tem study of in situ organic matter on continental margins occurrence and the monolayer hypothesis abstract tem photomicrographs show that organic matter in the continental margin sediments that we have examined is primarily patchy in distribution and occurs as 1 discrete discontinuous blebs and micro blebs of differentiated and undifferentiated protoplasm 2 bacterial cells and associated muco polysaccharide networks and 3 localized smears generally associated with clay minerals and domain junctions in clay rich flocs not as thin uniform grain coatings or as infillings of nicks or etch pits on sediment grains with high degrees of surface roughness this occurrence contradicts recent assertions that most organic matter in continental margins occurs as monolayer or monolayer equivalent coatings on mineral grains and inorganic bioclastic particles our results are based on tem photomicrographs of samples from the northern california continental slope that fall within the monolayer equivalent envelope defined by mayer 1994 marine snow from the overlying nepheloid layer and sediments from eckernforde bay in the baltic sea these samples were prepared specifically to preserve and image in situ sediment fabric and organic constituents textural evidence suggests that low permeabilities caused by the interaction between the organic inorganic and biologic components of the clay size fraction play a major role in determining organic matter preservation on continental margins

dating the quaternary progress in luminescence dating of sediments abstract luminescence dating comprises a collection of numerical age techniques that are among the most significant chronological tools currently used in quaternary research this paper briefly reviews the key historical developments in luminescence dating from its roots in thermoluminescence dating of heated minerals to the development of optical dating methods for sunlight exposed sediments we describe the principles and practicalities of the various techniques commonly used in luminescence dating including multiple aliquot single aliquot and single grain procedures and we discuss some of the latest approaches to recognising and minimising potential errors in age estimation e g by means of component analysis and dose distribution methods in optical dating the overview also introduces the other papers in this special issue of quaternary science reviews which address a selection of important issues in basic research technique development and application of luminescence dating to critical questions in the geological and archaeological sciences illustrated with examples from around the world and the last million years of earth history

comment on active coastal thrusting and folding and uplift rate of the sahel anticline and zemmouri earthquake area tell atlas algeria by s maouche m meghraoui c morhange s belabbes y bouhadad h haddoum tectonophysics 2011 509 69 80 abstract based on geomorphologic analyses and leveling survey of quaternary coastal indicators i e marine terraces and notches along of a 50 km long coastal stretch of the algerian coast west of algiers maouche et al 2011 interpret the coastal segment to have undergone high uplift rates i e 0 84 1 19 mm yr since last interglacial maximum mis 5e 122 6 ka in table 1 140 ka in maouche et al 2011 and 2 5 mm yr for the last 31 ka this uplift was said to be due to repeated seismic events that would have occurred during the last 140 ka and more particularly during the late pleistocene we raise major issues about the interpretation proposed by maouche et al 2011 these issues deal with 1 the use of previous chronological data and the chronostratigraphy proposed 2 processes involved in the creation of coastal staircase morphology on the coast west of algiers 3 anomalously high uplift rates compared to other available data on the same geomorphic features marine terraces in the same setting of reactivated passive margins and 4 the fold geometry used for modeling of fold growth and its implications for coseismic surface deformation and uplift estimates in other words we contest the statements that coseismic deformation is the cause of staircase morphology on the mediterranean coast west of algiers and that very large m 7 earthquakes have occurred there in the past

magnetic susceptibility as a high resolution correlation tool and as a climatic proxy in paleozoic rocks merits and pitfalls examples from the devonian in belgium low field magnetic susceptibility in measurements are quick and sensitive enabling the creation of high resolution records making in an attractive correlation tool and a proxy for paleoclimate and paleoenvironments in geologically young material foremost in cenozoic sediments in belongs to the geoscientist s toolkit however in is a convolved signal and may reflect other processes than the often implicitly inferred depositional conditions diagenesis remagnetization and low grade metamorphism can potentially obscure the original depositional in signal this aspect is particularly important when interpreting in records from paleozoic rocks here we review data obtained from a large sample collection of middle to upper devonian sections in belgium comparison of in trends with paleoenvironmental indicators facies and with detrital input proxies zr th ti al allowed to assess the persistence of depositional trends furthermore the in signal was deconvolved into its dominant mineralogical contributions with the help of magnetic property analysis the main results are pointing to a magnetic signal dominated by fine grained magnetite of which paleomagnetic analysis indicated a formation during carboniferous remagnetization this prompts a potentially strong influence of post depositional processes and it complicates the interpretation of in records in terms of depositional environments however in most of the sections there is a relatively good relationship between in trends and facies evolution and between in and geochemical proxies for detrital inputs this indicates that the newly formed magnetite grains would at least partly remain where they are formed and this allows a relative preservation of the original signal despite the strong influence of diagenesis two sections show a stronger impact of diagenesis where for about half of these sections the primary depositional information is lost the eifelian givetian monts de baileux section was selected for time series analysis of the in series the average spectral misfit asm method is applied to explicitly evaluate the null hypothesis of no orbital signal and in this section there is 99 05 chance that the ms signal is reflecting an orbital imprint

new palaeomagnetic results from the whin sill complex evidence for a multiple intrusion event and revised virtual geomagnetic poles for the late carboniferous for the british isles a large scale palaeomagnetic study 125 specimens from 88 sampling localities has been carried out on the whin sill complex and its associated dykes in northern england the dominant carrier of remanent magnetization of the doleritic rocks is relatively pure magnetite of pseudo single domain size and the characteristic remanent magnetizations are typically well defined and unidirectional regionally consistent palaeomagnetic directions are obtained from three geographically distinct parts of the whin sill complex here named as the holy island sill declination inclination d i 189 5 2 8 95 6 3 the alnwick sill d i 194 6 25 6 95 8 1 and the hadrian9s wall pennines sill d i 189 2 3 3 95 3 5 although the holy island sill and the hadrian9s wall pennines sill are of similar age c 296 ma and indistinguishable on palaeomagnetic grounds the difference in palaeomagnetic directions between them and the alnwick sill demonstrates the multi component nature of the complex magma flow indicators suggest that the holy island sill and the hadrian9s wall pennines sill may also represent separate intrusion events dykes local to the three sills have remanence directions corresponding to their respective sills and can tentatively be identified as their feeder dykes virtual geomagnetic poles for the three palaeomagnetic sites are holy island sill and holy island dyke 346 8e 35 4s alnwick sill high green dyke and st oswald9s chapel dyke 337 1e 47 1s hadrian9s wall pennines sill and hett dyke 347 1e 32 9s

a multivariate mixing model for identifying sediment source from magnetic measurements a sequential method for quantitative identification of sediment source components based on magnetic measurements has been developed and tested for sediments from the rhode river maryland simulated mixing tests and multiple regression were employed to establish numerical relationships between source component proportions and the magnetic measurements of mixtures on the basis of these multivariate mixing models source components of three estuarine sediment cores were estimated by linear programming the results strongly support the previous studies on this catchment which indicated a dramatic change in sediment source some 150 to 200 yr ago quantitative calculations are more useful and informative than purely qualitative descriptions

a theoretical treatment of paleointensity determination experiments on rocks containing pseudo single or multi domain magnetic particles a phenomenological theory of thermoremanent magnetization trm is applied to model the possible results of paleointensity determination experiments using the thellier method it is shown that intrinsic curvature of the arai plot for samples containing pseudo single or multi domain particles can be attributed exclusively to the presence of remanences which are unblocked below their blocking temperature thus the thermal demagnetization tail of partial trm ptrm is not a direct measure for a sample s tendency to yield a curved arai plot here it is proposed to use the advancing decay of a ptrm t1 t2 which during heating occurs already below the lower temperature t1 t2 as a more reliable pre selection criterion in addition the effect of an average magnetostatic interaction on the thellier experiment turns out to be negligible an extended thellier method which compares the thermal demagnetization of natural remanent magnetization with that of an artificial trm according to the applied trm theory should result in a perfectly linear modified arai plot even for pseudo single or multi domain samples if no alteration or viscous effects occur

coercive forces and coercivity spectra of submicron magnetites abstract remanent coercivity spectra have been determined for four dispersions of magnetite with mean particle sizes of 0 04 0 22 m using four different methods 1 acquisition of isothermal remanent magnetization irm in continuous fields 2 stepwise reversal of saturation irm by opposite polarity continuous fields 3 stepwise alternating field af demagnetization of saturation irm and 4 af demagnetization of weak field thermoremanent magnetization trm alternating field methods gave narrower distributions with lower median coercivities than continuous field cf methods the two cf spectra are offset the remanent coercive force hr which is the median coercivity determined by cf reversal of saturation remanence is always less than the median coercivity h r determined from irm acquisition the median destructive field of saturation irm h 1 2 the median coercivity determined by af demagnetization is less than eitherhr orh r the relation reported by dankers 1 h r h 1 2 2hr is obeyed for these samples and for a companion suite of single domain magnetites and maghemites ordinary coercive force hc is substantially affected by reversible magnetization and is a poor indicator of the median coercivity of remanence hc is much smaller thanh 1 2 hr orh r and varies in a different way with particle size

biological and physical controls on the flux and characteristics of sinking particles on the northwest atlantic margin biogenic matter characteristics and radiocarbon contents of organic carbon oc were examined on sinking particle samples intercepted at three nominal depths of 1000 m 2000 m and 3000 m 50 m above the seafloor during a 3 year sediment trap program on the new england slope in the northwest atlantic we have sought to characterize the sources of sinking particles in the context of vertical export of biogenic particles from the overlying water column and lateral supply of resuspended sediment particles from adjacent margin sediments high aluminum al abundances and low oc radiocarbon contents indicated contributions from resuspended sediment which was greatest at 3000 m but also significant at shallower depths the benthic source i e laterally supplied resuspended sediment of opal appears negligible based on the absence of a correlation with al fluxes in comparison caco3 fluxes at 3000 m showed a positive correlation with al fluxes benthic sources accounted for 42 63 of the sinking particle flux based on radiocarbon mass balance and the relationship between al flux and caco3 flux episodic pulses of al at 3000 m were significantly correlated with the near bottom current at a nearby hydrographic mooring site implying the importance of current variability in lateral particle transport however al fluxes at 1000 m and 2000 m were coherent but differed from those at 3000 m implying more than one mode of lateral supply of particles in the water column

the rodents from the late middle pleistocene hominid bearing site of j bel irhoud morocco and their chronological and paleoenvironmental implications abstract the rodents from the late middle pleistocene hominin bearing locality of j bel irhoud include the following species meriones shawii gerbillus grandis dipodillus campestris paraethomys ras lemniscomys barbarus mus cf spretus and eliomys sp we consider m shawii a living species as identical with the middle pleistocene meriones maghrebianus the mouse differs from the domestic mus musculus but does not clearly fit into mus spretus either the rare g grandis looks identical with the form from the middle pleistocene of thomas quarries which may suggest a rather early age for irhoud this is in agreement with the occurrence of paraethomys a genus unknown in the upper pleistocene of morocco but the absence of the arvicolid ellobius suggests that the site is younger than other middle pleistocene sites doukkala ii sidi abderrahmane d2 and irhoud derbala virage paleoecological indicators such as the taxonomic habitat spectrum or the relative abundances of gerbillinae and murinae suggest a less xeric environment than in many earlier and later sites diversity indices comparable to those of other middle pleistocene sites point to similarly favorable conditions before the major climatic crisis close to the middle upper pleistocene boundary that drastically reduced rodent diversity in north africa

laser ablation u series analysis of fossil bones and teeth abstract over the past decade we have applied laser ablation icp mass spectrometry u series analysis to a large number of bones and teeth the method is fast and provides high resolution data of u series isotopes which give insights into the complexity of uranium migration into within and out of bones in this paper we present our laser ablation approach in detail from the experimental set up to data reduction and uranium diffusion modelling laser ablation analysis can now be applied with minimum damage complete diffusion data sets can be obtained by laser drilling which leaves a hole of around 200 m in diameter and 1 2 mm depth if the natural u diffusion follows a simple single stage process valuable age information can be obtained in other cases highly complex u migrations have been observed which make any age assessment impossible two examples from wadjak and callao illustrate the potential of nearly non destructive laser ablation u series analysis of human skeletal tissues the results demonstrate the physical presence of modern humans in south east asia at a time when our species just started to migrate into europe

osl dating of the aterian levels at dar es soltan i rabat morocco and implications for the dispersal of modern homo sapiens the aterian is a distinctive middle palaeolithic industry which is very widely spread across north africa its dating and significance have been debated for nearly a century renewed interest in the aterian has arisen because of a recent proposal that its development and spread may be linked to the dispersal of anatomically modern humans the industry contains technological innovations such as thin bifacially flaked lithic points and pedunculates as well as evidence for personal ornaments and use of red ochre such markers as shell beads are believed to be indicative of symbolic behaviour dar es soltan i on the atlantic coast of morocco contains a thick sequence of aterian deposits that were thought to represent the later stages of development of this industry new optically stimulated luminescence dates and geomorphological study indicate a much older sequence and so far the earliest yet recorded ages for the aterian they suggest an appearance in the maghreb region during mis marine isotope stage 5

remagnetization of carbonate rocks in southern tibet perspectives from rock magnetic and petrographic investigations netherlands organization for scientific research nwo with a rubicon grant 825 15 016 institute for rock magnetism irm at the university of minnesota instruments and facilities program of nsf erc starting grant 306810 nwo vidi 864 11 004

a method for unmixing magnetic hysteresis loops 1 hysteresis loops provide essential information concerning both induced and remanent magnetizations and are an important tool for characterizing magnetic mineral assemblages although the hysteresis behavior of mixed natural magnetic assemblages has been a focal point of much recent work little progress has been made in unmixing of hysteresis loops into characteristic components unmixing strategies can act as cornerstones for interpretation of rock magnetic data and have become popular for characterizing isothermal remanent magnetization acquisition curves unmixing of hysteresis loops is however a challenging task because the individual component loops in the mixture must meet stringent shape constraints we present a new technique for decomposing an ensemble of hysteresis loops into a small number of end members based on linear mixing theory the end members are not based on type curves but instead are derived directly from the hysteresis data particular attention is paid to the form of the end members ensuring they meet the shape constraints expected for hysteresis loops of natural magnetic mineral assemblages marine sediments from the southern ocean and lake sediments from butte valley northern california provide case studies on which the proposed unmixing method is tested

eustatic and tectonic controls on quaternary ras leona marine terraces strait of gibraltar northern morocco well preserved quaternary staircased marine terraces appear on ras leona limestone relief this is a peculiar sector of the betic rif cordillera lying in the four way junction between the atlantic and the mediterranean and europe and africa the age and altitude correlation of the ras leona terraces with travertine covered lateral equivalent terraces fashioned in the neighbouring beni younech area and comparison with those along the moroccan atlantic coasts would suggest that the ras leona terraces were mainly formed by eustatic factors the importance of the eustasy is supported by further comparisons with spanish and moroccan mediterranean terraces and with different marine terraces developed on passive margin coasts around the world a tectonic event occurred mainly during the period between the formation of the maarifian and the ouljian terraces i e between 370 and 150 ka the moderate quaternary tectonic uplift deduced from the marine terraces and its comparison with uplifted marine terraces developed in active subduction setting disagrees with the model of an active eastwards subduction below the gibraltar tectonic arc

hominid cave at thomas quarry i casablanca morocco recent findings and their context the thomas quarry i locality was made famous in 1969 with the discovery of a human half mandible in a cave in 1985 further investigations revealed the presence of a lower acheulean assemblage in lower units of the section from 1988 onwards modern controlled excavations took place within the framework of the franco moroccan co operative project casablanca acheulean artefacts a rich mammalian fauna and four hominid teeth have been excavated from the cave the faunal set indicates an open woodland environment carcasses were processed by carnivores but cut marks are absent which raises the question of any human role in the bone accumulations stone knapping was mainly oriented towards flake production and a few bifaces have been imported into the site laser ablation icp ms dating combining the esr and u series data for the modelling of the u uptake has given an us esr age of 501 76 ka for a human premolar while new osl measurements yielded an age of 420 34 ka for sediments immediately above the dated tooth and 391 32 ka below nevertheless biostratigraphy and lithostratigraphy point towards a greater antiquity

comment on detecting uniaxial single domain grains with a modified irm technique by r mitra l tauxe and j s gee summary in a recent article mitra et al 2011 propose a modified irm technique to identify the symmetry of magnetic anisotropy in single domain particle ensembles they apply this technique to support an earlier suggestion that single domain grains in young mid ocean ridge basalts morb exhibit multiaxial anisotropy here it is shown that the design of their measurement is flawed in that they do not take into account that the outcome essentially depends on the initial demagnetization state of the sample before the experiment and on the coercivity distribution of the sample because all morb specimens measured by mitra et al 2011 carried their original nrm which closely resembles a thermally demagnetized state their measurements first of all reflect the coercivity distributions and domain states of the samples and contain little or no information about the symmetry of the magnetic anisotropy all arguments previously put forward in favour of a dominant uniaxial anisotropy in morb are therefore still valid

optically stimulated luminescence dating of sediments over the past 200 000 years optical dating of sediment using optically stimulated luminescence has become important for studying earth surface processes and this technique continues to develop rapidly a group of closely linked luminescence methods can be used to estimate the time since grains of quartz and feldspar were last exposed to daylight by detecting their subsequent response to environmental ionizing radiation exposure the technique is well suited to the dating of deposits as young as one year to several hundred thousand years recent technical developments have established a dating protocol with improved precision a high degree of reliability and an in built means to detect incomplete signal removal during deposition this approach has been extended to age estimation for single grains opening up a wider range of potential environments and new possibilities for understanding postdepositional grain movement ongoing research offers the possibility of significant age range extension and novel applications including low t

nonlinear preisach maps detecting and characterizing separate remanent magnetic fractions in complex natural samples natural remanent magnetization carriers in rocks can contain mixtures of magnetic minerals that interact in complex ways and are challenging to characterize by current measurement techniques here a non linear mapping scheme is described that efficiently enhances sensitivity and the resolution power of remanent preisach maps using this scheme a large dynamic range of magnetic moments and coercivities can be reliably resolved the method is applied to synthetic and natural standard samples containing magnetite and hematite as well as to natural samples from remanent magnetic anomalies where complex microstructures are observed it is shown that certain offset high coercivity patterns in remanent preisach maps may serve as fingerprints for exsolution structures of ilmenite in hematite or hematite in ilmenite and that in some magnetite bearing remanent anomalies the magnetite coercivity is increased beyond its intrinsic coercivity range experimental results and theoretical considerations indicate a minimal coercivity of about 10 mt for sd magnetite such that observation of lower coercivities implies psd or md grain sizes a diagnostic hematite pattern with a peak downwards offset of 17 2 of the intrinsic coercivity is found that is stable over a large range of intrinsic coercivities and may be related to shielding of internal defect or lamellar moments by a spin canting response to the internal field

explaining the klasies pattern kua ethnoarchaeology the die kelders middle stone age archaeofauna long bone fragmentation and carnivore ravaging abstract the caves at klasies river mouth krm in the southern cape province south africa continue to play an important role in the study of human evolution and debates about the origins of modern humans as with most palaeolithic sites the behavioural interpretations offered for the middle stone age msa inhabitants of the krm caves are based in large part on the interpretation of fragmentary faunal remains from the main site or caves 1 1a 1b and 2 excavated in 1967 68 by singer wymer 1982 using zooarchaeological patterns detected in ethnoarchaeological data collected among kua foragers of the eastern kalahari central district botswana as well as in data collected from die kelders cave 1 layer 10 south africa we offer an alternative explanation for a provocative pattern of skeletal part representation discovered in the krm msa archaeofauna over 20 years ago by richard klein 1976 the klasies pattern is characterized by the underrepresentation of large bovid upper limb elements relative to more anatomically complete small bovids to date the pattern has been interpreted in three different ways each with strikingly different implications for middle stone age msa middle palaeolithic mp human behaviour understanding the nature of the pattern is not only important for reconstructing msa human behaviour at krm but it is also important for understanding how the conduct of zooarchaeological analyses can profoundly influence our reconstructions of the course of human behavioural evolution the kua ethnoarchaeological data and experimental case studies unambiguously connect to site formation histories to zooarchaeological patterns at die kelders cave 1 layer 10 the ethnoarchaeological expectations are expressed archaeologically in a context analytically relevant to krm overall by joining the kua and the die kelders data we show how uniformitarian actualistic approaches can be productively employed in zooarchaeological interpretation the klasies pattern is likely to be an artefact of a widespread taphonomic sequence followed by a particular style of analysis employed for practical reasons by many zooarchaeologists we suggest that the situation is common and likely to be seriously distorting inferences about many archaeofaunas around the world more generally we show how uniformitarian studies offer a coherent framework for developing methods and generating data useful in making behavioural inferences from faunal remains rather than a human behavioural signal in the krm archaeofauna the klasies pattern has more to do with the methods of zooarchaeology than with the behaviour of ancient people

mineral and elemental indicators of post glacial changes in sediment delivery and deposition under a western boundary upwelling system cabo frio southeastern brazil abstract minerals and elements are important proxies that can provide information about variations in the delivery and deposition of coastal ocean sediments associated with past climate changes in this study postglacial changes in the accumulation of sediments on the upper shelf of southeastern brazil are linked to the evolution of regional paleoceanographic and continental paleoclimatic conditions during the last 14 4 kyr cal bp mineralogical and major and trace element analyses of a 14 c dated sediment core identify three main lithostratigraphic units of this core that reveal a succession of changes in sediment delivery and accumulation as postglacial sea level rose and holocene climate on land evolved the depositional setting has transitioned in response to the large sea level rise prior to 9 9 kyr cal bp from being a shallow water high energy environment to a deeper water one this location has since then been a lower energy environment that has persisted into modern times due to the high marine productivity associated with the cabo frio upwelling system in an oxygenated water column the sediments have shown a complex and dynamic redox condition making variations in redox sensitive trace elements indicative of changes in primary production and organic matter diagenesis at this location after sea level stabilized 9 kyr cal bp variations in fluxes of al fe ca and minerals were small indicating that climate driven changes had only secondary controls on delivery of detrital sediment components to the cabo frio shelf modern coastal upwelling conditions and the onset of mid shelf organic rich sediment deposition were established after 9 9 cal kyr bp

oldest human expansions in eurasia favouring and limiting factors 1 introductionon november 26e28 2008 an international conference wasorganised at the museum national d histoire naturelle paris france the topic was the oldest human expansions in eurasia under theaspect of the factors which could favour or limit the humansettlements while fossil human remains are scarce in eurasia lithicassemblages suggest at least two phases of human settlement or and techno cultural spread from africa to eurasia the rst one attested by mode 1 lithic industries is observed at dmanisi georgia at 1 8 ma in asia in china and pakistan around 2 ma and in europe for example in spain since 1 2e1 4 ma at orce atapuerca in italy monte poggiolo ca 1 ma pirro nord at least1 3 ma and in france pont de lavaud le vallonnet around 1 ma some dates in china and indonesia support the idea of earliersettlementsincontinentalandislandasiathanineurope whiletheoldest tool kit in africa dates to 2 6 ma kada gona ethiopia a second phase is marked by the appearance of new tools especially handaxes and cleavers these large tools do occur inafrica around 1 6e1 7 ma konso ethiopia kokiselei kenya andaround 1 4e1 2 ma in the middle east ubeidiya israel they areconsideredasthe rstindicatorsofacheuliantradition ormode2 consisting in shaping large tools on akes or blocks these toolsappear outside africa with different time lags according togeographical areas in asia the rst ones occur around 1 2 ma isampur india and then become more signi cant with anincreasing number of sites around 800 ka in eastern asia e china and south eastern asia ngebung java in western and southerneurope acheuliansitesonlyappeararound600e700ka asattestedbythe recent discoveriesin centreregion france la noira in chervalley and they become more numerous from 500 ka onwards inspain atapuerca galeria ambrona in italy visogliano castel diguido in northern and southern france somme river terraces caune de l arago in the european continent assemblages withbifaces characteristic of acheulian onlyoccurin a geographical areastretching from southern europe to great britain however theyare lacking in central europe and the rhine river is considered asa frontier but they do exist in the caucasus near the central asianborder while they are unknown further east in tadjikistan these two waves of populating probably include numerousarrivals and we do not know whether these arrivals led each timeto a permanentsettlement particularlyif the hominin groups weresmall and geographically dispersed this time lag between asia and europe regarding the peoplingphases and their consequences is debated today within the scien ti c community what could be the migratory paths from africa toboth asia and europe or from africa to asia then to europe whomoved homo antecessor homo heidelbergensis were there somecontacts between distinct human groups rather than shiftingpopulations these questions also concern the diffusion modalitiesof technical traditions and the effect of climatic and environmentalconditions on human movements the latter could explain chro nological lags and restriction of human settlements to some areasonly however it has to be kept in mind that convergencephenomena could also happen at a regional scale in the tool kits this may be the case for acheulian people the present state of knowledge on the earth s climatic storyduringthelasttwomillionyearsshowslocalphenomenacombinedto global changes for example increase of glaciations around800ka whenclimaticcyclesshiftedtothe100kaperiodicity astheeccentricity parameter of terrestrial orbit became more importantthan the obliquity of earth s axis earlier periodicity of 41 ka mis20 characterised by strong marine regression took place at thesame time as the matuyamaebrunhes geomagnetic inversion 780 ka and is considered as an accurate chronological marker recent results of various research teams contribute to builta more complete and precise picture of the past the betterknowledge of the palaeoenvironment allows a new appraisalregarding the spread of technical behaviours in relation to theenvironmental context highlighted by new issues concerningafrica some major questions were discussed during the conference 1 the geographical dispersal of each type of lithic industry 2 the chronological gaps in the hominin settlements in thevarious areas of eurasia 3 the periods when climatic or topographic variations had animportant role favouring or limiting the human expansion insome regions

a lock in model for the complex matuyama brunhes boundary record of the loess palaeosol sequence at lingtai central chinese loess plateau summary in most marine sedimentary records the matuyama brunhes boundary mbb has been found in interglacial oxygen isotope stage 19 in the magnetostratigraphic records of most chinese loess palaeosol profiles the mbb is located in loess layer l8 which was deposited during a glacial period the mbb at lingtai central chinese loess plateau also occurs in l8 and is characterized by multiple polarity flips the natural remanent magnetization is mainly carried by two coexisting components the higher coercivity harder component dominates in loess layers and is thought to be of detrital origin the lower coercivity softer component prevails in palaeosols and was most probably formed in situ by bio chemical processes a lock in model for the lingtai mbb record has been developed by extending the lithologically controlled pdrm model of bleil von dobeneck 1999 it assumes two lock in zones the nrm of the magnetically harder component is physically locked by consolidation shortly after loess deposition whereas the softer component is formed at greater depth by pedogenesis and acquires a chemical remanent magnetization of younger age at polarity boundaries grains carrying reversed and normal directions may therefore occur together within a single horizon the model uses arm coercivity spectra to estimate the relative contributions of the two components it is able to explain the observed rapid multiple polarity flips and low magnetization intensities as well as the stratigraphic shift of the lingtai mbb with respect to the marine records

detrital magnetizations from redeposition experiments of different natural sediments abstract we carried out several experiments with carbonate rich and clay rich sediments that were redeposited in plastic cubes or in 1 meter long cylindrical tubes with the aim of investigating the sensitivity of the depositional remanent magnetization drm to various environmental and physical parameters in contrast to previous studies we did not observe any difference in the drm acquired with or without saline water for either kind of sediment taking advantage of a gelatin that fixes the position of particles in suspension we were able to measure the magnetization of suspended sediments within water filled columns and thus to test the degree of alignment of magnetic grains the magnetization of clay rich sediments was not far from saturation but the magnetization was considerably reduced after deflocculation because the large flocs that favored alignment of magnetic grains were destroyed by the deflocculant similarly the large flocs found at the bottom of the deposition tubes also reveal an efficient magnetic alignment in contrast the weak magnetization of the carbonate rich sediments with small flocs yielded accurate and well grouped magnetization directions that were not sensitive to deflocculation only a fraction of magnetic grains was mechanically oriented by the field in this case because of the weak net magnetic moments of the grains embedded within small flocs the drm was constrained by redeposition in plastic cubes performed without gelatin and with different field intensities the drm intensity of the carbonate rich sediments is linearly related to field strength which attests to their suitability for studies of relative paleointensity tests performed with mud from several stratigraphic levels in different marine sediment cores failed to reveal a significant influence of carbonate content on drm which suggests a relatively minor role of lithological changes on records of relative paleointensity

sedimentary organic matter geochemistry of clayoquot sound vancouver island british columbia surface sediment samples from three interconnected fjords of clayoquot sound british columbia were density fractionated 1 6 g cm 3 to isolate discrete organic debris od from mineral associated organic matter mom total organic carbon oc values varied greatly ranging from 0 1 to 8 8 by weight with a general decreasing trend from fjord head to the continental shelf within the sediment terrestrial om was present either as vascular plant debris or soil mom down fjord the woody vascular plant material in the od fraction acquires nitrogen which is hypothesized to be due to the bacterial incorporation of nitrogen from the water terrestrial oc in the mom is incompletely replaced by marine oc within the fjords resulting in a 65 net loss of mom sediments deposited under oxic and intermittently anoxic water column conditions have organic carbon to surface area ratios oc sa ranging from 0 4 to 1 2 mg c m 2 similar to that of typical continental margin sediments given that temperate fjords contain an estimated 12 of the continental margin sediment deposited during the last 100 000 yr and that they bury at least a margin equivalent amount of oc either weight or surface area normalized we hypothesize that temperate fjords may contain 12 or more of the sedimentary oc buried during this time

approach to saturation analysis of hysteresis measurements in rock magnetism and evidence for stress dominated magnetic anisotropy in young mid ocean ridge basalt abstract young mid ocean ridge basalts contain titanomagnetite crystals of varying size and composition many studies of their hysteresis properties have found m rs m s ratios considerably above the theoretical limit of 0 5 for uniaxial single domain particles since titanomagnetite is a cubic mineral high m rs m s could occur due to cubic anisotropy which allows for m rs m s values up to 0 866 on the other hand titanomagnetites with high ti content possess extremely large magnetostriction constants already slight internal stress easily outweighs cubic anisotropy and enforces uniaxial behavior are high m rs m s ratios now a proof for very low internal stress no on the contrary previous studies on synthetic titanomagnetite with high m rs m s show that after annealing this ratio decreases a possible explanation is that insufficient saturation of the hysteresis loop used to infer m rs m s leads to underestimation of m s here a systematic experimental study on a young mid ocean ridge basalt using fields of up to 7 t demonstrates that indeed the m rs m s ratio of the single domain fraction does not significantly deviate from the theoretical value of 0 5 for uniaxial anisotropy it is further estimated that internal stress above 200 mpa is necessary to explain the observed hysteresis behavior a value which is consistent with recent independent approximations on the other hand theoretical loops for cubic minerals do not fit the observed data in order to assess the validity of m s determinations from hysteresis measurements an improved method to evaluate the approach to saturation behavior of hysteresis loops is developed it allows to recognize insufficiently saturated loops and thereby helps to avoid misinterpretation of standard m rs m s measurements when high fields are not accessible

assessment of the usefulness of lithic clasts from pyroclastic deposits for paleointensity determination 1 paleomagnetic and rock magnetic measurements were carried out on lithic clasts found within pyroclastic deposits to assess their potential for paleointensity determinations the use of multiple lithologies in a single paleointensity determination would provide confidence that the result is not biased by alteration within one lithology lithic clasts were sampled from three historically active volcanoes lascar in the chilean andes mt st helens united states and vesuvius italy at lascar triple heating paleointensity experiments allow development of new selection criteria for lithic clasts found within pyroclastic deposits using these criteria the lascar data yield a mean paleointensity of 24 3 1 3 t 1 n 26 which agrees well with the expected value of 24 0 t this indicates that pyroclastic rocks have promise for paleointensity determinations pyroclastics however still suffer from the range of problems associated with conventional paleointensity experiments on lava flows samples from mt st helens are strongly affected by multidomain md behavior which results in all samples failing to pass the paleointensity selection criteria at vesuvius md grains magnetic interactions and chemical remanent magnetizations contributed to failure of all paleointensity experiments rock magnetic analyses allow identification of the causes of failure of the paleointensity experiments however in this study they have not provided adequate preselection criteria for identifying pyroclastics that are suitable for paleointensity determination

biological and granulometric controls on sedimentary organic matter of an intertidal mudflat abstract a variety of measures of organic matter concentration and quality were made on samples collected from the top few mm of intertidal mudflat sediment over the course of a year in order to assess the relative importance of biological and sedimentological influences on sedimentary organic matter winter and summer were times of relatively fine grained sediment accumulation caused by biological deposition or stabilization processes and resulting in higher organic matter concentrations stable carbon isotope and br c ratios indicated a planktonic source of bulk organic matter ratios of organic carbon to specific surface area of the sediments were consistent with an organic monolayer coverage of sediment grains correction for changing grain size during the year showed no change in the organic concentration per unit surface area in spite of organic matter inputs by in situ primary production buildup of heterotroph biomass and mucus coatings and biodeposition of organic rich seston there were also no indications of changes in bulk organic quality measured as hydrolyzable carbohydrates and amino acids in response to these biological processes it is concluded that biological processes on a seasonal time scale affect the bulk organic matter of these sediments via a modulation of grain size rather than creation or decay of organic matter

the alkenone temperature signal in western north atlantic surface waters abstract haptophyte algae derived long chain c 37 c 39 alkenones and alkyl alkenoates were analyzed in euphotic zone particulate matter collected over a 7 yr period at the oceanic flux program bermuda atlantic time series ofp bats site in the western sargasso sea surface water temperatures at the site range annually from 19 to 29 c alkenone concentrations ranged from 1 in summer to 100 ng l 1 following the passage of storms highest seasonal concentrations occurred during the late winter and spring under stratified conditions alkenone concentrations in the surface mixed layer 0 20 m were generally 2 to 4 times higher than in the deep fluorescent maximum 75 110 m consistent with emiliania huxleyi concentration profiles haidar and thierstein 2001 and indicated that alkenone production primarily occurs within the upper euphotic zone in this region alkenone compound distributions and the temperature calibrations of c 37 and c 38 methyl and ethyl alkenone unsaturation u 37 k u 38me k and u 38et k respectively were remarkably similar to that observed in an e huxleyi strain previously isolated from the same area conte et al 1998 providing strong evidence that e huxleyi is the predominant alkenone synthesizer and that characteristics exhibited by randomly isolated clones in culture are in many cases consistent with those of populations in the region of origin the bermuda calibration of u 37 k vs water temperature u 37 k 1 9835 0 2004t 0 0034t 2 r 2 0 95 n 91 is nonlinear and falls along the same trendline as euphotic zone particulates from warm 15 c waters of the eastern north atlantic conte and eglinton 1993 and mediterranean ternois et al 1997 the combined north atlantic temperature calibration u 37 k 1 1365 0 1257t 0 0018t 2 r 2 0 963 n 134 differs significantly from published coretop sediment calibrations rosell mele et al 1995 muller et al 1998 based on sea surface temperature maps levitus and boyer 1994 having a steeper slope at temperatures 24 c the reasons are not clearly apparent and manifest a need for detailed studies linking production patterns in surface waters with the signal arriving at the seafloor to fully understand the generation of the sedimentary signal

a geochronologic framework for the ziegler reservoir fossil site snowmass village colorado abstract the ziegler reservoir fossil site near snowmass village colorado usa provides a unique opportunity to reconstruct high altitude paleoenvironmental conditions in the rocky mountains during the last interglacial period we used four different techniques to establish a chronological framework for the site radiocarbon dating of lake organics bone collagen and shell carbonate and in situ cosmogenic 10 be and 26 al ages on a boulder on the crest of a moraine that impounded the lake suggest that the ages of the sediments that hosted the fossils are between 140 ka and 45 ka uranium series ages of vertebrate remains generally fall within these bounds but extremely low uranium concentrations and evidence of open system behavior limit their utility optically stimulated luminescence osl ages n 18 obtained from fine grained quartz maintain stratigraphic order were replicable and provide reliable ages for the lake sediments analysis of the equivalent dose d e dispersion of the osl samples showed that the sediments were fully bleached prior to deposition and low scatter suggests that eolian processes were likely the dominant transport mechanism for fine grained sediments into the lake the resulting ages show that the fossil bearing sediments span the latest part of marine oxygen isotope stage mis 6 all of mis 5 and mis 4 and the earliest part of mis 3

physical interpretation of hysteresis loops micromagnetic modeling of fine particle magnetite 1 hysteresis measurements have become an important part of characterizing magnetic behavior of rocks in paleomagnetic studies theoretical interpretation is often difficult owing to the complexity of mineral magnetism and published data sets demonstrate remanence and coercivity behavior that is currently unexplained in the last decade numerical micromagnetic modeling has been used to simulate magnetic particles such simulations reveal the existence of nonuniform remanent states between single and multidomain known as the flower and vortex configurations these suggest plausible explanations for many hysteresis measurements yet fall short of explaining high saturation remanence high coercivity data such as those commonly observed in fine grained submarine basalts in this paper we review the theoretical and experimental progress to date in understanding hysteresis of geological materials we extend numerical simulations to a greater variety of shapes and sizes including random assemblages of particles and shapes more complex than simple rods and cubes our simulations provide plausible explanations for a wide range of hysteresis behavior

revisions to the age of the brunhes matuyama boundary and the pleistocene geomagnetic polarity timescale the currently referenced age of 730 ka for the brunhes matuyama b m geomagnetic polarity boundary mankinen and dalrymple 1979 is based largely on k ar and paleomagnetic data from postcollapse rhyolites in the valles caldera new mexico doell and dalrymple 1966 doell et al 1968 dating of sanidine from valles rhyolites by the 40a 39ar laser fusion technique indicates that samples critical to defining the b m boundary are up to 90 ka older than previously thought the new data combined with earlier results yield an age for the b m boundary of 780 10 ka 40ar 39ar ages from other samples suggest the jaramillo normal polarity subchron extended from 1010 to 915 ka

new middle pleistocene dental remains from qesem cave israel this study presents a description and comparative analysis of middle pleistocene permanent and deciduous teeth from the site of qesem cave israel all of the human fossils are assigned to the acheulo yabrudian cultural complex aycc of the late lower paleolithic the middle pleistocene age of the qesem teeth 400 200 ka places them chronologically earlier than the bulk of fossil hominin specimens previ ously known from southwest asia three permanent mandibular teeth c1 p4 were found in close proximity in the lower part of the stratigraphic sequence the small metric dimensions of the crowns indicate a consid erable degree of dental reduction although the roots are long and robust in contrast three isolated permanent maxillary teeth i 2 c 1 and m 3 and two isolated decidu ous teeth that were found within the upper part of the sequence are much larger and show some plesiomor phous traits similar to those of the skhul qafzeh speci mens although none of the qesem teeth shows a suite of neanderthal characters a few traits may suggest some affinities with members of the neanderthal evolu tionary lineage however the balance of the evidence suggests a closer similarity with the skhul qafzeh dental material although many of these resemblances likely represent plesiomorphous features am j phys anthropol 000 000 000 2010 v c 2010 wiley liss inc

behavior of u channels during acquisition and demagnetization of remanence implications for paleomagnetic and rock magnetic measurements abstract we have examined the effects of translation speed on the acquisition and demagnetization of remanence in u channels the speed at which the u channel moves through alternating and steady fields has a significant effect on the efficiency of remanence acquisition and demagnetization anhysteretic remanence arm acquisition and alternating field af demagnetization efficiency are inversely correlated with translation speed arm acquisition is most efficient at a track speed of 1 cm s whereas at higher speeds arm reaches an apparent saturation at low peak fields and has a soft coercivity spectrum during subsequent af demagnetization the dependence of magnetization acquired or removed on translation speed through alternating or steady fields is explained by the number of alternating field half cycles experienced as the sample is translated through the applied field and on the alternating field decay rate at slow translation speeds a u channel experiences a comparable number of alternating field cycles to that experienced by a stationary discrete sample at fast translation speeds the u channel experiences a factor of 100 fewer alternating field cycles and the conditions experienced by the u channel sample can be comparable to the natural reorganization time of the magnetic moments within the sediment particles during remanence acquisition and demagnetization at low decay rates the sample has more time in the blocking field and thus a more complete approach to equilibrium

isothermal magnetization of samples with stable preisach function a survey of hysteresis remanence and rock magnetic parameters isothermal magnetization curves like hysteresis loops initial curves back field curves acquisition curves and demagnetizing curves of isothermal remanent magnetization are commonly used for rock magnetic purposes in this study we investigate the relations among these curves and other useful magnetization curves saturation initial curve and induced and remanent hysteretic magnetization curves in order to compare coercivity and domain state parameters which can be derived from them most natural samples especially sediments are weakly magnetic and possess relatively stable preisach functions their magnetization states can therefore be described by classical preisach theory this approach verifies well known rules and establishes some formerly unreported relations between isothermal magnetization curves and parameters it is possible to point out sets of mathematically independent isothermal magnetization curves and to state theoretical interrelations between dependent curves by simply inspecting preisach diagrams furthermore we define six elemental isothermal magnetization curves from a general partition scheme of the preisach diagram they can be easily obtained from common measurements and generate all above mentioned curves the experimental applicability of our results is demonstrated for three single domain pseudo single domain multidomain marine sediment samples a physical rationale of the elemental curves reveals favorable properties for the investigation of interaction and domain state as a spin off from the general results a new hysteresis based procedure for the measurement of hcr is presented we also propose an apparently more robust hysteresis derived domain state parameter and a generalized version of the well known r parameter all presented methods can be applied without actually measuring preisach functions

organic matter preservation on continental slopes importance of mineralogy and surface area abstract theoretical considerations calculations and data reported by keil et al 1994a were used to assess the recent hypotheses that mineral surface roughness controls the specific surface area of continental margin sediments and that the matrix linked organic carbon content of continental margin sediments occurs as a monolayer or monolayer equivalent coating of organic compounds on the surfaces of detrital minerals and other detrital nonorganic grains mayer 1994 results of our analysis indicate that it is not the surface roughness of the terrigenous detrital framework grains that controls the specific surface area of most continental margin sediments even in the sand and silt fractions but rather the presence of nonspherical high surface area to volume particles primarily clays but also oxy hydroxides and ultra structured nonorganic bioclasts such as diatom frustules analysis of the mineralogy organic carbon content surface area and in situ microfabric of continental margin sediments off california in the mendocino and san luis obispo areas and off the state of washington indicate a strong correlation between the amount of matrix linked organic matter present and the suite of clay minerals data indicate that organic carbon appears to be preferentially sequestered in smectite rich sediments compared to those whose clay fractions are dominated by chlorite we suggest that this association is a function of differences in the site density and chemistry of the clays and differences in their flocculation behavior our data also indicate that organic carbon preservation on the three california transects all of which have a suboxic oxygen minimum zone that impinges on the sea floor is not significantly influenced by differences in bottom water oxygen concentration and carbon stable isotope data suggest no preferential preservation of continental organic matter over that of marine origin

rock magnetic property and paleointensity determination on historical santorini lava flows eight historical dacitic lava flows from santorini with ages between 46 a d and 1950 a d four of them within the past century have been subjected to detailed rock magnetic analyses and various experiments of absolute paleointensity thermomagnetic measurements and acquisition of isothermal magnetization have revealed the presence of two physically distinct magnetic phases with curie temperatures of 280 c and 500 c in most of the samples the second phase does not play a prominent role for the characteristic remanent magnetization which is dominated by titanomagnetite magnetostatic interaction is very limited and does not considerably change upon heating back field curve spectra indicate a good thermochemical stability of these dacitic lava samples which is also supported by the absence of noticeable changes in the remanent coercive force prior heating to 450 c hysteresis measurements show typical pseudo single domain behavior without noticeable superparamagnetism such characteristics were favorable to conduct and to test the most widely used experimental approaches for absolute paleointensity determination despite a success rate of 38 the microwave technique has provided rather scattered within flow determinations the results obtained from approaches involving alternating field demagnetization were biased by considerable differences between the nrm and the trm coercive force spectra we have also noticed that most determinations obtained by microwave heating differ from the historical field value at the site for the most recent flows last techniques involving double heating protocols were successful due to a dominant low curie temperature phase with a narrow grain size distribution the results were characterized by low dispersion and were found in good agreement with the historical field

bayesian methods applied to the interpretation of multiple osl dates high precision sediment ages from old scatness broch excavations shetland isles in this paper we illustrate the ways in which bayesian statistical techniques may be used to enhance chronological resolution when applied to a series of osl sediment dates such application can achieve an optimal chronological model by incorporating stratigraphic and age information the application to luminescence data is not straightforward owing to the sources of uncertainty in each date and here we present one solution to overcoming these difficulties and introduce the concept of unshared systematic errors using osl sediment dates from the site of old scatness broch shetland isles uk many measured with a high degree of precision we illustrate some of the ways in which bayesian techniques may be applied as a tool for assessing systematic errors when combined with independent chronological information and to determine the optimum chronological information for specific events and contexts we provide a detailed procedure for the application of bayesian methods to osl dates using the widely available radiocarbon calibration programme oxcal

relationship between median destructive field and remanent coercive forces for dispersed natural magnetite titanomagnetite and hematite summary remanent acquisition curves remanent hysteresis curves and alternating field demagnetization curves were determined for a number of artificial rock specimens containing well defined grain size fractions between 5 and 250 m of natural magnetite titanomagnetite and hematite from these curves the remanent acquisition coercive force h cr the remanent coercive force hcr and the median destructive field of irm h i were determined theoretically these parameters should be the same for an assembly of non interacting homogeneously distributed randomly oriented single domain grains for a given hematite specimen h cr hcr and h i have about the same value in spite of the strong grain size dependence of these parameters for each specimen of magnetite and titanomagnetite the value of h cr is larger than hcr which again is larger than h i however the ratios h cr hcr and h i hcr appear to have a different constant value an interesting relationship which appears to hold for dispersed magnetite titanomagnetite or hematite grains between 5 and 250 m independently of grain size quantity and packing density of the magnetic material is

organic matter sequestered in potential energy fields predicted by 3 d clay microstructure model abstract transmission electron microscopy tem observations confirm theoretical predictions of the location of organic matter om sequestered in fine grained sediment organo clay micro and nanoscale fabric images validate for the first time the protective adsorption model of om preservation preservation of om against enzymatic digestion is demonstrated predominately at locations consistent with our model of the potential energy field that is developed through interactions of clay minerals the om and pore water chemistry pores observed in 2 d fabric tem images of clay muds commonly appear to be totally encapsulated however the great majority of these pores are clearly demonstrated to be open in one or more directions when observed in rotated 3 d images despite the scarcity of completely closed pores om is preserved against enzymatic attack in those locations where the predicted 3 d potential energy of interaction between clay domains and om is attractive

marine resources exploitation by palaeolithic hunter fisher gatherers and neolithic tribal societies in the historical region of the strait of gibraltar this work has been financially supported by the benzu project spanish ministry of culture and ceuta government158 08 pv benzu cv the project dges har2008 06477 c03 02 the aecid hispanic moroccan projects pci a 2893 05 a 6317 06 and a 010823 07 and junta de andalucia project p07 hum 03015 authors are grateful to carol and paul beven and ana durante for their editorial assistance and to the anonymous referees for their helpful suggestions also we are grateful to ivan briz and marco madella for the corrections and suggestions

dissolution behaviour of fine grained magnetite and maghemite in the citrate bicarbonate dithionite extraction method mineral magnetic properties of soils and sediments are increasingly used as proxy parameters for environmental and palaeoclimate analysis to investigate which magnetic minerals contribute to the environmental signal in the samples chemical techniques such as the citrate bicarbonate dithionite cbd extraction method have been introduced in environmental magnetism studies this technique is assumed to distinguish lithogenic magnetite from pedogenic maghemite mineral content in soils and sediments unfortunately interpretation of the cbd extractions is not straightforward because the procedure is sometimes more suitable for distinction between grain size than for distinction between minerals the procedure of the cbd extraction technique was investigated to determine the influence of extraction temperature and iron oxide concentration on the dissolution behaviour of the samples synthetic samples were extracted at three different temperatures 60o 70o and 80oc at similar iron oxide concentration 5 wt and for three different concentrations 0 1 wt 1 wt and 5 wt at the same temperature 60oc our results show that a lower extraction temperature reduces the dissolution rate for all samples while decrease in iron oxide concentration increases the dissolution rate thus the parameters in the cbd procedure have a major influence on the dissolution behaviour of the samples in practice this means that when natural samples of differing iron oxide concentration are extracted with this technique the results of the extractions cannot be compared therefore the outcome of this type of extraction experiment can only be accurately interpreted when the effect of the procedure on the dissolution behaviour is taken into account 1999 elsevier science b v all rights reserved

diversity and distribution of echinoderms in the south eastern arabian sea shelf under the influence of seasonal hypoxia abstract the south eastern arabian sea seas margin represents a tropical eastern boundary upwelling system which is subjected to intense seasonal hypoxia in the continental shelf and impingement of oxygen minimum zone omz along the continental slope this paper provides the first comprehensive information on abundance diversity and distribution patterns of echinoderms which are highly sensitive to oxygen deficiency and anthropogenic disturbances in the continental shelf 20 250 m of the seas results are based on depth stratified and seasonally resolved sampling at 241 sites representing 8 latitudinal grids 4 depth strata from inner shelf to shelf edge using naturalist dredge and smith mcintyre grab echinoderms were the numerically dominant group among epifauna 42 with significant seasonal variations in relative abundance 71 during winter and 17 during summer monsoon fifty five species of echinoderms were identified among which ophiuroids showed highest diversity 24 species followed by echinoids 11 species and asteroids 8 species species richness of echinoderms was higher in the inner and mid shelf 20 80 m while the group was nearly absent in the shelf edge 150 250 m a significant negative correlation was noted between species richness and latitude and three distinct sub regions could be delineated based on species diversity and abundance the observed distribution patterns were found to be determined chiefly by sediment texture and bottom water dissolved oxygen along with anthropogenic disturbances bottom trawling echinoderms showed maximum abundance and species richness in the well oxygenated sandy sediments of the southern seas and very low species richness and abundance in relatively silty sediments of the northern seas which were characterised by high seasonal fluctuations in dissolved oxygen seasonal hypoxia the near absence of echinoderms in the shelf edge despite the availability of sandy substrates indicates that this group is more sensitive to the perennially low oxygen conditions prevailing here

the earliest occupation of north africa the moroccan perspective abstract the long sequence at casablanca covers the past 5 5 ma the oldest lithic assemblages are found in late lower pleistocene deposits ca 1 ma in unit l of thomas quarry 1 and consist of acheulean artefacts made from quartzite and flint the first human remains discovered in this area were found in younger middle pleistocene deposits and cover an important period of human evolution between homo erectus and modern homo they are associated with acheulean artefacts and rich faunal assemblages in caves littorina cave at sidi abderrahman caves at thomas quarries 1 and 3 the variability of acheulean assemblages is well documented following recent excavations in various sites around the well known locality of sidi abderrahman bears cave cap chatelier unit l and hominid cave at thomas quarry 1 rhino cave at oulad hamida quarry 1 sidi abderrahman extension and sidi al khadir open air sites the casablanca sequence offers useful data for comparison with those from other african areas where hominids appeared and developed and should thus be considered in the debate on the earliest occupation of europe

seasonal control on coastal dune morphostratigraphy under a monsoon climate mui ne dunefield se vietnam abstract having developed in the later quaternary period the mui ne dunefield representing the upper most portion of a major coastal barrier complex in se vietnam formed by wind regimes associated with the asian monsoon climate the barrier complex is 100 km long and higher than 150 m in elevation but despite its large dimensions research on its geomorphological and geological characterization is limited several active dune fields extend 2 10 km landwards from the coast while the rest of the barrier surface is stabilized we applied ground penetrating radar gpr and quartz optically stimulated luminescence osl dating to the transverse dunes of the mui ne dunefield to characterize the morphostratigraphy and recent aeolian sedimentation history currently the dunes have a relief of typically 5 10 m and a wavelength of 50 100 m they are driven by the northeasterly winter monsoon winds and reversed with minor relief in response to the southwesterly summer monsoon gpr profiles and osl ages define three morphostratigraphic units the modern holocene and pleistocene dune units the gpr data of the modern dune unit is dominated by a series of steep reflections that dip exclusively towards the west reflecting the winter monsoon and is punctuated by reactivation surfaces evidence for the wind reversal is not preserved in the sediment successions but is represented by reactivation surfaces thus a subunit bounded by the reactivation surfaces defines annual deposition the preservation potential of a subunit varies with the migration rate of the transverse dune and in the fastest migrating dunes approximately one subunit was preserved every year 1 1 0 6 subunit yr the modern dunes are generally younger than 100 years and have migrated wsw at net rates of 0 6 2 5 m yr the holocene dune unit is as thick as the modern unit although it spans a period ten times longer reflecting the lower preservation potential of the transverse dunes as sedimentary records due to erosion associated with their migration the rate of dune migration suggests that an aeolian contribution of coastal sands has occurred following the sea level highstand of the middle holocene accounting for the extent of the active dunefields this mode of the barrier accumulation is considered as an analogue for earlier highstand events however the dunefields only cover a fraction of the entire barrier it is thus inferred that barrier formation occurred over a long period probably encompassing several glacial interglacial cycles sand accumulation during the lowstand either by transport of sand from the subaerially exposed shelf and or reworking of sand emplaced during the prior highstand may contribute significantly to the barrier development

optical dating in archaeology thirty years in retrospect and grand challenges for the future in 1982 when richard klein first became one of the editors of this journal the luminescence dating community was embarking on a new phase of exploratory research attention was turning from the use of thermoluminescence tl dating to estimate the time of last heating of archaeological objects such as pottery and burnt flint to the tl dating of unheated sediments that had been transported by wind and then deposited on the landscape this revolutionary development enabled the extension of tl dating to sedimentary deposits in a variety of environmental settings and to the multitude of archaeological sites that lack suitably heated artefacts in sediment dating the age of most interest is usually the time elapsed since grains of quartz or feldspar were last exposed to sunlight as the energy of the sun s rays is sufficient to evict electrons from their light sensitive traps these traps are steadily refilled after sediment deposition and the longer the grains remain buried the more tl they will emit when measured in 1985 huntley and colleagues proposed optical dating as a simpler and superior means of stimulating the light sensitive traps in quaternary sediments and this is now the principal luminescence based method of dating geological and archaeological deposits optical dating is an umbrella term for an armada of acronyms the most common in archaeological contexts being osl optically stimulated luminescence tt osl thermally transferred osl irsl infrared stimulated luminescence and pirir post infrared irsl all of these variants are founded on the same basic tenet measurement of a light sensitive signal to determine typically the last time that sediment grains were sun bleached but each approach has its virtues and vices in this paper we review this family of luminescence dating techniques and look back on 30 years of optical dating in archaeology some of the more interesting and important achievements are highlighted including the critical insights gained in the last two decades from osl measurements of individual grains of quartz we also look to the future of optical dating in archaeological contexts efforts to extend the age limits of optical dating to older hominin and archaeological sites will remain a key goal and understanding how archaeological sites of all ages form and evolve over time could be improved greatly by combining micromorphology analysis with optical dating of undisturbed intact sediments the latter poses a series of particularly formidable technical challenges but if the past is any guide to the future then we can expect optical dating to illuminate much more of human history before celebrating its golden jubilee

percussion marks on bone surfaces as a new diagnostic of hominid behaviour since stone tool cut marks and carnivore tooth marks were first described systematically on plio pleistocene archaeological bone1 2 bone surface modification has played a prominent role in interpreting early archaeological site formation and hominid behaviour3 15 here we introduce a new class of bone surface modification which we call percussion marks percussion marks were produced during experimental breakage of marrow bones and occur as pits or grooves impressed on a bone s surface by natural protrusions on the granitic hammerstone and anvil used although percussion marks can superficially mimic carnivore tooth marks they nonetheless are closely associated with hammerstone impact notches and show consistent micromorphological features which distinguish them from tooth marks and other classes of bone surface modification given indications of prehistoric hammer stone breakage of marrow bones1 7 an awareness of percussion marks is critical for accurately identifying the biological agents of bone modification at archaeological sites and provides a new diagnostic of carcass processing by hominids

detection of live magnetotactic bacteria in south atlantic deep sea sediments abstract since they were first descrbed in 1975 1 magnetotactic bacteria have been observed in a wide variety of environments including soils 2 rivers freshwater lakes and coastal marine sediments 3 4 and in one case at a water depth of about 600 m in a hemipelagic sediment 5 here we report the first systematic findings of magnetotactic bacteria in pelagic and hemipelagic sediments of the eastern south atlantic different morphologies were identified cocci spirilla vibrionic and rod shaped forms at water depths to about 3000 m on the african continental margin between the equator and 30 s and on the walvis ridge in a pelagic environment about 1400 km off the coast no actively swimming magnetotactic bacteria could be detected in deeper waters magnetotactic bacteria were observed only in the upper 10 cm of the sediments with the highest concentrations always found in a well defined narrow subsurface layer the depth of this layer is dependent on the input and turnover rates of organic matter in the sediment measurements of oxygen and nitrate concentrations 6 7 provide an assignment of depth distributions of magnetotactic bacteria to the stratification of terminal electron acceptors in the sediment the data show clearly that the majority of marine magnetotactic bacteria live in the anaerobic zone in contrast to former assumptions that they may inhabit microaerobic layers 8 11

grain size dependence of initial susceptibility and saturation magnetization related parameters of four natural magnetites in the psd md range summary initial susceptibility coercive force and several types of remanent coercive forces were measured on a set of artificial rock specimens containing grain size fractions of a natural magnetite and titanomagnetite both of which are optically homogeneous and a natural titanomagnetite and titanomaghemite both of which show exsolution phenomena it was found subsequently that the optically homogeneous titanomagnetite contains some submicroscopic fe rich inclusions these inclusions are magnetically screened in coarse grains only for the lower grain sizes studied they have an appreciable influence on the data the size of the fractions varied from 5 to 250 m the parameters and several parameter ratios are plotted as a function of grain size several of these parameters can be used as mineralogical and grain size indicators the varying degree of exsolution of the minerals is reflected in the gradients of the plots from plots of initial susceptibility versus grain size it is concluded that the shape of the grains does not play a dominant role in determining the change of this parameter with grain size variation of the various parameters with grain size is explained in terms of a gradual transition from large psd grains to md grains without there being any sharp transition for titanomagnetite x 0 55 the transition takes place at grain sizes that are about 15 m larger than for magnetite

understanding the causes and consequences of past marine carbon cycling variability through models abstract on geological time scales the production and degree of recycling of biogenic carbon in the marine realm and ultimately its removal to sediments exerts a dominant control on atmospheric co 2 and hence variability in climate this is a highly complex system involving a myriad of inter connected biological chemical and physical processes for this reason alone linking observations often highly abstracted in the form of proxies to the primary processes involved and ultimately to explanatory hypotheses for specific geological events and transitions is challenging the past few decades have seen a progressive improvement in theoretical and process based understanding of the various components that make up the marine carbon cycle and hand in hand with this the development of numerical model representations of the complete system models have also been designed and or adapted with paleoclimate questions in mind and applied to quantitatively explore the role of the marine carbon cycle in both perturbations and long term geologic evolutionary trends in global climate and possible feedbacks between them however we must ask whether paleoclimate models incorporate sufficiently appropriate representations of the dynamics and sensitivities of the marine carbon cycle and indeed whether in the geological context we really know what these dynamics are here we provide a comprehensive overview of how marine carbon cycling and the biological carbon pump is treated in available paleoclimate models with the aim of critically evaluating their ability to help interpret past marine carbon cycle and climate dynamics to this end we first provide an overview of commonly used paleoclimate models and some of their associated paleo applications drawing from a wide range of global carbon cycle box models and earth system models of intermediate complexity emics secondly we review and evaluate the three dominant processes involved in the cycling of organic and inorganic carbon in the marine system and how they are represented in models namely biological productivity at the ocean surface remineralisation dissolution of particulate carbon within the water column and the benthic pelagic coupling at the seafloor we generate and employ illustrative examples using the model genie to show how different parameterisations of water column and sediment processes can lead to significantly different model projections our compilation reveals the prevalence of static parameterisations of marine carbon cycling among existing paleoclimate models which are commonly empirically derived from present day observations although such approaches tend to represent carbon transfer in the modern ocean well they are potentially compromised in their ability to reflect the true degree of freedom and strength of feedbacks with respect to past climate events particularly those characterised by environmental boundary conditions that differ fundamentally from today finally we discuss the importance of using models of different complexities and how questions of model uncertainty may start to be addressed

late cenozoic micromammal biochronology of northwestern africa abstract this synthesis aims to integrate former recent and unpublished data on fossil micromammals rodentia erinaceomorpha soricomorpha chiroptera from moroccan algerian and tunisian archeological and paleontological sites an updated biochronology of these taxa is established from the middle miocene to the holocene ten main biozones are defined they are characterized by specific faunal assemblages whose evolution and migrations were influenced by geologic and climatic events throughout the studied period during the miocene myocricetodontinae were dominant this period was followed by a progressive diversification among murinae gerbillinae and crocidurinae from the plio pleistocene onwards along with sporadic occurrences of european asian and sub saharan taxa before a decrease in small mammal diversity at the beginning of the late pleistocene while modern faunas stabilized overall the new biochronology matches well with the former ones however some slight discrepancies emerge notably because the former biochronologies were based on more sporadic data and often did not consider the whole small mammal faunas the present work represents the first complete biochronological synthesis of north african small faunas for the whole late cenozoic which should be useful for paleontologists and archeologists in providing an up to date framework into which future discoveries will easily find their place

magnetic hysteresis of 0 6 110 μm magnetites across the verwey transition we report saturation magnetization ms saturation remanence mrs coercive force hc and remanence coercivity hcr as a function of grain size d and temperature t for 0 6 135 m magnetites

depositional changes during the danian selandian transition in loubieng france zumaia spain and sidi nasseur tunisia insights from and limits of rock magnetism depositional changes are studied in three sections encompassing the danian selandian transition loubieng france zumaia spain and sidi nasseur tunisia using magnetic susceptibility as a proxy additional rock magnetic analyses are used to avoid ambiguous interpretation of magnetic susceptibility the magnetic susceptibility measured on 90 to 270 samples per section is mainly controlled by paramagnetic minerals and linked to detrital input major increases in the detrital input are correlated to the end of the latest danian event a hyperthermal and to the danian selandian boundary in loubieng two gradual increases in magnetic susceptibility within limestones beds precede the major detrital input increases and start synchronously with the beginning of the latest danian event and the onset of haematite deposition around the danian selandian boundary respectively this haematite is suspected to be of primary origin based among other things on low magnetic viscosity values which is used here as an indicator of diagenetic origin in haematite and goethite the red levels where haematite is interpreted to be of primary origin could be linked to the hyperthermal event previously hypothesized for the basal selandian the comparison of the magnetic susceptibility chemo and biostratigraphic data between the three sections highlights the condensed nature of the sedimentation around the danian selandian boundary in the sections of the atlantic realm the lower part of the selandian shows a particularly low sedimentation rate at zumaia compared to loubieng and sidi nasseur the latter displays the most complete record of the three

terrestrial environments during mis 11 evidence from the palaeolithic site at west stow suffolk uk abstract multidisciplinary investigations of the sequence at beeches pit west stow suffolk uk have a direct bearing the age of the hoxnian interglacial and its correlation with the continental holsteinian and with the global marine record at this site glacial deposits till and outwash gravels referable to the anglian lowestoft formation fill a subglacial channel cut in chalk bedrock above these glacial deposits a series of interglacial sediments occurs consisting of limnic tufaceous and colluvial silts lacking pollen but rich in shells ostracods and vertebrates lower palaeolithic flint artefacts of acheulian character have also been recovered including refitting examples charred material is abundant at certain horizons and many of the bones have been burned several discrete areas of burnt sediment are interpreted as hearths the molluscan fauna comprises some 78 taxa and includes species of considerable zoogeographical and biostratigraphical importance the land snail assemblage from the tufa consists of woodland taxa with no modern analogue including species that are either extinct e g zonitoides sepultus or which no longer live in britain e g platyla polita p similis neniatlanta pauli this is also the type locality of retinella lyrodiscus skertchlyi which belongs to a subgenus of zonitid land snail now living only on the canary islands there are indications from this fauna the lyrodiscus biome that the climate was wetter and perhaps warmer than the present day the vertebrate fauna is also noteworthy with species of open habitats such as rabbit oryctolagus cf cuniculus and of closed forest such as squirrel sciurus sp and garden dormouse eliomys quercinus present at different times the occurrence of southern thermophiles such as aesculapian snake zamenis longissimus indicates temperatures warmer than those of eastern england today the upper levels include much material reworked from the interglacial sediments although there is clear faunal evidence for climatic deterioration both the molluscan and vertebrate faunas suggest correlation of the interglacial sediments with the hoxnian uranium series dates from the tufa 455 ka bp tl dates from burnt flints 414 30 ka bp and a range of amino acid racemization data all support correlation of this interglacial with mis 11 however four osl dates from sand beneath the interglacial sequence yield a mean age of 261 31 ka bp far younger than all other age determinations and far younger than implied by the biostratigraphy archaeologically the site is unusual in showing prolonged human occupation within closed deciduous forest and evidence for controlled use of fire in a lower palaeolithic context biostratigraphical correlations with other lower palaeolithic sites support the suggestion that acheulian and clactonian industries both occurred in southern britain during the same substage of the hoxnian although not necessarily at precisely the same time the characteristics of the mis 11 interglacial in britain are discussed in the light of evidence from beeches pit and elsewhere

in situ u series dating by laser ablation multi collector icpms new prospects for quaternary geochronology the capabilities and potential applications of in situ dating of quaternary materials using laser ablation mc icpms are explored 234 u 238 u and 230 th 234 u can be measured with precision sufficient for dating at a spatial resolution of 100mm or better in samples that contain as a little as 1 ppm uranium moreover u and th concentrations and u series isotope ratios can be continuously profiled to determine changes in age that occur with sample growth e g in speleothems these capabilities additionally permit the dating of bones teeth and possibly molluscs which are subject to post mortem open system behaviour of useries isotopes and can be employed to elucidate processes of u series migration during weathering and diagenesis a drawback of laser ablation mc icpms is that it cannot in general provide u series age estimates with the high precision and accuracy of conventional tims or solution mc icpms methods however sample preparation is straightforward the amount of sample consumed negligible and it can be used to rapidly characterise or screen and select samples from which more precise and accurate dates can be obtained using conventional methods given further instrumental developments and the establishment of suitable matrix matched standards for carbonates and other materials we foresee that laser ablation mc icpms will play an increasingly important role in quaternary dating research r 2005 published by elsevier ltd

new age estimates for the palaeolithic assemblages and pleistocene succession of casablanca morocco marine and aeolian quaternary sediments from casablanca morocco were dated using the optically stimulated luminescence osl signal of quartz grains these sediments form part of an extensive succession spanning the pleistocene and contain a rich faunal and archaeological record including an acheulian lithic assemblage from before the brunhes matayama boundary and a homo erectus jaw from younger cave deposits sediment samples from the sites of reddad ben ali oulad j mel sidi abderhamane and thomas quarries have been dated in order to assess the upper limits of osl the revision of previously measured mammalian tooth enamel electron spin resonance esr dates from the grotte des rhinoceros oulad hamida quarry 1 incorporating updated environmental dose rate measurements and attenuation calculations also provide chronological constraint for the archaeological material preserved at thomas quarries several osl age estimates extend back to around 500 000 years with a single sample providing an osl age close to 1 ma in magnetically reversed sediments these luminescence dates are some of the oldest determined and their reliability is assessed using both internal criteria based on stratigraphic consistency and external lithostratigraphic morphostratigraphic and independent chronological constraints for most samples good internal agreement is observed using single aliquot regenerative dose osl measurements while multiple aliquot additive dose measurements generally have poorer resolution and consistency novel slow component and component resolved osl approaches applied to four samples provide significantly enhanced dating precision and an examination of the degree of signal zeroing at deposition a comparison of the osl age estimates with the updated esr dates and one u series date demonstrate that this method has great potential for providing reliable age estimates for sediments of this antiquity we consider the cause of some slight age inversion observed at thomas quarries and provide recommendations for further luminescence dating within this succession

optical dating and soil micromorphology at maccauley s beach new south wales australia the ability to position landscapes in a context of time and space is a particular goal of quaternary science research the lack of context for dating samples published previously for maccauley s beach an important site for the reconstruction of australian sea levels warranted a re evaluation of both the site stratigraphy and chronology in this study we combined optically stimulated luminescence osl dating of sedimentary quartz grains and soil micromorphology of the same samples to improve our understanding of the depositional history and chronology of the sediments this combination allowed the contextualization of samples not only in time and space but also in terms of their depositional histories the latter is important in osl dating where pre syn and post depositional processes can all influence the accuracy and precision of the final age estimates the sediment profile at maccauley s beach is made up of three major units the basal mottled mud layer has undergone extensive pedogenesis since deposition and only a minimum age of 14 7 2 7 ka could be calculated the overlying grey mud with osl ages from the bottom and top of the unit of 10 0 0 7 and 7 7 0 5 ka respectively shows evidence of soil structure collapse this unit correspond to the onset of the mid holocene sea level high stand for this region the overlying sand layer was first deposited at 7 5 0 4 ka with deposition continuing beyond 6 6 0 4 ka not only does the chronology presented constrain the timing of deposition and the extent of post depositional processes at maccauley s beach but the methodological approach used here can be applied to any site to aid in the interpretation of formation processes and assess their influence on osl age determination copyright 2014 john wiley sons ltd

aeolian beach ridges and their significance for climate and sea level concept and insight from the levant coast east mediterranean abstract relict beach ridges of aeolian origin and associated soils are often used for inferring relative sea level and climate with contrasting results most studies link the aeolian coastal deposits to regressive phases some to high sea level stands and a few to intermediate relative sea level positions we interpret the apparent contradictions as indicating the lack of an over arching concept and the inconsistent usage of sea level related terms in this paper we present an integrated morpho sedimentological concept for a microtidal mid latitudinal coast and review existing data from the levant east mediterranean coast to evaluate the concept and to eliminate nomenclatural confusion a coastal depositional environment in a semi arid environment consists of shallow marine aeolian and alluvial facies which together form an aeolian beach ridge complex as a package of strata which respond simultaneously to sea level change a transgressive complex forms through reworking or overstepping of the coastal foredune and a regressive complex forms by downstepping under transgression the aeolian beach ridge represents the highstand deposit and its adjacent shallow marine sediment is the transgressive deposit under regression the complex represents the falling stage and the associated downdip surface marks the lowstand on the levant coast we find chronologically well constrained offlapping aeolian beach ridges as parts of six downstepping beach ridge complexes formed between 200 ka and 10 ka the complexes represent the falling stage systems tract fsst of a short lived 5th order depositional sequence when the shoreline shifted from a position close to the modern coastline to the shelf or below the shelf edge three of these fssts and their up dip and down dip super bounding surface together form the 4th order 100 ka sequence of the last interglacial glacial cycle the absence of transgressive highstand and lowstand systems tract is explained by the poor preservation potential due to the small sediment budget of the complex the falling stage complex has a high preservation potential because sediment source area increases while the sand drift potential remains above the local threshold on the levant coast sand delivery to the backshore continued during relative sea level falls for distances of up to 10 km between dune and coastline which is unprecedented in most modern analogues the significance of the dune soil succession for climate is limited because the dunes are governed by relative sea level change the vegetation response to changes in precipitation is non linear and the dune dynamics are characterised by low resilience and hysteresis

magnetic properties of pelagic marine carbonates abstract pelagic carbonates are deposited far from continents usually at water depths of 3000 6000 m at rates below 10 cm kyr and are a globally important sediment type recent advances with recognition of widespread preservation of biogenic magnetite the inorganic remains of magnetotactic bacteria have fundamentally changed our understanding of the magnetic properties of pelagic carbonates we review evidence for the magnetic minerals typically preserved in pelagic carbonates the effects of magnetic mineral diagenesis on paleomagnetic and environmental magnetic records of pelagic carbonates and what magnetic properties can tell us about the open ocean environments in which pelagic carbonates are deposited we also discuss briefly late diagenetic remagnetisations recorded by some carbonates despite recent advances in our knowledge of these phenomena much remains undiscovered we are only at early stages of understanding how biogenic magnetite gives rise to paleomagnetic signals in sediments and whether it carries a poorly understood biogeochemical remanent magnetisation recently developed techniques have potential for testing how different magnetotactic bacterial species which produce different magnetite morphologies respond to changing nutrient and oxygenation conditions future work needs to test whether it is possible to develop proxies for ancient nutrient conditions from well calibrated modern magnetotactic bacterial occurrences a tantalizing link between giant magnetofossils and paleogene hyperthermal events needs to be tested much remains to be learned about the relationship between climate and the organisms that biomineralised these large and novel magnetite morphologies rather than being a well worn subject that has been studied for over 60 years the magnetic properties of pelagic carbonates hold many secrets that await discovery

some additional parameters to estimate domain state from isothermal magnetization measurements abstract domain state and mixing analysis based on isothermal magnetization measurements is often restricted to the use of the day plot in order to make more information from simple rock magnetic measurements accessible for the quantitative analysis of domain state four additional parameters are proposed two of them a hysteresis shape parameter and a coercivity ratio can be directly calculated from standard measurements of the hysteresis loop and backfield curve the other two a transient energy dissipation ratio and the viscosity of isothermal remanent magnetization require additional measurements which however do not increase measurement time noticeably the theoretical background of the above parameters is discussed their ability to discern domain state is shown for a small set of synthetic magnetite and titanomagnetite samples and in a case study of a transect from the rim to the center of a dredged mid ocean ridge basalt

methodological considerations in the optical dating of quartz abstract the optically stimulated luminescence from quartz grains extracted from sediments at two archaeological sites has been studied the sites were the upper palaeolithic site at hengistbury head dorset u k and the upper aterian site at chaperon rouge morocco problems associated with the technique of optical dating are discussed particularly the thermal treatment that is necessary to remove thermally unstable charge following artificial irradiation and the extrapolation of growth curves to estimate the equivalent dose the technique used is described and some preliminary dates are presented

influence of marginal highs on the accumulation of organic carbon along the continental slope off western india abstract twenty five surficial sediment samples were collected from the central western continental margin of india which consists of diverse physiographic entities continental slope shelf margin basin marginal high and the deep arabian basin at depths between 250 and 2050 m the sediments were studied to assess the relative importance of productivity oxygen minima grain size and bathymetry on organic carbon accumulation preservation the total organic carbon toc content in the study area varies from 0 70 to 5 86 highest values of organic carbon are recorded on the marginal highs 5 12 5 86 followed by shelf margin basin 3 53 4 22 and the continental slope 1 80 3 84 the organic carbon content is relatively low in the arabian basin 0 98 1 46 the sediments from marginal highs are characterized by high oc contents relative to upper slope at equivalent water depth and also the deeper shelf margin basin the elevated organic carbon concentrations on marginal high and upper slope are associated with coarse grained biogenic sediments while those in the shelf margin basin with fine grained silty clays the enrichment of organic carbon on the marginal highs is attributed to productivity related biogenic sediments and their faster burial it is surmised that diverse topographic features in the slope and the associated hydrodynamic processes also play an important role in the enrichment of organic carbon

monsoon triggered formation of quaternary alluvial megafans in the interior of oman a vast bajada consisting of coalescing low gradient 0 3 alluvial fans exceeding 100 km in length formed along the southwestern margin of the oman mountains it comprises an old fan sequence of inferred miocene to pliocene age termed barzaman formation diagenetically highly altered to dolomitic clays and a thin veneer of weakly cemented quaternary gravels a combination of remote sensing lithological analyses and luminescence dating is used to interpret the complex aggradation history of the quaternary alluvial fans from the interior of oman in the context of independent regional climate records from satellite imagery and clast analysis four fans can be discerned in the study area while two early periods of fan formation are tentatively correlated to the miocene pliocene and the early pleistocene luminescence dating allows the distinction of five phases of fan aggradation during the middle late pleistocene these phases are correlated with pluvial periods from marine isotope stage mis 11 through 3 when southern arabia was affected by monsoonal precipitation it is concluded that the aggradation of the alluvial fans was triggered by the interplay of increased sediment production during arid periods and high rainfall with enhanced erosion of hillslopes and transport rates during strong monsoon phases however the lack of fine grained sediments bioturbation and organic material implies that although the quaternary fans are sourced by monsoonal rains they formed in a semi arid environment thus it appears that in contrast to the oman mountains the interior was not directly affected by monsoonal precipitation

first order reversal curve forc diagrams for pseudo single domain magnetites at high temperature abstract the recently developed first order reversal curve forc technique for rapidly examining magnetic domain state has great potential for paleomagnetic and environmental magnetic investigations however there are still some gaps in the basic understanding of forc diagrams in particular the behavior of pseudo single domain psd grains and the contribution of magnetostatic interactions in this paper we address some of these problems we report the first forc diagrams measurements on narrowly sized and well characterized synthetic psd through multidomain md magnetite samples the forc diagrams evolve with grain size from single domain sd like to md like through the psd grain size range since each sample contains grains of essentially a single size individual psd grains evidently contain contributions from both sd like and md like magnetic moments in proportions that vary with grain size the evolving forc diagrams cannot be due to physical mixtures of sd and md grains of widely different sizes the forc diagrams were all asymmetric small psd samples have forc diagrams with a distinctive closed contour structure the distributions of the larger md grains display no peak and lie closer to the interaction field axis to assess the effect of magnetostatic interactions we measured forc diagrams between room temperature and the curie temperature on heating the forc distributions contract without changing shape until 500 c above this temperature the diagrams become more md like and in addition become more symmetric the temperature dependence of the interaction field parameter is proportional to that of the saturation magnetization in accordance with neel s interpretation of the preisach diagram the decrease in asymmetry with heating suggests that the origin of the asymmetry lies in magnetostatic interactions the magnetic hysteresis parameters as a function of temperature were determined from the forc curves as the grain size decreased the normalized coercive force was found to decrease more rapidly with temperature

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples

last interglacial coastal environments in the mediterranean saharan transition zone abstract the coast of tunisia stretches from the western mediterranean climate belt in the north to the saharan desert climate belt in the south the sediments of this coastal strip provide a record of sea level change if an accurate chronology of the coastal deposits is available we have here surveyed and analysed coastal sites and established a chronology based on optical dating techniques the optical ages range from 156 ka to 62 ka 2 level and cluster around the last interglacial period 125 75 ka our study shows that sea level rose after termination ii for about 25 ka leading to a transgressive deposit at 120 ka a disconformity shown by some deposits suggests a brief drop of sea level during this transgressional phase subsequently for around 40 ka the coastal area became covered by soils colluvia and aeolian sediments indicating a slowly falling sea level while the composition of sediments at the north coast did not change the deposits at the central and south coast experienced a drastic change from a quartz to a carbonate dominated sedimentation sometime during the last interglacial littoral sedimentation ceased at 70 ka when the coast became sediment starved in the course of the falling sea level