acheulian flint quarries in the madrid tertiary basin central iberian peninsula first data obtained from geoarchaeological studies abstract new investigations carried out over the last few years in the madrid tertiary basin have revealed a large number of acheulean sites used for the exploitation of flint the find is significantly important because it adds context to the understanding of the intense human activity in the central parts of the iberian peninsula during the middle pleistocene the sites are spread across an extensive zone of 500 ha set on a vast platform on the watershed between the manzanares and jarama rivers the tertiary sedimentary succession that forms the surface of the platform is comprised of about 20 m of thick green clay interbedded with several layers of flint from the miocene intermediate unit of the madrid basin during the second half of the middle pleistocene seasonal flows of streams eroded the clay leaving large numbers of flint nodules visible to the hominids investigations show a sustained period of active quarrying with much of the liberated material converted into hand crafted flint axes through the direct manipulation of the flint nodules the find is valuable especially due to sti exceptional state of preservation fossilized by sandy fluvial deposits whose sedimentation is controlled by complex localised subsidences caused by karstic processes the current study provides geoarchaeological background and explores different models for the formation of the sites and provides a preliminary analysis of the main acheulean assemblages and techniques for working flint nodules the research also adds a new rich perspective to our understanding of the region and the organized human exploitation of raw materials in the acheulean period the study complements the well known river terrace sites in the wider area showing the intensity and prevalence of flint extraction and use during the period and the handaxe tradition typology of the madrid region perez de barradas 1924 1929 santonja et al 1980 rus y querol 1981 rus y vega 1984 vvaa 2002 baena et al 2010

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

reconstructing holocene geomagnetic field variation new methods models and implications reconstructions of the holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long term solar terrestrial relationships and as relative dating tools for geological and archaeological archives here we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts igneous rocks and sediment records a new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data to reduce the influence of a few individual records all sedimentary data are resampled in 50 yr bins which also means that more weight is given to archaeomagnetic data during the inversion the sedimentary declination data are treated as relative values and adjusted iteratively based on prior information finally an alternative way of treating the sediment data chronologies has enabled us to both assess the likely range of age uncertainties often up to and possibly exceeding 500 yr and adjust the timescale of each record based on comparisons with predictions from a preliminary model as a result of the data adjustments power has been shifted from quadrupole and octupole to higher degrees compared with previous holocene geomagnetic field models we find evidence for dominantly westward drift of northern high latitude high intensity flux patches at the core mantle boundary for the last 4000 yr the new models also show intermittent occurrence of reversed flux at the edge of or inside the inner core tangent cylinder possibly originating from the equator less

archaeomagnetism at ebla tell mardikh syria new data on geomagnetic field intensity variations in the near east during the bronze age abstract thanks to systematic excavations conducted at tell mardikh ebla syria during more than 40 years we collected eleven groups of bronze age ceramic fragments defining a series of seven time intervals dated to between 2300 bc and 1400 bc archaeointensity experiments were performed using the triaxe protocol that takes into account both anisotropy thermoremanent magnetization and cooling rate effects the results complemented by three other data previously obtained from ebla allow the recovery of geomagnetic field intensity variations over nearly 1000 years characterized by a v shape with a distinct relative intensity minimum around the 18th century bc they also permit to constrain the occurrence of an intensity maximum between 2300 and 2000 bc together with other archaeointensity data obtained from syrian levantine and anatolian regions the results from ebla help to make emerging a coherent pattern of geomagnetic field intensity variations in the near east over the entire bronze period this evolution was marked by distinct intensity maxima at 2600 2500 bc 2300 2000 bc 1550 1350 bc and at the very beginning of the first millennium bc iron age the latter showing a much higher magnitude than the three older ones we discuss the fact that the detected geomagnetic field intensity maxima could be associated with the occurrence of archaeomagnetic jerks that appear synchronous within age uncertainties with significant regional climatic fluctuations

first directional archaeomagnetic results from syria evidence from tell mishrifeh qatna summary we report on the first archaeomagnetic directional data obtained from syria reliable palaeomagnetic directions were collected from four pyrotechnological archaeological structures dated by type of pottery and radiocarbon from the 19th to 8th century bc middle bronze to iron age in tell mishrifeh qatna syria fairly constant northward declination values within confidence limits were obtained whereas inclination values increased from 42 3 to 73 0 from the middle bronze to iron age at first approximation these new data are consistent with coeval archaeomagnetic directions from western europe and bulgaria the high inclination 73 0 2 8 documented for the iron age translating to a vgp latitude of 65 9 n suggests that very strong secular variation was occurring during the 8th century bc

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

palustrine lacustrine and alluvial facies of the norian owl rock formation chinle group four corners region southwestern u s a implications for late triassic paleoclimate abstract the upper triassic norian owl rock formation was deposited in a low gradient floodbasin at a subtropical paleolatitude the lower part of the formation consists predominantly of fine grained siliciclastic lithofacies deposited by sheetflood and sinuous streams on a muddy floodplain during a period of continuous basin aggradation nodular calcretes are increasingly mature higher in the formation suggesting increasingly episodic depositional conditions the upper part of the formation consists mostly of interbedded fine grained siliciclastic facies and laterally continuous ledges of limestone and sandstone the predominant limestone facies has brecciated to peloidal fabrics spar filled circumgranular cracks and root channeling the subordinate limestone facies displays wavy to irregular argillaceous lamination desiccation cracks and oscillation ripples and is vertically and laterally gradational with the brecciated facies the upper owl rock formation records deposition of aggrading sequences of alluvial sediments deposited during base level rise capped by highstand carbonates deposited in small perennial and ephemeral carbonate lakes and ponds base level lowstand in an overall semiarid climate resulted in extensive pedogenesis of the limestone and laterally equivalent alluvial facies basin wide variations in base level are interpreted as resulting from climatic fluctuations this depositional model is consistent with an interpreted trend towards aridification on the colorado plateau during the late triassic as pangea drifted northward from one climate zone to another

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

decadal scale variations in geomagnetic field intensity from ancient cypriot slag mounds geomagnetic models based on direct observations since the 1830s show that the averaged relative change in field intensity on earth s surface over the past 170 years is less than 4 8 per decade it is unknown if these rates represent the typical behavior of secular variations due to insufficient temporal resolution of archaeomagnetic records from earlier periods to address this question we investigate two ancient slag mounds in cyprus skouriotissa vouppes su1 fourth to fifth centuries ce 21 m in height and mitsero kokkinoyia mk1 seventh to fifth centuries bce 8 m in height the mounds are multilayered sequences of slag and charcoals that accumulated near ancient copper production sites we modeled the age height relation of the mounds using radiocarbon dates and estimated paleointensities using thellier type izzi experiments with additional anisotropy cooling rate and nonlinear trm assessments to screen out ambiguous paleointensity interpretations we applied strict selection criteria at the specimen sample levels to ensure objectivity consistency and robust error estimation we employed an automatic interpretation technique and put the data available in the magic database the analyses yielded two independent subcentury scale paleointensity time series the mk1 data indicate relatively stable field at the time the mound accumulated in contrast the su1 data demonstrate changes that are comparable in magnitude to the fastest changes inferred from geomagnetic models we suggest that fast changes observed in the published archaeomagnetic data from the levant are driven by two longitudinally paired regions the middle east and south africa that show unusual activity in geomagnetic models

history of earth s magnetic field and possible connections to core mantle boundary processes the core mantle boundary cmb sets boundary conditions for processes occurring within the core thus the history of the geomagnetic field is intimately connected with the history of the cmb information about one can often provide information about the other it is a simple matter to separate sources of external origin from those of internal origin but there is no unique way to specify the location of the internal sources indirect arguments suggest that sources within earth s outer core strongly dominate the field for spherical harmonic terms with degree less than about 14 and that crustal sources play an increasing role in harmonics with higher degrees building on the pioneering studies of roberts and scott and of backus in the 1960s the velocity field of the core fluid at the top of the outer core can be estimated from geomagnetic secular variation data however even with appropriate assumptions about location of the magnetic field source there is a serious nonuniqueness in inversion of the secular variation data to velocity field because magnetic field lines are not changed by movement of conductive fluid parallel to those field lines additional assumptions about the flow are therefore required sometimes leading to quite different estimates in the pattern of fluid flow the resulting velocity field estimates appear to be sensitive to conditions e g small lateral variations in temperature at the cmb consideration of mantle dynamics suggests that large changes in the cmb conditions probably occur on a 10 to 100 m y timescale secular variations with periods shorter than a million years but longer than several years almost certainly originate from processes operating in the outer core unfortunately there is not yet consensus as to what those processes are longer period variations in the paleomagnetic record including nonstationarities in the rates of magnetic field reversals in paleointensities and in paleosecular variation may reflect changes in cmb conditions because these boundary conditions are controlled primarily by mantle dynamics there have been several speculations regarding causal links between changes in earth s lithosphere and changes in earth s magnetic field finally the evidence linking lateral variations at the cmb to perceived systematics in polarity transition data is found to be intriguing but insufficient

the paleoclimatic interpretation of clay minerals in sediments a review abstract the application of paleoclimatic interpretation to clay minerals from continental and marine sediments is reviewed and the advantages of this method are indicated levels relatively rich in chlorite illite palygorskite and quartz are interpreted as corresponding to relatively dry periods while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale such as kaolinite smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season using this and similar schemes the paleoclimates of areas adjoining the mediterranean basin north sea north atlantic southern arctic equatorial and north west pacific and north phillipine sea are reconstructed clay minerals in sediments particularly marine sediments can be useful indicators of paleoclimatic conditions while they do not produce direct indications of climatic parameters they provide integrated records of overall climatic impact occasionally they may be superior to the more conventional paleoclimatic methods such as pollen or oxygen isotope analysis the limitations imposed on the paleoclimatic interpretation of clay minerals in sediments are discussed on the basis of examples the distinction between authigenic and detrital clay minerals is shown to be problematic particularly with regard to smectite the relationship between climatic parameters and clay mineral formation is complicated by the intervention of extra climatic factors such as topography geomorphology lithology and time post depositional diagenetic changes may not be recognized differentiation during transport due to size sorting or differential flocculation may overlap climate induced differentiation the association of clay mineral assemblages with specific source areas presents difficulties due to dispersal pathways that are affected by type of transport agency i e water ice or wind transport agencies are not constant with time by an interdisciplinary approach with the paleoclimatic information derived from clay minerals being correlated with that obtained from the analysis of microfossils and oxygen isotope data many of these limitations can be overcome

geomagnetic field intensity behavior in the middle east between 3000 bc and 1500 bc 1 an archeointensity study was carried out on 14 sites of syrian baked clay artifacts archeologically dated between 2500 bc and 1600 bc using an experimental protocol involving high temperature magnetization measurements well defined mean intensity values were derived for 13 different sites with three to nine results obtained at the fragment level per site results of similar ages are coherent and the new data set is in good agreement with previous archeointensity results obtained from the same region all together these data allow one to refine the evolution of the geomagnetic field intensity in the middle east during the third and the second millennium bc in particular they show the occurrence of three periods of rather sharp intensity increase at 2600 bc 2200 bc and 1600 bc possibly at the times of climatic cooling in the eastern north atlantic further suggesting a connection between the earth s magnetic field and multi decadal climatic events

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

update and sensitivity analysis of the neo deterministic seismic hazard assessment for egypt abstract the main goal of this work is to provide an update on the seismic hazard maps available for egypt that incorporates the results of recent studies i e revised historical earthquake catalogs morphostructural zonation data mz revised focal mechanism solutions and mechanical models of the lithospheric structure this is done within the framework of the neo deterministic seismic hazard assessment ndsha procedure that may effectively accommodate any reliable new information to adequately compute the earthquake ground motion maps i e pga pgv and pgd furthermore with the set of relevant scenario earthquakes this work provides a large dataset of synthetic seismograms particularly important for the areas that suffer from the endemic lack of useful strong motion time histories such as egypt setting the base toward detailed and comprehensive seismic microzonation studies ndsha aims to supply an envelope value in other words a value that should not be exceeded therefore it is immediately falsifiable and verifiable a sensitivity analysis based on the different ground motion maps computed adopting different a models for the earthquake source process b mechanical models of the crust and c mapmaker s preconceptions e g different seismotectonic models is provided the maps of difference and ratio between various ground motion maps computed for different variants are shown and discussed in order to explore the influence of using various input models the results provide the potential users with an adequate spectrum of choices and reliably assess and clearly communicate the possible uncertainties the availability of a wide spectrum of hazard maps is a prerequisite to supply valuable information for the significant improvement of a seismic code

geomagnetic field variations in western europe from 1500bc to 200ad part i directional secular variation curve abstract to improve the geomagnetic field secular variation curve svc of western europe during protohistoric times archaeomagnetic directions of 39 archaeological kilns or hearths from france were investigated the dating of each archaeological structure was established with archaeological or chronometric methods thirty seven of these structures are dated from the first millennium bc one from the end of the second millennium bc and the last one from the fourth millennium bc thermomagnetic curves unblocking temperatures and coercivities suggest that the main carrier of the remanent magnetization is a ti poor titanomagnetite archaeodirections were obtained by alternating field and thermal demagnetizations on almost 900 specimens the anisotropy tensor of thermoremanent magnetization was determined for 35 structures and 22 mean archaeodirections were corrected for anisotropy the new archaeodirections are very consistent with previously published data a new directional svc was built using bivariate statistics with selected western europe data located within 1000 km of paris selection criteria include the number of samples the dating reliability and the accuracy of the mean archaeodirection resulting secular variation between 1500bc and 0ad mainly shows large changes in declination while inclinations are bracketed between 65 and 75 the declinations show a strong maximum with values 30 35 around 800 750bc followed by a sharp decrease to values around 0 at 500bc and close to 7 around 250bc the main features of the secular variation from 1500bc to 0ad appear to be a dominant westward drift and two major changes around 800 and 250bc compared to the global and regional geomagnetic models the new reference data are better fitted by arch3k cst 1 and scha dif 3k than by arch3k 1 and cals3k 4 models the strong variation of the archaeodirection between 1000 and 500bc makes archaeomagnetism very useful for dating purposes

extended and revised archaeomagnetic database and secular variation curves from bulgaria for the last eight millennia the efforts of geophysicists to describe geomagnetic field behaviour in the past lead to creation of different geomagnetic field models on the other hand the established regional palaeosecular variations of geomagnetic elements are increasingly used for dating purposes in archaeology both of these goals can be achieved if sufficient amounts of long archaeomagnetic data sets exist for different geographical regions the accumulation of archaeomagnetic determinations began at the middle of the last century parallel with the progressive development of experimental methodology and acceptance criteria the presence of great number of old determinations requires their critical assessment the important question about the reliability of the associated dating intervals should be also re assessed all this requires the continuous refinement and extension of the accumulated databases this paper presents the last synthesis of bulgarian archaeomagnetic database and the local palaeosecular variation curves obtained using a statistical treatment based on bayesian approach rencurve software the rock magnetic characteristics of the newly included non published results are summarized

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

archaeomagnetic investigations in greece and their bearing on geomagnetic secular variation archaeomagnetic results are presented from kilns and other heated structures on mainland greece and on the islands of crete delos euboea and thasos they span the interval from the mid third millennium bce to the mid second millennium ce the results obtained are in good agreement with the comprehensive dataset from bulgaria and reveal secular variation with amplitudes of 25 in inclination and 30 in declination the sharp inclination low in the first few centuries ce now recognized at sites ranging from crete to britain is a robust geomagnetic feature reflecting a static flux pulse due to a magnetic source in the outermost core another much more pronounced inclination low early in the second millennium bce is tentatively identified the emerging greek secular variation curve provides archaeomagnetic dates for five kilns of hitherto uncertain age 2006 elsevier b v all rights reserved

archaeomagnetic study of five mounds from upper mesopotamia between 2500 and 700 bce further evidence for an extremely strong geomagnetic field ca 3000 years ago the distribution of archaeomagnetic data in eastern europe and the near and middle east shows a remarkable gap in turkey this study presents the first archaeomagnetic results from five different mounds in southeast turkey the northern part of mesopotamia the rock magnetic experiments indicate that in the majority of the samples the dominant magnetic carrier is magnetite which is stable to heating to temperatures of 700 1c in general the demagnetization diagrams are single component and all five sets display well defined characteristic magnetizations and clustered directions for the period between 2500 and 700 bce the declinations are between 3501 and 201 while inclinations are in the range of 49 641 the directional results are compared with the global geomagnetic field models cals7k 2 arch3k cst 1 and cals3k 4 and the data from the archaeomagnetic database geomagia50v2 the results are coherent with both the data and the models except for two nearcontemporaneous sets dating 2000 bce which are offset to the east by more than 201 with respect to cals7k 2 archaeointensity measurements were made using the microwave and conventional thermal thellier methods applied to five sets of samples four furnaces and a mud brick wall these yielded comparable and intriguing results while those from the furnaces are slightly higher than the cals7k 2 model and in agreement with the geomagia50v2 and the middle east data the results from the mud brick wall suggest a high intensity of 100 8 mt 17 7 10 22 am 2 a t 1000 bce this result is

a method for correcting geographically separated remanence directions for the purpose of archaeomagnetic dating summary spatial variations in the geomagnetic field must be taken into account if secular variation master curves and directional magnetic dates are to be optimized two methods for relocating remanence vectors have been proposed and in this paper their relative accuracies are compared using a numerical model based on the present day field a method which converts archaeomagnetic directions via a virtual geomagnetic pole is shown to be the more efficient transformation for an archaeomagnetic region the size of the british isles 900 km radius the maximum error in relocating vectors to a central location is predicted to be of the order of 1 2

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

insights on the geomagnetic secular variation in the eastern mediterranean first directional data from cyprus abstract the first directional archaeomagnetic results from cyprus are presented based on the study of seven baked clay structures excavated at the copper smelting site of agia varvara almyras situated some 20 km south of nicosia this ancient copper working site represents a unique example of complete primary production of the copper metal in cyprus in total five furnaces one ore roasting pit and an oven were sampled in situ for an archaeomagnetic investigation all the studied structures are well dated based on pottery finds and radiocarbon dates with ages ranging from 600 bce to 50 bce several rock magnetic experiments were performed to determine the main magnetic carrier and to investigate the thermal stability of the studied material the direction of the characteristic remanent magnetization chrm for each structure has been determined by demagnetization of 7 15 specimens in alternating magnetic fields up to 100 120 mt mean directions were calculated assuming a fisherian distribution and are well defined for five out of the seven structures studied the new directions are compared with the directional data and the secular variation curves available from the surrounding area and with the predictions of global geomagnetic field models they are an important contribution to improving our knowledge of the geomagnetic field variations in the eastern mediterranean and offer new insights about fast geomagnetic directional changes during the first millennium bce that were not previously identified by the available geomagnetic field models predictions in this area

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

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

models of miocene marginal lacustrine sedimentation in response to varied depositional regimes and source areas in the madrid basin central spain abstract a succession of lake complexes formed through miocene times in the madrid basin central spain the complex formed during the aragonian stage provides an outstanding opportunity to evaluate the role of source areas and depositional regimes in the construction of coeval marginal lacustrine deposits sedimentary facies of the aragonian lake indicate a shallow lake that was fringed to the nw and s by arkosic alluvium to the n by litharenitic alluvial fans and to the ne and e by alluvial fans distally dominated by large floodplains marginal lacustrine deposits in the arkosic realm mostly consist of mg smectites and dolomite sequences that laterally interfinger with sepiolite beds which were deposited in small discontinuous ponds in the distal alluvial fan areas occasionally micaceous rich sandy streams entered the lake forming sheets at their entry points in contrast the northern margin of the lake was formed by muddy flats which were influenced by fluctuation in the water table in this setting illitic mudstones are commonly interbedded with biotite rich flood sands showing a sheet like geometry meandering channels occasionally cut into the mud flats facies assemblages on this side of the lake were mainly derived from low grade metamorphic areas to the northeast the marginal lacustrine facies consist of silty clays carbonate paleosols and paludal to lacustrine limestones these facies reflect an interfingering between the lake and a wide stream floodplain system derived from a carbonate source area the mosaic of marginal lacustrine facies in the madrid basin during the aragonian is discussed in the light of lithological and geochemical factors related to variations in source areas

a geomagnetic field model for the holocene based on archaeomagnetic and lava flow data abstract we propose a new geomagnetic field model for the holocene period based on archaeomagnetic and lava flow data avoiding the use of lake sediment data the source of data comes from the geomagia50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 yr the model called sha dif 14k allows us to analyse the behaviour of the geomagnetic field for the last 14 000 yr from 12 000 bc to 1900 ad for the model construction we use the spherical harmonic analysis in space and the penalized cubic b splines in time both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core mantle boundary cmb to assure the convergence of the model for the last 3 ka the model predictions agree with those given by the global model arch3k 1 and the european model scha dif 3k for older epochs the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the holocene for the last 9 ka the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 bc and 3000 bc and the well known continuous decreasing trend of the geomagnetic field strength for the last millennium and a half a general view of the time average evolution of the geomagnetic field flux lobes at the cmb for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum this lobe vanishes when the dipolar field is decreasing the north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5 1 km yr and 3 7 km yr respectively the model shows that the geomagnetic field can be averaged as axial dipolar in 2000 yr within an error of 5 the typical uncertainty of the palaeomagnetic studies finally and following the recent definition of archaeomagnetic jerks we found 8 critical events in the time evolution of the geomagnetic field for the last 8 ka characterized by a maximum in the hemispheric asymmetry of the proposed model the model is available in the earth ref digital archive at http earthref org erda 1897

carbonates in alluvial fan systems an approach to physiography sedimentology and diagenesis abstract this paper deals with the modes of accumulation and distribution of terrestrial carbonates in semi arid alluvial fluvial generally clastic sedimentary environments it is shown that composition and distribution of the carbonate phases are controlled by physical transportation energy morphological slope gradient chemical precipitation evaporization processes and biochemical interaction with the respective subenvironment of mainly cyanophytes evaluation of recent and fossil examples from semi arid alluvial settings indicate that the physical processes produce carbonate sequences which like the clastic ones are fining upward corresponding to the intermittently active sedimentation on an alluvial fan the mineralogy of the carbonates seems to depend upon disproportioning of dissolved compounds in subsurface waters in down fan directions there is obviously a shift towards more evaporitic minerals in the distal parts in favour of high mg calcite dolomite or even gypsum biochemical carbonate production is in direct correspondence with the respective sedimentary subenvironment in terms of transport energy and sediment supply there is evidence that high energy proximal regimes are producing isolated biosedimentary structures whereas low energy areas distal interchannel floodplains are favourable for continuous structures like algal stromatolites and algal mats a newly proposed classification system based upon transport precipitation mode and sediment type is thought to be more useful for environmental analysis and reconstructions than purely descriptive ones neglecting the process of formation this is especially the case for the non active phases of alluvial fans when the area of deposition is sediment starved referring to the clastics the system takes into account that there are two general carbonate groups detrital allochthonous and chemical biochemical autochthonous ones the latter may be formed within the pores of the clastic sediments or may be due to sedimentation in open water pedogenic processes may themselves be the carbonate forming factor or they may superprint non pedogenic processes

models of the magnetic field at the core mantle boundary for 1715 1777 and 1842 models of the magnetic field at the core mantle boundary for 1715 0 1777 5 and 1842 5 are presented derived from original observations rather than from charts or grid point values the models produced using the method of stochastic inversion have surprisingly good resolution of the core field resolving small scale features which have only recently been identified in modern data the models show that secular variation is low over much of the core mantle boundary with clearly identifiable static slowly varying features in the core field westward drift is confined to a relatively small region in which the secular variation is more vigorous it is concluded that the effects of magnetic diffusion should not be ignored in studies of the secular variation

carbonate lake deposits associated with distal siliciclastic perennial river systems abstract the genesis of thick accumulations of carbonate lake deposits on the siliciclastic floodplains of perennial rivers situated below the regional spring line requires 1 a significant source for calcium in the watershed and 2 a protected area to accumulate calcite the phanerozoic record of fluvial deposits shows that anastomosing rivers with carbonate rich provenance situated in distal areas below the spring line are the best environments for floodplain accumulation of significant carbonate lake deposits anastomosing rivers exist below the regional spring line and have isolated flood basins generally protected from bedload by high levees receiving suspended and dissolved load during flooding events numerical modeling to test the rate of accumulation for these carbonate sediments was performed using stratigraphic data from the pennsylvanian succession containing floodplain limestones of the stewart quadrangle of athens county in ohio usa limestone volumes for six limestone units upper pittsburgh fishpot sewickley benwood arnoldsburg uniontown and waynesburg limestones were calculated with the assumption of overland input of dissolved calcite from carbonate source areas in comparing the calcium input rate to the amount of calcium calculated from limestone unit volumes overland transport of calcium ions not spring input can supply sufficient ions to accumulate thick carbonates over the short lifetime of floodplain lakes within anastomosing river systems

the secular variation of earth s magnetic field models of the magnetic field at the core mantle boundary at selected epochs from 1715 0 to 1980 0 reveal novel features in the field at the core these suggest that the flow of core fluid is coupled to the mantle and that magnetic diffusion is significant

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

the relationship between carbonate facies volcanic rocks and plant remains in a late palaeozoic lacustrine system san ignacio fm frontal cordillera san juan province argentina the san ignacio fm a late palaeozoic foreland basin succession that crops out in the frontal cordillera argentinean andes contains lacustrine microbial carbonates and volcanic rocks modification by extensive pedogenic processes contributed to the massive aspect of the calcareous beds most of the volcanic deposits in the san ignacio fm consist of pyroclastic rocks and resedimented volcaniclastic deposits less frequent lava flows produced during effusive eruptions led to the generation of tabular layers of fine grained greenish or grey andesites trachytes and dacites pyroclastic flow deposits correspond mainly to welded ignimbrites made up of former glassy pyroclasts devitrified to microcrystalline groundmass scarce crystals of euhedral plagioclase quartz and k feldspar opaque minerals aggregates of fine grained phyllosilicates and fiammes defining a bedding parallel foliation generated by welding or diagenetic compaction widespread silicified and silica permineralized plant remains and carbonate mud clasts are found usually embedded within the ignimbrites the carbonate sequences are underlain and overlain by volcanic rocks the carbonate sequence bottoms are mostly gradational while their tops are usually sharp the lower part of the carbonate sequences is made up of mud which appear progressively filling interstices in the top of the underlying volcanic rocks they gradually become more abundant until they form the whole of the rock fabric carbonate on volcanic sandstones and pyroclastic deposits occur with the nucleation of micritic carbonate and associated production of pyrite cyanobacteria which formed the locus of mineral precipitation were related with this nucleation the growth of some of the algal mounds was halted by the progressive accumulation of volcanic ash particles but in most cases the upper boundary is sharp and suddenly truncated by pyroclastic flows or volcanic avalanches these pyroclastic flows partially destroyed the carbonate beds and palaeosols microbial carbonate clasts silicified and silica permineralized tree trunks log stumps and other plant remains such as small branches and small roots inside pieces of wood interpreted as fragments of nurse logs are commonly found embedded within the ignimbrites the study of the carbonate and volcanic rocks of the san ignacio fm allows the authors to propose a facies model that increases our understanding of lacustrine environments that developed in volcanic settings

persistent high paleosecular variation activity in southern hemisphere for at least 10 000 years abstract direct observations of the geomagnetic field show that secular variation is strong in the atlantic hemisphere and comparatively reduced in the pacific region the dipole has been decaying since at least 1840 ad driven by growth and migration of reverse flux patches in the southern hemisphere we investigate whether anything like this modern pattern of geomagnetic secular variation persists and can be detected in global paleomagnetic field models synthesis of results from two new time varying spherical harmonic models shows that geographically distinct geomagnetic secular variation extends to at least 10 000 bp the models use the same database but differ in methodology leading to some regional differences in results consistent large scale surface features include strong average fields in the northern hemisphere and weaker fields with greater overall variability in the south longitudinal structure is present with weaker average fields in the western pacific than in the east and prominent negative inclination anomalies extending beneath indonesia across africa and to brazil but weaker anomalies in the central pacific marginally positive inclination anomalies occur west of the americas paleosecular variation activity peaks at high southern latitudes and there is a pattern of reduced activity at equatorial and mid latitudes beneath the pacific although the dipole has exhibited both growth and decay over the interval 0 10 000 bp our results show that geomagnetic paleosecular variation is preferentially focused in similar geographic regions to secular variation seen in the modern field

sheet flow dominated gravel fans of the non marine middle cenozoic simmler formation central california abstract alluvial fan conglomerates of the middle cenozoic simmler formation in the cuyama gorge and southern la panza range of west central california were deposited in two half graben basins on the basis of paleocurrents and down fan fining of sediment both to the northeast the basins are thought to have been adjacent to the then active nacimiento and la panza faults three contiguous conglomerate lithofacies from most proximal to most distal are 1 clast supported crudely stratified coarse conglomerate with imbrication proximal talus and powerful sheet flow 2 clast supported well bedded internally unstratified conglomerate with common imbrication less common grading and thin interbedded coarse sands mid to upper fan deposits of highly sediment charged density modified grain flow sheet flows 3 stratified sandy conglomerate with imbrication distal alluvial sheet flows two additional lithofacies cut across the first three 4 parallel bedded graded coarse sands turbidity currents in floodbasin lakes and 5 matrix supported very poorly sorted conglomerates cohesive debris flows the alluvial fan deposits of the more northeasterly basin are overlain directly by the marine vaqueros formation the fans were dominated by sheet flow events the lack of cross bedding and minor occurrence of channels indicate that permanent streams were not established cohesive debris flows were unimportant the relationship of fan gravels both to the lake turbidites and to the conformably overlying marine sands indicates the existence of fan deltas as a result of late cenozoic transcurrent movement on the la panza fault a strand of the early san andreas system the two half graben basins have been moved so as to create a sedimentary mismatch

trace fossils and rhizoliths as a tool for sedimentological and palaeoenvironmental analysis of ancient continental evaporite successions abstract recognition of evaporite formations from continental tertiary basins of spain provides evidence that trace fossils including rhizoliths can be abundant in some saline lake systems and their study helps in palaeoenvironmental interpretation of ancient continental evaporite sequences six main types of trace fossils have been distinguished and include 1 networks of small rhizoliths 2 large rhizoliths 3 tangle patterned small burrows 4 isolated large burrows 5 l shaped traces and 6 vertebrate tracks rhizoliths were related to both marginal areas of hypersaline lakes and lakes of moderately high saline waters in these settings pedoturbation resulted from colonization by grasses and bushes of distinct lake subenvironments the activity of burrowing invertebrate faunas was especially intense in lakes of moderately concentrated brines from which gypsum was the main evaporite mineral deposited a specific gypsum lithofacies bioturbated gypsum deposits forming thick massive beds has a widespread occurrence in many of the basins tangle patterned small burrows and minor isolated large burrows constitute the typical trace fossil types within the gypsum the traces are interpreted as having been caused by burrowing insect larvae probably chironomids coleopterans and annelids the behaviour of these organisms in recent lake environments yields information about the salinity range of lake waters from which gypsum precipitated concentration values averaging 100 150 g l may be thus deduced though some organisms involved in the formation of the traces can tolerate higher salinities the combined analysis of lithofacies and trace fossils from the lacustrine evaporite sequences contributes to the study of distinct saline lake subenvironments as well as changes in the sedimentary evolution of the lake systems consequently trace fossils can provide valuable insight for palaeoenvironmental analysis of at least some evaporite formations that accumulated in continental settings

the role of pre existing faults in basin evolution constraints from 2d finite element and 3d flexure models the lithospheric driving forces which cause intraplate basin deformation are relatively constant over large areas consequently lateral variations in deformation and stress and strain concentrations seem to be primarily caused by pre existing heterogenities in the rheological signature of the continental lithosphere underlying the sedimentary basins in this paper we explore the weak character of upper crustal faults and their control on basin shape for a number of case studies on intraplate phanerozoic basin settings using a 2d finite element and a 3d flexure model of key importance is the integration of seismic data and field observations with the tectonic modelling allowing the investigation of deformation processes and their expressions on different scales operating on different levels of the lithosphere finite element models for sub basin scales incorporating weak upper crustal faults predict strong control of these weak zones on local stress distributions and subsequent deformation in agreement with observed deformation patterns slip along upper crustal faults control stress distribution and subsequent faulting in overlying sedimentary rocks the effect of weak upper crustal fault movements on basin wide regional upper crustal flexure is looked at in two case studies on 1 extensional tectonics in the lake tanganyika rift zone east africa and 2 compressional tectonics in the central system and tajo basin central spain both settings indicate that basement warpings are controlled by large amounts of slip along so called weak crustal scale border faults which are mostly planar adopting border fault displacements in the 3d flexure model the results indicate low effective elastic thickness eet values in a range of 3 7 km for induced basement deflection patterns in accordance with observations the low eet values most likely reflect a partly decoupling of upper crustal and subcrustal deformation facilitated by the weak lower crust and in agreement with standard rheological assumptions for phanerozoic lithosphere in contrast the inferred weakness of upper crustal faults relative to surrounding rock is not evident from uniform rheological assumptions however observations of reactivations of faults which are not preferably aligned with the stress field and reactivations of basin deformation on long time scales are in support of this feature

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

unusual twinning features in large primary gypsum crystals formed in salt lake conditions middle miocene madrid basin spain palaeoenvironmental implications reply abstract a gypsum formation in the middle miocene saline lake deposits of the madrid basin is composed of large twinned crystals displaying an unusual habit characterised by the twin re entrant angles systematically opening downward such a habit is an exception to the commonly accepted mottura s rule for the growth of large twinned crystals which have been observed in marine derived evaporitic settings the crystals twinned along 100 are composed of elongated sub crystals formed by the intersection of the pinacoid 010 and the hemipyramid 111 field and petrographic evidence indicate a primary origin by subaqueous growth on the bottom ruling out a secondary origin brine composition dominated by ca na so 4 cl can be one of the several factors potentially controlling the selective growth of this habit further observations could indicate that such inverted twinned crystals may be considered diagnostic of gypsum growth in continental settings as such a pattern has not been recognised in marine evaporite formations

palustrine sedimentation and associated features grainification and pseudo microkarst in the middle miocene intermediate unit of the madrid basin spain abstract a rather thick sequence 50 75 m of lacustrine limestones forms the uppermost part of the intermediate unit middle miocene in the ne part of the madrid basin central spain a gradual change from distal alluvial to open lake facies is recorded in this area red mudstones passing vertically to strongly mottled limestones are typical of the transition from distal alluvial to marginal lake deposits a wide variety of facies occur in the marginal lacustrine facies association all of them showing pedogenic features e g root traces alveolar septal structures pseudo microkarst micrites and biomicrites are interpreted as open lacustrine deposits although not as strongly pedogenically modified as the marginal lacustrine facies they still show evidence of subaerial exposure the carbonate sequence was deposited in a low gradient shallow lake system in which slight fluctuations in the water level caused extensive emergence pedogenic processes affected most of the lake deposits but modification was more intense in the marginal facies biogenic activity and mechanical reworking at lake margins led to the formation of pedogenic diagenetic pseudo microkarst and peloidal and or intraclastic limestones

sheet flow deposits of graded beds and mudstones on an alluvial sandflat playa system upper triassic blomidon redbeds st mary s bay nova scotia the 400 m of blomidon redbeds accumulated in a semi arid rift valley in the subtropics at st mary s bay these redbeds are 64 sandy mudstone playa mudflats 25 graded beds sandflats at the toes of alluvial fans 10 fissile claystone playa lakes and 1 channel sandstone stream channels flash floods in mountains south of the valley flowed down alluvial fans to spread out to the north east as sheet flows on sandflats and playa mudflats deceleration of the sheet flows deposited graded beds 2 83 cm in thickness on the sandflats and thin layers of mud on the playas nine sequences consisting of arrangements of six lithologies compose 90 of the graded beds in order of decreasing abundance these are ripple cross laminated siltstone horizontally laminated mudstone fining upward ripple cross laminated siltstone ripple cross laminated sandstone horizontally laminated mudstone cross bedded sandstone horizontally laminated mudstone ripple cross laminated sandstone ripple cross laminated siltstone rippledrift cross laminated siltstone horizontally laminated mudstone fining upward ripple drift cross laminated siltstone cross bedded sandstone ripple cross laminated siltstone and cross bedded sandstone ripple cross laminated siltstone horizontally laminated mudstone the sheet flows perhaps up to 1 m in depth had a high concentration of suspended load deposition was dominantly during lower flow regime conditions and moderate to rapid flow deceleration there are 32 thinning and fining up cycles where a sandflat package of graded beds is transitionally followed by a playa package of sandy mudstone the cycles range in thickness from 1 3 to 13 3 m averaging 4 6 m each cycle is initiated by avulsion to a new active channel network on a fan gradual abandonment of the channel network produces the thinning and fining up cycle the cycles are grouped in three 60 70 m fining up megacycles upwards within each megacycle the packages of sandy mudstone compose a progressively larger proportion of the cycles each megacycle evidently was initiated by a brief period of tectonic movement on the border faults that produced greater relief of the highlands relative to the valley floor subsequent erosion gradually lowered the relief to yield a fining up megacycle