first archaeomagnetic secular variation curve for the iberian peninsula comparison with other data from western europe and with global geomagnetic field models 1 a first secular variation sv curve for the iberian peninsula was computed by hierarchical bayesian method using a total of 134 archaeomagnetic directions with ages ranging from 775 to 1959 a d a general agreement is observed between the iberian curve and the french and german sv curves although some interesting differences were found such as the occurrence of lower inclinations between the 11th and 14th centuries in the iberian curve the analysis of these three reference curves indicates that sv in western europe is characterized by three major directional changes at 125 200 and 1350 a d it is suggested that these cusps are regional features of the geomagnetic field the iberian curve has been compared with the predictions of the jackson calsk7k 2 and hongre global models despite large differences recognized between these models even for the dipolar terms they predict reasonably well the iberian archaeomagnetic sv

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

on the relationship between climate and neandertal fire use during the last glacial in south west france abstract both environmental and cultural factors dictate how when and where hunter gatherers use fire in the landscape as well as how well evidence for any one fire will preserve in the archaeological record variability in the production and preservation of anthropogenic fire traces can potentially skew our perception of fire use in the past with this in mind the research presented in this article weighs in on the debate concerning neandertal fire use and fire making specifically the assertion that neandertals were unable to produce fire for themselves sandgathe et al 2011a 2011b this hypothesis is based on the inferred correlation between climatic deterioration concurrent lowering of lightning ignited fire frequencies and reduced signals for fire use in layers presumably deposited during the lower pleniglacial marine isotope stage 4 at the middle palaeolithic sites of roc de marsal and pech de l aze iv aquitaine basin southwestern france the logic being that if neandertals could produce fire at will fire use signals would remain largely consistent throughout the deposits despite there being limited access to natural fires in the landscape during this colder period this review challenges these assertions at multiple scales by looking at regional lightning and fire regime dynamics comparing the fire signals observed at roc de marsal and pech de l aze iv to those of other sites nearby and around france and exploring the various environmental and cultural factors likely influencing these signals ultimately the data suggests that estimated reductions in lightning frequencies and fire regime during the lower pleniglacial and colder stadial periods in general were not adequate to severely limit neandertal access to natural fire while possible artefactual evidence for neandertal fire making challenges the assumption that they were at all reliant on lightning ignited fire moreover at the nearby neandertal site of combe grenal the majority of the layers exhibiting evidence of fire use have cold climatic signals suggesting the fire use trends observed at roc de marsal and pech de l aze iv are potentially local expressions of changes in regional site use patterns possibly brought on by increased reliance on highly mobile migratory reindeer prey species and reductions in local woodfuel availability during cold periods other factors potentially reducing the archaeological visibility of cold climate fire use are discussed

three dimensional distribution of minerals in the sediments of hayonim cave israel diagenetic processes and archaeological implications the mineral components of the sediments that accumulate in an archaeological site constitute a potentially rich source of information on the diagenesis and in turn the archaeology of the site this detailed three dimensional study of the mineral assemblages in mainly the mousterian sediments of hayonim cave incorporates more than 2100 infrared analyses performed on site during the excavation as well as diverse analyses in the laboratory three major mineral assemblages are identified the calcite dahllite cd assemblage the assemblage comprising mainly montgomeryite leucophosphite and siliceous aggregates lmvs and a highly altered sediment in which the clays have broken down and silica was released the boundaries between these assemblages were mapped in detail the overall picture is one of extreme heterogeneity with sharp variations occurring over distances of a few centimetres the relation between the cd and lmvs assemblages shows that it is a product of post depositional diagenesis whereas the altered clay assemblage formed beneath an erosional unconformity the cd and lmvs assemblages were derived primarily from an accumulation several metres thick of ash deposits produced by humans ash is thus shown to be a major component of the sediments of this cave the distribution of the cd assemblage reflects to a large extent the locations of two active springs seepages in the cave the distribution of the cd assemblage also faithfully maps the distribution of bones in the cave showing that their distribution is a function of preservational conditions and not human activities stineret al 2001 the conditions that produced the erosional unconformity also resulted in severe alteration of the clays and other mineral components of these sediments the erosion process and the fact that the thickness of this altered zone decreases towards the centre of the cave indicates that the diagenetic driving force was probably climatic the three dimensional distributions of the mineral assemblages have a direct bearing on the dating of the cave by thermoluminescence and electron spin resonance

basement hydrogeology and fortification of the channel islands legacies of british and german military engineering the islands of jersey guernsey alderney and sark lie close to the normandy coast of france they expose a largely precambrian crystalline basement of metamorphic and igneous rocks jersey and alderney also expose some early palaeozoic clastic sediments and all have a thin but widespread quaternary sedimentary cover the three largest islands were progressively fortified by the british between the early 13th and mid 19th centuries and by german forces during occupation in world war ii a legacy illustrated by the castles forts and numerous german coastal fortifications that still adorn them a german military geologist based on jersey from mid 1941 to mid 1944 and a military geological team on guernsey and alderney during 1942 generated hydrogeological maps and reports that were then in advance of understanding of crystalline basement aquifers elsewhere in the british isles all the major documents have now been found in germany the usa and uk although none survived on the islands themselves geological mapping and hydrogeological studies postwar under the auspices of the british geological survey were completed without access to german data however german and british data together now facilitate an appraisal of the heavily stressed aquifers on these small hard rock islands over an unusually long 65 year timespan

secular variation of the earth s magnetic field in the balkan region during the last eight millennia based on archaeomagnetic data summary the first archaeomagnetic secular variation sv curves for the whole southern balkan peninsula are presented these are based on all data within a 700 km circle centred at thessaloniki 40 60on 23 00oe this data set consists of 325 directional and 625 intensity data mainly from greece bulgaria serbia and southern hungary some data from southern italy are also included the sliding moving window technique was used to calculate a continuous sv curve for intensity while the directional sv curves were calculated using the bivariate extension of the fisher statistics these curves are well constrained and clearly show the main features of the geomagnetic field variation in this region during the last eight millennia comparisons with the predictions of the scha dif 3k and scha dif 8k regional and the cals7k 2 and arch3k 1 global geomagnetic field models show a good agreement for the last 3000 years but differences for older times the balkan sv curves identify several rapid changes of the geomagnetic field in eastern europe and can be used as reference curves for archaeomagnetic dating in the balkan peninsula

ash deposits in hayonim and kebara caves israel macroscopic microscopic and mineralogical observations and their archaeological implications abstract a study of the hearths and ash layers preserved in hayonim and kebara caves israel showed that they are composed of one or several different minerals these include the polymorph of caco3 calcite a variety of phosphate minerals and a suite of siliceous minerals the major component of the latter are siliceous aggregates that are present in wood detailed studies of the mineral associations in these fossil ash layers as well as in fresh wood ash using optical and scanning electron microscopy in the back scattered electron mode together with elemental analyses showed that ash in these caves undergoes a series of diagenetic changes the best preserved ash layers resemble fresh ash and are composed mainly of calcite with minor amounts of siliceous minerals the calcite reacts with phosphate rich solutions to form carbonated apatite and with time the latter dissolves and a variety of other phosphate containing minerals form with each diagenetic change some of the more soluble minerals are lost and ultimately only the ash derived siliceous minerals remain in both caves there are local accumulations of such siliceous minerals that are metres thick in fact ash derived minerals in general are major components of the sediments in both kebara and hayonim caves their diagenesis involves a hugh reduction in volume which in turn may have important effects on the geological structures and stratigraphy of the sediments the changing mineralogy of the sediments due to diagenesis complicates the use of present day estimates of radiation content of the sediments for correcting age estimates by thermoluminescence and electron spin resonance finally the presence of the relatively stable ash derived siliceous minerals in a sedimentary layer in other caves could be a useful means of identifying the presence of ash in other archaeological sites where macroscopic hearth features are absent

archaeomagnetic secular variation in the uk during the past 4000 years and its application to archaeomagnetic dating this paper examines the limitations and deficiencies of the current british archaeomagnetic calibration curve and applies several mathematical approaches in an attempt to produce an improved secular variation curve for the uk for use in archaeomagnetic dating the dataset compiled is the most complete available in the uk incorporating published results phd theses and unpublished laboratory reports it comprises 620 archaeomagnetic directional data and 238 direct observations of the geomagnetic field and includes all relevant information available about the site the archaeomagnetic direction and the archaeological age a thorough examination of the data was performed to assess their quality and reliability various techniques were employed in order to use the data to construct a secular variation sv record moving window with averaging and median as well as bayesian statistical modelling the sv reference curve obtained for the past 4000 years is very similar to that from france most differences occurring during the early medieval period or dark ages two examples of dating of archaeological structures medieval and pre roman are presented based on the new sv curve for the uk and the implications for archaeomagnetic dating are discussed

different mechanisms of magnetisation recorded in experimental fires archaeomagnetic implications abstract we present here the archaeomagnetic and rock magnetic results obtained from the experimental recreation of prehistoric fires on a clayish soil substratum by using a system of thermocouples that allows the control of temperatures and heat penetration with depth the magneto mineralogical transformations as well as the ability to acquire magnetic remanences are studied a detailed set of rock magnetic analyses carried out both on surface and depth with a millimetre scale resolution shows the creation of post burn magnetite over the entire surface of the hearth thus promoting a distinguishable magnetic enhancement on the basis of a detailed control of temperatures interesting differences between areas centre vs periphery were observed and two different mechanisms of magnetisation have been recorded the central area which exceeded 600 c acquired a thermal remanent magnetisation trm and the periphery which was heated up to 300 c recorded a thermo chemical tcrm remanent magnetisation the most noticeable mineralogical changes are focused to the first centimetre of the central area where single domain magnetite has been created the implications of these results for archaeomagnetic and palaeointensity studies as well as their utility for the detection of fire in archaeological sites are discussed

a multichannel seismic investigation of upper crustal structure at 9 n on the east pacific rise implications for crustal accretion reprocessed multichannel seismic profiles from the 9 n segment of the east pacific rise reveal prominent shallow subbasement events these events are identified as wide angle reflections from the base of seismic layer 2a based upon modeling of expanding spread profile data and velocity functions the layer 2a reflections typically increase from 0 15 s after the seafloor reflection at the rise axis to 0 3 0 45 s within 1 2 km of the axis corresponding to an increase in layer thickness of 200 600 m no further systematic increase in layer thickness is observed although lateral variability of the order of a few hundred meters in thickness is observed at greater offsets from the rise axis however the intermittent character of the imaged layer 2a reflection is attributed to focusing and defocusing of energy by the seafloor bathymetry rather than necessarily to intrinsic lateral variability at the base of the layer the base of layer 2a is interpreted as corresponding to the transition between the extrusive section pillow basalts and sheet flows and a sheeted dike complex the rapid thickening of the layer near the rise axis is attributed to successive lava flows burying the initially shallow top of the sheeted dike complex as the layer passes through the neovolcanic zone lateral variability of layer 2a can significantly affect the imaging of the underlying axial magma chambers as average velocities within layer 2a are approximately half that of layer 2b for an along axis profile apparent along axis variability in the depth of the axial magma chamber is traced to variability in the thickness of layer 2a caused by wandering of the profile relative to axis within the resolution of the data the time delay of the magma chamber reflection relative to the base of layer 2a is constant

tomographic imaging of the shallow crustal structure of the east pacific rise at 9 30 n compressional wave travel times from a seismic tomography experiment at 9 30 n on the east pacific rise are analyzed by a new tomographic method to determine the three dimensional seismic velocity structure of the upper 2 5 km of oceanic crust within a 20 18 km2 area centered on the rise axis the data comprise the travel times and associated uncertainties of 1459 compressional waves that have propagated above the axial magma chamber a careful analysis of source and receiver parameters in conjunction with an automated method of picking p wave onsets and assigning uncertainties constrains the prior uncertainty in the data to 5 to 20 ms the new tomographic method employs graph theory to estimate ray paths and travel times through strongly heterogeneous and densely parameterized seismic velocity models the nonlinear inverse method uses a jumping strategy to minimize a functional that includes the penalty function horizontal and vertical smoothing constraints and prior model assumptions all constraints applied to model perturbations are normalized to remove bias we use the tomographic method to reject the null hypothesis that the axial seismic structure is two dimensional three dimensional models reveal a seismic structure that correlates well with cross and along axis variations in seafloor morphology the location of the axial summit caldera and the distribution of seafloor hydrothermal activity the along axis segmentation of the seismic structure above the axial magma chamber is consistent with the hypothesis that mantle derived melt is preferentially injected midway along a locally linear segment of the rise and that the architecture of the crustal section is characterized by an en echelon series of elongate axial volcanoes approximately 10 km in length the seismic data are compatible with a 300 to 500 m thick thermal anomaly above a midcrustal melt lens such an interpretation suggests that hydrothermal fluids may not have penetrated this region in the last 103 years asymmetries in the seismic structure across the rise support the inferences that the thickness of seismic layer 2 and the average midcrustal temperature increase to the west of the rise axis these anomalies may be the result of off axis magmatism alternatively the asymmetric thermal anomaly may be the consequence of differences in the depth extent of hydrothermal cooling

paleomagnetic evidence for low temperature emplacement of the phreatomagmatic peperino albano ignimbrite colli albani volcano central italy the peperino albano approximately 19 36 ka old is a phreatomagmatic pyroclastic flow deposit cropping out along the slopes of the associated albano maar colli albani volcano italy the deposit exhibits lateral and vertical transitions from valley pond to veneer facies as well as intracrater facies we present the results of a paleomagnetic study of thermal remanent magnetization trm of the lithic clasts of the peperino albano ignimbrite that provide quantitative estimates of the range of emplacement temperatures across the different facies of the ignimbrite emplacement temperatures estimated for the peperino albano ignimbrite range between 240 and 350 c with the temperatures defined in the intracrater facies being generally lower than in the valley pond and veneer facies this is possibly due to the large size of the sampled clasts in the intracrater facies which when coupled with low temperature at the vent were not completely heated throughout their volume during emplacement the emplacement temperatures derived from the paleomagnetic results are in good agreement with the presence of un burnt plants at the base of the ignimbrite indicating that the temperature of the pyroclastic flow was lower than the temperature of ignition of wood paleomagnetic results from the peperino albano confirm the reliability of the paleomagnetic approach in defining the thermal history of pyroclastic flow deposits

estimating the approximate firing temperature of burnt archaeological sediments through an unmixing algorithm applied to hysteresis data abstract estimating the temperature to which burnt archaeological sediments and soils have been exposed in antiquity is of interest as it may well elucidate the interpretation of specific features certain semi industrial activities such as metal working or the production of pottery are often associated with the controlled use of intense high temperature processes 500 c exposure to such high temperatures will inevitably lead to the thermal alteration of commonly found iron minerals within the soil magnetic measurements made on a series of soil samples subjected to controlled laboratory heating confirms both the sensitivity of iron minerals to thermal alteration and also suggests a correlation between the maximum exposure temperature and the hysteresis properties from this data a method for estimating the maximum exposure temperature of burnt archaeological samples recovered from similar soil types is proposed based on the application of a linear unmixing model this model compares hysteresis data from the archaeological samples to an end member data set created from the laboratory heated soil the maximum exposure temperature for the archaeological samples is estimated from the relative proportion of known temperature end members present within the final model describing the experimental hysteresis data the validity of the model is demonstrated through application to samples recovered from a series of actualistic fire experiments and a range of burnt archaeological features recovered during excavation of a multi period site at yarnton near the city of oxford uk a further application of the method to determine the fidelity of samples collected for archaeomagnetic dating is presented from the excavation of a large hearth type features at whitby north yorkshire uk

three archaeomagnetic applications of archaeological interest to the study of burnt anthropogenic cave sediments abstract recent archaeomagnetic studies carried out on mid to late holocene burnt anthropogenic cave sediments have shown that under certain conditions these materials are suitable geomagnetic field recorders archaeomagnetic analyses carried out on these contexts constitute a rich source of information not only for geophysical purposes in terms of reconstructing the variation of earth s magnetic field in the past but also from the archaeological point of view for example by archaeomagnetic dating here we report three different archaeomagnetic applications to the study of burnt cave sediments i archaeomagnetic dating ii determining palaeotemperatures and iii assessing post depositional processes the first case study is a dating attempt carried out on a late holocene bronze age burnt level from el mirador cave burgos spain using the directional european secular variation curve several dating intervals were obtained for the last burning of this combustion feature considering the archaeological evidence and the independent radiometric 14 c dating available the possible ages obtained are discussed this is the first archaeomagnetic dating obtained in these contexts so far the second case study is an application of the method to determine the last heating temperatures reached by the carbonaceous facies of these fires stepwise thermal demagnetization of oriented samples can be used to quantitatively estimate heating temperatures an intermediate normal polarity component interpreted as a partial thermo remanence ptrm with maximum unblocking temperatures of 400 450 c was systematically identified revealing the last heating temperatures experienced by this facies these temperatures were confirmed with partial thermomagnetic curve experiments finally archaeomagnetic analyses on a partially bioturbated burning event were performed in order to evaluate until what spatial extent the burnt sediments were affected by post depositional mechanical alteration processes for each case study the archaeological implications are discussed highlighting the potential of archaeomagnetic methods to retrieve archaeological information

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

are burnt sediments reliable recorders of geomagnetic field strength abstract this study tests if burnt soils and sediments can provide reliable records of geomagnetic field strength at the time of burning by carrying out an experiment to reproduce the prehistoric use of fire on a clayish soil substratum rock magnetic experiments showed that in the upper 0 1 cm of the central part of the burnt surface remanence is a thermoremanent magnetization carried by single domain magnetite and that samples are thermally stable fourteen specimens from that area were subjected to paleointensity experiments with the coe method 1967 an intensity of 42 9 5 7 t was estimated below 440 c whereas at higher temperatures magneto mineralogical alterations were observed corresponding successful microwave intensity determinations from two specimens gave a mean value of 47 6 t both results are in reasonable agreement with the expected field value of 45 2 t burnt soils of archeological fires thus have the potential to record accurately the paleofield strength and may be useful targets for archeointensity investigations coincident results obtained from two different paleointensity determination methods support this conclusion

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

a preliminary secular variation reference curve for archaeomagnetic dating in austria the construction of a secular variation sv reference curve for a region for which little or no archaeomagnetic directions are available is presented here a sv curve is illustrated for austria centred on radstadt 47 38 n 13 45 e and based on data from sites in other countries less than 500 km away the published data were selected on site characteristics of n 3 and k 50 and dated within 400 yr this yielded 170 directions from which a sv curve was derived using bayesian techniques the obtained reference curve represents the past 2300 yr new data mainly from austria substantiate this curve and confirm the validity of the techniques employed which can therefore be applied for similar situations another test has been made using the german reference curve for dating the austrian archaeological sites here a systematic shift to older times in the order 30 110 yr occurs

estimating baking temperatures in a roman pottery kiln by rock magnetic properties implications of thermochemical alteration on archaeointensity determinations summary absolute past geomagnetic field intensity determinations requiring laboratory heating are labourious and the success rate is rather low mostly because of induced thermochemical magnetic mineral alterations archaeomagnetic intensity determinations are mainly limited to displaced ceramics produced in kilns in this study the suitability of an in situ baked structure is investigated different magnetic properties of baked material taken from the combustion chamber wall and floor of a roman pottery kiln with variable colouring are examined in dependence on the distance to the combustion chamber the temperature distribution is re constructed based on rock magnetic experiments after stepwise heating the rock magnetic temperature estimates agree fairly well with a mathematical heat conduction model demonstrating the penetration of heat into the combustion chamber wall the rock magnetic results show that blackish and greyish coloured kiln parts that had been in close contact with the fuel during ancient kiln operation are not suitable for intensity determinations although sufficiently baked they strongly alter during laboratory heating and new remanence carrying minerals are formed the brownish coloured material at a distance 65 80 mm away from the combustion chamber seems to be most suitable as its magnetic properties remain nearly unchanged during laboratory heating rock magnetic and modelled temperature estimates for this material consistently indicate ancient baking temperatures of about 600 c the model demonstrates that cooling takes longer in the inner parts of the combustion chamber wall retarded cooling affects the blocking temperatures and hence the strength of the thermoremanent magnetization the variability of cooling rates should be taken into account when investigating archaeointensities of specimens cut from large samples or of samples taken from different parts of a kiln

preservation of anthropogenic materials under different geochemical processes a mineralogical approach minerals that are preserved or formed inside the sediment or soil can be used to determine whether primary anthropogenic constituents bones phytoliths organic matter charcoal etc would have been affected by diagenesis stability diagrams of the minerals that describe the chemical system under investigation can be constructed and then tested in the field in this approach it is assumed that the stability of the archaeological material of interest is known except for bone there are not many studies on the stability of other archaeological materials this approach does not provide information on the former presence of an archaeological material in the sediment or soil but only whether these materials are stable in such an environment some indirect indication may be provided by unique mineral associations but much more has to be done in this direction

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

scanning electron microscope analysis of sediments from tabun cave mount carmel israel received 6 february 1984 revised ms accepted 30 august 1984 scanning electron microscope analysis of sediments from tabun cave has revealed a detailed palaeoenvironmental history for the area basal units garrod s f and g layers derive from wind blown materials intermediate units e are wind blown derivatives but with marine modification and the upper units d b c exhibit only aeolian modification to grain surfaces as had been previously postulated the analyses also provide supporting evidence for chemical alteration phases within the sediments keywords scanning electron microscope aeolian sub aqueous sediment cave environmental reconstruction introduction prehistoric cave sediments have been studied for at least the past 40 years lais 1941 most workers especially those active in europe bonifay 1956 miskovsky 1973 laville 1975 have tended to use the same analytical tool kit generally consisting of grain size and morphometric studies and a few chemical mineralogical analyses such as ph calcimetry organic matter clay and heavy mineral studies within the last decade however other techniques have begun to make their impact both as independent methods in their own right or as complements to more classical procedures principal among these are micromorphology goldberg 1979a b and scanning electron microscopy em of quartz grains tankard 1974 bull 1981a b this latter technique is now becoming more widely accepted as recent statistical analysis culver et al 1983 has shown that the various suites of quartz grain surface textures can be used to indicate past environments of modification as was initially intimated nearly 20 years ago see krinsley doornkamp 1973 for review in this study we present an application of the technique to an archaeologically related problem cf tankard 1974 and attempt to show how these results and interpretations compare with those based on more classical sedimentological techniques goldberg 1973 1980 farrand 1979

the black layer of middle palaeolithic combustion structures interpretation and archaeostratigraphic implications certain aspects of the formation processes of simple flat archaeological combustion structures such as those present in the middle palaeolithic record remain unexplained such kind of combustion structures are commonly affected by postdepositional agents and often their only distinct well preserved component is a thin black lens on the ground hence understanding the nature of this black lens is essential towards archaeological interpretation from an interdisciplinary microstratigraphic approach we present a case study in which for an entire experimental series of flat combustion structures the black layer represents the fire altered topsoil on which the fire was made parallel analysis of archaeological middle palaeolithic combustion structures from the site of el salt alicante spain reveal similar patterns leading to significant implications for archaeological interpretation in the light of these results special attention must be paid to the formation processes of flat middle palaeolithic combustion features as black layers and the material contained in them are not necessarily linked with combustion but with preceding activities or events in such cases black layers represent intact remnants of occupation surfaces concealing significant behavioural and palaeoenvironmental information relevant to the reconstruction of middle palaeolithic societies

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

archaeomagnetic secular variation in germany during the past 2500 years summary the german archaeomagnetic data set was supplemented with 35 new directions from ger man sites mainly dating from the past 3000 yr together with archaeomagnetic data from the neighbouring countries of germany a database of 166 reliable archaeomagnetic directions has been compiled for the reference area which is defined by a 500 km radius circle around gottingen the retrieved directions come from well dated archaeological structures and about 40 per cent of the dating relay on natural science methods such as radiocarbon thermolumines cence dendrochronology dating or historical documents from this data set a secular variation sv reference curve has been calculated using a bivariate algorithm which fits a natural cubic spline based on roughness penalty to declination inclination and time simultaneously the error tube surrounding this curve was obtained from bayesian modelling of the experimental errors which can also take stratigraphic information into account the obtained sv reference curve for the past 2500 yr is similar to that from france but also significant differences are seen comparison of the curves does not show a simple westward drift of the sv pattern the german reference curve allows archaeomagnetic dating in the reference area and extends this dating technique to sites situated in middle europe

bone preservation in kebara cave israel using on site fourier transform infrared spectrometry abstract the distribution of bones in kebara cave israel is very heterogeneous in order to address the question of whether the bone concentrations were created secondarily by differential dissolution or represent the original burial distributions a portable fourier transform infrared spectrometer ftir was operated on site it was used to map the distribution of the minerals in the sediments in order to delineate the zone in which original ash derived calcite was preserved as well as the zone in which carbonate apatite dahllite was still preserved the bone distribution in the former zone must be primary as calcite is less stable than dahllite the mineral phase of bone the boundary between the zone containing dahllite in the sediments and the zone in which it was absent also essentially mapped the southernmost distribution of bones in the cave the distribution of bones in the dahllite zone is thus also likely to be original supporting this notion was the observation that the bones at the periphery of the concentrations were not less well preserved than those in the centre except at one location which coincided with the boundary of the dahllite zone in the third zone the bones appear to have been lost by dissolution the operation of an ftir on site proved to be an efficient and useful method for resolving this important archaeological problem

a regional archeomagnetic model for europe for the last 3000 years scha dif 3k applications to archeomagnetic dating 1 the available european database of archeomagnetic field values and instrumental data has been used to produce a regional model for the geomagnetic field in europe for the last 3000 years from 1000 b c to 1900 a d connecting with the epoch covered by the igrf models this new model scha dif 3k constitutes an improvement with respect to the previous regional archeomagnetic model scha di 00 f which used relocated values and was only valid for the last 2000 years the new model has been obtained by least sums of absolute deviation inversion of paleomagnetic data using spherical cap harmonics for the spatial representation of the field and sliding windows in time an algorithm has been developed to jointly model the three archeomagnetic elements declination inclination and intensity the resulting model provides the direction and intensity of the earth s magnetic field over the european continent northern africa and western asia for the last 3000 years the fit to the european archeomagnetic database is more accurate than that provided by global archeomagnetic models in addition this model represents a step forward in archeomagnetic dating studies since the relocation error is avoided and can also be used to study the rapid changes of the geomagnetic field archeomagnetic jerks that have been recently proposed

new directional archeomagnetic data of burned cave sediments from switzerland and geomagnetic field variations in central europe this paper presents new directional archeomagnetic data from nine meso neolithic fireplaces sampled in a cave shelter at arconciel in western switzerland rock magnetic measurements indicate a homogenous magnetic mineralogy in all fireplaces with magnetite as the main magnetic carrier the remanent magnetization is stable and generally shows one characteristic directional component nine new directions which were obtained from arconciel are combined with 356 other archeomagnetic data from a circular area with a radius of 700 km around this site to obtain a penalized least square spline fit for the past 9000 yr we found in general good agreement with other local compilations such as the balkan curve the regional scha dif 8k model and with lake sediments from uk fennoscandia and switzerland nevertheless a time lag of several centuries is observed for a declination maximum between the archeomagnetic spline fit and the other european data records around 5900 bc this time lag is also observed in the swiss lake sediment record therefore we interpret this shift as a local feature of the earth s magnetic field

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

a matlab tool for archaeomagnetic dating a matlab tool for archaeomagnetic dating has been developed in this work well dated palaeosecular variation curves psvcs can be used to date archaeological artefacts with unknown ages the archaeomagnetic direction declination and or inclination and the archaeointensity obtained from the archaeological artefact are compared with a master psvc in addition historical lava flows with controversial ages can be dated using this methodology the dating process follows the descriptions given by lanos 2004 which is based on the combination of temporal probability density functions of the three geomagnetic field elements here we develop an interactive tool in matlab code to carry out archaeomagnetic dating by comparing the undated archaeomagnetic or lava flow data with a master psvc the master psvcs included with the matlab tool are the different european bayesian curves and those generated using both regional and global geomagnetic field models a case study using all the psvcs available in europe and some undated archaeomagnetic data has been carried out to analyze how the different psvcs affect the dating process in addition the dating uncertainty and the relocation error have been analyzed in the european region results show that some regional bayesian psvcs and the regional scha dif 3k archaeomagnetic model are the best choices to obtain an accurate date in europe moreover when it is available the full geomagnetic field vector must be used for archaeomagnetic dating

regional modeling of the geomagnetic field in europe from 6000 to 1000 b c we have developed a first low degree regional geomagnetic model for the european continent valid for the period 6000 1000 b c from a selected compilation of sedimentary and archeomagnetic data the scha dif 8k model this model provides information about both direction declination and inclination and intensity of the earth s magnetic field by connecting it with our previous model scha dif 3k valid from 1000 b c to 1900 a d and the igrf we furnish continuous geomagnetic field information for the last 8000 years in europe it has been developed using the revised spherical cap harmonic analysis in 2 dimensions technique r scha2d and using the norm of the earth s magnetic field to constrain the inversion problem the size of the cap is 22 and the maximum degree of the expansion is 2 the linearization problem was solved by using the truncated taylor s series applied to the expressions representing the relationship between the declination inclination and intensity data and the cartesian components of the geomagnetic field we used the geocentric axial dipole gad field as our initial or reference field for time we used the classical sliding overlapping window method the size of the window was set to 100 years shifted by 50 years we compared the model s prediction with the input data with the global cals7k 2 model and with new independent data the regional model shows a better fit to the input and to the independent data than the global model especially in terms of intensity and agrees with the virtual axial dipole moment given by other studies for the last 8000 years the european geomagnetic field has recorded rapid changes or archeomagnetic jerks the average field for the last 8000 years in europe is indistinguishable from the gad field

palaeomagnetic studies of burned rocks an assemblage of rocks such as comprising a fireplace will acquire a remanent magnetization upon cooling parallel to the ambient geomagnetic field and thus will share a common direction of magnetization detailed palaeomagnetic analyses of oriented samples will reveal whether these rocks have remained in situ since the last heating event or whether these rocks have moved or represent discard material thermal demagnetization makes it possible in many cases to estimate the maximum temperature which a given rock has experienced the direction of magnetization can be used to reposition rocks to their cooling position and the cooling history of boiling stones can be reconstructed for some rocks this paper presents results obtained from burned rocks from various archaeological sites

first directional european palaeosecular variation curve for the neolithic based on archaeomagnetic data neolithic cha1colithic and bronze age anthropogenic cave sediments from three caves from northern spain have been palaeomagnetically investigated 662 oriented specimens corresponding to 39 burning events ash carbonaceous couplets from the three sites with an average of 16 samples per fire were collected 26 new archaeomagnetic directions have been obtained for the time period ranging from 5500 to 2000 yr ca bc these results represent the oldest archaeomagnetic directions obtained from burnt archaeological materials throughout all western europe magnetisation is carried by pseudo singie domain low coercivity ferromagnetic minerals magnetite magnetite with no significant isomorphous substitution and or maghaemite rock magnetic experiments indicate a thermoremanent origin of the magnetisation although a thermochemical magnetisation cannot be excluded combination of the new data presented here and the recent updated bulgarian database allows us to propose the first european palaeosecular variation psv curve for the neolithic a bootstrap method was applied for the curve construction using penalised cubic b splines in time the new palaeosecular variation curve is well constrained from 6000 bc to 3700 bc the period with the highest density of data showing a declination maximum around 4700 bc and a minimum in inclination at 4300 bc which are not recorded by the recent global calslok 1 b and regional scha dif 8k models due to the use of lake sediment data dating resolution by using the proposed psv curve oscillates from approximately 30 yr to 200 yr for the period 6000 to 1000 yr bc reaching similar resolution as radiocarbon dating considering the good preservation age control and widespread occurrence of burnt archaeological materials across southern europe they represent a new source of data for geomagnetic field modelling as well as for archaeomagnetic dating

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

distribution analysis of errors due to relocation of geomagnetic data using the conversion via pole cvp method implications on archaeomagnetic data summary secular variation master curves are built up using geomagnetic historical observations or archaeomagnetic data from a limited area and their use is usually restricted to regions of around 1000 km radius relocation of data within this distance is a common practice to enable comparison of data although the errors due to such process are rarely taken into account a detailed analysis of the distribution of relocating geomagnetic data has been done using three popular sets of geomagnetic models igrf 9 gufm and cals7k 2 this study improves the error analysis of relocating geomagnetic directions made up to date and expands it to geomagnetic intensities maximum errors correlate with the non dipole to dipole field ratio archaeomagnetists could use this analysis to valuate the error introduced by reducing data

three millennia of directional variation of the earth s magnetic field in western europe as revealed by archeological artefacts directional secular variation of the geomagnetic field over the last 2000 years has been defined in western europe from numerous archeomagnetic studies however the number of archeomagnetic results for older periods is much more limited for this reason we present new data obtained from fired archeological structures found in two french sites loupiac and aspiran dated within the first millennium b c latest bronze earliest iron age transition 850 700 b c and iron age 525 475 b c respectively from a compilation of archeomagnetic results from western europe great britain italy and france and northern africa tunisia we propose a directional secular variation curve for western europe that covers the entire first millennium b c this curve exhibits a large clockwise motion with rapid changes during the first half of the millennium while the last four centuries b c are characterized by weak variations

formation processes through archaeobotanical remains the case of the bronze age levels in el mirador cave sierra de atapuerca spain el mirador site has a sequence formed by burnt dung resulting from pastoral activities during the bronze age and the neolithic period because there is a high sediment variation in the profile facies descriptions were used to guide the archaeologists in their work paleobotanical and mineralogical analyses were used to describe and understand the formation of the facies from the mir 4 level furthermore the paleobotanical results serve to reconstruct the landscape in atapuerca during the bronze age most seeds recovered are from triticum aestivum durum but other cereals and also leguminoseae and fruits have been identified charcoal analysis has yielded mainly deciduous and evergreen quercus pollen analysis has revealed a low arboreal cover with pinus quercus and riverside trees most of the pollen record corresponds to herbs such as poaceae and asteraceae all these results indicate a mosaic of different biota with forest pastureland and cultivated fields near the site most of the phytoliths come from the leaves and stems of festucoid grasses however there are some differences in the phytolith type and number the amount of faecal spherulites the mineralogical composition and the percentage of multicellular structures that indicate that not all the facies in the site have been formed in the same way thus the work carried out has demonstrated that some facies are related more to agricultural activities than to pastoralism activities and that other facies have been affected by incipient diagenetic processes

geomagnetic field variations in western europe from 1500 bc to 200 ad part ii new intensity secular variation curve abstract in order to extend the secular variation curve svc of archaeointensity in western europe to the first millennium bc we studied 24 kilns and hearths in place two displaced hearths and six sets of pottery sherds from french archaeological sites archaeological artefacts radiocarbon and dendrochronology dated the acquisition of the thermoremanent magnetization trm carried by the studied objects rock magnetism experiments suggest that the main carrier of the magnetization is a ti poor titanomagnetite archaeointensity was determined by the thellier thellier classical protocol with ptrm checks a strict criteria set was applied to select only the most reliable results with linear nrm trm diagrams 55 of total specimens this study demonstrates that pottery sherds with two trms give reliable archaeointensities in the low temperature interval if the nrm trm diagram is adequately adjusted eighteen new mean archaeointensities 14 corrected from the anisotropy of trm and 16 from cooling rate were computed the comparison with previously published western europe paleointensities show a strong dispersion between data primarily due to their variable quality western europe data were weighted following the archaeointensity protocol the number of specimens per site and the type of studied materials in order to better highlight the secular variation of archaeointensity during the first millennium bc the svc built with sliding windows of 160 years shifted every 50 years presents at paris a maximum of 90 t around 800 bc and a minimum of 60 t around 250 bc these archaeointensity maximum and minimum correspond to cusps of the geomagnetic field direction in western europe this new curve is consistent with mesopotamian and eastern europe data the archaeointensity secular variation in western europe predicted by global geomagnetic models cals3k 4 arch3k 1 and arch3k cst 1 is smoother than our svc we used our directional dataset herve et al 2013 to build a new western europe vgps and vdms mean curves comparison with the predictions given by the global models points out a possible persistent non dipole fields effect over europe between 1000 bc and 600 500 bc finally we note that the strong variations of intensity of the geomagnetic field with a mean decrease rate per century close to 6 t will be useful for archaeomagnetic dating purposes

palaeomagnetic determination of emplacement temperature of vesuvius ad 79 pyroclastic deposits the city of herculaneum was hurried under 20 m of pyroclastic deposits during the ad 79 eruption of vesuvius whose crater is only 7 km to the east these deposits have been interpreted as the deposits of mudflows1 or hot pyroclastic flows2 5 maury s studies6 of incinerated wood in herculaneum demonstrate heating to at least 400 c we have studied the variation of remanent magnetism with temperature for specimens taken from the deposits including specimens of the matrix material and of embedded lithic fragments we conclude that the temperature of the deposit at emplacement is unlikely to have been greater than 400 c which further supports the interpretation of the pyroclastic deposits at herculaneum as largely ignimbrites hot pyroclastic flow deposits

crustal resistivity structure at 9 50 n on the east pacific rise results of an electromagnetic survey 1 we report the first results of an extensive electromagnetic survey of the east pacific rise epr at 9 50 n which used the magnetometric resistivity mmr technique to measure the electrical resistivity structure of the seafloor in the vicinity of the spreading center ten seafloor magnetometers were deployed in areas of known hydrothermal activity in axial sites devoid of venting and further off axis to a distance of approximately 4 km data collected at off axis sites show higher seafloor resistivities than at axial sites this response is opposite to that expected from porosity controlled resistivity structure with a thicker high porosity extrusive layer 2a off axis as required by seismic data an explanation for the reduced axial resistivities is that the uppermost few hundred meters of crust are much hotter beneath the ridge crest than a few kilometers off axis lowering the pore fluid resistivity

volcanic eruption of the mid ocean ridge along the east pacific rise crest at 9 45 52 n direct submersible observations of seafloor phenomena associated with an eruption event in april 1991 in april 1991 we witnessed from the submersible alvin a suite of previously undocumented seafloor phenomena accompanying an in progress eruption of the mid ocean ridge on the east pacific rise crest at 9 45 n 52 n the volume of the eruption could not be precisely determined although comparison of pre and post eruption seabeam bathymetry indicate that any changes in ridge crest morphology resulting from the eruption were 10 m high effects of the eruption included 1 increased abundance and redistribution of hydrothermal vents disappearance of numerous vent communities and changes in characteristics of vent fauna and mineral deposits within the eruption area since december 1989 2 murkiness of bottom waters up to tens of meters above the seafloor due to high densities of suspended mineral and biogenic particulates 3 destruction of a vent community by lava flows mass wasting and possible hydrovolcanic explosion at a site known as tubeworm barbecue in the axial summit caldera asc at 9 50 6 n 4 near critical temperatures of hydrothermal vent fluids ranging up to 403 c 5 temporal variations over a 2 week interval in both temperatures and chemical isotopic compositions of hydrothermal fluids 6 unusual compositions of end member vent fluids with ph values ranging to a record low of 2 5 salinities ranging as low as 0 3 wt nacl one twelfth that of seawater and dissolved gases reaching high concentrations 65 mmol l for both co2 and h2s 7 venting at temperatures above 380 c of visually detectable white vapor that transformed to plumes of gray smoke a few centimeters above vent orifices 8 disorganized venting of both high temperature fluids black and gray smoke and large volumes of cooler diffuse hydrothermal fluids directly from the basaltic seafloor rather than from hydrothermal mineral constructions 9 rapid and extensive growth of flocculent white bacterial mats species unknown on and under the seafloor in areas experiencing widespread venting of diffuse hydrothermal fluid and 10 subseafloor downslope migration of magma normal to the ridge axis in a network of small scale 1 5 m diameter lava tubes and channels to distances at least 100 200 m outside the asc we suggest that in april 1991 intrusion of dikes in the eruption area to 200 m beneath the asc floor resulted in phase separation of fluids near the tops of the dikes and a large flux of vapor rich hydrothermal fluids through the overlying rubbly cavernous lavas low salinities and gas rich compositions of hydrothermal fluids sampled in the eruption area are appropriate for a vapor phase in a seawater system undergoing subcritical liquid vapor phase separation boiling and phase segregation hydrothermal fluids streamed directly from fissures and pits that may have been loci of lava drainback and or hydrovolcanic explosions these fissures and pits were lined with white mats of a unique fast growing bacteria that was the only life associated with the brand new vents the prolific bacteria which covered thousands of square meters on the ridge crest and were also abundant in subseafloor voids may thrive on high levels of gases in the vapor rich hydrothermal fluids initially escaping the hydrothermal system white bacterial particulates swept from the seafloor by hydrothermal vents swirled in an unprecedented biogenic blizzard up to 50 m above the bottom the bacterial proliferation of april 1991 is likely to be a transient bloom that will be checked quickly either by decline of dissolved gas concentrations in the fluids as rapid heat loss brings about cessation of boiling and or by grazing as other organisms are re established in the biologically devastated area

assessing post depositional processes in archaeological cave fires through the analysis of archaeomagnetic vectors abstract this paper presents a methodological application of archaeomagnetism and rock magnetism as a tool to evaluate post depositional mechanical alterations in archaeological cave fires most taphonomic and post depositional studies on anthropogenic sediments have mainly focused on the diagenetic alterations that these contexts undergo from a geochemical point of view however physical alterations are still largely assessed from mere macroscopic observations of the burnt facies comprising these fires this paper compares the archaeomagnetic directions recorded in the ashes of two holocene fires from the mirador cave sierra de atapuerca burgos spain one apparently well preserved and the other clearly bioturbated vector analyses of archaeomagnetic directions together with the study of magnetic properties combined with field macroscopic observations can provide a powerful tool to assess when a fire is actually in situ the anisotropy of magnetic susceptibility ams in both fires exhibits a dominant sedimentary fabric produced by compaction and also exhibits differences between the areas mechanically disturbed within these fires from those which are not the following set of magnetic features was identified when an archaeological fire preserves its primary position i univectoral and high intensity nrm orthogonal demagnetisation diagrams in ashes ii koenigsberger q n ratio values higher than unity indicative of an undisturbed thermo remanence trm or a partial thermoremanence p trm and iii a good clustering of characteristic directions defining an statistically representative mean archaeomagnetic direction the concurrence of these observations can be used as criterion to determine when an archaeological cave fire is physically in situ thus allowing a correct interpretation of the archaeological record

storage or cooking pots inferring pottery use through archaeomagnetic assessment of palaeotemperatures abstract in this paper we report the results of an archaeomagnetic and rock magnetic study performed on a set of neolithic and chalcolithic potsherds from el portalon de cueva mayor site sierra de atapuerca burgos spain to investigate their thermal history and obtain information about their function during ancient times two types of palaeomagnetic behaviour have been observed one yields stable and univectorial magnetization diagrams type 1 while the other yields multivectorial diagrams with an intermedium component interpreted as a partial thermoremanence p trm type 2 acquired during a partial reheating of the pottery during their use to investigate the connection of these two types with the ancient function of the potsherds a set of modern pots was experimentally fired and then partially reheated al known temperatures the results obtained reproduced patterns similar to those observed in the archaeological samples type 1 univectorial samples that reached only a high heating temperature 600 c during their manufacture were most probably used as storage vessels by contrast type 2 multivectorial samples probably recorded a p trm acquired during their last use reheating related to cooking activities

linking site formation processes to magnetic properties rock and archeomagnetic analysis of the combustion levels at riparo gaban italy this study focuses on archeomagnetic directional data that are obtained from combustion levels in the riparo gaban rock shelter northern italy in order to assess the degree of disturbance in the sediments and to provide new information to evaluate evolution of the geomagnetic field in the mid holocene combustion levels consist of ash rubefied levels or partially burned material and mixtures of these or polygenic material rock magnetic investigations show that superparamagnetic to single domain magnetite is the main carrier of the remanent magnetization but small amounts of hematite and maghemite may also be present in the different materials rock magnetic parameters e g the koenigsberger ratio q or the reversibility of thermomagnetic can be related to the degree of burning and the dispersion parameter k to the degree of preservation the grouping of archeomagnetic directions of a specific level is strongly dependent on the degree of physical disturbances directional means from thirteen levels can be compared with reference curves for paleosecular variation based on geomagnetic field models and other archeomagnetic data the data from this study are in agreement with other archeomagnetic data from the balkans in the time period 4900 bc to 4600 bc