holocene glacial activity and climatic variations in the swiss alps reconstructing a continuous record from proglacial lake sediments cores recovered from proglacial lake silvaplana swiss alps were investigated to examine the influence of holocene glaciers on lacustrine sedimentation during times of glacial activity in the catchment the sedimentation in the lake is dominated by the input of silt and clay sized material delivered by glacial meltwaters the deposition of fine grained material and the formation of varves reflect the existence of glaciers in the catchment and can therefore be used for the reconstruction of glacial history sedimentation rates are up to nine times higher in the varved than in the non varved sediments indicating significantly higher erosion rates under glaciated catchment conditions glacial varves were deposited in lake silvaplana during glacial retreat in the latest pleistocene and early holocene until 9400bp non varved deposits having a higher organic content and coarser grain sizes accumulated at lower rates when glacial activity was absent or negligible within the catchment between 9400 and 3300 bp

mineral magnetic record of late quaternary climatic changes in a high alpine lake the magnetic properties of a sediment core from a high altitude lake in the swiss alps were compared with palynological and geochemical data to link climatic and mineral magnetic variations according to pollen data the sediments extend from the present to the younger dryas i e they cover more than 10 000 years of environmental change in the alps the major change in magnetic properties corresponds to the climatic warming of the early holocene high coercivity magnetic minerals that characterize the late glacial period almost disappeared during the holocene and the concentration of ferrimagnetic minerals increased sharply the contribution of superparamagnetic grains also decreased in the holocene sediments similar variations in sp content and coercivity of smaller magnitude are found in the holocene and are interpreted to represent minor climatic variations comparison with the historical record of the last 1000 years confirms this interpretation the magnetic mineralogy the superparamagnetic contents and the irm intensity in the coarse grained late glacial sediments are similar to those measured in the catchment bedrock this indicates a detrital origin the different properties and the higher concentration of magnetic minerals in the holocene sediments are due to authigenic phases magnetic properties provide a high resolution record of climatic change they are sensitive even to small variations that are not recorded in the pollen or loi data magnetic parameters show fine scale variation and constitute a valuable supplement to conventional climatic indicators 1999 elsevier science b v all rights reserved

a new scalidophoran animal from the cambrian fortunian stage of south china and its implications for the origin and early evolution of kinorhyncha abstract kinorhyncha is a cycloneuralian phylum with about 240 extant species and it was not until 2015 that the first and only fossil kinorhynch species eokinorhynchus rarus was reported here we describe a new scalidophoran animal zhongpingscolex qinensis gen et sp nov from the cambrian fortunian kuanchuanpu formation at zhangjiagou section southern shaanxi province south china the holotype and only specimen possesses morphology comparable to that of e rarus they both possess heterogeneous trunk annuli and compared with e rarus z qinensis gen et sp nov lacks a neck phylogenetic analysis resolves z qinensis gen et sp nov as the sister group of e rarus both constituting stem lineage derivatives of kinorhyncha the evolutionary scenario from the last common ancestor of crown group scalidophora to the last common ancestor of total group kinorhyncha includes the acquisition of a much shortened body with a relatively low body length to width ratio heterogeneous trunk annuli and macroannuli with simple armatures the spines large spinose sclerites and annular rings of rectangular plates are autapomorphic to e rarus and segments zonites with independent cuticular plates as in crown group kinorhynchs were evolved later

magnetic susceptibility of soil an evaluation of conflicting theories using a national data set magnetic susceptibility values for topsoils across england arc combined with data for soil type geochemistry and concentrations of magnetotactic bacteria in order to evaluate different theories for explaining soil magnetism strongly magnetic soils in unpolluted areas are found over weakly magnetic substrates and are dominated by ultrafine superparamagnetic grains magnetotactic bacteria are present in insufficient concentrations to account for strongly magnetic soils and crop burning is discounted as a major factor a small number of samples show high values associated with either airborne magnetic particulates from pollution or residual primary ferrimagnetic minerals from igneous substrates the results are used to construct a new mechanism for the formation of secondary ferrimagnetic minerals that links abiological weathering and biological fermentation processes the fundamental driving force in the mechanism is fe supply which may be linked to climate observed causative associations between climate and the magnetic susceptibility of loess palaeosol sequences are supported by the findings

potbellies wasp waists and superparamagnetism in magnetic hysteresis because the response of a magnetic substance to an applied field depends strongly on the physical properties of the material much can be learned by monitoring that response through what is known as a magnetic hysteresis loop the measurements are rapid and quickly becoming part of the standard set of tools supporting paleomagnetic research yet the interpretation of hysteresis loops is not simple it has become apparent that although classic single domain pseudo single domain and multidomain loops described in textbooks occur in natural samples loops are frequently distorted having constricted middles wasp waisted loops or spreading middles and slouching shoulders potbellies such complicated loops are often interpreted in oversimplified ways leading to erroneous conclusions the physics of the problem have been understood for nearly half a century yet numerical simulations appropriate to geological materials are almost unavailable in this paper we discuss results of numerical simulations using the simplest of systems the single domain superparamagnetic sd sp system examination of the synthetic hysteresis loops leads to the following observations 1 wasp waisting and potbellies can easily be generated from populations of sd and sp grains 2 wasp waisting requires an sp contribution that saturates quickly resulting in a steep initial slope and potbellies require low initial slopes the sp contribution approaching saturation at higher fields the approach to saturation is dependent on volume hence the cube of grain diameter therefore there is a very strong dependence of hysteresis loop shape on the assumed threshold size 3 we were unable to generate potbellies using an sp sd threshold size as large as 30 nm and wasp waists cannot be generated using a threshold size as small as 8 nm the occurrence of both potbellies and wasp waists in natural samples is consistent with a room temperature threshold size of some 15 nm 5 4 simulations using a threshold size of 15 20 nm with populations dominated by sp grain sizes that is with a small number of sd grains produce synthetic hysteresis loops consistent with measured hysteresis loops and transmission electron microscopic observations from submarine basaltic glass 5 simulations and measurements using two populations with distinct coercivity spectra can also generate wasp waisted loops a relatively straightforward analysis of the resulting loops can distinguish the latter case from wasp waisting resulting from sp sd behavior

the use of mineralogic techniques as relative age indicators for weathering profiles on the atlantic coastal plain usa abstract textural geochemical and mineralogic study of soils and weathering profiles has led to the practice of applying varioys weathering parameters as relative age indicators in our studies examined the entire thickness of weathered sediment i e the weathering profile for evidence of weathering induced changes in both sand and clay sized mineralogy and used two techniques for relative age determinations these techniques were developed as tools to support geologic mapping one of our techniques for determining relative ages is based on the depth of weathering as recorded by progressive loss of denrital sand sized minerals upward in the weathering profile this is our preferred tool especially in areas where weathering profiles have been truncated we have found a gradual trend of increasing loss of labile sand sized minerals e g hornblendes feldspars and increasing depth of weathering with increasing age of the deposit of significance to many research programs this technique does not require expensive instruments such as an x ray diffractometer our other technique depends on accumulation of stable secondary clay sized minerals in the upper part of the weathering profile in our study area on the atlantic coastal plain of the united states the stable assemblage consists of vermiculite kaolinite gibbsite and iron oxides and hydroxides this technique can be effective for relative age determinations where profiles have not been truncated and can provide useful information on depositional and erosional history however in areas of widespread erosion and profile truncation such as the carolinas the utility of this technique for relative age determinations is limited there soils were partially or completely removed in many localities in relatively recent times

geomagnetic and mineral magnetic characterization of the anthropocene geomagnetic and mineral magnetic data provide geological indices that are both independent of human impact i e geomagnetic and respond to human induced environmental impact i e mineral magnetic we provide the first discussion of such magnetic events for help in defining the anthropocene within the holocene a potential geomagnetic marker for the anthropocene is the low dipole latitude at c 2700 cal a bp which is associated with distinct palaeosecular variation features in northerly mid to high latitude sites mineral magnetic records from lake and marine sediments identify major deforestation and soil delivery events from catchment systems in many parts of the world during the last 4000 years in europe clusters of these events occur around both 2600 cal a bp and ad 1100 the former coinciding with a low in geomagnetic field dipole latitude and peak intensity mineral magnetic records in peats and lake sediments can reflect particulate pollution from fossil fuel burning the expansion of major coal burning began c ad 1800 in western europe and eastern north america but around ad 1900 this expanded due to more widely distributed coal use and this event is the most clear mineral magnetic marker for the base of the anthropocene

palacomagnetic and rock magnetic investigation of late pleistocene loess deposits in belgium abstract the results of a palaeomagnetic and rock magnetic investigation of two loess profiles of late pleistocene age in tongrinne tg and rocourt rc in belgium are given we examined the possibility of using this type of sediment which is strictly speaking eolian in origin to gain information about the dynamic behaviour of the ancient geomagnetic field the influence of geological processes especially those known to occur in periglacial environments were examined a field test was applied to the upturned strata near a fossil frost wedge of weichselian age in tongrinne to demonstrate that at least some large directional changes found in periglacial sediments and which could be mistaken for excursions cannot be attributed to the earth s magnetic field but are due to mechanical disturbances the drm arm method and the requirements for uniformity by levi et al to obtain relative geomagnetic palaeointensities were tested on those loess deposits which contain a large silt fraction

coupled and decoupled responses of continental and marine organic sedimentary systems through the paleocene eocene thermal maximum new jersey margin usa 1 the flux of sediment and organic carbon from continents to the coastal ocean is an important factor governing organic burial in coastal sediments and these systems preserve important records of environmental and biogeochemical conditions during past global change events burial of organic materials in coastal systems can be promoted by chemical resilience or through protection by association with mineral surfaces but the role and influence of these processes on organic records from ancient sediments is poorly known we studied sediment and organic matter burial as particulate organic matter pom and mineral bound organic matter mom in near shore marine sediments from the wilson lake core new jersey usa that span the paleocene eocene thermal maximum petm a climatic perturbation 55 9 myr ago our results show that distinct pom and mom fractions can be isolated from sediments both fractions appear to be dominated by terrestrial material but pom consisted primarily of recently synthesized material whereas mom included a significant fraction of pre aged organic matter from soils or ancient sediments variation in organic burial through the petm is associated with changes in inorganic nitrogen burial clay mineralogy and clastic grain size that we associate with enhanced continental weathering erosion and redeposition of ancient kaolinites and eustatic sea level variation respectively these results provide a new perspective on factors governing carbon burial and carbon isotope records in ancient marine margin settings and offer information on rate and phasing of late paleocene early eocene earth system changes that may constrain interpretations of the cause of the petm climate change event

secular variation in north america during historical times summary the secular variation of the declination inclination and total force of the geomagnetic field has been plotted for 74 locations in north america a comparison of the occurrences of maxima and minima in the sv clirves from different stations shows little evidence of drift in north america although a declination maximum exhibits westward drift up to 1915 all other extrema in declination inclination and total intensity occur almost simultaneously over a wide area the major feature of sv in north america appears to be a 4000 nt decrease in the total field since 1850 which may be due to a decrease in the dipole moment coupled with the decay of a large non dipole anomaly situated under the continent short period changes in the rate of decrease are possibly jerks of the magnetic field maximum entropy spectral analysis of all three components of the field indicates periods of 102 and 53 yr

paleomagnetic dating of postglacial sediment offshore lake superior minnesota wisconsin u s a abstract four gravity cores and two piston cores obtained from offshore regions of lake superior were analyzed for variations in geomagnetic declination and inclination in natural remanent magnetization nrm sedimentation rates in offshore lake superior 20 cm 1000 yr are much slower than in great lakes environments where paleomagnetic dating has been applied before typically 1 m 1000 yr five of the six cores could be correlated on the basis of declination and four of the six could be correlated on the basis of inclination absolute age assignment to declination events by correlation to a radiocarbon dated core from lake st croix minnesota tentatively shows that sedimentation rates in lake superior have changed from relatively fast to relatively slow to intermediate values in postglacial times

long term features of drifting and standing non dipole fields as determined from holocene palaeomagnetic secular variations summary geomagnetic field motions of holocene secular variations are investigated using a separation method the palaeomagnetic secular variations from britain north america and australia have been subjected to maximum entropy method analyses based on the results of spectral analyses the secular variations are separated by band pass filters into low frequency components generally including the period band 1800 3600 yr and high frequency components generally including the period band 1000 1200 yr there is an interval from 4200 to 1700 yr bp which shows clockwise rotational motions in the low frequency components of all three sites westward drifting of geomagnetic fields may be globally dominant swinging or elliptical looping motions constrained to a certain direction were observed in the low frequency components of the british data the time duration for the persistence of the swinging motion constrained to a certain direction was 3500 years or so which could be the lifetime of an oscillating stationary field the duration of the transitional motion was 1000 1300 years which may indicate the recurrence time of a stationary field

mineral magnetic characterization of anthropogenic magnetic phases in the danube river sediments bulgarian part abstract magnetic methods have been widely used for delineation of environmental pollution of soils and sediments under certain conditions during the last decade a number of structure sensitive magnetic characteristics coercive force coercivity of remanence remanent magnetization were utilized for deduction of the grain size of the anthropogenic particulate matter which serves as a proxy for the evaluation of the distance from the pollution source possible health effects etc however up to now there is no detailed study on the influence of the morphology internal structure and phase composition of anthropogenic particles on the corresponding magnetic characteristics the aim of the present investigation is to obtain detailed microscopic magnetic and microchemical data on single grains from polluted river sediments and thus to check the validity of the classical grain size dependent trends of coercivity and remanence parameters obtained for natural and synthetic magnetites for the anthropogenic magnetic phases single anthropogenic particles from magnetic extracts have been separated from several sites along the bulgarian part of the danube river which show the strongest magnetic enhancement results from the combined magnetic thermomagnetic analysis and magnetic hysteresis microscopic optical and scanning electron microscopy sem and microchemical electron microprobe analysis empa study on single anthropogenic particles show that there is a general trend for significant underestimation of the physical size of the anthropogenic particles due to the following reasons 1 in most cases the spherules possess a complex internal structure in which the magnetic phase is presented as dendrites exsolved within a glassy non magnetic aluminosilicate matrix 2 the surface morphology is characterized by orange peel or dendritic structures or smaller strongly magnetic spherules are adhered to the surface magnetic mineralogy as deduced from single grain thermomagnetic k t analysis and further elucidated by microprobe data on the same particles shows that magnetite is the main ferromagnetic phase in isolated cases significant al substitution leads to a decrease of t c down to 500 c hysteresis parameters for all studied single grains of physical sizes varying from 39 m up to 1 5 mm fall mainly in the pseudo single domain psd range on the basis of the results from single grain magnetic measurements a new approach for semiquantitative estimation of the degree of anthropogenic pollution is proposed

a 15 000 year isotopic record from lake zurich of deglaciation and climatic change in switzerland abstract ostracod and pelecypod carbonate preserved since the latest pleistocene in the bottom sediments of lake zurich was probably formed under constant temperature conditions temporal shifts in the oxygen isotype ratios for those carbonates therefore correspond to shifts in the isotopic character of the net lake inflow alpine deglaciation which released isotopically light meltwaters commenced prior to ca 15 000 yr b p and was essentially completed in northern switzerland by 12 4000 250 yr b p well before substantially increased atmospheric heat was available from either increased insolation or an increased atmospheric co 2 content the early holocene climate for the region was characterized by minor short term fluctuations in mean annual air temperatures and an overall amelioration of up to 2 c contemporaneously precipitated authigenic and biogenic carbonates have recorded partitioning of carbon isotopes between surface and bottom waters during photosynthetic production and subsequent oxidation of organic matter in the lake the degree of that partitioning provides an index of the relative production rates which were low in the late pleistocene meltwater lake but considerably enhanced during the holocene

a stratigraphical basis for the anthropocene recognition of intimate feedback mechanisms linking changes across the atmosphere biosphere geosphere and hydrosphere demonstrates the pervasive nature of humankind s influence perhaps to the point that we have fashioned a new geological epoch the anthropocene to what extent will these changes be evident as long lasting signatures in the geological record to establish the anthropocene as a formal chronostratigraphical unit it is necessary to consider a spectrum of indicators of anthropogenically induced environmental change and to determine how these show as stratigraphic signals that can be used to characterize an anthropocene unit and to recognize its base it is important to consider these signals against a context of holocene and earlier stratigraphic patterns here we review the parameters used by stratigraphers to identify chronostratigraphical units and how these could apply to the definition of the anthropocene the onset of the range of signatures is diachronous although many show maximum signatures which post date1945 leading to the suggestion that this date may be a suitable age for the start of the anthropocene

computer synthesis of geomagnetic palaeosecular variations computer models designed to synthesize palaeosecular variations of the geomagnetic field cast doubt on some widely accepted palaeomagnetic dogmas westward or eastward drift cannot be uniquely deduced from the sense of rotation of the geomagnetic vector the use of unit vectors in statistical analyses leads to systematic errors which render investigation of the global symmetry of the palaeofield more difficult than previously supposed at least some geomagnetic excursions may be regarded as large amplitude secular variations

secular variation of the geomagnetic field data from the varved clays of soviet karelia abstract in the territory of soviet karelia 62 n 34 e a paleomagnetic study of varved clays at six sections situated in the north of lake ladoga and in the west and east of lake onega has been carried out the sections are located in different zones of deglaciation and overlap in age they cover the time interval from 16 000 to 10 200 years bp the sediment age has been defined from varvometric data palynological and radiocarbon analyses as well as from the information about geological and geomorphological development of the region the laboratory study reveals that considerable paleomagnetic information can be obtained from the varved clays geochronological and paleomagnetic studies have been carried out for each section the geomagnetic origin for the variations of magnetic properties declination inclination has been demonstrated the result of these studies is presented in a magnetochronological plot of declination and inclination variations for the northwest territory of european u s s r in the time interval 16 000 10 200 years bp maximum amplitude of the declination variation reached 70 12 000 years bp inclination variation is 50 smaller the characteristic periods for declination are 800 1750 2100 2200 and 2500 years and for inclination 900 1750 1850 2600 2700 years respectively as obtained by spectral analysis the virtual geomagnetic pole vgp moves both clockwise and counter clockwise the latter is generally predominant vgp does not reach values lower than 60 n the detailed curves of declination and inclination can be used for regional magnetostratigraphic studies and for correlation of sediments in adjacent regions such as finland and sweden

an anomalous detrital sediment magnetization summary palaeomagnetic directions in 84 samples of swedish varved clay were found to be closely related to the slope of deposition existing models for the bedding error which permit grain rotation only about horizontal axes fail to account for the sequence of remanence inclinations a revised model which invokes post depositional rotation about axes normal to the bed is in good agreement with the observations and predicts an increase in remanence noise for sediments formed on tilted surfaces under certain conditions

new macrobenthic cycloneuralians from the fortunian lowermost cambrian of south china abstract although morphology based phylogenetic analyses and molecular data suggested that the cycloneuralians might have emerged in the ediacaran period the oldest known fossil remains of cycloneuralians were first reported from the cambrian fortunian stage of south china and to date four genera and species as well as nine indeterminate forms have been described here we report the latest discoveries of cycloneuralians from the fortunian kuanchuanpu formation at zhangjiagou lagerstatte dahe village xixiang county southern shaanxi province south china a new genus and species dahescolex kuanchuanpuensis n gen n sp is described and a previously reported genus and species eopriapulites sphinx is re described dahescolex kuanchuanpuensis n gen n sp is suggested to be a stem lineage derivative of scalidophora whereas e sphinx may represent a stem lineage derivative of cycloneuralia from the fragments discovered the new specimens are suggested to have reached millimeters in dimension and the original individuals are estimated to have dimensions in centimeter hence falls within the size range of macrobenthos therefore at least some of the fortunian cycloneuralians can be considered macrobenthic and it is suggested here that the cycloneuralia may have originated in the fortunian macrobenthos

absolute dating of the late glacial period in switzerland using annually laminated sediments abstract results of a high resolution late glacial ams 14 c chronology from rotsee central switzerland have given evidence that the atmospheric radiocarbon concentration was not constant between 13 000 and 9500 yr b p this resulted in three marked phases of constant radiocarbon age at 12 700 at 10 000 and at 9500 yr b p new results of a late glacial varve chronology from soppensee central switzerland suggest that the younger two phases of constant 14 c age each had a duration of ca 400 calendar years the length of the late glacial chronozones has been calculated on the basis of these replicate varve counts and a comparison with their estimated duration in radiocarbon years shows that the estimated duration of the chronozones bolling ca 800 calendar yr vs 1000 14 c yr and younger dryas ca 900 calendar yr vs 1000 14 c yr agree with the expected time span whereas the estimated duration of the allerod chronozone ca 400 calendar yr vs 1000 14 c yr is substantially shorter than expected furthermore a tentative comparison of varve ages and 14 c ages suggests that the varve chronology is more than 1000 yr offset toward older ages from the radiocarbon chronology during the late glacial period

neoproterozoic to early cambrian small shelly fossil assemblages and a revised biostratigraphic correlation of the yangtze platform china abstract small shelly fossils ssfs occur widely on the yangtze platform and have great potential for biostratigraphic subdivision of pre trilobitic early cambrian strata based on the ssf record of the shallow water realm five biozones can be recognized for the meishucunian stage in ascending order the biozones are anabarites trisulcatus protohertzina anabarica assemblage zone paragloborilus subglobosus purella squamulosa assemblage zone watsonella crosbyi assemblage zone formerly heraultipegma yunnanensis zone poorly fossiliferous interzone sinosachites flabelliformis tannuolina zhangwentangi assemblage zone in addition one ssf biozone is recognized for the overlying qiongzhusian stage pelagiella subangulata taxon range zone the formerly used siphogonuchites triangularis paragloborilus subglobosus zone and heraultipegma yunnanensis zone are discussed and redefined approximately 80 species of ssfs were screened for their spatial and temporal distribution on the yangtze platform variations in lithofacies and biofacies can be recognized throughout the yangtze platform extending over an area of 2000 900 km in a deeper water shelf setting the first zone is represented by the protohertzina anabarica kaiyangites novilis assemblage zone while younger zones are not recognized in the southern region at the northern platform margin the qiongzhusian is represented by the ninella tarimensis cambroclavus fangxianensis assemblage zone and the rhombocorniculum cancellatum taxon range zone the southeastern shaanxi western hubei region followed a slightly different lithological and faunal development than the rest of yangtze platform indicating a stronger similarity with parts of east gondwana some taxa such as w crosbyi p subangulata r cancellatum microdictyon effusum a trisulcatus protohertzina unguliformis and p anabarica occur nearly worldwide and support an international correlation of early cambrian sequences between the yangtze platform and smaller west gondwanan blocks siberia newfoundland and australia the six investigated zones of the yangtze platform comprise an interval spanning the early nemakit daldynian to the late atdabanian early botoman stage on the siberian platform palaeobiogeographic analysis revealed a strong taxic similarity between the yangtze platform and the tarim platform a smaller number of species are shared with other west gondwanan platform fragments such as india and iran palaeobiogeographic results do not support the previously reported position of the south china block between australia and siberia during the early cambrian

rock magnetic studies on sediments from erlongwan maar lake long gang volcanic field jilin province ne china summary detailed rock magnetic investigations were carried out on two 23 m long sediment cores from erlongwan maar lake ne china the completely laminated sediment sequence of the lake is interrupted by 410 graded layers with thicknesses between 0 1 and 150 cm magnetite of psd size was identified as the main magnetic carrier mineral by temperature dependent measurements of the saturation magnetization and determination of hysteresis parameters the minerogenic components in the laminated sediments and the graded layers are nearly identical and their rock magnetic characteristics reflect the prevailing conditions anoxic or oxic during deposition the most reliable criteria for estimating the availability of oxygen is whether an increase in minerogenic influx is linked to a shift in the magnetic grain size spectrum to coarser oxic or finer anoxic grains comparison of different rock magnetic parameters indicative for magnetic grain size and coercitivity revealed that the s ratio which is known to reflect the presence of high coercive minerals is grain size indicative in sediments with a monomineralic magnetic composition

latest paleocene lithologic and biotic events in neritic deposits of southwestern new jersey in the southwestern new jersey coastal plain four drill holes contain continuous neritic sedimentation across the paleocene eocene boundary calcareous nannofossil zone np 9 np 10 boundary significant lithologic and biotic changes occur in these strata near the top of the paleocene global warming increased precipitation and other oceanographic and climatic events that have been recognized in high latitude deep oceanic deposits of the latest paleocene also influenced mid latitude shallow marine and terrestrial environments of the western north atlantic the diverse well preserved calcareous nannofossil flora that is present throughout the entire new jersey boundary section accurately places these events within the uppermost part of the upper paleocene zone np 9 several rapid but gradational changes occur within a 1 1 m interval near the top of zone np 9 the changes include 1 a change in lithology from glauconitic quartz sand to clay 2 a change in clay mineral suites from illite smectite dominated to kaolinite dominated 3 a change in benthic foraminiferal assemblages to a lower diversity fauna suggestive of low oxygen environments 4 a significant increase in planktonic foraminiferal abundance and 5 an increased species turnover rate in marine calcareous nannofossils pollen was sparse in the new jersey drill holes but terrestrial sporomorph species in virginia exhibit increased turnover rates at a correlative level foraminiferal assemblages and lithology indicate that relative sea level rose in new jersey at the same time as these late paleocene events occurred in late biochron np 9 the higher sea levels influenced sediment type and absolute abundance of planktonic foraminifers in the deposits above the initial increase of kaolinite in the upper part of zone np 9 the kaolinite percentage continues to increase and the maximum kaolinite value occurs in the uppermost part of zone np 9 there are few changes in either the sediments or the biota precisely at the zone np 9 np 10 boundary in new jersey the clay rich deposits with a high kaolinite clay mineral suite the lowered diversity benthic foraminiferal assemblages the abundant planktonic foraminiferal specimens and the calcareous nannofossil assemblages continued essentially unchanged into the earliest eocene zone np 10 within the lower part of zone np 10 the kaolinite percentage decreased to very low values

magnetic mineralogy and its implication of contemporary coastal sediments from south china magnetic parameters have been widely used as a rapid cost effective and non destructive method to assess whether their magnetic properties reflect the development history in the pearl river delta three sediment cores collected from south china coastal waters were selected for magnetic research the results indicate that the predominant ferrimagnetic mineral is magnetite with an additional smaller amount of surprisingly high coercive greigite fine grained superparamagnetic and single domain particles of magnetite and the relative contribution of greigite are increased when the total concentration of ferrimagnetic minerals is higher three well known stages of the chinese history i e iron smelting cultural revolution and the latest phase of opening and reforming were identified in the vertical variation of magnetic concentration parameters although the record of the three cores is not completely consistent the results point out that magnetic concentration parameters can reflect the development and pollution history in surrounding coastal areas

magnetic particle characterization in the seine river system implications for the determination of natural versus anthropogenic input 1 this study presents an innovative application of well established environmental magnetic proxy parameters on fluvial sediments with the aim to trace geological and human induced processes in the complex seine river drainage system in northern france we seek to identify environmental fingerprints of mechanical and chemical weathering processes the regional distribution of the suspended material and changes in the balance of natural input versus anthropogenic pollution in order to reach these goals we applied a combination of rock magnetic and advanced scanning electron microscopic techniques on a large number of sediment trap samples generally we observe an increase in magnetic concentration coupled with a coarsening in magnetic grain size downstream of the seine river system furthermore the dominant magnetomineralogy changes from high coercivity minerals upstream in more rural areas to magnetite dominated assemblages downstream each river segment shows its specific trend line depending on regional initial input weathering conditions drainage area and potential pollution sources one major outcome of this study is the observed significant correlation between anthropogenic antimony rich iron oxide particles and the magnetic concentration this shows the potential of magnetic remanence measurements as proxy parameters for specific heavy metal pollution concentrations hence the environmental magnetic study presented herein serves to identify major trends as well as local particularities and leads to quantitative analyses of the contributions of individual tributaries in the seine river system

pollen and oxygen isotope analyses on late and post glacial sediments of the tourbiere de chirens dauphine france the sequence of vegetation phases in the late glacial was studied in a sediment section from the bog tourbiere de chirens by means of pollen analysis 18o16o ratios of samples of lacustrine marl obtained from the same profile reflect variations of 18o16o in precipitation and thus provide an additional independent paleoclimatic record the observed 18o16o variations agree well with the climatic history as deduced from pollen analysis the climatic transition from the oldest dryas to the bolling period sensu lato as well as the beginning and end of the younger dryas cold phase is marked by abrupt changes in the 18o16o ratio which were observed also in other regions of the alps these drastic climatic changes probably took place simultaneously over large areas of central europe and occurred within short time spans

geomagnetic palaeosecular variation 0 13 000 yr bp as recorded in sediments from three maar lakes from the west eifel germany summary geomagnetic palaeosecular variation psv profiles have been obtained from 12 cores raised from three maar lakes in the west eifel germany age control is provided by varve chronology analysis of mean inclinations suggests that a post depositional remanent magnetization pdrm was acquired in all three lakes a lock in time of 150 yr corresponding to an average lock in depth of 24 cm has been determined from a comparison with archaeomagnetic sv data stacked psv results demonstrate directional geomagnetic field behaviour through the late and post glacial in central europe and show good agreement with the holocene british master curve turner thompson 1982 psv results suggest that westward drift of the non dipole field was not persistent over the last 13 000 yr spectral analyses yield declination variations with durations of about 1800 yr in the younger holocene 0 5000 yr bp and 4300 yr between 5000 and 13 000 yr bp the inclination exhibits swings of 1000 yr duration in the younger holocene and about 2000 yr in the older part moreover inclination spectra suggest the presence of one inclination variation with a very long duration approaching the length of the time span investigated 8600 yr

late glacial climatic oscillations as recorded in swiss lake sediments regional pollen assemblage zones for the late glacial period of the swiss plateau are introduced and defined they include four major zones artemisia juniperus hippophae betula pinus paz with several subzones pollen and oxygen isotope analyses on lacustrine sediments from several lakes in the area reveal four distinct phases of climatic oscillation in the time period of 13 000 9500 yr bp the first oscillation termed the aegelsee fluctuation occurs shortly before 12 000 yr bp and varve counts suggest its duration was ca 100 yr it is characterised by a short decrease in the oxygen isotopes as well as a short increase in nap associated with a depression in birch pollen values the second oscillation which occurs in the 18o record shortly before the deposition of the laacher see tephra ca 11 000 yr bp is termed the gerzensee fluctuation it occurs during a pine dominated phase and its vegetational effects cannot be determined palynologically the most prominent regressive phase is the younger dryas biozone ca 10 700 10 000 yr bp characterised by an increase in heliophilous nap and low 18o values the younger dryas biozone can often be subdivided palynologically into two parts a first part rich in grasses and juniper and a second part with higher filipendula and birch values during the preboreal biozone another distinct oscillation is evidenced only in the oxygen isotope ratios comparison of the swiss oxygen isotope profiles with the greenland dye 3 record suggests that not only the three major shifts in the 18o curves but also the minor ones are closely comparable suggesting some common climatic control

a geomagnetic secular variation study 31000 19 500 bp in western canada summary palaeomagnetic results from 212 horizons spread evenly through an 18 m sedimentary sequence in southern british columbia are reported radiocarbon ages suggest that the sequence spans the interval from 31 200 to 19 500 yr bp no evidence for any large geomagnetic excursions such as the so called mono lake excursion is found but a distinctive pattern of normal secular variation is observed with declination and inclination swings of 45 and 25 peak to peak amplitude respectively for the most part the secular variation consists of low amplitude oscillations about the field vector of a geocentric axial dipole expected at the site latitude but three relatively large perturbations occur at approximately 4000 yr intervals these perturbations systematically bias the overall mean to shallow inclinations and easterly declinations in a manner reminiscent of the spatially non isotropic secular variation model proposed by cox the bias involved is about 6 in declination and 3 in inclination overall mean d 5 8 e i 64 2 95 0 9 n 212 horizons which leads to a pole which is both far sided and right handed if the horizons involved in the three major perturbations are eliminated the mean direction d 1 2 e i 67 2 95 0 8 n 125 horizons does not differ from that of a geocentric axial dipole despite the small cone of confidence

stratigraphic and climatic implications of clay mineral changes around the paleocene eocene boundary of the northeastern us margin abstract kaolinite usually is present in relatively small amounts in most upper paleocene and lower eocene neritic deposits of the northern us atlantic coastal plain however there is a short period less than 200 000 k y in the latest paleocene upper part of calcareous nannoplankton zone np 9 when kaolinite dominated clay mineral suites replaced the usual illite smectite dominated suites during this time of global biotic and lithologic changes kaolinite increased from less than 5 of the clay mineral suite to peak proportions of 50 60 of the suite and then returned to less than 5 in uppermost paleocene lowermost eocene strata this kaolinite pulse is present at numerous localities from southern virginia to new jersey these sites represent both inner and middle neritic depositional environments and reflect input from several river drainage systems thus it is inferred that kaolinite rich source areas were widespread in the northeastern us during the latest paleocene erosion of these source areas contributed the kaolinite that was transported and widely dispersed into shelf environments of the salisbury embayment the kaolinite increase which occurred during a time of relatively high sea level probably is the result of intensified weathering due to increased temperature and precipitation the southern extent of the kaolinite pulse is uncertain in that uppermost paleocene beds have not been identified in the southern atlantic coastal plain the late paleocene kaolinite pulse that consists of an increase to peak kaolinite levels followed by a decrease can be used for detailed correlation between more upbasin and more downbasin sections in the salisbury embayment correlations show that more upbasin paleocene eocene boundary sections are erosionally truncated they have varying portions of the kaolinite increase and if present at all discontinuous portions of the subsequent kaolinite decrease as these truncated sections are disconformably overlain by lower eocene strata rapid erosional removal of large parts of the most kaolinite rich p e boundary clay deposits occurred by early eocene time erosion of the kaolinite rich p e boundary beds was enhanced during times of sea level fall when kaolinite rich sediments were redeposited to produce kaolinite spikes in basal beds of lower and middle eocene sequences that have little or no kaolinite elsewhere in the sequence in contrast more downbasin sites document only the upper decreasing part of the kaolinite pulse the absence of strata documenting the earlier kaolinite increase is attributed to slow sedimentation condensed interval as a result of a significant sea level rise that ponded most sediments in shallower waters combined with the probable subsequent erosional removal of these thin downbasin deposits by oceanic currents

magnetic discrimination of pyrrhotite and greigite bearing sediment samples by using bulk samples rock magnetic measurements were performed to discriminate between pyrrhotite and greigite bearing shallow marine sediments that are now uplifted above sea level in southwestern taiwan thermal demagnetization of a composite isothermal remanent magnetization irm was found to be effective in differentiating between the two types of sediments to check the thermal instability and estimate the true unblocking temperature tb spectra of sediments containing these minerals saturation irms sirms were imparted at each temperature step during demagnetization while pyrrhotite bearing samples showed unambiguous tb temperature spectra greigite bearing samples underwent considerable alteration which is responsible for most of the decrease in magnetization during thermal demagnetization such thermal instability of greigite is a practical and important clue for its identification zero field warming of irm from 5 to 300 k sensitively indicates the presence of pyrrhotite and trace magnetite in bulk samples without any magnetic separation

holocene sediment dynamics in an upland temperate lake catchment climatic and land use impacts in the english lake district accelerated erosion and transport of fine sediment from upland temperate catchments can reflect increased erosivity and or erodibility due in turn to climatic and or human forcing identification of sediment fluxes and sources over holocene timescales can both enable understanding of the relative impacts of these forcings and provide perspective on recent sediment fluxes here we present a 5500 yr record of sediment fluxes and sources from lake bassenthwaite in the english lake district utilizing magnetic measurements and fuzzy clustering coupled with independent pollen and archaeological records to identify the timing and impact of catchment disturbance this record shows that recent sediment flux increases ie within the last 150 years are unprecedented in scale throughout the mid late holocene and appear to be in response to specific human changes occurring within the catchment earlier episodes of human activity from the mid holocene onwards show no link with increased lake sediment fluxes

study of secular variation 2000 bc 1900 ad based on comparison of contemporaneous records in marine sediments and baked clays abstract paleomagnetic records derived from a marine sediment core for the region of the mouth of the yellow river are presented and compared with relevant archaeomagnetic results some characteristics of the secular variation of declination for the east asia region during the last 4500 yr are discussed

palaeomagnetic evidence for stationary sources of geomagnetic secular variation abstract asymmetrical curvilinear patterns of secular variation with approximately superposed outward and return trajectories can be attributed to stationary magnetic sources in the core some appropriate palaeomagnetic examples are presented here

palaeomagnetic study of the holocene and upper pleistocene sediments from lake barombi mbo cameroun first results abstract the analyses of the stable deposition and post depositional remanent magnetization carried by the lacustrine sediments contained in a 24 m sequence collected from the bottom of the maar lake barombi mbo cameroun yield well defined declination and inclination oscillations which can be attributed to palaeosecular variations of the local geomagnetic field the transformation to a time scale based on the interpolation and extrapolation of 14 c ages allows comparison of this record with contemporaneous records obtained in other parts of the world the successive inclination peaks can be individually identified with those found in western europe in spite of small chronological discrepancies which are in the range of the standard deviation of the ages normalization of the nrms by anhysteretic magnetization provides a profile of relative palaeointensities which shows similarities with that reconstructed from the same time interval in a sequence from western europe although an important phase shift appears

geomagnetic secular variations in greece through the last 6000 years obtained from lake sediment studies summary geomagnetic declination and inclination secular variation curves have been constructed back to 6000 yr bp from palaeomagnetic measurements of sediments cored in lakes volvi trikhonis and begoritis greece they have been dated by palynological studies and by comparison with observatory and archaeomagnetic records radiocarbon ages are all affected by the old carbon factor cores from all three lakes contain a thin ash layer which we associate with the pompeii eruption of vesuvius in ad 79 averaged curves of secular variations of declination and inclination have been computed for the whole study the broader scale pattern of secular variations is basically similar to lake sediment records from the uk poland and switzerland though finer detail in the structure of some of the principal features is resolved

magnetic parameters trace elements and multivariate statistical studies of river sediments from southeastern india a case study from the vellar river this contribution constitutes a new study using magnetic parameters and trace element determinations of pollutants in river sediments from the tamil nadu state the vellar river covers a total length of about 200 km and flows into the bay of bengal sediment samples were collected at different sediment depths up to 90 cm from 12 sites to investigate their magnetic properties 27 samples and the contents of trace elements 21 out of 27 samples along the river as well as to perform magnetic studies for various grain size fractions 16 sub samples the magnetic results of magnetic susceptibility and remanent magnetizations suggest that the magnetic signal of these sediments is controlled by ferrimagnetic minerals magnetite like minerals and a minor contribution of antiferromagnetic carriers such as hematite minerals detailed studies of selected samples showed a higher magnetic concentration in finer grain sized fractions and a slightly different magnetic mineralogy magnetic concentration dependent parameters evidenced high values which together with the background values allowed us to identify magnetic enhancement at some sites the pearson correlation and multivariate statistical studies principal component analysis canonical correlation analysis supported the relationship between the magnetic and chemical variables in particular magnetic susceptibility anhysteretic and isothermal remanent magnetization are closely correlated to co cr cu fe v zn and the pollution load index in addition principal coordinate analysis and fuzzy c means cluster analysis allowed us to make a classification and to perform a magnetic chemical characterization of the data into four groups thereby identifying critical possibly polluted sites from the vellar river

the palaeomagnetism and magnetic fabric of cave sediments from pwll y gwynt south wales abstract this paper describes the palaeomagnetism of 37 samples of clay from pwll y gwynt powys the laminated sediments are shown to have acquired a depositional remanent magnetisation in both normal and reversed polarity geomagnetic fields magnetic susceptibility anisotropy results from a tilted clay layer suggest that the transition from a strike oriented to a dip oriented magnetic lineation occurs close to a slope of 20 a slumped clay unit is found to contain a well defined magnetic fabric which can be related to shearing processes during emplacement

allerod younger dryas lake temperatures from midge fossils in atlantic canada remains of freshwater midges are abundant in lake sediments and their species distributions are closely related to the surface water temperature of lakes their distributions thus provide a powerful tool for paleoclimatology the distribution of species in a core from splan pond in atlantic canada indicates that there were abrupt transitions in late glacial temperatures between warm and cold states the transitions are correlative with the well known warm allerod and cold younger dryas events in europe these data thus confirm the inference from palynological data that these events affected regions on both sides of the atlantic

magnetic signature of heavy metals pollution of sediments case study from the east lake in wuhan china detailed magnetic measurements and geochemical analyses were performed on 114 sediment samples collected from the east lake wuhan city china to establish a possible link between the enhanced concentration of anthropogenic magnetic particles and heavy metals with known sources relatively higher magnetic susceptibility values mass specific 150 10 8 m3 kg 1 were observed for samples near the pollution sources e g the wuhan iron and steel company wisc the qingshan thermal power plant qtpp the banks driveways of the lake and near the sightseeing route of yachts on the lake moreover is positively correlated to the concentration of pb correlation coefficient r 0 682 but negatively or weakly correlated with both zn and cu in contrast anhysteretic remanent magnetization arm is significantly correlated with these major heavy metals r 0 645 for zn arm 0 699 for pb arm and 0 841 for cu arm respectively which indicate that arm serves a better indicator for the pollution of heavy metals in this lake thermomagnetic analysis combined with magnetic hysteresis measurements revealed that magnetites in the pseudo single domain multidomain grain size regions are dominant scanning electron microscopy and energy dispersive x ray examinations of the magnetic extracts showed that these fe rich particles have different morphologies orange peel structure hollow structure with adhered smaller particles zr rich melted like irregular particles pear shaped spherules and spherules with slick surfaces these features are typical for particles produced by anthropogenic activities because of the genetic relationship between the environmental setting of the east lake and the nearby pollution sources this study suggests that in situ magnetic surveys are sensitive to evaluate the environmental pollution on the lake bottom

mercury deposition and methylmercury formation in narraguinnep reservoir southwestern colorado usa abstract narraguinnep reservoir in southwestern colorado is one of several water bodies in colorado with a mercury hg advisory as hg in fish tissue exceed the 0 3 g g guideline to protect human health recommended by the state of colorado concentrations of hg and methyl hg were measured in reservoir bottom sediment and pore water extracted from this sediment rates of hg methylation and methyl hg demethylation were also measured in reservoir bottom sediment the objective of this study was to evaluate potential sources of hg in the region and evaluate the potential of reservoir sediment to generate methyl hg a human neurotoxin and the dominant form of hg in fish concentrations of hg ranged from 1 1 to 5 8 ng l n 15 and methyl hg ranged from 0 05 to 0 14 ng l n 15 in pore water generally were highest at the sediment water interface and overall hg correlated with methyl hg in pore water r 2 0 60 p 0007 n 15 net hg methylation flux in the top 3 cm of reservoir bottom sediment varied from 0 08 to 0 56 ng m 2 day mean 0 28 ng m 2 day n 5 which corresponded to an overall methyl hg production for the entire reservoir of 0 53 g year no significant point sources of hg contamination are known to this reservoir or its supply waters although several coal fired power plants in the region emit hg bearing particulates narraguinnep reservoir is located about 80 km downwind from two of the largest power plants which together emit about 950 kg hg year magnetic minerals separated from reservoir sediment contained spherical magnetite bearing particles characteristic of coal fired electric power plant fly ash the presence of fly ash magnetite in post 1970 sediment from narraguinnep reservoir indicates that the likely source of hg to the catchment basin for this reservoir has been from airborne emissions from power plants most of which began operation in the late 1960s and early 1970s in this region

atmospheric mineral dust in dryland ecosystems applications of environmental magnetism irm mean of 67 samples 6 72 10 3 am 2 kg 1 is more than two orders of magnitude greater than that for underlying paleozoic and mesozoic sedimentary rocks this contrast is mainly caused by the presence of silt size titanium bearing magnetite particles in the surficial deposits and their absence in bedrock because of their size composition and isolated location the magnetite particles represent a component of atmospheric dust likely deposited over the past few centuries the positive correlation of sediment irm values with amounts of potential plant nutrients reveals the importance of atmospheric dust to soil fertility over much of the american southwest subsequent disturbance of landscapes by domestic livestock grazing as an example commonly results in wind erosion which then depletes exposed surfaces of original aeolian magnetite and associated fine grained sediment declines in soil fertility and water holding capacity in these settings can be estimated in some field settings via decreases in magnetic susceptibility relative to nearby undisturbed areas along gentle hillslope gradients of the colorado plateau field measures for aeolian magnetite demonstrate that the redistribution of deposited atmospheric dust influences landscape level patterns in the distribution of invasive exotic plant species our results indicate that environmental magnetism has high potential for assessing the development and degradation of dry landscapes elsewhere

magnetic properties of marine limestones numerous paleomagnetic investigations have been carried out on limestones but their rock magnetic properties have often been neglected in this review geological and rock magnetic factors which determine whether marine limestones are suitable for paleomagnetic study are summarized and laboratory techniques for the identification of the magnetic mineralogy are evaluated the conditions under which pelagic limestones form are especially favorable for the acquisition of a stable primary natural remanence nrm probably by a postdepositional alignment process the effectiveness and timing of acquisition of this remanence are influenced by the thoroughness of bioturbation other remanence components can be acquired during diagenesis in the soft sediment right after deposition or much later even in the indurated limestone the magnetic mineralogy of a limestone is difficult to describe optically because of the small grain size and low concentration magnetic techniques are more convenient direct analysis of extracted magnetic minerals is handicapped by the difficulty of obtaining a representative extract a particularly useful technique involves combined observations of isothermal remanent magnetization irm acquisition in strong fields up to at least 4 t and the subsequent destruction of this irm during stepwise or continuous thermal demagnetization the magnetic minerals most commonly identified by these techniques are magnetite goethite hematite and maghemite these magnetic minerals occur in different combinations in the marine limestones of central europe and the mediterranean realm pyrite is common in certain limestones where it can be the precursor of an unwelcome late goethite pyrrhotite may be responsible for unstable magnetization in the swiss helvetic limestones but otherwise is rare thermal demagnetization of some limestones causes changes of susceptibility and coercivity at quite low temperatures 300 400 c due to the breakdown of a metastable mineral such as maghemite goethite or pyrrhotite at high temperatures above 500 c pronounced changes of magnetic mineralogy occur in all limestones because of the growth of new magnetite this necessitates great care in interpretation of thermal demagnetization of high blocking temperature components and often results in observational difficulties due to viscous remanent vrm behavior of the newly formed magnetite vrm is a widespread component of nrm in many limestones but it can usually be removed effectively by standard magnetic cleaning techniques the susceptibility serves as a simple control of mineralogical change during heating and can serve as an indicator of lithologic variation of magnetic mineral concentration and type in magnetostratigraphic profiles the susceptibility is anisotropic and shows a classical depositional pattern of the distribution of principal axes however the probable postdepositional mechanism of nrm acquisition especially in bioturbated sediments implies that the anisotropy pattern results from postdepositional compaction of the sediment

intraspecific variation of radial symmetry number of a 535 million year old jellyfish abstract although modern jellyfishes are stably tetramerous intraspecific variation of radial symmetry number is not uncommon and spans from unimery to octamery however intraspecific variation of radial symmetry number among fossil cnidarians is rarely reported we report a single new specimen of quadrapyrgites quadratacris from the cambrian fortunian kuanchuanpu formation at the zhangjiagou lagerstatte in southern shaanxi province south china quadrapyrgites quadratacris has previously been interpreted to be a coronate scyphozoan with stable tetramery the new specimen has morphology well comparable with the previously reported specimens of q quadratacris with the exception that it is pentamerous this is the first report of intraspecific variation of radial symmetry number among the fortunian cnidarians it demonstrates that tetramery is stable for quadrapyrgites with pentamery as less common intraspecific variation and that the fortunian scyphozoans have acquired the ability of regulating and changing their radial symmetry number during their alternation of generations

mineral magnetic characterization of sediment sources from an analysis of lake and floodplain sediments in the catchments of the old mill reservoir and slapton ley south devon uk research on suspended sediment transport in the catchments of the old mill reservoir and slapton lower ley south devon has attempted to discriminate changing catchment sources on the basis of downcore variations in the mineral magnetic properties of lake reservoir and floodplain sediments here we examine these downcore variations and also explore the variability in catchment sources and the influence of topographic controls on mineral magnetic signatures of topsoils and subsoils particle size controls on the mineral magnetic signatures are explored by an analysis of a fractionated sediment sample whilst the possible impact of diagenesis is assessed by an examination of the mn profiles in the lake and reservoir sediments from this analysis it is evident that the mineral magnetic signatures of well sorted floodplain deposits are more likely to reflect the particle size composition of the transported material by contrast the mineral magnetic record in the sediment of slapton ley appears to be most strongly influenced by dissolution of magnetic minerals the sediment of the old mill reservoir provides the only suitable record for the application of a simple mixing model which is developed in order to quantify changes in the relative contribution of topsoil and subsoil through time the research has important implications for attempting to reconstruct sediment sources in highly eutrophic lakes and emphasizes the uncertainty in the application of simple mixing models 1998 john wiley sons ltd

environmental magnetic responses of urbanization processes evidence from lake sediments in east lake wuhan china summary we present a study on the environmental magnetic response to urbanization processes from nine sediment cores from east lake in wuhan china the concentration of magnetic particles heavy metals and organic matter in the upper 2 18 cm of the sediment cores have been significantly elevated due to the input of coarse magnetite grains from industrial e g power generation and steelmaking and other anthropogenic activities e g vehicle emissions concentration related magnetic parameters such as magnetic susceptibility saturation isothermal remanent magnetization and anhysteretic remanent magnetization are significantly correlated with concentration of heavy metals and organic matter for example pearson s correlation coefficients are 0 921 for cu 0 660 for pb and 0 848 for loss on ignition respectively the magnetic properties of the lake sediments document the pollution history caused by human impact on the lake catchment during urbanization the environmental quality of the lake was fairly good before the 1960s magnetic heavy metal and organic matter contents of the sediments were low and relatively constant which indicates relatively stable natural inputs from the lake catchment pollution trends since the 1960s are reflected in downcore magnetic property variations of the lake sediment the concentration of magnetic particles in the lake sediments started to increase since 1957 when the wuhan iron and steel company and the qingshan thermal power plant which are located upwind of the lake were built and put into production lake pollution was further aggravated since the acceleration of industrialization and urbanization in east lake area in the 1980s which is verified by the elevated concentration of heavy metals and organic matter in the sediments the magnetic mineral concentration in the lake sediment increased continuously until it peaked in the 1990s and has remained a high level since then these results suggest that magnetic properties respond sensitively to environmental status and that the magnetic properties of sediments can provide an excellent record of the industrial and anthropogenic history in an urban lake catchment

long period geomagnetic secular variations since 12 000 yr bp a comparison of secular variation records of the geomagnetic field inclination obtained from palaeomagnetic studies of european and north american post glacial and late glacial sediments suggests that geomagnetic westward drift has persisted through the past 12 000 yr between 12 000 and 2 500 yr bp the overall average drift rate was between 0 14 and 0 16 deg yr 1 at 2 500 yr bp it is tentatively suggested that the drift rate increased and rose to a maximum of nearly 0 5 deg yr 1 before decreasing to historically observed values of 0 25 deg yr 1

late quaternary paleomagnetic record of the goderich basin lake huron paleomagnetic analysis of two cores taken of the late quaternary sequence of the goderich basin lake huron resulted in high resolution declination inclination intensity of magnetization j magnetic susceptibility k and q ratio j k curves there was a consistent relative relationship of the features along the curves of all five parameters for both cores studied which confirms the reproducibility of the method and suggests that paleomagnetic curves can be used for time parallel correlation of the late quaternary sequence of the goderich basin

holocene and recent sediment accumulation rates in southern lake michigan abstract rates of sediment accumulation in lake michigan are a key component of its geologic history and provide important data related to societal concerns such as shoreline erosion and the fate of anthropogenic pollutants previous attempts to reconstruct holocene rates of sediment accumulation in lake michigan as well as in the other laurentian great lakes have been bedeviled by the effect of refractory terrestrial material on radiocarbon ages from total organic carbon samples of lake sediments ams radiocarbon ages on small samples of biogenic carbonate ostracodes and mollusks in lake michigan provide accurate holocene ages the present bicarbonate reservoir effect is estimated from shells of mollusks collected live before atmospheric nuclear testing to be 250 yr from paired samples of biogenic carbonate and terrestrial macrofossils the past reservoir effect is thought to be less than 500 yr the radiocarbon ages indicate a distinct decrease in sediment accumulation rates throughout the southern basin of lake michigan at about 5 ka about the time when lake level stabilized at the nipissing level after rising rapidly for several thousand years average rates of sediment accumulation for the historic period the last 150 yr can be estimated from radioisotopes 210 pb and 137 cs pollen stratigraphy and changes in sediment properties associated with human activity multiple methods are necessary because at any given site problems arise in the assumptions or applicability of one or more methods in general the mass accumulation calculations suggest that sediments were deposited 4 to 11 times faster in the historic period than before human settlement the character of the sediment did not change in a dramatic way but sediment magnetic properties suggest shifts in the sources of sediment the data suggest that some of the changes in sources and or character of the sediment occurred just before human settlement and were probably related to climatic changes associated with the little ice age

on the current state of lake sediment palaeomagnetic research summary it is now possible to obtain high quality records of geomagnetic secular variations in the direction though not the magnitude of the ancient field type curves are presented for four regions namely north america west europe argentina and australia constructed by fitting cubic splines to data stacked from numbers of cores of post glacial sediments ways in which the results can be used to investigate the grosser properties of the ancient field are discussed

archaeo and paleosecular variation and long term asymmetries of the geomagnetic field this report summarizes progress made during the last four years in i obtaining records of the geomagnetic secular variation using paleomagnetic techniques ii analysis and modelling of the secular variation and iii the study of asymmetries in the time averaged field seen both as departures from the geocentric axial dipole model and as statistical differences between polarity states

laacher see tephra a widespread isochronous late quaternary tephra layer in central and northern europe a late quaternary tephra layer widespread in central and northern europe resulted from explosive plinian and phreatomagmatic eruptions of the laacher see volcano 11 000 yr b p the tephra is distinguished from other late quaternary andesitic rhyolitic airfall tuff layers in northern europe and from basaltic or trachytic tuff deposits in southern europe by its phonolitic composition and abundance of sanidine plagioclase clinopyroxene amphibole and sphene the proximal tephia sequence at laacher see is divided into three main deposits the predominantly plinian deposits of lower and middle laacher see tephra llst and mlst and phreatomagmatic deposits of the upper laacher see tephra ulst the mlst member is further subdivided into beds a b and c1 c2 and c3 the chemical composition of the magma is highly differentiated phonolite in the llst to mlst b sections but mafic phonolite in the mlst c1 to ulst sections all deposits are considered to be isochronous the frequency maximum of 16 radiocarbon datings indicating an eruption about 11 000 50 yr b p distal ash was deposited in three main fans directed to the northeast lst traced up to 1 100 km distance south lst traced up to 600 km and southwest lst traced up to 100 km tephrostratigraphic correlation of the distal ash deposits is based on a the major element composition of glass shards b lithology and c heavy mineral analyses the northeastern fan consists of deposits from llst mlst b and mlst c1 eruptive phases the southern fan comprises mlst a mlst c2 and ulst deposits and the southwestern fan consists exclusively of ash from the ulst eruptive phase northeastern transport of ash during eruptive phases with high plinian eruption columns but southern and southwestern transport of ash along phases of relatively low eruption columns are interpreted in terms of prevailing southwesterly paleowinds at high altitudes tropopause level but northerly winds dominating in the lower atmosphere the laacher see eruption columns were emplaced into an atmosphere vertically zoned with respect to paleowind directions which also explains the near vent shifting of llst mlst b and mlst c1 iso pach axes from east southeast to northeast within the first 20 km of transport

a stable isotope tree ring timescale of the late glacial holocene boundary late glacial and holocene tree ring chronologies like deep sea sediments or polar ice cores contain information about past environments changes in tree ring growth rates can be related to past climate anomalies and changes in the isotope composition of tree ring cellulose reflect changes in the composition of the atmosphere and the hydrosphere we have established a 9 928 year absolutely dated dendrochronological record of holocene oak quercus robur quercus petraea and a 1 604 year floating late glacial and early holocene chronology of pine pinus sylvestris from subfossil tree remnants deposited in alluvial terraces of south central european rivers the pine sequence provides records of dendro dated 14c 13c and 2h patterns for the late younger dryas and the entire preboreal 10 100 9 000 yr bp through the use of dendrochronology radiocarbon age calibration and stable isotope analysis we suggest that the late glacial holocene transition may be identified and dated by 13c and 2h tree ring chronologies

sudden changes in north atlantic circulation during the last deglaciation sudden changes in the flow of warm atlantic surface waters into the norwegian sea occurred frequently during the last deglaciation typically involving shifts in sea surface temperature of 5 c in fewer than 40 years these led to equally large and rapid changes in atmospheric temperatures and to shifts in atlantic deep thermo haline circulation and ice sheet melting rates

lake sediment record of the geomagnetic secular variation in britain during holocene times summary a palaeomagnetic record of the geomagnetic secular variation during the last 10000 years has been obtained from 10 cores of sediment from loch lomond scotland lake windermere north england and llyn geirionydd north wales a time scale is provided by 30 radiocarbon age determinations and pollen analyses on several of the cores the main swings and much fine detail of both declination and inclination records repeat well between cores and between lakes and the overall record is much more detailed than previous european records the new record shows that neither declination nor inclination swings have been periodic over the past 10000 years but that the main swings have become progressively shorter in duration during that time each swing is characterized by fine detail which enables use of the record as a secondary method of dating other european sediments the motion of the geomagnetic vector has been predominantly clockwise throughout the time period spanned but confirms a period of anticlockwise motion from 1100 to 600 bp first discovered by british archaeomagnetic investigations the record agrees with british and czechoslovakian archaeomagnetic records but not with japanese archaeomagnetic or north american lake sediment records this suggests that the secular changes are controlled by local growing and decaying drifting sources rather than by wobbling of the main geomagnetic dipole

magnetic properties and geochemistry of the active oxidation front and the youngest sapropel in the eastern mediterranean sea summary magnetic properties irm arm xin s ratio at 0 3 t room temperature rt hysteresis and thermomagnetic curves and geochemical data fe s mn al ti organic c were studied in two eastern mediterranean boxcores abc26 and bc19 at a resolution of 3 5 mm the boxcores contain sapropel s1 9 6 kyr bp at a few decimetres below seafloor the magnetic fraction consists predominantly of single domain sd to pseudo singledomain psd magnetite in the entire cores the original input of magnetic grains comes from two sources aeolian dust both cores and volcanic ash from the minoan eruption of santorini core bc19 only non steady state diagenesis has changed the magnetic mineralogy considerably in these alternating organic rich organic poor sediments during deposition of sapropel s1 reductive diagenesis and pyritization in and just below the sapropel caused lower magnetic intensities coarser magnetic grain sizes and partial maghemitization in thermomagnetic curves two types of pyrite can be identified one oxidizes below 450 uc and the other above 450 uc the higher oxidation temperature is predominantly found below the sapropel this may be related to the microtexture of pyrite which is euhedral below sapropels and mainly framboidal within sapropels since the end of sapropel deposition a downward moving oxidation front has oxidized the upper half c 5 cm of the sapropel the oxidized part of the sapropel is enriched in diagenetically formed fe oxides with relatively high coercivity and arm the maximum coercivity is found in a distinct layer between the present day mn and fe redox boundaries at the top of the unoxidized sapropel the freshly precipitated fe oxides in this centimetre thick layer contain a mixture of superparamagnetic sp grains and high coercivity sd magnetite higher in the oxidized zone the freshly precipitated fe oxides have aged into generally slightly lower coercivity sd grains with relatively high arm in addition to the diagenetic formation of fe oxides at the top of the sapropel formation of a ferrimagnetic fe monosulphide may have occurred within the sapropel during later stages of diagenesis which may have enhanced the arm signal in the organic rich interval in particular

can the greenland climatic jumps be identified in records from ocean and land sharp jumps in climate punctuate the records from borings in the greenland ice cap during the time interval 60 000 to about 20 000 yr ago rapid fluctuations are also seen in foraminifera records for cores from the northern atlantic and in a pollen record from a core from a bog in the vosges mountains in france in this paper we present a new radiocarbon chronology for northern atlantic deep sea core v23 81 which permits comparison with the radiocarbon dated vosges mountains pollen record because of the lack of a 14c chronology for the greenland ice record and of distortions peculiar to each of the three records it is not yet possible to say whether or not the events are genetically related

magnetic spherules from recent fluvial sediments in alberta canada characteristics and possible origins magnetic spherules were recently recovered in recent fluvial sediments in alberta canada and have been studied using x ray diffraction electron microprobe scanning electron microscope and neutron activation analysis results show that these spherules are composed of magnetite wustite and hematite some of them contain iron metal cores the similarities in morphology mineralogy and internal structure of these spherules to spherules of extraterrestrial origin found in other environments suggest that some of these spherules from alberta might also be of extraterrestrial origin in spite of their unusual compositions

multiple mechanisms of remagnetization involving sedimentary greigite fe3s4 sedimentary greigite fe3s4 is being increasingly implicated as the carrier of late diagenetic remagnetizations in fine grained marine and terrestrial sediments we have conducted detailed scanning electron microscope observations on polished sections from such sediments coupled with elemental microanalysis to identify greigite and to characterize the mode of occurrence and the relationships between the observed greigite and other authigenic and detrital mineral phases this detailed observational work in conjunction with recently published work has enabled identification of several mechanisms for remagnetization involving greigite 1 neoformation of greigite on the surfaces of early diagenetic framboidal and nodular pyrite 2 greigite growth within cleavages of detrital sheet silicate grains 3 neoformation of greigite on the surfaces of authigenic clays smectite illite 4 greigite nucleation on the surfaces of siderite 5 greigite growth on the surface of gypsum that resulted from earlier oxidation of nodular pyrite many other mechanisms for greigite neoformation are conceivable the key variables are appropriate redox conditions for generation of sulphide and availability of iron from the dissolution of a wide range of possible reactive detrital and authigenic iron bearing minerals documentation of a wide range of mechanisms for neoformation of greigite provides compelling evidence that sediments containing greigite should be routinely suspected of remagnetization which will complicate or compromise studies of environmental magnetism and geomagnetic field behaviour

the palaeomagnetism and magnetic fabric of cave sediments from gronligrotta and jordbrugrotta norway summary twenty four oriented specimens of laminated clay were obtained from vertical sections in two caves in northern norway studies of the magnetic remanence and susceptibility anisotropy show that the magnetization is depositional in origin and due to magnetite the palaeomagnetic record in one section is correlated with results from a swiss lake sediment core to suggest an age of 9600 6800 yr bp for the cave clay it is shown that the susceptibility lineation produced on gently sloping surfaces was predominantly controlled by gravity and cannot therefore be used directly to estimate the palaeoflow or palaeofield directions

a paleomagnetic record from tangle lakes alaska large amplitude secular variation at high latitudes a paleomagnetic study of a core from the tangle lakes area of alaska has provided information about the nature of secular variation between 2 700 and 4 600 years b p the data indicate that the amplitudes of fluctuations in inclination and declination were substantially larger than those which would be expected from the present configuration of the geomagnetic field from this single site it is not possible to determine whether the observed secular variation arises mainly from the dipole or the non dipole component of the field if the dipole component is responsible then the data indicate that about 3 350 years b p the geomagnetic pole shifted by about 20 in a period of less than 150 years this shift is comparable to one proposed to have occurred about 500 years ago

wasp waisted hysteresis loops mineral magnetic characteristics and discrimination of components in mixed magnetic systems rock magnetic studies of complex systems that contain mixtures of magnetic minerals or mixed grain size distributions have demonstrated the need for a better method of distinguishing between different magnetic components in geological materials hysteresis loops that are constricted in the middle section but are wider above and below the middle section are commonly observed in mixed magnetic assemblages such wasp waisted hysteresis loops have been widely documented particularly with respect to rare earth permanent magnets basaltic lava flows remagnetized paleozoic carbonate rocks and an increasingly wide range of other rocks our modelling combined with a review of previous work indicates that there are several conditions that give rise to as well as magnetic properties that are characteristic of wasp waisted hysteresis loops first at least two magnetic components with strongly contrasting coercivities must coexist this condition can arise from either mixtures of grain sizes of a single magnetic mineral or a combination of magnetic minerals with contrasting cocrcivities or a combination of these two situations second materials that give rise to wasp waisted hysteresis loops will have relatively high ratios of the coercivity of remanence to coercive force b cr b c because b0 is controlled by the soft low coercivity component whereas bcris controlled by the hard high coercivity component third values of b cr b c 10 usually only occur for strongly wasp waisted loops when the low coercivity component comprises an overwhelmingly large fraction of the total volume of magnetic grains fourth a given mixture of superparamagnetic and single domain sd grains is more likely to give rise to wasp waisted hysteresis loops than an equivalent mixture of sd and multidomain grains fifth our results provide empirical confirmation that the total magnetization of a material is the sum of the weighted contributions of each component in the absence of significant magnetic interaction between particles thus to contribute significantly to wasp waisted behavior a mineral magnetic component must give rise to a significant portion of the total magnetization of the rock as a result minerals with weak magnetic moments such as hematite need to occur in large concentrations to cause wasp waistedness in materials that also contain ferrimagnetic minerals we outline a method for determining the magnetic components that can give rise to wasp waisted hysteresis loops this method is based on high and low temperature magnetic measurements that are used to identify the dominant remanence bearing mineral s and on mineral magnetic techniques that are used to discriminate between different magnetic domain states the method is illustrated with several examples from archaeological geological and synthetic materials

magnetite in sediments as an indicator of coal combustion abstract magnetic susceptibility gives an accurate measurement of the magnetite concentration in sediments in all geographical areas studied the magnetite concentration in recent lake estuarine and ocean sediments has been affected by coal burning which releases magnetite spheres to the atmosphere graphs of percent magnetite and percent spheres vs depth age in the various sediments can be used to give information on the history of coal burning in an area as well as the efficiency of air pollution controlling devices chromium zn ti and fe concentrations in the sediments were affected by the input of magnetic spheres cadmium cu mn ni and pb concentrations were not affected

magnetic properties of sedimentary greigite fe3s4 new data are presented here that document the previously poorly known magnetic characteristics of sedimentary greigite fe3s4 several diagnostic magnetic properties can be used in conjunction to rapidly screen sediments to detect the presence of greigite such discriminants are necessary because greigite displays a similar or higher range of coercivities compared to most ferrimagnetic minerals and the commonly used method of alternating field demagnetization cannot be used to distinguish between palaeomagnetic remanence components due to greigite and other ferrimagnetic minerals sedimentary greigite has high ratios of the saturation isothermal remanent magnetization to magnetic susceptibility mrs which are accompanied by hysteresis ratios of mrsms 0 5 and bcr bc 1 5 ms is the saturation magnetization bc is the coercive force and bcr is the coercivity of remanence greigite has no low temperature phase transition whereas the ferrimagnetic iron sulphide pyrrhotite undergoes a major phase transition at about 34 k and unoxidized magnetite displays the verwey transition at 118 k low temperature measurements may therefore prove valuable in distinguishing between magnetite pyrrhotite and greigite although the absence of a low temperature transition cannot be taken as definitive evidence for the presence of greigite greigite also displays characteristic high temperature behaviour with a major drop in magnetization between 270 and 350 c determination of the mrs ratio is an excellent means of rapidly screening sediments to identify stratigraphic intervals that may contain greigite subsequent low and high temperature analyses can then provide unambiguous identification of greigite and enable the evaluation of the presence of other magnetic minerals

geomagnetic secular variations 0 14 000 yr bp as recorded by lake sediments from argentina summary palaeomagnetic and sedimentological studies carried out on the bottom sediments from three lakes in western argentina are described at the within lake level five lithological units could be broadly defined and were useful as a general guide in defining detailed correlations based on the magnetic susceptibility k and intensity of remanent magnetization j in one of the three lakes el trebol it was possible to derive a closer lithologically based correlation and this was consistent with that based on the magnetic parameters inter lake correlation was derived from the inclination and declination patterns considered as a pair also taking account of a set of radiocarbon age determinations to remove any ambiguities all the individual measurements were transformed to a time scale prior to stacking to produce type curves the records for laguna el trebol and brazo de campanario extend back to about 6000 radiocarbon years before present while lago morenito provides a record extending back to about 14000 radiocarbon years before present the records exhibit variations with similar overall characteristics to those previously obtained for europe and north america but there appears to be no correlation with the northern hemisphere patterns on a swing to swing basis both clockwise and anticlockwise precession of the geomagnetic vector is evident both from spectral analysis of declination inclination pairs and vgp paths

hornblende etching and quartz feldspar ratios as weathering and soil development indicators in some michigan soils weathering can be used as a highly effective relative age indicator one such application involves etching of hornblende grains in soils etching increases with time duration and decreases with depth in soils and surficial sediments other variables related to intensity of weathering and soil formation are generally held as constant as possible so as to only minimally influence the time etching relationship our study focuses on one of the variables usually held constant climate by examining hornblende etching and quartz feldspar ratios in soils of similar age but varying degrees of development due to climatic factors we examined the assumption that the degree of etching varies as a function of soil development even in soils of similar age the spodosols we studied form a climate mediated development sequence on a 13 000 yr old outwash plain in michigan their pedogenic development was compared to weathering related data from the same soils in general soils data paralleled weathering data hornblende etching was most pronounced in the a and e horizons and decreased rapidly with depth quartz feldspar ratios showed similar but more variable trends in the two most weakly developed soils the q f ratio was nearly constant with depth implying that this ratio may not be as effective a measure as are etching data for minimally weathered soils our data indicate that hornblende etching should not be used as a stand alone relative age indicator especially in young soils and in contexts where the degree of pedogenic variability on the geomorphic surface is large d 2004 university of washington all rights reserved

assessment of suspended particulate pollution in the bhadra river catchment southern india an environmental magnetic approach open cast mining generates sediment in river systems at globally significant scales one of the challenges in attributing measured sediment loads to upstream mining activities is establishing the source of sediments that are a mixture of natural and mining based materials the environmental magnetic data mass specific magnetic susceptibility anhysteretic remanent magnetisation isothermal remanent magnetisation and inter parametric ratios on 57 samples of suspended sediment from the bhadra river in the sahyadri the western ghat of india have been used in this study samples were collected upstream adjacent to and downstream of kudremukh a mountainous and high rainfall site where the largest mechanised open cast mine in south asia was located graphical and multivariate analyses and modelling of the data show that on average 29 of the river suspended load downstream of the mine is derived from mining and allied activities at kudremukh although the mine occupies less than 5 of the catchment the contribution of primary ore is the maximum 18 followed by transitional hard weathered ore 7 and weathered ore 4 the model has done a fairly good job of unmixing the sum of errors is 71 000 for four samples modelling of samples with small mass seems to produce large errors this investigation demonstrates the utility of environmental magnetic data which can be obtained in a simple and rapid manner and the unmixing of such data in identifying the contribution of mining activities to the total suspended sediment load