why are geomagnetic excursions not always recorded in sediments constraints from post depositional remanent magnetization lock in modelling abstract many geomagnetic excursions have been documented during the brunhes chron however high resolution paleomagnetic studies of sediments often provide evidence of few if any excursions we have investigated the reasons for this observation by modelling the post depositional remanent magnetization pdrm lock in process a cubic lock in function produces more rapid lock in compared to linear and exponential functions proposed in the literature we therefore used a cubic function to model best case scenarios for the quality of the paleomagnetic record when a high frequency geomagnetic input signal is convolved with the sediment lock in function for a wide range of sedimentation rates even for a lock in depth of 10 cm where 95 of the pdrm is locked in 5 cm below the surface mixed layer an input signal containing abundant excursions with 1 kyr duration is smoothed so drastically at low sedimentation rates 1 3 cm kyr that no excursions are recorded excursions are further attenuated by increasing the lock in depth as well as by sampling at discrete stratigraphic intervals the pdrm process acts as a low pass filter for high frequency secular variation signals even at moderate sedimentation rates 10 cm kyr we have also modelled the effects of modulation of sedimentation rate by a climatic forcing function e g insolation even though the average sedimentation rate might be substantial pdrm recording becomes much less reliable in intervals where sedimentation rates are lowest in these cases some excursions are reliably recorded in detail while others may not be recorded at all our modelling suggests that in order to consistently detect the presence of geomagnetic excursions it is ideal to work with sediments that maintain minimum sedimentation rates above 10 cm kyr if the normal spectrum of geomagnetic field behaviour contains abundant excursions failure to document excursions in many apparently high resolution analyses probably results from pdrm lock in within relatively slowly deposited sediments or to unrecognized intervals of slow sedimentation in environments with higher average sedimentation rates

geomagnetic field for 0 3 ka 2 a new series of time varying global models 1 steadily increasing numbers of archeomagnetic and paleomagnetic data for the holocene have allowed development of temporally continuous global spherical harmonic models of the geomagnetic field extending present and historical global descriptions of magnetic field evolution the current work uses various subsets of improved data compilations details of which are given in a companion paper by donadini et al 2009 and minor modifications of standard modeling strategies using temporally and spatially regularized inversion of the data and cubic spline parameterizations for temporal variations to produce five models with enhanced spatial and temporal resolution for 0 3 ka spurious end effects present in earlier models are eliminated by enforcing large scale agreement with the gufm1 historical model for 1650 1990 a d and by extending the model range to accommodate data older than 3 ka age errors are not considered as a contribution to data uncertainties but are included along with data uncertainties in an investigation of statistical uncertainty estimates for the models using parametric bootstrap resampling techniques we find common features but also significant differences among the various models indicating intrinsic uncertainties in global models based on the currently available holocene data model cals3k 3 based on all available archeomagnetic and sediment data without a priori quality selection currently constitutes the best global representation of the past field the new models have slightly higher dipole moments than our previous models virtual axial dipole moments vadms calculated directly from the data are in good agreement with all corresponding model predictions of vadms these are always higher than the spherical harmonic dipole moment indicating the limitations of using vadms as a measure of geomagnetic dipole moments

a 14 000 year sediment yield record from western germany based on annually laminated lake sediments the reconstruction of sediment yield data for the catchment of lake holzmaar 205 8 ha in the eifel mountains western germany is based on high resolution geochemical and physical analyses of an absolutely dated sediment record this technique provides flux rates of allochthonous minerogenic deposition for the last 13 840 years the pleistocene holocene transition is characterized by instable soils and vegetation caused by adjustment of the catchment to interglacial climatic conditions these instabilities are the reason for elevated mean sediment yields in the catchment of 16 t km 2 yr 1 until 9800 cal bp during most of the holocene erosive processes are insignificant and sediment yields are very low 1 5 t km 2 yr 1 since humans cleared the forests for agriculture and early industrial purposes the natural environment has been disturbed and sediment yields increased to mean values of 14 t km 2 yr 1 during the last 2750 years comparisons of reconstructions from the eifel area with similar data from southern sweden and with measured data from lakes reservoirs and monitoring sites suggest that quantitative reconstructions based on lake holzmaar sediments may be regarded as reliable despite uncertainties related to the methods of reconstruction applied

a record of soil loss from butrint southern albania using mineral magnetism indicators and charcoal ad 450 to 1200 mineral magnetic and charcoal analyses were carried out on two sections 0 6 km apart on the vrina plain at shen delli a suburb of roman butrint ancient buthrotum southern albania using a chronology developed by archaeomagnetic dating the two sections postdate roman archaeological structures on the site providing a sediment record between c ad 450 and 1200 environmental magnetic data were analysed using cluster analysis to interpret a consistent stratigraphic development between the two sections above the archaeo logical remains on the western side of the shen deli settlement marsh clay sedimentation started ad 450 500 contemporaneous with evidence of site occupation anthropogenic activity is evident from the high macro charcoal content which declines at ad 750 800 and may mark the end of settlement in the vicinity both sections show similar sedimentation rates which when extrapolated suggest that marsh growth to the present day levels would have been completed between about ad 1500 and 1600 from about ad 750 to 850 sedimentation continued consistently across the site with low microcharcoal input but an increasingly important pres ence of magnetic minerals including superparamagnetic magnetite associated with top soil input between ad 1050 and 1200 the input from magnetically enhanced topsoil had increased tenfold over 300 years earlier indicating that soil erosion was a major sediment source this marked increase in soil loss could be due either to different land management practices or to local deforestation whether this change in topsoil loss is linked to climatic changes associated with the beginning of the mediaeval warm period c ad 1000 1400 needs further investigation

millennial scale cyclicity in the geodynamo inferred from a dipole tilt reconstruction constraining past changes in the strength and configuration of the geomagnetic field provides a valuable perspective on the processes that govern the geodynamo here we update a modelled dipole tilt reconstruction for the last 9000 years by using palaeomagnetic records that originate from globally well distributed sites some features predicted by earlier dipole models become more distinct due to added data sets we identify a dominant 1350 year cycle in the dipole tilt variations and two preferred states of the dipole axis with north geomagnetic pole longitudes confined to either c 120 degrees west or c 30 degrees east the dipole tilt reconstruction is shown to be consistent with independent geomagnetic field intensity data from western eurasia which show generally higher intensities when the dipole is tilted towards this region our study implies that vadm reconstructions that are constrained by a biased spatial distribution of data can show variations resulting from dipole tilt instead of true dipole moment the preferred states of the modelled dipole axis can be related to the four semi stationary high latitude flux lobes that have been observed at the core mantle boundary in long term time averaged palaeomagnetic field models the tilt episodes towards 30 degrees east in the northern hemisphere are perhaps related to the appearance of a high intensity flux lobe beneath western eurasia the dipole tilt reconstruction is highly correlated to millennial scale variations in the length of day that have been reconstructed from ancient records of eclipses which indicates that the cyclicity may constitute an important component in core flow dynamics c 2011 elsevier b v all rights reserved less

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

the record of magnetic mineral and heavy metal deposition at regent street bog fredricton new brunswick canada measurements of isothermal remanence and of heavy metal concentrations are presented for two recent moss increment dated cores from hummocks of ombrotrophic peat from regent street bog fredricton new brunswick canada the magnetic record from both profiles appears to be closely related to the documented history of industrial and urban development in the region the heavy metal record displays greater variation between elements and profiles and mirrors less consistently the documentary record some vertical mobility within the peat column is inferred for all the metal elements measured

use wear analysis of an amudian laminar assemblage from the acheuleo yabrudian of qesem cave israel in this paper the results of use wear analysis of an amudian lithic assemblage recently discovered at qesem cave israel are presented although very old this assemblage maintains well preserved traces of use that indicate that butchering activities and plants collecting were carried out at the site cut marks on faunal remains confirm the observations obtained by use wear analysis

fennostack and fennorpis varve dated holocene palaeomagnetic secular variation and relative palaeointensity stacks for fennoscandia a holocene palaeomagnetic secular variation master curve fennostack and a relative palaeointensity curve fennorpis for fennoscandia are presented these curves were produced by stacking palaeomagnetic data obtained from six annually laminated varved lake sediment sequences and one non laminated sediment sequence the six independent varve chronologies were combined to form a timescale which extends between the present year and 10 200 cal yr bp smoothed inclination and declination curves show trends that are similar to a palaeomagnetic secular variation curve for the united kingdom except that the ages of most of the statistically significant features are a few hundred years younger in the fennoscandian data set these differences are most likely due to excessively old ages of the united kingdom features produced by the radiocarbon dating of bulk sediments the standardized relative palaeointensity stack shows that the intensity of the geomagnetic field in fennoscandia was highest at 2300 cal yr bp and lowest at 7000 cal yr bp three palaeointensity peaks pips and three palaeointensity lows pils are identified in fennorpis and indicate that the intensity of geomagnetic field varied significantly on millennial scales in this region during the holocene but there is much scatter in the reconstruction prior to 8000 cal yr bp higher frequency palaeointensity features present in individual records are not significant in the stacked data set which implies that these are a result of local environmental bias significant discrepancies exist between the data and the output of the cals7k 2 geomagnetic field model for the last 7000 yr in particular the largest declination swing observed in the data at 2670 cal yr bp feature f is not produced by the model which is most likely due to the influence of an inaccurately dated icelandic secular variation curve on the model result short term trends in standardized relative palaeointensity do differ from the model output but it is difficult to make a comparison because of the relative nature of the sediment record better absolute palaeointensity data are needed to reduce uncertainties in reconstructions of past geomagnetic field strength

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

detecting climatic signals in an anthropogenically disturbed catchment the late holocene record from the petit lac d annecy french alps historical and documentary records from the petit lac d annecy indicate that human activities have been the dominant geomorphic process shaping the catchment during the late holocene with deforestation agriculture and artificial drainage profoundly affecting both the pace and spatial distribution of soil erosion the impact of past climatic change on the evolution of the catchment is less certain because of the lack of long term climate records for the site previous attempts to use the sediment record from the lake to investigate the role past climate change may have played were hampered by the difficulty in isolating and disentangling the climatic signal preserved within the archive because of overprinting of human activity this is a common problem in regions with a long history of human activity in the landscape in this study we use a range of novel statistical techniques including cross correlation and cross spectral analysis to assess the relative importance of climate in driving landscape dynamics the statistical analysis is carried out on an updated high resolution palaeo environmental data set from the petit lac d annecy the results of the statistical analysis indicate that regional climate phenomena such as the atlantic multidecadal oscillation are partly responsible for landscape dynamics at petit lac d annecy throughout the late holocene we find that the petit lac d annecy catchment typically requires decades or longer to respond to changes in precipitation reflecting the stochastic nature of river sediment storage and transport the use of a 4 yr integrated lake core record effectively attenuates the signal shredding effect of shorter term internally generated sediment transport processes nonetheless the lake record of climatically induced geormorphic process responses is weak compared with the pervasive impact of human activities

geomagnetic field evolution during the laschamp excursion abstract since the last geomagnetic reversal 780 000 years ago the earth s magnetic field repeatedly dropped dramatically in intensity this has often been associated with large variations in local field direction but without a persistent global polarity flip the structure and dynamics of geomagnetic excursions and especially the difference between excursions and polarity reversals have remained elusive so far for the best documented excursion the laschamp event at 41 000 years bp we have reconstructed the evolution of the global field morphology by using a bayesian inversion of several high resolution palaeomagnetic records we have obtained an excursion scenario in which inverse magnetic flux patches at the core mantle boundary emerge near the equator and then move poleward contrary to the situation during the last reversal leonhardt r fabian k 2007 paleomagnetic reconstruction of the global geomagnetic field evolution during the matuyama brunhes transition iterative bayesian inversion and independent verification earth planet sci lett 253 172 195 these flux patches do not cross the hydrodynamic boundary of the inner core tangent cylinder while the last geomagnetic reversal began with a substantial increase in the strength of the non dipolar field components prior to the laschamp excursion both dipolar and non dipolar field decay at the same rate this result suggests that the nature of an upcoming geomagnetic field instability can be predicted several hundred years in advance even though during the laschamp excursion the dipolar field at the earth s surface was dominant the reconstructed dynamic non dipolar components lead to considerable deviations among predicted records at different locations the inverse model also explains why at some locations no directional change during the laschamp excursion is observed

holocene palaeoenvironmental change and the impact of prehistoric salt production in the seille valley eastern france the seille valley in eastern france was home to one of europe s largest iron age salt industries sedimentology palynology and geochronology have been integrated within ongoing archaeological investigations to reconstruct the holocene palaeoenvironmental history of the seille valley and to elucidate the human environment relationship of salt production a sedimentary model of the valley has been constructed from a borehole survey of the floodplain and pollen analyses have been undertaken to reconstruct the vegetation history alluvial records have been successfully dated using optically stimulated luminescence and radiocarbon techniques thereby providing a robust chronological framework the results have provided an insight into the development of favourable conditions for salt production and there is evidence in the sedimentary record to suggest that salt production may have taken place during the mid to late bronze age the latter has yet to be identified in the archaeological record and targeted excavation is therefore underway to test this finding the development of the iron age industry had a major impact on the hydrological regime of the valley and its sedimentological history with evidence for accelerated alluviation arising from floodplain erosion at salt production sites and modification of the local fluvial regime due to briquetage accumulation on the floodplain this research provides an important insight into the environmental implications of early industrial activities in addition to advancing knowledge about the holocene palaeoenvironmental and social history of this previously poorly studied region of france

geomagnetic excursions knowns and unknowns geomagnetic excursions are short lived episodes when earth s magnetic field deviates into an intermediate polarity state understanding the origin frequency amplitude duration and field behavior associated with excursions is a forefront research area within solid earth geophysics recent advances in excursion research are summarized here and key further research is suggested to resolve major unanswered questions improving the global distribution of excursion records particularly from the southern hemisphere obtaining high resolution sedimentary excursion records with good age control from sites with sedimentation rates 10 cm kyr obtaining volcanic excursion records coupled with high precision geochronology and estimating excursion duration with high chronological precision will all facilitate hypothesis testing concerning the deep earth dynamics that generate geomagnetic excursions

global changes in intensity of the earth s magnetic field during the past 800kyr recent advances in palaeomagnetic and dating techniques have led to increasingly precise records of the relative intensity of the earth s past magnetic field at numerous field sites the compilation and analysis of these records can provide important constraints on changes in global magnetic field intensity and therefore on the earth s geodynamo itself a previous compilation for the past 200 kyr integrated 17 marine records into a composite curve1 with the geomagnetic origin of the signal supported by an independent analysis of 10be production made on different cores2 the persistence of long term features in the earth s magnetic intensity or the existence of long term periodic changes cannot however be resolved in this relatively short time span here we present the integration of 33 records of relative palaeointensity3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 into a composite curve spanning the past 800 kyr we find that the intensity of the earth s dipole field has experienced large amplitude variations over this time period with pronounced intensity minima coinciding with known excursions in field direction reflecting the emergence of non dipole components no stable periodicity was found in our composite record and therefore our data set does not support the hypothesis that the earth s orbital parameters have a direct and strong influence on the geodynamo

chlorine 36 evidence for the mono lake event in the summit grip ice core abstract a distinct peak has been discovered in the 36 cl data from the grip ice core between the dansgaard oeschger d o events 6 and 7 at approximately 32 kyr bp this peak can be attributed to a minimum of the geomagnetic dipole field associated with the mono lake event since the 36 cl peak reflects a higher production rate of all cosmogenic radionuclides it has an impact on the 14 c dating of the last ice age furthermore it provides an additional time marker similar to a peak found earlier corresponding to the laschamp event at approximately 39 kyr bp

palaeosecular variation of the earth s magnetic field during the last 10000 years based on the annually laminated sediment of lake nautajarvi central finland a palaeomagnetic study of the lake nautajarvi sediment sequence in central finland demonstrates that varved lake sediments can provideregionally applicable secular variations curves for holocene stratigraphic correlation and age control based on x ray radiography and digital image analysis techniques we constructed an inherent and continuous varve chronology for the lake nautajarvi varve sequence which covers nearly 10000 years with an estimated counting error of less than 1 and a mean sedimentation rate of 0 66 mm yr 1 we reconstructed a record of the palaeomagnetic secular variation psv of the earth s magnetic field in this nearly 7 m long section of clastic organic varves mineral magnetic measurements indicated that pseudosingle domain magnetite is the major carrier of the remanence psv shows many of the familiar features of declination and inclination that have previously been recorded in northern europe in addition the lake nautajarvi record contains a continuous record of relative palaeoi

revisiting the hunting versus scavenging debate at flk zinj a gis spatial analysis of bone surface modifications produced by hominins and carnivores in the flk 22 assemblage olduvai gorge tanzania abstract this study presents a taphonomic examination of the ca 1 84 million year old ma bovid fauna from flk level 22 flk zinj bed i olduvai gorge using a new gis spatial analysis approach the flk zinj site contains some of the best preserved evidence for meat eating by hominins and has been used extensively in reconstructions of early hominin behavior however despite numerous interpretations of site function there is currently no consensus regarding how hominins acquired carcasses at flk zinj some interpretations argue that early stone age hominins had early access to fleshed carcasses through hunting or active scavenging while others argue hominins had late access to largely defleshed carcasses through passive scavenging in this study gis was used to record bone preservation in the flk zinj assemblage as well as in several modern experimentally modified bone assemblages which are used for comparison the placement of hominin and carnivore produced modifications was documented on bones from these assemblages and the gis spatial analyst was used to identify patterning in tooth mark clusters as well as patterning in cut mark locations this analysis suggests hominins had early access to fleshed carcasses at flk zinj particularly of smaller prey which they may have acquired through hunting damage patterns on larger carcasses are more difficult to interpret but are consistent with early access through hunting or aggressive scavenging a reanalysis of carnivore tooth mark frequencies on the flk zinj bovid fauna also supports an early access scenario

holocene geocentric dipole tilt model constrained by sedimentary paleomagnetic data paleomagnetic data although undeniably limited have been used to constrain complex time varying geomagnetic field models here we present four different versions of a time varying geocentric dipole model for the past approximately 9000 years based on a limited selection of sedimentary paleomagnetic data with good spatial coverage the robustness of the modeling approach is evaluated using modern magnetic observation station data provided by the world data centre for geomagnetism in edinburgh and we discuss the magnitude of the error introduced by insufficient data coverage the prediction in terms of directional variations is tested against paleomagnetic data from 63 different sedimentary sites and compared to results from recently published spherical harmonic geomagnetic field models we find that the dipole estimate can explain the paleomagnetic data almost as well as the more complicated spherical harmonic models specific areas and records are identified where there are significant differences between the performance of the dipole estimate and the spherical harmonic models our results suggest that many of the differences between the dipole model predictions and the paleomagnetic data can be related to poor paleomagnetic quality and or the lack of accurate and precise time control inherent to some of the records these results agree with valet et al 2008 who suggested that the cals7k 2 model probably underestimates the dipole contribution in order to reduce the misfit between the inversion and the data we conclude that better paleomagnetic data and associated time control are needed to improve global geomagnetic field models less

holocene secular variation in western north america paleomagnetic record from fish lake harney county oregon an 8 9 m composite section of lake sediment from fish lake steens mountain southeastern oregon has provided a high resolution record of holocene geomagnetic secular variation in western north america the section is composed of overlapping core segments with stratigraphic control based on six tephra layers and other thin distinct bands and with age control from 37 radiocarbon dates the 455 paleomagnetic samples possess a strong and stable magnetic remanence which is carried by pseudo single domain magnetite paleomagnetic records for individual core segments show low scatter and high serial correlation and where the segments overlap there is excellent agreement between records the azimuthal orientation of the composite section was recovered from the known direction of the geomagnetic field at the time of the climactic eruption of mount mazama tephra which is present in fish lake both internal and external evidence including the correspondence with an archaeomagnetic record from the southwestern united states support the conclusion that the fish lake record represents the history of geomagnetic field behavior during at least the last 10 000 years b p analysis of that record reveals that the average geomagnetic direction can not be distinguished from that of a geocentric axial dipole field and that the overall circularity of the field was clockwise but the detailed behavior was quite complex angular standard deviations of both field directions and virtual geomagnetic poles differ significantly from the values predicted from theoretical models of secular variation but are consistent with those of other holocene records when the record from fish lake is compared to the proposed type curve for east central north america there is excellent agreement for the past 6000 years provided the curves are offset by about 400 years this offset corresponds to a rate of westward drift of about 0 062 yr beyond about 6000 radiocarbon years ago good agreement between the two curves occurs when there is no offset suggesting that the field was standing rather than drifting during this time

paleosecular variations 0 19 000 years recorded by sediments from escondido lake argentina abstract paleomagnetic and sedimentological studies carried out on four cores about 11 m long from the bottom sediments of escondido lake southwestern argentina are described this lake is geologically related to the set of lakes of glacial origin located in western patagonia using several magnetic studies the predominance of pseudo single single domain magnetite as main carrier as well as an increase of concentration and grain size with depth was determined the pairs of magnetic susceptibility and intensity of remanent magnetization profiles show a good correlation with the sedimentological macroscopic descriptions and also with those of shorter cores previously studied the stability of the natural remanent magnetization was investigated by alternating field demagnetization within lake correlation was based on lithology magnetic susceptibility and intensity of remanent magnetization because the patterns of these parameters showed similarity for every core radiocarbon dating suggests higher deposition rates during the early stage of the lacustrine basin late pleistocene the transfer function depth age also allowed constructing a secular variation record from south argentina for the past 19 000 years the declination and inclination logs show some anomalous directions at about 18 000 calibrated years

use and re use re knapped flakes from the mode 1 site of fuente nueva 3 orce andalucia spain the presence of some flaked flakes at the mode 1 site of fuente nueva 3 1 2 ma poses the problem of the use and re use of flakes as cores for obtaining smaller cutting tools the industry is characterized by small flint flakes and cores as well as by numerous limestone heavy duty tools both of the raw materials were collected from local alluvial and colluvial sources the assemblage presents a significant dimensional dichotomy with on the one hand large sized limestone percussion tools and on the other hand small sized flint debitage flint plates blocks or nodules were obtained from local secondary deposits there are very few flint cores and the average flake size is only 3 cm some of the flakes display opposite ventral surfaces indicating that they were obtained from larger flakes used as cores in addition a few intensively exploited flint cores conserve convex surfaces corresponding to their original flake matrices no appreciably large sized flint flakes have so far been found at the site suggesting that some phases of the knapping sequences were carried out further away however a few flakes could have been expediently re knapped in situ what can this behavioural choice tell us about early hominin behaviour at fuente nueva 3 the re use of flint flakes as makeshift cores implies a two step operative scheme involving the choice of a suitable blank that was further reduced on site this raises questions about raw material transport during the earliest periods of european mode 1

secular variation of the geomagnetic dipole during the past 2000 years we have constructed a very simple model of a time varying geocentric dipole based on the archeomagnetic records obtained at four widely separated sites on the globe for the past 2 ka the predictions of the model in terms of directional variations have been tested against actual archeomagnetic data from 12 sites distributed over the globe they were also compared with the hongre et al 1998 time varying spherical harmonic model and with the cals7k 2 model by korte et al 2005 we find that the misfits between the predictions of our simple dipole model and the data are equivalent to those of the spherical harmonic models for the european sites and not strikingly larger for the rest of the world many discrepancies can be accounted for by uncertainties inherent to the archeomagnetic records which along with the small number and poor geographical distribution of sites leads us to conclude that the present state of the database does not allow the extraction of secular variations described by terms going beyond degree 2 it appears also that dipole tilt could be responsible for the main part of the secular variation associated with time constants exceeding 102 years in a second step we used the paleointensity records contained in the same database to construct the curve depicting the variations of the true dipole moment the present decrease of the dipole did not begin prior to 1000 years ago and the dipole was actually increasing from 0 until a d 500 the dipole moment of cals7k is lower than the present estimate probably due to large repartition of energy to higher harmonics to minimize the misfit between the inversion and the data the tilt and strength of the dipole can predict the dipole field at any site and were used to derive the contribution of the nondipole field to values of paleointensity at paris during the past 2 ka the results show that the archeomagnetic jerks are associated with various configurations depending on the phase relationship between the nondipolar and dipolar parts of the field

rock magnetic analyses as a tool to investigate archaeological fired sediments a case study of mirador cave sierra de atapuerca spain summary here we report a detailed mineral magnetic study of neolithic burnt levels in the mirador cave sierra de atapuerca burgos spain to reconstruct the burning history and to investigate their suitability for archaeomagnetic purposes as a consequence of the ancient burning a characteristic facies sequence was developed along the holocene stratigraphy from top to bottom it includes i 2 10 cm ash layers ii 2 cm underlying rubefied layers and iii clay mainly unburnt and of variable thickness in some cases a thermally altered facies 2 6 cm with a heterogeneous texture was identified facies tf usually between rubefactions and the unburnt levels 126 oriented samples from 4 units mir12 15 18 and 21 and a 2 m section all comprised between units mir21 6380 40 14c bp and mir9 5090 40 14c bp were analysed with rock magnetic methods in addition bulk sediment from each facies that comprise the neolithic sequence was investigated measurements included stepwise alternating field and thermal demagnetization of natural remanent magnetization nrm viscosity experiments determination of the anisotropy of the magnetic susceptibility ams the susceptibility frequency dependence at room temperature and determination of the temperature dependence of the susceptibility additional experiments consisted in the determination of the behaviour of anhysteretic and isothermal irm remanences magnetic hysteresis loops first order reversal curve diagrams and thermal demagnetization of three axial irm it appeared that the facies all show a fairly similar magnetic mineralogy and grain size dominated by low titanium magnetite that is often partially maghaemitized main differences constitute the amount of superparamagnetic particles that is higher in unburnt strata concurring with a less well defined nrm behaviour the magnetic mineral concentration is notably higher in ashes this homogeneity strongly suggests that similar sources and burial conditions prevailed during neolithic times agreeing with archaeological observations and favoured by rapid burial conditions very limited alterations have been deduced ams data revealed the absence of fluid flow in the ash lenses sampled demagnetization revealed a stable single nrm component in ashes a single or two component nrm in rubefactions and less stable multicomponent behaviour in clays in ashes magnetic minerals are likely secondary in origin formed by low temperature oxidization soon after burning although this thermochemical nature of the nrm invalidates the use of these sediments for palaeointensity studies archaeomagnetic directional data can be successfully obtained because the burning and oxidation are closely confined in time

the site of ain hanech revisited new investigations at this lower pleistocene site in northern algeria abstract new archaeological investigations have been carried out at the oldowan site of ain hanech in northeast algeria the archaeological horizons are delineated and positioned relative to the regional stratigraphy preliminary palaeomagnetic analysis reveals normal polarity for the oldowan occurrences that may be correlated with the olduvai subchron on the indication of the vertebrate faunal biozonation broken up bones associated with stone artefacts and contained in a silty deposit mixed with sand and gravels were excavated from two archaeological sites the bone assemblage includes equids bovids elephant and rhinoceros and dominated by equus tabeti taphonomic patterns indicate that bones were buried rapidly over a period of years and while the site was occupied the lithic artefacts are fresh and represent a coherent assemblage including small debitage the artefacts made of limestone and flint include flaked cobbles whole flakes various fragments and retouched pieces a microwear study undertaken on pieces made of flint indicates the use of two simple flakes and of one denticulate for meat processing the stone artefact assemblage may be considered as a north african variant of the oldowan

morava river floodplain development during the last millennium stražnicke pomoravi czech republic floodplain sediments deposited along the lower course of the morava river eastern czech 206 pb 207 pb and pop ddt pcb analysis and 137 cs activity data thecu trienmethodwasusedforstratigraphicallycorrelatingthesedepositsbasedonthevariationofexpand able clay minerals in the sediments the resulting stratigraphic pattern reveals the alluvial history of the cur rently active river channel system since the end of the first millennium ad fine overbank clayey sediments deposited during the mediaeval warm period were eroded from cultivated fields newly formed during mediaeval colonization between 1250 and 1450 these fine deposits are overlain by coarser floodplain sedi mentsofthe littleiceage indicatingachangeinthesedimentsourcesincethesixteenthcentury ad anda substantial increase in the sediment load in the second half of twentieth century the straunicke pomoravi floodplaindepositsrepresentavaluablepalaeoenvironmentalarchiveofthelastmillennium containingrecords offluvialprocessesconsiderablyalteredbyhumanactivities

multi proxy evidence of late holocene human induced environmental changes at lake pupuke auckland new zealand abstract new zealand was the last major landmass in the world to be colonised by people despite the short time depth of human presence in the country there is ongoing debate about the date of earliest arrival of people that resulted in the emergence of two contrasting colonisation hypotheses the early hypothesis and the short prehistory to decide between both hypotheses we employed a range of multi proxy investigations geochemistry stable isotopes and mineral magnetism on a lacustrine sequence from lake pupuke a maar lake in the city of auckland and an area potentially among the first places in new zealand to have been colonised by early people the environmental history reconstructed from the multi proxy evidence identified a clear lack of catchment disturbance from c 2000 b p until several decades before the eruption of the rangitoto volcano the nature and abruptness of disturbance unambiguously point to anthropogenic forcings and are likely to mark the onset of prehistoric human colonisation at the site linear interpolation between independently dated tephrochronostratigraphic marker beds present in the sediments allowed to date this event to c 610 cal yr b p this date is in compliance with the short prehistory for this region

a summary of brunhes paleomagnetic field variability recorded in ocean drilling program cores the ocean drilling program odp has recovered many long sediment sequences from around the world that contain medium to high resolution paleomagnetic records of brunhes age these records have provided an important new global view of geomagnetic field variability during stable magnetic dipole polarity that could not be recovered by conventional terrestrial or deep sea piston coring the odp paleomagnetic records of directional variability can be routinely recovered and used regionally as a very highresolution relative chronostratigraphic tool 200 yr resolution odp paleomagnetic records of brunhes age relative paleointensity have dramatically improved our understanding of global geomagnetic field intensity these records document the global scale pattern of paleointensity and demonstrate its use as a high resolution relative chronostratigraphic tool that under ideal conditions could have a precision of 500 yr odp paleomagnetic records and associated oxygen isotope chronostratigraphies have also greatly improved our understanding of the number and ages of brunhes geomagnetic field excursions and their relationship to normal directional secular variation and paleointensity variability although significant progress has been made though odp paleomagnetic studies of brunhes aged sediments it is clear that more work is needed to further resolve and define the detailed global pattern of brunhes psv and its relationship to excursions and true polarity reversals

the late holocene history of gormire lake ne england and its catchment a multiproxy reconstruction of past human impact sedimentary evidence spanning the last 3500 years from cores taken from the centre of gormire lake cleveland northeast england points to two periods of deforestation and catchment erosion the first mainly late iron age romano british phase began c 200 bc and ended c ad 600 the second began c ad 1200 the time of early monastic activity and continued into the nineteenth century the chronology for the core rests on 137cs 210pb and 14c measurements and on the history of lead accumulation in the sediments the majority of the ams 14c dates are shown to be too old to varying degrees depending on the source of the organic matter in the sediments the record of vegetation change is derived from pollen analysis evidence for changes in sediment composition and source and for catchment erosion comes from magnetic measurements element analyses using xrf and organic biogeochemical analyses there is a high degree of coherence between all these lines of evidence interpretation of the magnetic record

middle paleolithic sidescrapers were resharped or recycled a view from nesher ramla israel abstract the resharpening of sidescrapers is a widely discussed issue in recent middle paleolithic studies however in the levantine record the evidence for sidescraper resharpening is meager the middle paleolithic site of nesher ramla israel represents a rare case in which sidescrapers were frequently modified by removal of longitudinal spalls from their edges both parent sidescrapers and spalls long sharpening flakes lsf are abundant throughout the site s stratigraphy providing a rare opportunity for a complementary study of both artifact groups the aim of the present study is to reconstruct the life history of sidescrapers retrieved from nesher ramla we ask how the lsf removal changed the morphology of the sidescraper edge at which stage of the sidescraper life history it occurred what was the purpose of lsf removal and was it a part of a recycling system aimed at producing a new edge tool type or the maintenance of the existing tool edge the studied artifacts 100 parent sidescrapers and 60 complete lsf were sampled randomly from the most intensively occupied and richest layers of the site our results suggest that sidescraper edge modification was a well mastered and skillful process that resulted in standardized and morphologically distinct products in most cases the sidescrapers were not further retouched after the lsf removal this leads us to propose that the major goal was to transform the sidescraper into a tool with a sharp straight and flat edge the lsf removal at nesher ramla provides an exceptional case in which a simple raw edge was deliberately manufactured at the expense of the previously retouched edge this reinforces the previous assumptions that simple raw edges were often preferred over retouched ones

a use wear interpretation of the most common raw materials from the olduvai gorge naibor soit quartzite abstract this paper presents for the first time an experimental protocol for the assessment of use wear produced when using precambrian and metamorphic white naibor soit quartzite nq flakes nq is the most recurrent raw material from the archaeological sites of the olduvai gorge during the early stone age esa the objective of this study is to provide a preliminary description of the experimentally produced use wear traces that can be applied to the analysis of sites like the acheulean site of thiongo korongo tk olduvai gorge tanzania or other sites from olduvai where nq was used to tool production this experimental protocol incorporates a broad range to tasks including plant processing underground storage organs usos wood herbaceous plants and canes and carcass processing butchery and bone processing the most novel activity of this experimental protocol is the processing of usos for this we have replicated different steps of tuber processing including the cutting peeling and scraping of five varieties of usos beta vulgaris daucus carota ipomoea batatas pastinaca sativa and zingiber officinale with differences in hardness fibrosity water content and peel regularity after analysing micro and macro wear traces on the experimental flakes several criteria for distinguishing between different activities scraping cutting peeling sawing cutting butchery and the different materials being processed were identified these criteria are based on the presence continuity and morphology of macro scars along with the presence distribution nature and intensity of different micro traces micro scars attrition striations pits rounding polish additionally we have identified several processes that limit the formation of traces including the tendency of some activities to weaken nq edges and shorten the duration of use

sediment magnetic signature of land use and drought as recorded in lake sediment from south central minnesota usa abstract sediment magnetic properties of a short core from sharkey lake mn record the effects of euroamerican settlement and climate change over the last 150 yr the onset of european style farming led to increased erosion reflected in high values of concentration dependent parameters such as magnetic susceptibility isothermal remanent magnetization irm and anhysteretic remanent magnetization arm these high values are only partially due to increased supply of terrigenous material to the lake and recent sediment contains an additional component of authigenic fine single domain magnetite most likely magnetosomes from magnetotactic bacteria high organic productivity in the lake during the 1920s to 1940s drought increased this authigenic component resulting in highly magnetic fine grained sediment a comparison with older holocene sediment from the same lake shows that over time most of the fine magnetic signal is lost after deposition leading to decreases in magnetization and a bimodal grain size distribution of ultrafine superparamagnetic grains and coarser multidomain particles evident from measurements of arm irm ratios hysteresis measurements and low temperature analyses the effects of dissolution and the superposition of climate and land use signals complicate the use of recent sediments as modern analogs for sediment magnetic analyses

the direction of the earth s magnetic field at london 1570 1975 the observations of magnetic declination and dip made in london over the past 400 years comprise one of the longest and most complete series of such data for anywhere in the world they give an indication of secular change on a time scale intermediate between that of recent observatory measurements and of archaeomagnetic measurements we have attempted to catalogue all direct measurements of declination and dip paying particular attention to completeness in the earlier years and tracing the data to their original source wherever possible sufficient details of the observations are given for an assessment of their reliability and accuracy the data are then corrected to a single site fitted with a continuous smooth curve and discussed

geomagnetic field hemispheric asymmetry and archeomagnetic jerks abstract we investigate the origin of the so called archeomagnetic jerks detected in the french archeomagnetic record over the past three millennia although only very large scale global archeomagnetic field models are currently available we show that the occurrence of archeomagnetic jerks is intimately linked to what we define as most eccentric events i e periods of time when a simple description of the geomagnetic field in terms of an eccentric dipole reveals the center of this eccentric dipole to strongly move away from the earth s center from the behavior of the much better known historical field we interpret the evolution of the center of the eccentric dipole as reflecting the production and gathering of flux patches at the core mantle boundary within preferential hemispheres archeomagnetic jerks would thus correspond to episodes of maximum geomagnetic field hemispheric asymmetry such most eccentric events could also provide an explanation for some of the properties previously reported in the long term paleomagnetic field

a 2400 yr record of natural events and anthropogenic impacts in intercorrelated terrestrial and marine sediment cores waipaoa sedimentary system new zealand the waipaoa sedimentary system spans 100 km from terrestrial upland to continental rise alluvial buffering has little effect on sediment flux at the outlet of this mesoscale dispersal system and hinterland to margin transport is accomplished rapidly because of this synergy the floodplain and shelf depocenters are sensitive to changes in sediment production in the hinterland and natural and anthropogenically forced changes in sediment source dynamics that occur at several temporal and spatial scales leave distinctive signals in the stratigraphic record manifested as variations in sediment properties these signals appear in intercorrelated sediment cores from a headwater riparian storage area and the major terrestrial and marine repositories for sediment discharged during the past 2 4 k y the signals represent the landscape response to vegetation and land use change short term fluctuations in climate that affect surface properties and processes and extreme storms and subduction thrust earthquakes extreme storms are the minimum geomorphologically effective event preserved in the sediment records lower magnitude storms that are integral components of the prevailing hydrometeorological regime create high frequency fluctuations in sediment properties and collectively contribute to event sequences of 100 yr duration events and event sequences comprise a hierarchy of temporally sensitive phenomena the impacts of which are conditioned by frequency and magnitude by contrast vegetation disturbance is a spatially sensitive phenomenon that directly impacts sediment source areas and lowers the threshold of landscape sensitivity to erosion for this reason the taupo eruption of 1 718 ka and the piecemeal vegetation changes that occurred after the arrival of polynesian settlers also generated strong depositional signals after european colonization deforestation of the hinterland altered landscape sensitivity and precipitated the transition to an erosional regime that impacted sediment production and dispersal across the entire magnitude frequency spectrum of events regulating sediment delivery to and transport in stream channels no other perturbation had such a profound impact on the late holocene depositional record

reconstructing the holocene geomagnetic field abstract knowledge of the holocene evolution of earth s magnetic field is important for understanding geodynamo processes in the core is necessary for studying long term solar terrestrial relationships and can provide useful age constraints for archeologicaland stratigraphic applications continuous time varying global field models based on archeo and paleomagnetic data are useful tools in this regard we use a comprehensive data compilation and recently refined modelling strategies to produce cals10k 1b the first time varying spherical harmonic geomagnetic field model spanning 10 ky the model is an average obtained from bootstrap sampling to take account of uncertainties in magnetic components and ages in the data and hence has version number 1b instead of 1 this model shows less spatial and temporal resolution than earlier versions for 0 3 ka and particularly aims to provide a robust representation of the large scale field at the core mantle boundary cmb we discuss the geomagnetic dipole evolution and changes in holocene magnetic field morphology at the cmb as shown by the new reconstruction the results are compatible with earlier models cals3k 3 and cals3k 4 for 0 3 ka but reveal some clear deficiencies in the 0 7 ka cals7k 2 model prior to 3 ka cals10k 1b is able to resolve mobile and structurally evolving high latitude radial field flux lobes at the cmb in both hemispheres as well as persistent non zonal structure in the 10 ky average contributions to the average field from time varying structures in the equatorial indonesian australian region are particularly striking

experimental protocols for the study of battered stone anvils from olduvai gorge tanzania abstract percussive activities are highly relevant in the economy of modern hunter gatherer societies and other primates and are likely to have been equally important during the palaeolithic despite the potential relevance of percussive activities in the early stone age attempts to study battered artefacts are still rare in order to establish protocols of analysis of battered tools this paper pursues an interdisciplinary approach combining techno typological refit use wear and gis studies of experimental anvils from olduvai gorge tanzania the main aim is to classify types of damage on battered artefacts according to the percussive task performed and hence identify patterns that can be used to interpret the oldowan and acheulean evidence our results indicate that abrasion marks on anvil surfaces are typical of nut cracking while bone breaking leaves characteristic scars and abrasion marks on the edges of anvils pounding of soft materials such as meat and plants also causes battering of anvils producing morphological and spatial patterns that can be discerned from the heavy breakage of anvils during bipolar flaking by integrating macroscopic microscopic and spatial analyses of experimental stone tools this paper contributes to create a referential framework in which early stone age battered artefacts can be interpreted

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

the mineral magnetic record in recent ombrotrophic peat synchronised by fine resolution pollen analysis mineral magnetic measurements of recent ombrotrophic peat have been used to reconstruct particulate pollution history this requires that the magnetic record is not seriously distorted by post depositional dissolution authigenic growth diagenetic change or downwash of the magnetic minerals fine resolution pollen analysis supports the view that at each site magnetic changes between profiles are synchronous it thus strengthens the chronological and palaeoenvironmental value of the magnetic record

the record of land use change and soil erosion in the late holocene sediments of the petit lac d annecy eastern france pollen chemical and magnetic analysis of a 6 m core from the petit lac d annecy provides a record of land use change and soil erosion spanning the last 2000 years variations in the magnetic properties of the sediments especially above 3 m in the core can be linked to the history of soil inwash over the last 1000 years these changes together with parallel ones in element concentrations and pollen frequencies both concentrations and percentages can be interpreted by reference to the land use history in the catchment during medieval and post medieval times peak deforestation and human impact on vegetation and soils is recorded from the eleventh to fourteenth centuries and again during the eighteenth century the present study suggests that future detailed analyses of the laminated sediments of the lake could provide a precisely datable fine resolution environmental history of the lake and its drainage basin

geomagnetic field for 0 3 ka 1 new data sets for global modeling 1 paleomagnetic and archeomagnetic records are used in both regional and global studies of earth s magnetic field we present a description and assessment of five newly compiled data sets also used in the companion paper by korte et al 2009 to produce a series of time varying spherical harmonic models of the geomagnetic field for the last 3000 years data are drawn from our compilation of lake sediment records and from the online database geomagia50v2 the five selections are available from the earthref digital archive at http earthref org cgi bin erda cgi n 944 data are grouped according to the source of material and we conducted separate assessments of reliability for archeomagnetic artifacts and lava flows the arch3k dat data set and for sediments sed3k dat the overall number of data is 55 greater than in previous compilations constrained data sets were selected using different criteria for each group winnowing of archeological data was based on uncertainties supplied by the original data providers the lake sediment data assessment relied on preassigned age uncertainties and one or more of the following comparisons with archeomagnetic data from the same region regional consistency among several lakes and consistency with global archeomagnetic models we discuss relative merits of a larger unconstrained data set or a smaller possibly more reliable one the constrained data sets eliminate a priori up to 35 of the available data in each case and rely on potentially subjective assessments of data quality given the limited data available our analyses indicate that iterative rejection of a small number 1 1 5 of outlying data during global field modeling is a preferable approach specific regional comparisons among the models and data support the conclusion that korte et al s outlier free cals3k 3 model based on all available measurements from sediments and archeological artifacts currently provides the best global representation of the 0 3 ka field the arch3k 1 model provides a better fit to the denser european archeomagnetic data and may be better in that region

lake sediments erosion and landscape change during the holocene in britain and ireland abstract lakes are excellent repositories of air borne and especially stream borne materials it has long been recognised that lake sediments contain a strong record of catchment soils via the inputs of minerogenic and chemical erosional products to these may be added a variety of palaeoecological indicators including pollen fungi sphagnum leaves and faunal remains pollen analysis in particular enables land use change to be assessed over many millennia and demonstrates the landscape impacts of woodland clearance grazing and crop cultivation radiocarbon dating provides a chronology for environmental and agricultural change and acts as an indicator of erosion in its own right the use of such indicators to reconstruct past instances and patterns of erosion is demonstrated with reference mainly to 50 british and irish lake sites and especially those which have produced signals of erosion in the form of accelerated sediment accumulation and inversed or reversed sequences of radiocarbon dates during the mid and late holocene sites displaying even or decreased sedimentation through time are concentrated in northern and northwestern scotland and have either no clear signs of human impact or only so towards the latter part of the holocene this pattern probably reflects a combination of factors including low population densities thin soils and the sealing effect of blanket peat in contrast all sites with accelerated erosion have indications of anthropogenic impact this is often prior to levels of increased sedimentation showing a delay in system response while the spread of dates for the start of the rise in sediment accumulation spans 6200 940 bp three clusters are evident at 5295 4970 4530 4235 and 2980 2810 bp radiocarbon inversions mostly reversals are evident for 18 sites no obvious causal patterning is indicated and they probably demonstrate no more than the fact that catchment soils including peats around a particular site were pushed beyond an erosional threshold sufficient to age the sediments deposited within the lakes it is hoped that improvements in data quality will allow the refinement of such exercises in the future and that lakes will be valued as repositories of long term landscape sensitivity

relative geomagnetic paleointensity of the brunhes chron and the matuyama brunhes precursor as recorded in sediment core from wilkes land basin antarctica abstract paleomagnetic and rock magnetic investigation was performed on the 35 m long md03 2595 cado coring adelie diatom oozes piston core recovered on the continental rise of the wilkes land basin east antarctica analysis of the characteristic remanent magnetization chrm inclination record indicates a normal magnetic polarity for the uppermost 34 m of the sequence and a distinctive abrupt polarity change at the bottom of the core this polarity change which spans a 27 cm thick stratigraphic interval represents a detailed record of the matuyama brunhes m b transition and it is preceded by a sharp oscillation in paleomagnetic directions that may correlate to the m b precursor event paleomagnetic measurements enable reconstruction of geomagnetic relative paleointensity rpi variations and a high resolution age model was established by correlating the cado rpi curve to the available global reference rpi stack indicating that the studied sequence reaches back to ca 800 ka with an average sedimentation rate of 4 4 cm ka orbital periodicities 100 ka and 41 ka were found in the chrm inclination record and a significant coherence of chrm inclination and rpi record around 100 ka suggests that long term geomagnetic secular variation in inclination is controlled by changes in the relative strength of the geocentric axial dipole and persistent non dipole components moreover even if the relatively homogeneous rock magnetic parameters and lithofacies throughout the recovered sequence indicates a substantial stability of the east antarctic ice sheet during the middle and late pleistocene influence of the 100 ka and 41 ka orbital periodicities has been detected in some rock magnetic parameters indicating subtle variations in the concentration and grain size of the magnetic minerals linked to orbital forcing of the global climate

mineral magnetism and geomagnetic secular variation of marine and lacustrine sediments from central italy timing and nature of local and regional holocene environmental change abstract sediment core palaeomagnetic and mineral magnetic records from two crater lakes in central italy and from the western margin of the adriatic sea have been used to evaluate local and regional responses to holocene environmental change in all cores sediment magnetism reflects the interplay between catchment material and the in situ production of bacterial magnetite magnetotactic bacteria in the lakes the earliest holocene sediments record a waning catchment input that we attribute to rising lake levels and increased tree cover in the catchment from 9000 to 5000 yr bp both lakes become anoxic a consequence of water mass stratification driven by high lake levels bottom water anoxia also developed in the adriatic with sapropel s1 produced between 9000 and 7000 yr bp subsequently the lake and adriatic mineral magnetic records show evidence for increased catchment delivery consistent with pollen evidence for bronze age deforestation in the lakes this evidence is first recorded at 4300 yr bp and a number of distinct clearance events are recorded in comparison at adriatic site rf93 30 lithogenic input increases abruptly at 3500 yr bp and is followed by a slowly changing record of waxing and waning sediment delivery inter site comparisons of palaeomagnetic data point to a possible link between the magnitude of the bacterial magnetite component and the recorded magnetic inclination the sites are at near identical latitudes and have similar sediment accumulation rates but the adriatic sites have a core average magnetic inclination that is some 10 steeper than the lake average values we suggest that the large dipole moment of the magnetosome chains which in life produce the passive alignment of the bacterium along the local geomagnetic field line produce a more faithful albeit smoothed record of the geomagnetic field

improving geomagnetic field reconstructions for 0 3 ka global geomagnetic field reconstructions on millennial time scales can be based on comprehensive paleomagnetic data compilations but especially for older data these still suffer from limitations in data quality and age controls as well as poor temporal and spatial coverage here we present updated global models for the time interval 0 3 ka where additions to the data basis mainly impact the south east asian alaskan and siberian regions we summarize recent progress in millennial scale modelling documenting the cumulative results from incremental modifications to the standard algorithms used to produce regularized time varying spherical harmonic models spanning 1000 bc to 1990 ad from 1590 to 1990 ad gauss coefficients from the historical gufm1 model supplement the paleomagnetic information in addition to absolute paleointensities calibrated relative paleointensity data from sediments are now routinely included iterative data rejection and recalibration of relative intensity records from sediments ensure stable results bootstrap experiments to generate uncertainty estimates for the model take account of uncertainties in both age and magnetic elements and additionally assess the impact of sampling in both time and space based on averaged results from bootstrap experiments taking account of data and age uncertainties we distinguish more conservative model estimates cals3k nb representing robust field structure at the core mantle boundary from relatively high resolution models cals3k n for model versions n 3 and 4 we assess the impact of newly available data and modifications to the modelling method by comparing the previous cals3k 3 the new cals3k 4 and the conservative new model cals3k 4b we conclude that with presently available data it is not feasible to produce a model that is equally suitable for relatively high resolution field predictions at earth s surface and robust reconstruction of field evolution avoiding spurious structure at the core mantle boundary cmb we presently consider cals3k 4 the best high resolution model and recommend the more conservative lower resolution version for studies of field evolution at the cmb

on the possible occurrence of archaeomagnetic jerks in the geomagnetic field over the past three millennia abstract archaeomagnetism can provide a high resolution full vector description of the earth s magnetic field for the past several thousand years we analyse the bulk of archaeomagnetic data both direction and intensity obtained recently in western europe and the eastern mediterranean covering the past three millennia we demonstrate a remarkable coincidence between sharp cusps in geomagnetic field direction and intensity maxima two clear ones at ad 200 and 1400 two presently less well constrained at 800 bc and ad 800 these sharp changes may constitute a new feature of geomagnetic secular variation archaeomagnetic jerks with time characteristics intermediate between geomagnetic jerks and magnetic excursions

use wear analysis of obsidian artifacts from later stone age shell midden sites on the red sea coast of eritrea with experimental results this paper presents results of use wear study on lithic artifacts from two later stone age sites gelalo and misse on the red sea coast of eritrea the sites produced large quantities of lithic artifacts in association with mollusk shells and ostrich eggshell beads but it is unclear if all the stone tools were required for bead and mollusk shell processing the study involved recording of microfracture damage traces in order to infer the use material and the manner in which the artifacts were used a large percentage of the analyzed samples from gelalo and misse preserve wear patterns suggestive of human use the diagnostic wear types include 1 dense step snap crushing and hinge fractures typically confined on the working edges and 2 feather scars organized in a scalar manner visible on the ventral and dorsal surfaces of the active parts the observed damage patterns suggest cutting and engraving medium to hard materials the evidence is incomplete for more generalization about the specific activities carried out at the sites a brief experimental study involving ostrich eggshell drilling oak twig sawing and bark scraping meat slicing and mollusk shell sawing and drilling was carried out to aid interpretation of wear features observed on the archaeological specimens wear traces produced by sawing mollusk shell and oak wood showed close affinity to those observed on the archaeological specimens the study contributes important information about early holocene site use on the red sea coast of eritrea the close association of used lithic artifacts symbolic objects beads and broken shell remains indicates that the sites were habitation areas

age of the mono lake excursion and associated tephra abstract the mono lake excursion mle is an important time marker that has been found in lake and marine sediments across much of the northern hemisphere dating of this event at its type locality the mono basin of california has yielded controversial results with the most recent effort concluding that the mle may actually be the laschamp excursion earth planet sci lett 197 2002 151 we show that a volcanic tephra ash 15 that occurs near the midpoint of the mle has a date not corrected for reservoir effect of 28 620 300 14c yr bp 32 400 gisp2 yr bp in the pyramid lake basin of nevada given the location of ash 15 and the duration of the mle in the mono basin the event occurred between 31 500 and 33 300 gisp2 yr bp an age range consistent with the position and age of the uppermost of two paleointensity minima in the napis 75 stack that has been associated with the mle philos trans r soc london ser a 358 2000 1009 the lower paleointensity minimum in the napis 75 stack is considered to be the laschamp excursion philos trans r soc london ser a 358 2000 1009

geomagnetic field intensity during the last 60 000 years based on 10be and 36cl from the summit ice cores and 14c abstract based on 10 be 36 cl and 14 c records we reconstruct past changes in the geomagnetic field intensity under the assumption that radionuclide records are mainly influenced by changes in their production rates subsequent comparison of these records with independent geomagnetic field reconstructions allows us to assess the reliability of our approach and to identify periods where our method or the geomagnetic field reconstructions might be problematic the geomagnetic field derived from the 10 be flux to summit in central greenland agrees well with independent geomagnetic field intensity reconstructions however compared to independent palaeomagnetic data the radionuclide record suggests increased geomagnetic field intensities especially for the period from 20 000 to 30 000 years bp 36 cl from the grip ice core agrees well with the 10 be record for the last ice age and hence also the reconstructed geomagnetic field based on the tree ring radiocarbon record it is possible to reconstruct geomagnetic field intensity changes during the holocene a comparison of radiocarbon based and independent geomagnetic field reconstructions indicates that changes in the carbon cycle significantly influenced the atmospheric radiocarbon concentration before 10 000 years bp

active percussion tools from the oldowan site of barranco leon orce andalusia spain the fundamental role of pounding activities in hominin lifeways abstract dated to 1 4 mya the barranco leon site orce andalusia spain is currently the oldest and richest late lower pleistocene stone tool assemblage discovered so far in europe archeological and paleontological remains are found clearly associated in lacustrine deposits traversed by a small channel this paper provides new data about the lithic assemblage from level d focusing on the abundant active percussion implements that form a part of the highly divers set of limestone macro tools unique to this assemblage morpho technological and experimental analysis of these tools allows us to hypothesize about the kinds of activities that might have been carried out by hominins at this site experimental work allows us to define percussive trace morphologies and to identify new types of percussion tools in the collection beyond those of classical ellipsoidal morphology analysis of the stone surfaces used for active percussion demonstrates that while some of the tools could have been used for stone knapping other hammer morphologies are not well adapted for this kind of activity the morphology of the tools and the type of percussion damage displayed on their active surfaces provide criteria with which to widen the activity range of the hominins that used them this study of the percussion instruments from barranco leon contributes essential data with which to buttress the growing interest in the macro component of oldowan stone toolkits african and eurasian sites and their possible uses

holocene palaeomagnetic secular variation recorded in multiple lake sediment cores from eastern finland summary holocene palaeomagnetic secular variation psv in inclination and declination recorded in the sediment remanent magnetization of two small lakes lake lehmilampi 63 37 n 29 06 e and lake kortejarvi 63 37 n 28 56 e in eastern finland is presented as an outcome of systematic coring eight cores 300 753 cm in length were investigated all samples lehmilampi n 1320 kortejarvi n 943 were subjected to palaeo and mineral magnetic analyses the directions of the characteristic remanent magnetization chrm were obtained from progressive alternating field demagnetization of the natural remanent magnetization nrm followed by principle component analysis the younger sections of the sediment columns in the studied lakes are annually laminated providing detailed chronologies for dating psv features back to 5100 cal bp the underlying older sections of the cores were dated by palaeomagnetic pattern matching in respect to varve dated lake nautajarvi psv data ojala saarinen 2002 thus yielding a composite age model covering nearly the whole holocene epoch average sedimentation rates ranging from 0 68 to 0 74 mm yr 1 enabled recording of changes in the geomagnetic field at decadal resolution the carriers of remanence are dominantly magnetite of stable single domain to pseudo single domain grain size accompanied by magnetic minerals of harder coercivity the sediments from both lakes exhibit strong and stable single component magnetizations nearly throughout the whole cores the sediment magnetization lock in delay is estimated to range between 80 and 100 yr psv data were transformed into time series and subsequently stacked to comprise north karelian stack and fisher statistics were used to calculate mean directions together with the 95 per cent confidence level 95 a comparison of declination and inclination features of the north karelian stack with previously published data expresses remarkable similarity therefore confirming the similar source behind the changes in the nrm directional records the high quality of the psv data extracted from lehmilampi and kortejarvi in terms of dating as well as amplitude reconstruction have a high potential to improve existing and future geomagnetic field models

microwear analysis of mousterian quartz tools from the navalmaillo rock shelter pinilla del valle madrid spain the study of wear marks on palaeolithic quartz tools allows an understanding of how they were used the present work reports a functional study of a sample of mousterian quartz industry from level f of the navalmaillo rock shelter pinilla del valle madrid spain this level a palimpsest preserves the remains of a neanderthal occupation traceological inspection revealed the tools made at the site were very versatile

continuous global geomagnetic field models for the past 3000 years abstract several global geomagnetic field models exist for recent decades but due to limited data availability models for several centuries to millennia are rare we present a continuous spherical harmonic model for almost 3 millennia from 1000 b c to 1800 a d based on a dataset of directional archaeo and paleomagnetic data and axial dipole constraints the model named continuous archaeomagnetic and lake sediment geomagnetic model for the last 3k years cals3k 1 can be used to predict both the field and secular variation comparisons and tests with synthetic data lead to the conclusion that cals3k 1 gives a good general large scale representation of the geomagnetic field but lacks small scale structure due to the limited resolution of the sparse dataset in future applications the model can be used for comparisons with additional new data for that time span for better resolved regions the agreement of data with cals3k 1 will provide an idea about the general compatibility of the data with the field and secular variation in that region of the world for poorly covered regions and time intervals we hope to iteratively improve the model by comparisons with and inclusion of new data animations and additional snapshot plots of model predictions as well as the model coefficients and a fortran code to evaluate them for any time can be accessed under http www mahi ucsd edu cathy holocene holocene html the whole package is also stored in the earthref digital archive at http www earthref org

late holocene vegetation change in the sierra madre oriental of central mexico abstract past vegetation and climate changes reconstructed from a sediment core from laguna atezca molango mexico provide new insights into the environmental and cultural histories of the sierra madre oriental during the last 1700 yr pollen microscopic charcoal sediment chemistry loss on ignition and magnetic susceptibility indicate that three phases of human occupation deforestation and erosion ca a d 280 890 ca a d 1030 1420 and ca a d 1680 present alternate with two phases of abandonment ca a d 890 1030 and ca a d 1420 1680 forest composition of the two abandonment phases differed with cloud forest taxa liquidambar ostrya carpinus ulmus etc dominating the pollen record during the first phase and quercus and pinus pollen characterizing phase two these differences may reflect a climate change in which the second phase was drier than the first alternatively the increase in pinus and quercus may have been caused by a human induced decline in soil fertility the laguna atezca record also differs from several other mesoamerican paleoenvironmental records in that it shows no evidence of drought at the end of the classic period ca a d 900

use wear analysis of the late middle pleistocene quartzite assemblage from the gran dolina site td10 1 subunit sierra de atapuerca spain abstract quartzite has been poorly studied from a functional point of view since the foundation of use wear analysis as the method was largely built upon the observation of wear on fine grained raw materials e g chert in the case of the middle pleistocene gran dolina td10 1 site in spain ca 300 kya the sole raw material that can provide functional information for the artifacts used by the human occupants of the site is quartzite a sample of 51 quartzite artifacts was mainly analyzed with scanning electron microscopy and functional interpretation was possible for 36 of them the activities identified were mostly connected to the butchering of animals but bone and hide scraping as well as woodworking were also present the performance of activities other than butchering supports the idea that the site was used as a residential camp during the deposition of the basal part of the td10 1 subunit lower td10 1 this study demonstrates the possibility of obtaining functional data from relatively ancient artifacts made of a coarse grained lithology considering that metamorphic quartzose materials often dominate early and middle pleistocene lithic assemblages all over the world the standardization of the functional reading of quartzite will allow acquiring countless functional data with which to reconstruct ancient human behavior

mineral magnetic analyses of sediment cores recording recent soil erosion history in central tanzania abstract sediment cores covering the period from ca 1835 to 1988 ad were retrieved from lake haubi located in a severely eroded area in the kondoa district central tanzania the results of mineral magnetic analyses undertaken on the sediment cores reflect two distinctly different depositional environments before ca 1902 ad the basin formed a seasonally inundated swamp which subsequently turned into a lake the swamp sediment is black uniform and extremely clay rich it contains antiferromagnetic minerals e g haematite but lacks ferrimagnetic minerals e g magnetite due to post depositional dissolution the lake sediment is also very clay rich but laminated here ferrimagnetic minerals magnetite dominate the magnetic assemblage the soil erosion history of the catchment has been reconstructed using results based on the mineral magnetic analyses and on the sedimentation rates obtained from 210 pb datings whereby variations in magnetic concentrations and ratios attributed to variations in sediment influx are assumed to reflect soil erosion within the catchment the results from the magnetic analyses are in general agreement with the sedimentation rates high sediment accumulation occurred around the turn of the century and increased generally since 1935 with particularly high rates between ca 1945 and 1950 and from ca 1955 to the present the reconstructed soil erosion history has been compared to both historical records of anthropogenic activity in the kondoa district and to rainfall data from this comparison we infer that effects on soil erosion from variations in rainfall are subordinate to those induced by man

the identification and biogeochemical interpretation of fossil magnetotactic bacteria magnetotactic bacteria which most commonly live within the oxic anoxic transition zone oatz of aquatic environments produce intracellular crystals of magnetic minerals specifically magnetite or greigite the crystals cause the bacteria to orient themselves passively with respect to the geomagnetic field and thereby facilitate the bacteria s search for optimal conditions within the sharp chemical gradients of the oatz the bacteria may also gain energy from the redox cycling of their crystals because magnetotactic bacteria benefit from their magnetic moments natural selection has promoted the development of traits that increase the efficiency with which the intracellular crystals impart magnetic moments to cells these traits also allow crystals produced by magnetotactic bacteria called magnetofossils when preserved in sediments to be distinguished from abiogenic particles and particles produced as extracellular byproducts of bacterial metabolism magnetofossils are recognizable based on their narrow size and shape distributions distinctive morphologies with blunt crystal edges chain arrangement chemical purity and crystallographic perfection this article presents a scheme for rating magnetofossil robustness based on these traits the magnetofossil record extends robustly to the cretaceous and with lesser certainty to the late archean because magnetotactic bacteria predominantly live in the oatz the abundance and character of their fossils can reflect environmental changes that alter the chemical stratification of sediments and the water column the magnetofossil record therefore provides an underutilized archive of paleoenvironmental information several studies have demonstrated a relationship between magnetofossil abundance and glacial interglacial cycles likely mediated by changes in pore water oxygen levels more speculatively a better developed magnetofossil record might provide constraints on the long term evolution of marine redox stratification more work in modern and ancient settings is necessary to explicate the mechanisms linking the abundance and character of magnetofossils to ancient biogeochemistry

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

assessing the function of pounding tools in the early stone age a microscopic approach to the analysis of percussive artefacts from beds i and ii olduvai gorge tanzania this study explores the function of quartzite pounding tools from olduvai gorge tanzania using microscopic and use wear spatial distribution analysis a selection of pounding tools from several bed i and ii assemblages excavated by mary leakey 1971 were studied under low magnification 100 and the microscopic traces developed on their surfaces are described experimental data and results obtained from analysis of the archaeological material are compared in order to assess activities in which pounding tools could have been involved results show that experimental anvils used for meat processing nut cracking and or bone breaking have similar wear patterns as those observed on archaeological percussive artefacts this is the first time that a microscopic analysis is applied to early stone age pounding artefacts from olduvai beds i and ii and this paper highlights the importance that percussive activities played during the early pleistocene suggesting a wider range of activities in addition to knapping and butchering

does earth s magnetic field secular variation control centennial climate change abstract we obtained new archeointensity data from french faience potsherds dated from the 17th to 19th century these results further document the occurrence of sharp changes in geomagnetic field secular variation in western europe over the past three millennia the intensity variation curve shows several maxima whose rising parts appear to coincide in time with the occurrence of cooling events documented in this region from natural and historical data this coincidence suggests a causal link between enhanced secular variation of the geomagnetic field and climate change over centennial time scales challenging the role of solar forcing as the sole factor provoking these climatic variations we propose that the archeomagnetic jerks described by gallet et al 1 y gallet a genevey v courtillot on the possible occurrence of archeomagnetic jerks in the geomagnetic field over the past three millennia earth planet sci lett 214 2003 237 242 may engage the mechanism for centennial climate change

temporal variations of strength and location of the south atlantic anomaly as measured by rxte abstract the evolution of the particle background at an altitude of 540 km during the time interval between 1996 and 2007 is studied using the particle monitor of the high energy x ray timing experiment on board nasa s rossi x ray timing explorer a special emphasis of this study is the location and strength of the south atlantic anomaly saa the size and strength of the saa are anti correlated with the 10 7 cm radio flux of the sun which leads the saa strength by 1 year reflecting variations in solar heating of the upper atmosphere the location of the saa is also found to drift westwards with an average drift rate of about 0 3 yr following the drift of the geomagnetic field configuration superimposed to this drift rate are irregularities where the saa suddenly moves eastwards and where furthermore the speed of the drift changes the most prominent of these irregularities is found in the second quarter of 2003 and another event took place in 1999 we suggest that these events are previously unrecognized manifestations of the geomagnetic jerks of the earth s magnetic field

the world s oldest stone artefacts from gona ethiopia their implications for understanding stone technology and patterns of human evolution between 2 6 1 5 million years ago the systematic archaeological and geological survey and excavations at gona between 1992 1994 led to the discovery of well flaked stone artefacts which are currently the oldest known from anywhere in the world more than 3000 surface and excavated artefacts were recovered at 15 localities documented east and west of the kada gona river based on radioisotopic dating 40 ar 39 ar and magnetostratigraphy the artefacts are dated between 2 6 2 5 million years ago ma eg10 and eg12 from east gona are the most informative with the highest density providing the best opportunity for characterizing the oldest assemblages and for understanding the stone working capability of the earliest tool makers slightly younger artefact occurrences dated to 2 4 2 3 ma are known from hadar and omo in ethiopia and from lokalalei in kenya cut marked bones dated to 2 5 ma from bouri in ethiopia are now providing important clues on the function of these artefacts in addition australopithecus garhi known from contemporary deposits at bouri may be the best candidate responsible for the oldest artefacts surprisingly the makers of the gona artefacts had a sophisticated understanding of stone fracture mechanics and control similar to what is observed for oldowan assemblages dated between 2 0 1 5 ma this observation was corroborated by the recent archaeological discoveries made at lokalalei because of the similarities seen in the techniques of artefact manufacture during the late pliocene early pleistocene it is argued here that the stone assemblages dated between 2 6 1 5 ma group into the oldowan industry the similarity and simplicity of the artefacts from this time interval suggests a technological stasis in the oldowan 2000 academic press

biostratigraphy of the late early pleistocene eopleistocene of the southern fore urals region russia abstract a summary of published and unpublished data on the stratigraphy of the late early pleistocene eopleistocene of the southern urals region is presented in this paper the summary follows previous reviews about the characteristics of the pleistocene deposits of the easternmost part of europe the improvement and unification of the regional quaternary stratigraphic scheme is the main aim of these investigations in this paper we describe deposits of different origin which constitute the regional stratigraphic units tyulyan raevka udryak khlebodarovka dombarovka blagovar and oktyabrsky horizons are characterized during the late early pleistocene eopleistocene the southern fore urals region was characterized by continental climate conditions and by four phases of incisions of the hydrographic network that were related to regional uplift as well as to the lowering of the base level and the subsequent regression of the late akchagylian sea fossil molluscs ostracods mammals and pollen are used for the reconstruction of the palaeoenvironmental conditions and the biostratigraphical positions of the main localities during raevka khlebodarovka and blagovar times the climate was cool and forest steppe landscapes with prevalent open spaces existed the climate during the tyulyan udryak and dombarovka and oktyabrsky times was warm and during these periods the areas of deciduous and coniferous forests expanded in the forest steppes the molluscan fauna of the early eopleistocene was a transitional fauna from the pliocene to the quaternary because the wet and warm climate which was favourable to the pliocene mollusc species continued in the southern fore urals during the early eopleistocene the mammalian assemblages are the basis for the biostratigraphical subdivision the deposits are biostratigraphically correlated to the lower eopleistocene on the basis of the appearance of the first unrooted voles allophaiomys and prolagurus together with late species of the mimomys genus at the end of the eopleistocene the unrooted voles terricola and lagurina were numerous the first microtus appeared late species of mimomys were not numerous and archidiskodon trogontherii appeared in the mammal faunas of the region the small mammals of the tyulyan and udryak times represent the odessa faunal assemblage the mammal fauna of the oktyabrsky time corresponds to the tiraspol faunal assemblage the units are correlated with the upper villafranchian galerian stages interval in the western european stratigraphical timescale

impacts of human activity on the late holocene development of the subaqueous yangtze delta china as shown by magnetic properties and sediment accumulation rates development of the yangtze delta during the late holocene and its relationship to human activities in the drainage basin was analyzed using data from 16 cores collected from distributaries to the

a 1 4 million year old bone handaxe from konso ethiopia shows advanced tool technology in the early acheulean in the past decade the early acheulean before 1 mya has been a focus of active research acheulean lithic assemblages have been shown to extend back to 1 75 mya and considerable advances in core reduction technologies are seen by 1 5 to 1 4 mya here we report a bifacially flaked bone fragment maximum dimension 13 cm of a hippopotamus femur from the 1 4 mya sediments of the konso formation in southern ethiopia the large number of flake scars and their distribution pattern together with the high frequency of cone fractures indicate anthropogenic flaking into handaxe like form use wear analyses show quasi continuous alternate microflake scars wear polish edge rounding and striae patches along an 5 cm long edge toward the handaxe tip the striae run predominantly oblique to the edge with some perpendicular on both the cortical and inner faces the combined evidence is consistent with the use of this bone artifact in longitudinal motions such as in cutting and or sawing this bone handaxe is the oldest known extensively flaked example from the early pleistocene despite scarcity of well shaped bone tools its presence at konso shows that sophisticated flaking was practiced by 1 4 mya not only on a range of lithic materials but also occasionally on bone thus expanding the documented technological repertoire of african early pleistocene homo

variations in the geomagnetic dipole moment during the holocene and the past 50 kyr all absolute paleointensity data published in peer reviewed journals were recently compiled in the geomacia50 database based on the information in geomagia50 we reconstruct variations in the geomagnetic dipole moment over the past 50 kyr with a focus on the holocene period a running window approach is used to determine the axial dipole moment that provides the optimal least squares fit to the paleointensity data whereas associated error estimates are constrained using a bootstrap procedure we subsequently compare the reconstruction from this study with previous reconstructions of the geomagnetic dipole moment including those based on cosmogenic radionuclides be 10 and c 14 this comparison generally lends support to the axial dipole moments obtained in this study our reconstruction shows that the evolution of the dipole moment was highly dynamic and the recently observed rates of change 5 per century do not appear unique we observe no apparent link between the occurrence of archeomagnetic jerks and changes in the geomagnetic dipole moment suggesting that archeomagnetic jerks most likely represent drastic changes in the orientation of the geomagnetic dipole axis or periods characterized by large secular variation of the non dipole field this study also shows that the holocene geomagnetic dipole moment was high compared to that of the preceding similar to 40 kyr and that similar to 4 10 22 am 2 appears to represent a critical threshold below which geomagnetic excursions and reversals occur c 2008 elsevier b v all rights reserved less

microwear polishes on early stone tools from koobi fora kenya the functions of the stone artefacts made and used by early hominids has been a matter for speculation however recent experimental work has demonstrated that microscopically distinct wear polishes form on tools of cryptocrystalline silica when used on different materials and that these microwear polishes survive on ancient implements1 3 we have now examined 54 artefacts from five early pleistocene archaeological sites dated to 1 5 myr ago in the koobi fora region of kenya for microwear polishes and other traces of use wear traces were found on nine artefacts variously resembling traces induced experimentally by cutting soft animal tissue and soft plant material and by scraping and sawing wood these results greatly extend the time range for which microwear polish analysis is applicable and increase the evidence of early hominid adaptation

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

dynamics of the laschamp geomagnetic excursion from black sea sediments abstract investigated sediment cores from the southeastern black sea provide a high resolution record from mid latitudes of the laschamp geomagnetic polarity excursion age constraints are provided by 16 ams 14c ages identification of the campanian ignimbrite tephra 39 28 0 11 ka and by detailed tuning of sedimentologic parameters of the black sea sediments to the oxygen isotope record from the greenland ngrip ice core according to the derived age model virtual geomagnetic pole vgp positions during the laschamp excursion persisted in antarctica for an estimated 440 yr making the laschamp excursion a short lived event with fully reversed polarity directions the reversed phase centred at 41 0 ka is associated with a significant field intensity recovery to 20 of the preceding strong field maximum at 50 ka recorded field reversals of the laschamp excursion lasting only an estimated 250 yr are characterized by low relative paleointensities 5 relative to 50 ka the central fully reversed phase of the laschamp excursion is bracketed by vgp excursions to the sargasso sea 41 9 ka and to the labrador sea 39 6 ka paleomagnetic results from the black sea are in excellent agreement with vgp data from the french type locality which facilitates the chronological ordering of the non superposed lavas that crop out at laschamp olby in addition vgps between 34 and 35 ka reach low northerly to equatorial latitudes during a clockwise loop inferred to be the mono lake excursion

geomagnetic field stability reversal events and excursions abstract it has been suggested that there are several reverse subchrons in the brunhes and this suggestion is gaining some acceptance however such a suggestion has fundanmental implications for the reversal process because it implies that the reverse polarity state has been substantially less stable than the normal polarity state during the brunhes chron analysis of the latest polarity reversal timescale confirms that there is no reason to reject the hypothesis of a common stability for the two polarity states the cretaceous superchron appears to be a time when the reversal rate slowed to the point where the reversal process actually halted so does not indicate any difference in the stability of the two polarity states after examining the data we found no convincing evidence for even a single reversal event during the brunhes and we conclude that the only reversal excursions that are sufficiently well documented for the brunhes are the laschamp and the blake further we note that the question of whether of large excursions represent aborted reversals is unresolved so excursion data should not at this stage be grouped with transition polarity data finally we note that most of the time the nearly axially symmetric normal and reverse polarity states appear to be remarkably stable

international geomagnetic reference field the eleventh generation the eleventh generation of the international geomagnetic reference field igrf was adopted in december 2009 by the international association of geomagnetism and aeronomy working group v mod it updates the previous igrf generation with a definitive main field model for epoch 2005 0 a main field model for epoch 2010 0 and a linear predictive secular variation model for 2010 0 2015 0 in this note the equations defining the igrf model are provided along with the spherical harmonic coefficients for the eleventh generation maps of the magnetic declination inclination and total intensity for epoch 2010 0 and their predicted rates of change for 2010 0 2015 0 are presented the recent evolution of the south atlantic anomaly and magnetic pole positions are also examined