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[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.

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Background: GEOMAGIA50.v3 for sediments is a comprehensive online database providing access to published paleomagnetic, rock magnetic, and chronological data obtained from lake and marine sediments deposited over the past 50 ka. Its objective is to catalogue data that will improve our understanding of changes in the geomagnetic field, physical environments, and climate. Findings: GEOMAGIA50.v3 for sediments builds upon the structure of the pre-existing GEOMAGIA50 database for magnetic data from archeological and volcanic materials. A strong emphasis has been placed on the storage of geochronological data, and it is the first magnetic archive that includes comprehensive radiocarbon age data from sediments. The database will be updated as new sediment data become available. Conclusions:The web-based interface for the sediment database is located at http://geomagia.gfz-potsdam.de/ geomagiav3/SDquery.php. This paper is a companion to Brown et al. (Earth Planets Space doi:10.1186/s40623-015-0232-0, 2015 and describes the data types, structure, and functionality of the sediment database.

S U M M A R YDetailed rock magnetic investigations were carried out on a set of samples with defined ratios of haematite and magnetite. The measured parameters provide a reference for interpreting common rock magnetic parameters in investigations of sediments. The contribution of haematite to the magnetic fraction must exceed 95 wt-% of the magnetic fraction when mixed with magnetite in order to visibly influence grain size and coercitivity indicative magnetic parameters. Coercivity of remanence (B CR ) and coercive force (B C ) do not change in the same way with increasing haematite content, which results in a peak B CR /B C value at around 99.5 wt-% haematite. Variations in haematite content can be ignored when interpreting most rock magnetic parameters, especially grain size indicative parameters for samples where haematite contents range from 0 to 98 wt-%. The S-ratio is still the most sensitive parameter for estimating the relative amount of haematite in magnetite/haematite mixtures. A combination of S-ratio, the saturation isothermal remanent magnetization divided by the low field magnetic susceptibility (SIRM/κ LF ) and B CR is the most effective way to identify haematite in natural samples . Our results agree with literature data and fill the gap between results obtained either from pure magnetite or haematite with comparable grain sizes.

Laminated lake sediments from the Dead Sea basin provide high-resolution records of climatic variability in the eastern Mediterranean region, which is especially sensitive to changing climatic conditions. In this study, we aim on detailed reconstruction of climatic fluctuations and related changes in the frequency of flood and dust deposition events at ca. 3300 and especially at 2800 cal. yr BP from high-resolution sediment records of the Dead Sea basin. A ca. 4-m-thick, mostly varved sediment section from the western margin of the Dead Sea (DSEn – Ein Gedi profile) was analysed and correlated to the new International Continental Scientific Drilling Program (ICDP) Dead Sea Deep Drilling Project core 5017-1 from the deep basin. To detect even single event layers, we applied a multi-proxy approach of high-resolution microscopic thin section analyses, micro-X-ray fluorescence (µ-XRF) element scanning and magnetic susceptibility measurements, supported by grain size data and palynological analyses. Based on radiocarbon and varve dating, two pronounced dry periods were detected at ~3500–3300 and ~3000–2400 cal. yr BP which are differently expressed in the sediment records. In the shallow-water core (DSEn), the older dry period is characterised by a thick sand deposit, whereas the sedimentological change at 2800 cal. yr BP is less pronounced and characterised mainly by an enhanced frequency of coarse detrital layers interpreted as erosion events. In the 5017-1 deep-basin core, both dry periods are depicted by halite deposits. The onset of the younger dry period coincides with the Homeric Grand Solar Minimum at ca. 2800 cal. yr BP. Our results suggest that during this period, the Dead Sea region experienced an overall dry climate, superimposed by an increased occurrence of flash floods caused by a change in synoptic weather patterns.

Corbetti caldera is the southernmost large volcanic system in Ethiopia, and has been categorized at the highest level of uncertainty in terms of hazard and risk. Until now, the number and frequency of past explosive eruptions at Corbetti has been unknown, due to limited studies of frequently incomplete and patchy outcrop sequences. Here we use volcanic ash layers preserved in sediments from three Main Ethiopian Rift lakes to provide the first detailed record of volcanism for the Corbetti caldera. We show that lake sediments yield more comprehensive, stratigraphically resolved dossiers of long-term volcanism than often available in outcrop. Our eruptive history for Corbetti spans the past 10 k.y. and reveals eruptions at an average return period of ~900 yr. The threat posed by Corbetti has until now been underestimated. Future explosive eruptions similar to those of the past 10 k.y. would blanket nearby Awassa and Shashamene, currently home to ~260,000 people, with pumice-fall deposits, and would have significant societal impacts. A lake sediment tephrostratigraphic approach shows significant potential for application throughout the East African Rift system, and will be essential to better understanding volcanic hazards in this rapidly developing region.