[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.

ISSN : 0956-540XInternational audienceA Bayesian hierarchical modelling is proposed for the different sources of scatter occurring in archaeomagnetism, which follows the natural hierarchical sampling process implemented by laboratories in field. A comparison is made with the stratified statistics commonly used up to now. The Bayesian statistics corrects the disturbance resulting from the variability in the number of specimens taken from each sample or site. There is no need to publish results at sample level if a descending hierarchy is verified. In this case, often verified by archaeomagnetic data, only results at site level are useful for geomagnetic reference curve building. Typically, a study with at least 20 samples will give an α95i 5 per cent close to the optimal α95i for a fixed site number mi and if errors are random with zero mean (no systematic errors). The precision on the curve itself is essentially controlled, through hierarchical elliptic statistics, by the number of reference points per window and by dating errors, rather than by the confidence angles α95ij at site level (if a descending hierarchy). The Bayesian elliptic distribution proposed reveals the influence of the window width. The moving average technique is well adapted to numerous and very well dated data evenly distributed along time. It is not a global functional approach, but a (linear) local one

S U M M A R YThe German archaeomagnetic data set was supplemented with 35 new directions from German 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 Göttingen. 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, thermoluminescence, 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.

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S U M M A R YA catalogue has been compiled of existing published and unpublished archaeomagnetic directional data from sites in Germany. The data comprise 125 results dated mainly in the past two millennia. The stability of the natural remanent magnetization was proven for most structures with at least a Thellier viscosity test, although for the majority of the data the direction is based on the characteristic remanent magnetization obtained from demagnetization experiments. Rock magnetic experiments carried out on the samples from many of the sites reveal that the dominant magnetic carrier is magnetite, often oxidized or with impurities. For many sites the archaeological age estimate is supported by physical dating methods. While the Roman epoch (0-400 AD) and the period from medieval to modern times (800-1700 AD) are reasonably well covered with data, the time interval in between and the first millennium BC are only poorly covered. The geographical distribution of data throughout Germany shows a concentration along the Rhine valley during Roman times, with in general a better coverage to the north. Nevertheless this data set clearly shows the secular variation during the past three millennia, and it extends the European archaeomagnetic data set considerably.

SUMMARY 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.

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