimens of s fusiformis were small sized and their carbon isotope values suggest they were re deposited shallow water specimens that had been transported down to the central deep basin as part of a suspension load after a major faunal extinction in 1979 1980 s fusiformis of all sizes suddenly appeared in large numbers and their carbon isotopic values were similar to the signal from registered in the recent living fauna within the deep basin this suggests that the opportunistic s fusiformis established itself in the deep basin as a consequence of the severe low oxygen event and the faunal crash of the previously dominating skagerrak kattegat fauna less

a late quaternary magnetic record of tunisian loess and its climatic significance magnetic measurements for a 10 m loess palaeosol sequence from the matmata plateau in southern tunisia show significant down profile variations in concentrations of pedogenic ferrimagnetic minerals the sequence appears to correlate with regional and global records of climate change over the past 70 kyr there is strong evidence from comparisons of mineral magnetic properties in modern soils and palaeosols that the sequence holds a proxy record of winter precipitation

high benthic fertility and taphonomy of foraminifera a case study of the skagerrak north sea abstract the skagerrak basin is a deep water extension of the north sea it is of particular interest as an analogue for past epicontintal shelf basins because it presents environmental contrasts with the adjacent shelf seas in this study the distribution patterns of benthic foraminifera have been used to infer taphonomic and oceanographic processes only by separating living from dead assemblages is it possible to interpret taphonomic changes the transport of foraminiferal tests to the danish slope is inferred from the presence there of dead exotic tests whose provenance is considered to be from the south the abundance of detrital organic matter on the danish slope is likewise inferred to be sourced from the same direction thus the danish slope is interpreted to be a depositional sink apart from transport another taphonomic process is the dissolution of calcareous tests this is clearly demonstrated both by the fragility of some tests as viewed under the microscope and by the disparity between the composition of the living and dead factor associations in the deep basin in particular the two predominantly calcareous living associations are replaced by a single predominantly agglutinated dead association due to carbonate dissolution the danish slope of the skagerrak basin is demonstrated to be an area of high benthic fertility this is based on the high density of living stained benthic foraminifera comparable with that of the mississippi delta particularly the abundance of stainforthia fusiformis an opportunistic species and tubular agglutinated forms the fertility is linked with the high abundance of particulate organic matter here previous regional studies have focused on total living plus dead distributions of 100 or 125 m sized foraminifera these factor assemblages are distinct from the 63 m living and dead associations described here

alluvial sediment or playas what is the dominant source of sand and silt in desert soil vesicular a horizons southwest usa 1 vesicular a av soil horizons form beneath desert pavements from the accretion of aeolian sediment dust commonly thought to be derived primarily from desiccating pluvial lakes and playas with contributions from ephemeral washes and alluvial fans particle size distributions of av horizons are typically bimodal with primary modes of very fine silt and fine sand suggesting that the horizon matrix is derived from multiple sources here we conduct detailed chemical and physical analysis of both av horizon soil samples and potential sources of aeolian sediment to better constrain the relative contributions of dust associated with the development of av horizons geochemical data from both sand 125 250 m and silt 2 32 m fractions in av horizons and potential dust sources in the eastern mojave desert and western sonora desert usa point to large contributions from nearby sources including distal alluvial fans and washes and comparably lower contributions from regional sources such as playas the silt mode is derived from suspension transport of dust and the fine sand mode is derived from saltating sand the desiccation of pluvial lakes in the mojave desert is commonly believed to have driven episodes of aeolian activity contributing to sand dunes and av horizon formation we propose that alluvial fans and washes are underappreciated as desert dust sources and that pulses of dust from late pleistocene and holocene alluvial fans dwarfed pulses of dust from desiccating pluvial lakes in the eastern mojave desert

geochemical and mineralogical evidence for sahara and sahel dust additions to quaternary soils on lanzarote eastern canary islands spain africa is the most important source of dust in the world today and dust storms are frequent on the nearby canary islands previous workers have inferred that the sahara is the most important source of dust to canary islands soils with little contribution from the sahel region soils overlying a late quaternary basalt flow on lanzarote canary islands contain in addition to volcanic minerals quartz and mica exotic to the island s bedrock kaolinite in the soils also likely has an exotic origin trace element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and african dust major element geochemistry clay mineralogy and interpretation of satellite imagery suggest that dust additions to the canary islands come not only from the sahara desert but also from the sahel region

a major change in the dinoflagellate cyst flora of gullmar fjord sweden at around 1969 1970 and its possible explanation

late pleistocene and holocene dune activity and wind regimes in the western sahara desert of mauritania the western sahara desert in mauritania is dominated by extensive sand seas consisting largely of linear dunes analyses of landsat images geomorphic and stratigraphic studies and optically stimulated luminescence dating of dunes in the azefal agneitir and akchar sand seas provide evidence that three main generations of dunes were formed during the periods 25 15 ka centered around the last glacial maximum 10 13 ka spanning the younger dryas event and after 5 ka the wind regimes that occurred during each of these periods were significantly different leading to the formation of dunes on three distinct superimposed trends northeast north northeast and north and the development of the sand seas as composite geomorphic features

on the formation of desert loess sequences of quartz rich coarse 20 63 m silt occur in many low and midlatitude unglaciated arid and semiarid areas and have been termed desert loess the processes by which these deposits are generated have been debated for decades all hypotheses to explain their origin seek to provide mechanisms for the generation of silt sized material without glacial grinding which is the main process involved in the production of coarse silt at high latitudes possible mechanisms for the formation of coarse silt in arid regions include derivation from preexisting siltstones mechanical weathering of silicate rocks and abrasion of sand grains in active dune environments during intense transport events examination of the characteristics of desert loess and field and laboratory experiments to assess the role of dune areas as a source of coarse silt by abrasion and or resuspension of residual fines suggests that many loess sequences are dominated by locally derived coarse silt improvements in the characterization of desert loess particle size mineralogy and geochemistry are needed however to identify sources and sinks of coarse silt especially when combined with climatic back trajectory analysis properly scaled experiments and modeling of particle collisions will also help to better quantify the effectiveness of abrasion in the generation of coarse silt in support of field observations

abrasion derived sediments under intensified winds at the latest pleistocene leading edge of the advancing sinai negev erg abstract quaternary desert loess and sandstone loessite relationships in the geological record raise questions regarding causes and mechanisms of silt formation and accretion in the northern sinai negev desert carbonate terrain only sand abrasion in active erg could have produced the large quantities of quartzo feldspathic silts constituting the late quaternary northwestern negev loess in the continuum of source medium to fine sand of dunes to sink silts in loess the very fine sand is unaccounted for in the record this weakens the sand abrasion model of silt formation as a global process here we demonstrate that as predicted by experiments abrasion by advancing dunes generated large quantities of very fine sand 60 110 m deposited within the dune field and in close proximity downwind this very fine sand was generated 13 11 ka possibly synchronous with the younger dryas under gusty sand dust storms in the southeastern mediterranean and specifically in the northern sinai negev erg these very fine sands were washed down slope and filled small basins blocked by the advancing dunes outside these sampling basins it is difficult to identify these sands as a distinct product we conclude that ergs are mega grinders of sand into very fine sand and silt under windy quaternary and ancient aeolian desert environments

holocene oceanographic and glacial changes recorded in maxwell bay west antarctica abstract three holocene core sections from maxwell bay south shetland islands west antarctica are investigated using ms grain size toc foraminifera 18o and 13c 14c and 210pb in order to examine holocene oceanographic glacial and climatic changes in the region they come from 190 221 and 333 m water depths and the bay margin proximal locations complementing earlier studies from the deep central part the three records vary between locations and reflect combined marine and terrigenous influence from the open ocean and surrounding islands respectively the longest and best dated composite section comes from the inner part of the bay core jtc jpc 17 and extends back to 6 3 cal kyr bp close to the termination of the holocene climatic optimum a combination of dating problems and mixed foraminiferal assemblages prevented reliable interpretation of core jpc 15 from the outer part of the bay core jpc 16 collected from the inner bay near the inlet between king george and nelson islands revealed repeated highs in planktonic neogloboquadrina pachyderma occurrence during last 3000 yr these highs are interpreted as indicating periods of decreased meltwater flow into the bay and thus greater influence of open marine surface waters core jtc jpc 17 located closest to king george island and the collins ice cap records increased glacial conditions at 2000 cal yr bp this event is recorded by turbidite deposition at core site jpc 16 major components of the benthic foraminiferal assemblage indicate decreasing tolerance to near glacier or near shore conditions however local climate variability appears to have overall little impact on benthic foraminiferal biota thus it is unlikely that in similar settings recent warming would be strongly manifest as changes in benthic foraminiferal communities stable isotopic analysis is based on cassidulinoides parkerianus and globocassidulina biora subtle decrease in 18o at 3500 cal yr bp followed by episodic increases at 1000 cal yr bp and in the youngest part of the record appear to correlate with the period prior to the beginning of the neoglacial with medieval warm period and with post little ice age warming respectively the latest event is also marked by a significant increase in sediment accumulation rate in the second half of the 20th century

oxygen isotopes in meteoric calcite cements as indicators of continental paleoclimate because meteoric water 18 o values decrease with decreasing ambient temperature and increasing latitude 18 o values of meteoric calcite cement should exhibit a similar relation with paleolatitude and be an indicator of continental paleotemperatures to test this we compiled isotopic and paleolatitude data for 20 meteoric cements and nine speleothems ranging in age from devonian to modern and in paleolatitude from 3 5 to 83 mean 18 o values for meteoric cements and speleothems both show the same negative correlation with paleolatitude the 18 o vs latitude trend for these carbonates is almost identical to that predicted for modern inland environments but differs from the trend for coastal environments this suggests that the ground water controlling the ultimate composition of meteoric cement is derived predominantly from inland recharge if it is assumed that the modern meteoric water 18 o vs temperature relation is valid for the past and that insignificant evaporation occurred prior to carbonate precipitation then coastal and inland paleotemperatures can be calculated from the 18 o values of meteoric calcite 18 o mcl and seawater 18 o sw by using the equations t coastal 13 3 32 6 0 231 0 0613 18 o mcl 18 o sw and t inland 17 8 16 2 0 572 0 1233 18 o mcl 18 o sw where t is temperature in c calcite precipitated from coastal meteoric water at temperatures between 0 and 25 c will exhibit a narrow range in 18 o 6 to 4 where 18 o sw 0 the 18 o of calcite precipitated from inland meteoric water will be sensitive to paleotemperature ranging from 14 to 5 where 18 o sw 0 for temperatures of 0 to 25 c

influences of eolian and pedogenic processes on the origin and evolution of desert pavements well developed desert pavements are present above eolian deposits that mantle flows of the cima volcanic field located in the mojave desert california soil stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements eolian dust 1 accelerates mechanical fragmentation of flow rock providing the source material for pavements and 2 accumulates slowly below basaltic colluvium in flow depressions eventually promoting development of cumulate soils below the evolving stone pavement an increase in dust flux during the holocene has raised ancient pleistocene pavements as much as 20 cm above the former land surface the results of our studies demonstrate for the first time that most desert pavements do not form by deflation by overland flow or by upward migration of stones through a slowly formed clayey argillic horizon desert pavements are born and maintained at the surface

contrasting re os magmatic fractionation in planetary basalts abstract this work reports the first re os isotopic results for lunar basalts and eucrites both re and os concentrations are found to be very low and re os ratios are close to chondritic this contrasts with the much higher than chondritic re os ratio of terrestrial basalts osmium displays a rather uniform solid liquid fractionation in different planetary bodies moon earth eucrite parent body mars whereas rhenium is about three orders of magnitude more incompatible in terrestrial basalt genesis we argue that this is a function of oxygen fugacity in the source regions of basalts

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

late quaternary redeposited loess soil developmental sequences south yemen abstract episodic desert loess and paleosol sequences in south yemen provide a late pleistocene to holocene record of climatic change and soil development at sana one paleosol based on its thickness and development formed during mid or early holocene time in approximately four thousand years the 2akb horizon sample of this paleosol has a 14 c age of 7750 300 years at ibb the 2abtb horizon of another paleosol has a 14 c age of 33 100 years deposition silt very fine sand clay for the sana site calculates to average 110 g m 2 yr 1 and includes 3 3 g or less of caco 3 m 2 yr 1 this rate of desert loess and carbonate deposition is probably 2 to 5 times greater than that in the lahontan basin of the united states during the last 13 kyr and about 2 to 5 times higher than that in the southwestern united states today it is about the same as the 12 cm kyr 1 170 g m 2 yr 1 estimated for central north iran and the 10 cm kyr 1 0 1 mm yr 1 estimated for the netivot section of the negev of israel but some 7 to 9 times less than the rate estimated for wisconsinan loess in iowa thickness of desert loess examined and the calculated rate of deposition indicate that the crater has been receiving desert loess for at least 15 kyr and that the crater is pre holocene pedogenic development of the camborthids and haplargids in the ground soils and that of the argillic horizons in the sana paleosols suggest that these soils formed in a somewhat more humid phase than the present warm tropical semi arid environment the occurrence of mollic epipedons in the sana paleosols but not in the ground soils is evidence of a more humid past climate mid or early holocene the ibb paleosol which formed at least partly during a more humid part of the late pleistocene is even more strongly developed than the mid or early holocene sana paleosols

late quaternary paleoenvironments and paleoclimatic conditions in the distal andean piedmont southern mendoza argentina abstract the andean piedmont of mendoza is a semiarid region covered by extensive and partially vegetated dune fields consisting of mostly inactive aeolian landforms of diverse size and morphology this paper is focused on the san rafael plain srp environment situated in the distal andean piedmont of mendoza 34 30 s and reports the sedimentology and osl chronology of two representative exposures of late quaternary deposits including their paleoenvironmental and paleoclimatic significance eleven facies including channel floodplain fluvio aeolian interaction and reworked pyroclastic and aeolian deposits were described and grouped into two facies associations fa1 and fa2 fa1 was formed by unconfined sheet flows minor channelized streams and fluvial aeolian interaction processes fa2 was interpreted as aeolian dune and sand sheet deposits osl chronology from the srp sedimentary record indicates that between ca 58 39 ka and ca 36 24 ka mis 3 aggradation was governed by ephemeral fluvial processes fa1 under generally semiarid conditions during mis 2 the last glacial maximum ca 24 12 ka a major climatic shift to more arid conditions is documented by significant aeolian activity fa2 that became the dominant sedimentation process north of the diamante atuel fluvial system the inferred paleoenvironmental conditions from the srp sections are in broad agreement with regional evidence

quantifying dust emissions from desert landforms eastern mojave desert usa abstract the measurement of natural dust emissions from desert landforms is crucial in environmental hazard assessment and field checking the accuracy of global dust models more than 500 individual dust measurements from eight common desert landforms in southern california were collected using the pi swerl portable in situ wind erosion lab the largest emitters of dust are dry washes 13 787 to 0 007 mg m 2 s 1 dunes playa margins distal alluvial fans and lacustrine beaches low emitters include salt crusted playas 0 692 to 0 002 mg m 2 s 1 silt clay crusted playas and desert pavements high emissions are a function of saltating sand that bombards the surface liberating dust sized particles for entrainment low dust emissions are primarily a function of surface crusting gravel armoring and vegetation density pi swerl measurements reveal that emission rates can vary by at least three orders of magnitude reflecting local variability in soil texture and continuity of surface crusts shear stress partitioning models can be applied to dust data measured by the pi swerl to account for large surface roughness features such as vegetation the results presented here give an approximation of the contributions to atmospheric dust loading by landforms in the mojave desert and can potentially be used to improve atmospheric dust models

sahara and sahel vulnerability to climate changes lessons from holocene hydrological data abstract the examination of more than 1500 paleohydrological dated records collected between 10 and 28 n during the last 50 years have been used to improve our knowledge and understanding of the sahara and sahel vulnerability to the atlantic monsoon changes in the long term we have analyzed the distribution of water bodies mainly lakes and wetlands over time and space the central saharan massifs played a major role in favoring water supply to the lowlands throughout the whole african humid period in addition distinct east west dynamics is recorded with humidity starting and stopping several millennia earlier to the east than to the west of the sahara a series of time lags are discussed 1 between the maximum of deep fresh water lake formation during the early holocene and the maximum of water body extensions during the mid holocene which highlight the primary role of aquifer water level in lake response to climate change 2 between the hydrological history of the sahara and the sahel and the forcings mainly insolation changes during the early and mid holocene which involves complex interactions between remnant ice sheet in the northern hemisphere open water bodies in the sahara and sahel and the atlantic monsoon system