intensity of the geomagnetic field in western europe over the past 2000 years new data from ancient french pottery 1 we studied 14 groups of french pottery fragments dated between the 4th and 16th centuries the potsherds were analyzed using the thellier and thellier 1959 method revised by coe 1967 intensity values were corrected for thermoremanent magnetization trm anisotropy and cooling rate dependence of trm acquisition we first analyzed modern ceramics produced following ancient techniques and fired in a wood burning kiln inside of which field intensity was measured the recovered mean intensity is within 3 of the expected value which proves the reliability of our experimental procedure thermal experiments carried out at rapid and slow cooling rates clearly indicate that the cooling rate correction is critical in archeointensity studies our data indicate that large variations in intensity occurred in france over the last 2000 years two relative maxima in intensity are observed one between the 8th and 10th centuries and the second between the 14th and 15th centuries similarities are observed between the archeointensity data from france and ukraine yielding some evidence for eastward drift of geomagnetic sources between western and eastern europe from a d 800 to a d 1700 we also show that the dipole moment evolution proposed by mcelhinny and senanayake 1982 and yang et al 2000 for the last two millennia is likely biased toward higher values mainly because of the absence of correction for the cooling rate dependence of trm acquisition in most published archeointensity studies we finally underline a possible relationship valid at least in western europe between changes in direction and intensity of the geomagnetic field

two thousand years of archeointensity from west africa this study presents 17 archeointensity estimates from senegal and mali two neighboring countries in west africa for the period 1000 bce to 1000 ce the archeological artifacts used in this study were collected during the course of two separate projects together spanning 22 years and across 8 separate excavations a primary objective of this study was to get accurate dates hence only samples with independent age constraints from pottery style detailed stratigraphy and 14c dates were used a total of 236 specimens from 63 samples were subjected to a double heating paleointensity experiment izzi method from which 95 specimens were selected using a set of very strict selection criteria the paleointensity results were corrected for differential cooling rate effects and remanence anisotropy additionally we demonstrate the equivalence of using tensors derived from anhysteretic and thermal remanences for correcting remanent anisotropy of the specimens and use the former for the anisotropy correction our data show good agreement with the most recent paleosecular variation model but are lower than the pre existing data which are mostly from egypt and morocco the presence of substantial non axial dipolar contributions in the region is evident when virtual axial dipole moments vadms from the published literature are calculated for 20 latitudinal bands and compared with our data the average vadm values show a distinct latitudinal gradient a prominent feature of this dataset is an intensity high observed prior to 700 ce in both senegal and mali comparing this peak with existing records from regions further to the north suggests a small but significant temporal offset and is interpreted to be additional evidence for a geomagnetic field with a significant and rapidly changing non axial dipolar contribution

archaeomagnetism of burnt cherts and hearths from middle palaeolithic amud cave israel tools for reconstructing site formation processes and occupation history abstract apart from magnetostratigraphy archaeomagnetism is rarely used in middle and late pleistocene sites here we present detailed palaeomagnetic analyses of cemented hearths and burnt chert items from amud cave israel 68 55 ka two types of materials common in levantine middle palaeolithic cave sites both materials are shown to be recorders of the geomagnetic field and were used to reconstruct either the ancient field direction for cemented hearths or intensity palaeointensity for chert at the time of the last burning or shortly after we test the utility of palaeomagnetic data to further our understanding of temporal aspects of occupations in the cave by comparing the dispersion of the palaeomagnetic data to the known characteristics of geomagnetic secular variation in the holocene we show that divergent palaeointensities can help identify diachronic burning events suggesting different activity patterns in two areas of the cave additionally we used palaeomagnetic directional vectors to distinguish between a well preserved hearth and one that had been mixed prior to cementation using rock magnetic investigations we demonstrate that magnetic methods can be used as a relatively fast and inexpensive method to identify burning of cherts in antiquity above 500 c the palaeomagnetic results are in agreement with results of previous studies at amud cave obtained by other independent methods this study shows that palaeomagnetic methods can serve as a powerful tool in the study of palaeolithic sites

geomagnetic intensity spike recorded in high resolution slag deposit in southern jordan article i nfo in paleomagnetism periods of high field intensity have been largely ignored in favor of the more spectacular directional changes associated with low field intensity periods of excursions and reversals hence questions such as how strong the field can get and how fast changes occur are still open in this paper we report on data obtained from an archaeometallurgical excavation in the middle east designed specifically for archaeomagnetic sampling we measured 342 specimens from 72 samples collected from a 6 1 m mound of well stratified copper production debris at the early iron age 12th 9th centuries bce site of khirbat en nahas in southern jordan seventeen samples spanning 200 yr yielded excellent archaeointensity results that demonstrate rapid changes in field intensity in a period of overall high field values the results display a remarkable spike in field strength with sample mean values of over 120 t compared to the current field strength of 44 t a suite of 13 radiocarbon dates intimately associated with our samples tight control of sample location and relative stratigraphy provide tight constraints on the rate and magnitude of changes in archaeomagnetic field intensities

full vector archaeomagnetic records from anatolia between 2400 and 1350 bce implications for geomagnetic field models and the dating of fires in antiquity abstract anatolia as one of the busiest crossroads of ancient civilizations provides an ideal platform for archaeomagnetic studies previous results from the middle east have suggested the occurrence of a strong peak in geomagnetic intensity at 1000 bce associated with dramatic field strength variations that could require a radical rethinking of geodynamo theory the behavior of the field in the centuries preceding this peak remains poorly constrained however here we present the results of full vector archaeomagnetic experiments performed on 18 sets of samples from three archaeological sites belonging to assyrian trade colony and hittite periods associated rock magnetic analyses showed that the major magnetic carrier is magnetite chemically stable up to 700 c and the magnetic mineral assemblage is composed mostly of non interacting psd grains the directional results are compared with existing data and with the most recent global geomagnetic field models pfm9k 1b and sha dif 14k the directions are in remarkably good agreement with sha dif 14k which is based on archaeomagnetic and lava flow data together with our earlier results from anatolia we triple the existing database of directions for the 700 year long period 2200 1500 bce over a large region from greece to azerbaijan and from moldavia ukraine to egypt three archaeointensity methods thermal izzi thellier microwave thellier and the multi specimen protocol msp produced virtual axial dipole moment estimates 9 0 10 9 10 22 am 2 that are somewhat higher than contemporaneous regional and global data and model predictions suggesting that the field was already substantially stronger than today more than 800 years prior to the reported peak in addition to constraining geomagnetic variability our data also allow us to assign relative dates to inferred fire events in the assyrian trade colony period sites this allows us to conclude that the fire events at the largest site kultepe were not all contemporaneous with one another and with the abandonment of the site as has been previously hypothesized

depositional remanent magnetization toward an improved theoretical and experimental foundation the first theoretical predictions for the behavior of magnetic particles in water were that sedimentary magnetizations would be fully aligned with the ambient field yet redeposition experiments showed a strong and quasi linear dependence on the external field this empirically observed linearity has served as the fundamental assumption of sedimentary paleointensity studies for decades we present redeposition experiments which suggest instead that the relationship between depositional remanence drm and applied field may frequently be curved for magnetic fields in the range of the earth s numerical simulations using a flocculation model can explain the redeposition data and suggest that drm will be significantly non linear when the flocs are small several microns there is a strong dependence of floc size on salinity particularly in low salinity environments floc size has a profound influence on the efficiency of drm hence low salinity environment may give results with poor reproducibility the size of the floc in which magnetic particles are embedded is not accounted for in current methods of normalization yet is the most important parameter on the bright side however it now seems possible to quantitatively explain paleointensity in sedimentary systems opening the door to absolute paleointensity estimates from sediments whose key parameters of floc size distribution and settling times can be constrained

long term variations in palaeointensity we compile a dataset of reliable palaeointensity estimates based both on published work and on new data from basaltic glass the basaltic glass data more than double the number of reliable thellie

time variations in geomagnetic intensity 1 after many years spent by paleomagnetists studying the directional behavior of the earth s magnetic field at all possible timescales detailed measurements of field intensity are now needed to document the variations of the entire vector and to analyze the time evolution of the field components a significant step has been achieved by combining intensity records derived from archeological materials and from lava flows in order to extract the global field changes over the past 12 kyr a second significant step was due to the emergence of coherent records of relative paleointensity using the remanent magnetization of sediments to retrace the evolution of the dipole field a third step was the juxtaposition of these signals with those derived from cosmogenic isotopes contemporaneous with the acquisition of records new techniques have been developed to constrain the geomagnetic origin of the signals much activity has also been devoted to improving the quality of determinations of absolute paleointensity from volcanic rocks with new materials proper selection of samples and investigations of complex changes in magnetization during laboratory experiments altogether these developments brought us from a situation where the field changes were restricted to the past 40 kyr to the emergence of a coherent picture of the changes in the geomagnetic dipole moment for at least the past 1 myr on longer timescales the field variability and its average behavior is relatively well documented for the past 400 myr section 3 gives a summary of most methods and techniques that are presently used to track the field intensity changes in the past in each case current limits and potential promises are discussed the section 4 describes the field variations measured so far over various timescales covered by the archeomagnetic and the paleomagnetic records preference has always been given to composite records and databases in order to extract and discuss major and global geomagnetic features special attention has been devoted to discussing the degree of confidence to be put in the data by considering the integration of multiple data sets involving different techniques and or materials

testing the accuracy of absolute intensity estimates of the ancient geomagnetic field using copper slag material abstract the middle eastern copper slag is a promising new material for studying intensity variations in the geomagnetic field with high resolution and precision the purpose of this study is to test the accuracy of archaeointensity estimates determined using copper slag by addressing two questions 1 does slag material display the magnetic properties required for valid thellier experiments and 2 what is the accuracy of the archaeointensity estimates derived from thellier style experiments on optimal samples we address the first question through a comprehensive microscopic and magnetic study of representative archaeological slag samples in order to identify the properties responsible for optimal behavior in thellier experiments to address the second question we reproduced slag samples in the laboratory under controlled magnetic fields and analyzed them using the same izzi paleointensity technique used for the ancient slag microscopic analyses of the archaeological slag show that ferromagnetic phases occur as three dimensional dendritic structures whose branches consist of submicron elongated particles magnetic analyses show that these dendrites behave as an assemblage of shape controlled single domain like particles and that their magnetization is thermoremanent we conclude that slag material can be magnetically suitable for valid thellier experiments the laboratory produced slag material demonstrated similar magnetic and mineralogical properties as the archaeological slag izzi experiments showed that non linear trm acquisition even at field strengths similar to earth s and trm anisotropy are important factors to monitor during paleointensity studies of slag material anisotropy and non linearity are probably related to the dendritic shape of the oxide grains intensity estimates derived from three laboratory produced slag samples demonstrated accuracy to within 5 after applying the required corrections

high fidelity paleointensity determination from historic volcanoes in japan 1 providing high fidelity paleointensity estimates is pivotal to identify temporal fluctuation of ancient geomagnetic field despite abundance of available paleointensity data in japan only dozen of them satisfy modern standards with systematic alteration checks high fidelity paleointensity estimates were obtained from historic andesitic lavas collected from mt aso ojodake 700 bc mt kirishima iwoyama ad 1768 ohachi ad 1235 and mt sakurajima an ei ad 1779 nabeyama ad 764 766 variation of geomagnetic field intensity is distinctively different from the prediction of global models arch3k 1 cals3k 3 cals3k 4 cals7k 2 and cals10k 1b for the past 4000 years in japan the compilation of high fidelity thellier data set in japan showed two obvious high intensities at ad 590 765 and ad 1330 1435 and one low intensity at 700 bc these time intervals with anomalous high low intensities are nearly identical to three of the four potential archeomagnetic jerks recognized from the european archeomagnetic data implying that the archeomagnetic jerks were global or at least northern hemispheric features to improve the poor representation of regional geomagnetic field variation with respect to the global model prediction more high fidelity paleointensity determinations are required in east asia

refining the archaeomagnetic dating curve for the near east new intensity data from bronze age ceramics at tell mozan syria abstract uncertainty in radiocarbon dates for the near east caused by a bimodal distribution of ages due to the natural fluctuations of 14 c in the atmosphere has demonstrated the need for an alternative absolute dating technique to aid in the construction of site chronologies here we present a new archaeointensity reference curve model for the first three millennia bce for the levant syria israel jordan for use in archaeomagnetic dating and contribute twelve new intensity results to an increasingly dense geomagnetic field record for the period between 2400 and 1200 bce in the near east archaeomagnetic analysis was conducted on ceramic samples i e pottery sherds from seven sequential and well constrained occupational layers at the site of tell mozan bronze age urkesh in northeastern syria resulting in a 90 success rate by specimen n 42 for archaeointensity determination and an 86 correspondence between the model and the archaeologically derived dates within one standard deviation 1 age standard deviations as low as 24 years were obtained after integration with stratigraphic constraints we also outline the techniques and sampling procedures of archaeomagnetic dating in a manner suitable for the non paleomagnetist while detailing methodology for archaeomagnetic researchers

toward an optimal geomagnetic field intensity determination technique 1 paleointensity determinations based on double heating techniques in field zero field cooling zero field in field cooling and two in field steps with opposite laboratory fields are generally considered to be functionally interchangeable producing equally reliable paleointensity estimates to investigate this premise we have developed a simple mathematical model we find that both the zero field first and in field first methods have a strong angular dependence on the laboratory field parallel orthogonal and anti parallel while the two in field steps method is independent of the direction of the laboratory produced field contrary to common practice each method yields quite different outcomes if the condition of reciprocity of blocking and unblocking temperatures is not met even with marginal 10 tails of partial thermoremanence our calculations suggest that the zero field first method with the laboratory produced field anti parallel to the natural remanence nrm is the most robust paleointensity determination technique when the intensity of the lab induced field is smaller than ancient field however the zero field first method with the laboratory field parallel to the nrm is the optimum approach when the intensity of the lab induced field is larger than the ancient field by far the best approach however is to alternatethe infield zerofield iz steps with zerofield infield zi steps

changes in the intensity of the geomagnetic field a new more reliable technique has been used to determine the ancient intensity of the earth s magnetic field using samples of baked clay from eight sites in the eastern mediterranean the resultant power spectrum reveals a single strong component with a period of 1430 years the reproducibility of the results obtained with the new method also makes limited archaeomagnetic dating with a precision of between about one and two hundred years between 900 bc and ad 400 possible

the effect of remanence anisotropy on paleointensity estimates a case study from the archean stillwater complex paleomagnetism of archean rocks potentially provides information about the early development of the earth and of the geodynamo precambrian layered intrusive rocks are good candidates for paleomagnetic studies such complexes are commonly relatively unaltered and may contain some single domain magnetite armored by silicate mineral grains however layered intrusives often have a strong petrofabric that may result in a strong remanence anisotropy magnetic anisotropy can have particularly disastrous consequences for paleointensity experiments if the anisotropy is unrecognized and if its effects remain uncorrected here we examine the magnetic anisotropy of an anorthosite sample with a well developed magmatic foliation the effect of the sample s remanence fabric on paleointensity determinations is significant paleointensities estimated by the method of thellier and thellier range from 17 to 55 t for specimens magnetized in a field of 25 t we describe a technique based on the remanence anisotropy tensor to correct paleointensity estimates for the effects of magnetic fabric and use it to estimate a paleointensity for the stillwater complex mt usa of 32 t adjusted for the effects of slow cooling

continuous geomagnetic field models for the past 7 millennia 2 cals7k 1 we present two continuous global geomagnetic field models for recent millennia cals3k 2 covering the past 3000 years and cals7k 2 covering 7000 years from 5000 bc to 1950 ad the models were determined by regularized least squares inversion of archeomagnetic and paleomagnetic data using spherical harmonics in space and cubic b splines in time they are derived from a greatly increased number of paleomagnetic directional data compared to previous efforts and for the first time a significant amount of archeointensity data is used in this kind of global model allowing the determination of evolution of geomagnetic dipole strength while data accuracy and dating uncertainties remain a limitation reliable low resolution global models can be obtained the results agree well with previous results from virtual axial dipole moment vadm studies from archeomagnetic intensity data apart from a systematic offset in strength a comparison of model predictions with the previous 3000 year model cals3k 1 gives general agreement but also some significant differences particularly for the early epochs the new models suggest that the prominent two northern hemisphere flux lobes are more stationary than cals3k 1 implied extending considerably the time span of stationary flux lobes observed in historical models between 5000 bc and 2000 bc there are time intervals of weak dipole moment where dipole power is exceeded by low degree nondipole power at the core mantle boundary model coefficients and evaluation code can be obtained from the earthref digital archive erda together with animations and snapshots plots for every 100 years at http www earthref org detailed urls for the different material are listed in appendix a

the effects of secondary mineral formation on coe type paleointensity determinations theory and simulation thellier type experiments are the most widely applied approaches for determining the absolute paleointensities of earth s magnetic field one major problem however is that specimens are prone to thermal alteration due to the intensive thermal treatment during experiments linear arai plots with acceptable partial thermal remanent magnetization ptrm checks have been considered as evidence for the absence of or negligible effects of thermal alteration and as reliable indicators of high quality paleointensity estimates however by simulating the coe variant of the thellier method on assemblages of single domain sd magnetite particles it is demonstrated that new magnetic minerals which form during thermal treatments can result in linear concave up or concave down arai plots depending on the magnetic properties of both the primary and secondary magnetic phases among this range of behavior pseudoideal arai plots which are linear with acceptable ptrm check statistics would lead to paleointensity underestimates it is further demonstrated that ptrm checks are proportional to the degree of underestimate with a magnetic granulometry dependency for sd particles due to the complexity of this dependency ptrm check statistics are only comparable when specimens have similar magnetic properties this suggests that a universal threshold for ptrm check statistics is not likely to be effective since the criteria of linearity and low ptrm check statistics are insufficient to guarantee the fidelity of the estimates auxiliary rock magnetic methods such as temperature dependent hysteresis parameters and anhysteretic remanent magnetization are highly recommended to identify the presence of alteration

large geomagnetic field anomalies revealed in bronze to iron age archeomagnetic data from tel megiddo and tel hazor israel abstract geomagnetic field measurements from the past few centuries show heightened secular variation activity in the southern hemisphere associated with the south atlantic anomaly saa it is uncertain whether geomagnetic anomalies at a similar scale have existed in the past owing to limited coverage and uncertainties in the paleomagnetic database here we provide new evidence from archaeological sources in the levant suggesting a large positive northern hemisphere anomaly similar in magnitude to the saa during the 9th 8th centuries bce called levantine iron age anomaly we also report an additional geomagnetic spike in the 8th century the new dataset comprises 73 high precision paleointensity estimates from ca 3000 bce to 732 bce and five directional measurements between the 14th and the 9th centuries bce well dated pottery and cooking ovens were collected from twenty archaeological strata in two large contemporaneous stratigraphical mounds tells in israel tel megiddo and tel hazor the new data are combined with previously published data and interpreted automatically using the pmagpy thellier gui program the tel megiddo and tel hazor data sets demonstrate excellent internal consistency and remarkable agreement with published data from mesopotamia syria the data illustrate the evolution of an extreme geomagnetic high that culminated in at least two spikes between the 11th and the 8th centuries bce iron age in the levant the paleomagnetic directional data of the 9th century bce show positive inclination anomalies and deviations of up to 22 from the averaged geocentric axial dipole gad direction from comparison of the levantine archaeomagnetic data with igrf model for 2015 we infer the levantine iron age anomaly between the 10th and the 8th centuries bce is a local positive anomaly the eastward extent of the anomaly is currently unknown

nonlinear thermoremanence acquisition and implications for paleointensity data abstract in paleointensity studies thermoremanence is generally regarded as a linear function of ambient magnetic field at low fields comparable to that of the present day earth we find pronounced nonlinearity at low fields for a class of materials with silicate hosted magnetite that otherwise perform well in paleointensity experiments we model this nonlinearity with narrow size ranges of large acicular single domain grains which are most likely in a vortex state i e nonuniformly magnetized sometimes labeled pseudosingle domain simple trm theory predicts that even certain single domain particles will also exhibit a nonlinear response saturating in fields as low as the earth s such behavior although likely to be rare may bias some paleointensity estimates the bias is especially pronounced when the laboratory field is higher than the ancient field fortunately the fundamental assumption that thermoremanence is proportional to applied field can and should be routinely checked at the end of successful paleointensity experiments by adding two extra heating steps

a paleointensity technique for multidomain igneous rocks 1 we developed a paleointensity technique to account for concave up arai diagrams due to multidomain md contributions to determine unbiased paleointensities for 24 trial samples from site ga x in pleistocene lavas from floreana island galapagos archipelago the main magnetization carrier is fine grained low titanium magnetite of variable grain size we used a comprehensive back zero forth bzf heating technique by adding an additional zero field heating between the thellier two opposite in field heating steps in order to estimate paleointensities in various standard protocols and provide internal self consistency checks after the first bzf experiment we gave each sample a total thermal remanent magnetization ttrm by cooling from the curie point in the presence of a low 15 t laboratory applied field then we repeated the bzf protocol with the laboratory applied ttrm as a synthetic natural remanent magnetization nrm using the same laboratory applied field and temperature steps to obtain the synthetic arai signatures which should only represent the domain state dependent properties of the samples we corrected the original arai diagrams from the first bzf experiment by using the arai signatures from the repeated bzf experiment which neutralizes the typical md concave up effect eleven samples meet the arai diagram post selection criteria and provide qualified paleointensity estimates with a mean value for site ga x of 4 23 1 29 t consistent with an excursional geomagnetic field direction reported for this site

small scale structure of the geodynamo inferred from oersted and magsat satellite data the geodynamo in the earth s liquid outer core produces a magnetic field that dominates the large and medium length scales of the magnetic field observed at the earth s surface1 2 here we use data from the currently operating danish oersted3 satellite and from the us magsat2 satellite that operated in 1979 80 to identify and interpret variations in the magnetic field over the past 20 years down to length scales previously inaccessible projected down to the surface of the earth s core we found these variations to be small below the pacific ocean and large at polar latitudes and in a region centred below southern africa the flow pattern at the surface of the core that we calculate to account for these changes is characterized by a westward flow concentrated in retrograde polar vortices and an asymmetric ring where prograde vortices are correlated with highs and retrograde vortices with lows in the historical 400 year average magnetic field4 5 this pattern is analogous to those seen in a large class of numerical dynamo simulations6 except for its longitudinal asymmetry if this asymmetric state was reached often in the past it might account for several persistent patterns observed in the palaeomagnetic field7 8 9 10 we postulate that it might also be a state in which the geodynamo operates before reversing

application of copper slag in geomagnetic archaeointensity research 1 paleointensity and archaeointensity studies since the 1950s have produced numerous geomagnetic intensity data for the last seven millennia as a consequence of different experiments and materials there is a complex and internally inconsistent picture of the geomagnetic field behavior in this study we present data using a recently developed experimental design on a heretofore unexploited recording medium copper slag deposits our results based on hundreds of specimens from various archaeometallurgical sites of the southern levant demonstrate the applicability of copper slag material for archaeointensity studies in addition to frequently exhibiting good experimental behavior slag has further advantages such as dense multilayer deposits and in cases embedded charcoals which open the door to data sets with excellent age control and resolution the data presented here augment the high quality database from the middle east and support previously observed periods of rapid change of the intensity of the geomagnetic field

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

extreme geomagnetic field variability indicated by eastern mediterranean full vector archaeomagnetic records the magnetic field of the earth can exhibit considerable variations at short time scales even as short as decades the archaeomagnetic studies of middle eastern artefacts mainly from israel and jordan show evidence for an exceptionally high intensity period from 1050 700 bc which displays two distinct spikes over the levant the levantine iron age anomaly liaa its exact duration and geographical extent are still poorly known despite the wealth of ancient settlements the extensive cultural heritage and a long history of trade and immigration the archaeomagnetism of turkey and cyprus remains largely unexplored this study presents a large data set of ancient directions and intensities from seven archaeological sites in the eastern mediterranean covering a time span of 2000 yrs the recorded directions from thirteen sets of samples are coherent with our earlier findings yet show significantly larger swings than existing field models in particular we confirm the very large swing in inclination we found earlier from 1910 1850 bc that is also captured by the greek psv curve and shallower by more than 10 than predicted by existing field models consequently these models require substantial revision in this region we were able to determine the archaeointensity from five sets of mud bricks from the thirteen attempted allowing us to provide the full field vector furthermore we present thirty one new archaeointensity results from potsherds and mud bricks that considerably enhance existing data especially when a set of strict selection criteria is applied fourteen sets of potsherds from a single site tell atchana provide the longest sequence recorded so far in turkey from 2100 to 1350 bc we find exceptionally high intensities of 145 and 175 zam2 around 700 bc in well dated mud bricks and potsherds from two different locations tell tayinat and kilise tepe supporting extreme geomagnetic field variability in the region moreover these two high intensities confirm the younger spike of the liaa in turkey

possible impact of the earth s magnetic field on the history of ancient civilizations we report new archeointensity results from iranian and syrian archeological excavations dated from the second millennium bc these high temperature magnetization data were obtained using a laboratory built triaxial vibrating sample magnetometer together with our previously published archeointensity results from mesopotamia we constructed a rather detailed geomagnetic field intensity variation curve for this region from 3000 bc to 0 bc four potential geomagnetic events archeomagnetic jerks marked by strong intensity increases are observed and appear to be synchronous with cooling episodes in the north atlantic this temporal coincidence strengthens the recent suggestion that the geomagnetic field influences climate change over multi decadal time scales possibly through the modulation of cosmic ray flux interacting with the atmosphere moreover the cooling periods in the north atlantic coincide with episodes of enhanced aridity in the middle east when abrupt societal changes occurred in the eastern mediterranean and mesopotamia although the coincidences discussed in this paper must be considered with caution they lead to the possibility that the geomagnetic field impacted the history of ancient civilizations through climatically driven environmental changes triggering economic social and political instability

solar activity reconstructed over the last 7000 years the influence of geomagnetic field changes 1 the long term solar activity as manifested by sunspot number has been recently reconstructed on multi millennium time scales by s k solanki et al 2004 from the measured concentration of 14 c in tree rings the exact level of the reconstructed solar activity depends however on independently evaluated data of the geomagnetic dipole strength variations recently a new series of the palaeomagnetic dipole moment reconstruction for the last 7000 years has been presented by m korte and c g constable 2005a on the basis of a thorough analysis of global samples the new palaeomagnetic series yields a systematically lower dipole moment in the past compared to the earlier geomagnetic reconstructions we have revised the earlier sunspot activity reconstruction since 5000 bc using the new geomagnetic data series and found that it is roughly consistent with the previous results during most of the period although the revised sunspot number values are in general higher nonetheless it is confirmed with the new palaeomagnetic series that the sun spends only 2 3 of the time in a state of high activity similar to the modem episode this strengthens the conclusion that the modem high activity level is very unusual during the last 7000 years

core flow constraints on extreme archeomagnetic intensity changes abstract recent studies ben yosef et al 2009 shaar et al 2011 propose extreme archeomagnetic intensity changes termed spikes in the range 4 5 t year c a 1000 bc in the near east around 40 to 50 times larger than values typical of the present day in order to investigate whether such extreme changes are consistent with a model of the source region of the magnetic field namely the fluid flow at the surface of earth s core we construct upper bounds for instantaneous magnetic intensity change at an arbitrary site on the earth s surface these bounds are constrained by the amount of kinetic energy available to sustain the change taken here to be a prescribed value for the root mean squared surface velocity of 13 km yr as inferred from the current state of the core further we focus attention on two end members of optimised core surface flow structure unrestricted and purely toroidal as the derivation of the bounds demands complete knowledge of the geomagnetic field at the core surface we model the unknown field by means of a monte carlo approach extending to high degree the chaos 4 epoch 2010 ad and cals10k1 b epoch 1000 bc geomagnetic field models using 2000 realisations for each family of stochastic field models we find that optimised core flows are always large scale and that they tend to generate a non dipole quadrupole dominated secular variation at the earth s surface the dependence of the upper bounds as a function of site location reflects the large scale structure of the intensity itself stronger field permits more rapid change for the site in the near east purely toroidal flows have upper bounds of approximately 0 62 0 02 t year whereas unrestricted flows increase this bound to 1 20 0 02 t year we favour the former as more geophysically sound on the account of a large body of previous results from core surface flow inversions and consistency with the existence of a stratified layer at the top of the core even if we allow for a generous threefold increase in the prescribed rms velocity and a concomitant threefold increase in the bound we conclude that the reported occurrences of extreme intensity changes as suggested in the near east are not compatible with the commonly accepted structure of core surface flow however it may be that an explanation for spikes lies beyond our current perception of core dynamics and future work would be further motivated by seeking corroborative evidence of rapid intensity change from sites elsewhere on earth s surface we therefore also discuss the form that the secular variation would take in the case of simultanenous archeomagnetic spikes

geomagnetic intensity variations for the past 8 kyr new archaeointensity results from eastern china abstract in this study we have carried out paleointensity experiments on 918 specimens spanning the last 7 kyr including pottery fragments baked clay and slag collected from shandong liaoning zhejiang and hebei provinces in china approximately half of the specimens yielded results that passed strict data selection criteria and give high fidelity paleointensities the virtual axial dipole moments vadms of our sites range from 2 10 22 to 13 10 22 am 2 at 2250 bce our results suggest a paleointensity low of 2 10 22 am 2 which increases to a high of 13 10 22 am 2 by 1300 bce this rapid less than 1000 yrs six fold change in the paleointensity may have important implications for the dynamics of core flow at this time our data from the last 3 kyr are generally in good agreement with the arch3k 1 model but deviate significantly at certain time periods from the cals3k 4 and cals10k 1b model which is likely due to differences in the data used to constrain these models at ages older than 3 ka where only the cals10k 1b model is available for comparison our data deviate significantly from the model combining our new results with the published data from china and japan we provide greatly improved constraints for the regional model of eastern asia when comparing the variations of geomagnetic field in three global representative areas of eastern asia the middle east and southern europe a common general trend of sinusoidal variations since 8 ka is shown likely dominated by the dipole component however significant disparities are revealed as well which we attribute to non dipolar components caused by movement of magnetic flux patches at the core mantle boundary

detecting multidomain magnetic grains in thellier palaeointensity experiments the thellier technique is the most commonly used method for absolute palaeointensity studies it is based on thellier s laws stating that partial thermoremanent magnetisations ptrms are independent and additive which however only are true for non interacting single domain sd grains for multidomain md grains individual ptrms are not independent and thellier palaeointensity experiments on rocks with a significant proportion of md grains may therefore lead to erroneous palaeofield estimates by introducing a ptrm tail check in the coe version of the thellier technique j geophys res 72 1967 3247 we present a simple method to detect and discard such rocks the usefulness of the ptrm tail check is exemplified by thellier palaeointensity experiments performed on two palaeomagnetic sample collections with different magnetomineralogy miocene baked sediments from french massif central are shown to be ideal for thellier studies with the remanent magnetisation residing in thermally stable sd grains for palaeocene eocene basaltic lavas from faeroe islands 64 of otherwise acceptable palaeointensity estimates are discarded due to the failure of ptrm tail checks indicating the presence of significant concentrations of md grains 2001 elsevier science b v all rights reserved

the secular variation of the geomagnetic field in egypt in the last 5000 years the palaeo intensities fa of the geomagnetic field in egypt at some ages are determined by archaeomagnetic measurements and found to be fa 36 2 t at 3100 b c fa 46 8 t at 3000 b c fa 36 5 t at 2780 b c 49 0 t at 2500 b c 36 4 t at 2200 b c 57 5 t at 1990 b c 62 1 t atca 1400 b c 61 5 t at 1400 b c 69 9 t at 600 b c 59 3 t at 550 b c 79 9 t at 460 b c 73 7 t at 450 b c 69 7 t at 320 b c 56 2 t at a d 50 64 9 t at a d 400 54 4 t at a d 300 57 5 t at a d 700 and 43 0 t at a d 1975

continuous geomagnetic field models for the past 7 millennia 1 a new global data compilation 1 a global data set of archeomagnetic and paleomagnetic data covering the past 7000 years has been compiled it consists of 16 085 results of inclination 13 080 of declination and 3188 of intensity for the time span 5000 bc to 1950 ad declination and inclination data come partly from existing databases and partly from original literature a new global compilation of intensity data for the millennial scale is included data and dating uncertainties are discussed as we attempted to obtain an internally coherent data set the global distribution of the data is very inhomogeneous in both time and space all the data are compared to predictions from the previous 3000 year global model cals3k 1 this collection of data will be useful for global secular variation studies and geomagnetic field modeling although southern hemisphere data are still underrepresented in particular we will use it in a further study to update and extend the existing global model cals3k 1 the huge increase in data compared to the previous compilation will result in significant changes from current models as we might have missed some suitable data we encourage the reader to notify us about any data that have not been included yet and might fit in as improving our global millennial scale models remains our aim for the future the data files described in this paper are available from the earthref digital archive erda at http earthref org cgi bin erda cgi n 331

high temperature archeointensity measurements from mesopotamia we present new archeointensity results obtained from 127 potsherds and baked brick fragments dated from the last four millennia bc which were collected from different syrian archeological excavations high temperature magnetization measurements were carried out using a laboratory built triaxial vibrating sample magnetometer triaxe and ancient field intensity determinations were derived from the experimental procedure described by le goff and gallet le goff and gallet earth planet sci lett 229 2004 31 43 as some of the studied samples were previously analyzed using the classical thellier and thellier thellier and thellier ann geophys 15 1959 285 376 method revised by coe coe j geophys res 72 1967 3247 3262 a comparison of the results is made from the two methods the differences both at the fragment and site levels are mostly within 5 which strengthens the validity of the experimental procedure developed for the triaxe the new data help to better constrain the geomagnetic field intensity variations in mesopotamia during archeological times with the probable occurrence of an archeomagnetic jerk around 2800 2600 bc

strength of the geomagnetic field in the cretaceous normal superchron new data from submarine basaltic glass of the troodos ophiolite 1 we present here new paleointensity data from 39 sampling sites collected from the quenched margins of pillow lavas and dikes exposed within the troodos ophiolite similar to 92 ma formed during the cretaceous normal superchron cns a period of approximately 40 million years when the geomagnetic field reversed extremely infrequently if at all monte carlo simulations suggest that a minimum of 25 estimates are necessary for a reasonably robust estimate for the average field strength our data suggest a dipole strength equivalent to the present field or nearly twice the post cns average the mean and standard deviation of the dipole moment 81 43 zam 2 z 10 21 from the 57 data points compiled here agree remarkably well with those predicted from the long paleointensity record derived from dsdp site 522 the new data set for the cns suggests a picture of a strong and stable field during the period of time when it stopped reversing moreover the similarity of the cns data with the present geomagnetic field suggests that it is presently in a state of unusual polarity stability

first report of bird tracks aquatilavipes from the cedar mountain formation lower cretaceous eastern utah abstract more than 130 footprints representing 43 trackways of birds avian theropods and two non avian theropods occur as seven separate assemblages on loose blocks recovered from the poison strip member of the cedar mountain formation near the stikes quarry locality in eastern utah six of assemblages four with bird tracks and two with small non avian theropod tracks are inferred to originate from the same stratigraphic horizon and can therefore be considered part of the same ichnofauna the seventh assemblage comes from a different horizon a few meters above that yielding the other six assemblages the bird tracks are all attributed to the ichnogenus aquatilavipes a track type morphologically similar to those of modern shorebirds the ichnogenus is also known from broadly coeval ichnofaunas from south dakota and canada and the identification is confirmed by detailed comparative analysis of available aquatilavipes samples using bivariate and multivariate analyses this is the first definitive report of bird tracks from the cedar mountain formation and the first evidence of birds from this otherwise richly fossiliferous unit the ichnofauna is therefore quite unique in comparison with others from this same formation

a new approach for geomagnetic archaeointensity research insights on ancient metallurgy in the southern levant we present results from an archaeointensity investigation based on a relatively unexploited recording medium copper slag deposits together with a recently improved experimental design for the archaeointensity experiment we demonstrate the applicability of this medium as well as other archaeometallurgical artifacts for the study of the ancient geomagnetic field intensity in addition to archaeointensity data from well dated archaeological contexts we obtained reliable archaeointensity results from poorly dated or contentious archaeometallurgical sites in the southern levant these results shed new light on the dating of these sites among them the copper smelting installation of timna 39b a site that has important implications for the beginning of metallurgy during the fifth millennium bce the paper also aims to introduce archaeointensity research to the archaeologist scholar and to encourage further collaboration between the disciplines in future research

partial melting of a c rich asteroid lithophile trace elements in ureilites ureilites are among the most common achondrites and are widely believed to sample the mantle of a single now disrupted c rich body we analyzed 17 ureilite samples mostly antarctic finds and determined their incompatible trace element abundances in order to remove or reduce the terrestrial contamination which is marked among antarctic ureilites by light ree enrichment we leached the powdered samples with nitric acid the residues display consistent abundances which strongly resemble those of the pristine rocks all the analyzed samples display light ree depletions negative eu anomalies low sr eu n and zr eu n ratios which are correlated two groups of ureilites groups a and b are defined compared to group a group b ureilites which are the less numerous tend to be richer in heavy rees more light ree depleted and display among the deepest eu anomalies in addition olivine cores in group b ureilites tend to be more forsteritic mg 81 9 95 2 than in group a ureilites mg 74 7 86 1 incompatible trace element systematics supports the view that ureilites are mantle restites ree modelling suggests that their precursors were rather ree rich ca 1 8 2 x ci and contained a phosphate phase possibly merrillite the ree abundances in ureilites can be explained if at least two distinct types of magmas were removed successively from their precursors aluminous and alkali rich melts as exemplified by the almahata sitta trachyandesite alm a and al and alkali poor melts produced after the exhaustion of plagioclase from the source partial melting was near fractional group b ureilites which are probably among the least residual samples to dynamic with melt porosities that did not exceed a couple of percent group a ureilites the ureilite parent body upb was almost certainly covered by a crust formed chiefly from the extrusion products of the aluminous and alkali rich magmas it is currently uncertain whether the al and alkali poor melts produced during the second phase of melting reached the surface of the body the fact that initial silicate melting of ureilitic precursors would have produced relatively low density liquids capable of forming an external crust to the upb casts doubt on models that invoke chondritic outer layers to achondritic asteroids

eight thousand years of geomagnetic field intensity variations in the eastern mediterranean 1 twenty new intensity determinations of the ancient geomagnetic field have been obtained from groups of potsherds and brick fragments from syria these artifacts archeologically well dated from 6000 b c to approximately a d 1200 have been analyzed using the thellier and thellier 1959 method as modified by coe 1967 intensity values have been corrected for the effects of anisotropy of thermal remanent magnetization and cooling rate our results indicate that field intensities were moderate in syria from 6000 b c to 3500 b c with values of 30 40 t there was a significant increase in intensity by a factor of 2 from 3500 b c to 700 b c which was interrupted by a moderate decrease between 2550 b c and 1750 b c during more recent periods our results show an intensity minimum approximately a d 200 and a maximum around the tenth century comparison with different data sets from the eastern mediterranean and central asia shows that geomagnetic field intensity variations were consistent at this large regional scale at least over the last 5 millennia

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

geomagnetic field intensity how high can it get how fast can it change constraints from iron age copper slag article the intensity of the geomagnetic field varies over different time scales yet constraints on the maximum intensity of the field as well as for its maximum rate of change are inadequate due to poor temporal resolution and large uncertainties in the geomagnetic record the purpose of this study is to place firm limits on these fundamental properties by constructing a high resolution archaeointensity record of the levant from the 11th century to the early 9th century bce a period over which the geomagnetic field reached its maximum intensity in eurasia over the past 50 000 years we investigate a 14 c dated sequence of ten layers of slag material which accumulated within an ancient industrial waste mound of an iron age copper smelting site in southern israel depositional stratigraphy constrains relative ages of samples analyzed for paleointensity and 14 c dates from different horizons of the mound constrain the age of the whole sequence the analysis yielded 35 paleointenisty data points with accuracy better than 94 and precision better than 6 covering a period of less than 350 years most probably 200 years we construct a new high resolution quasi continuous archaeointensity curve of the levant that displays two dramatic spikes in geomagnetic intensity each corresponding to virtual axial dipole moment vadm in excess of 200 zam 2