Abstracts

An Early Bronze Age Necklace from Tell Abu Al–Kharaz, Jordan Valley

The aim of this study is the investigation of the Early Bronze Age necklace (N405) which was unearthed at Tell Abu al-Kharaz in 1991. The necklace consists of beads of both man-made and shaped natural materials including parts of mollusc shells. The context in which the necklace was discovered, which also showed an Egyptian connection, will be described. The scientific methods used in the characterization of the beads include XRD (X-ray diffraction) analysis, long and short ultraviolet fluorescence and Instrumental Neutron Activation Analysis (INAA). The molluscs were also classified.

Adsorption of ions onto high silica volcanic glass

Chemical fingerprint techniques are frequently applied to airborne volcanic eruption products, so-called tephra, such as ash and pumice for archeological and geoscientific purposes. However, in some cases, a meaningful interpretation of the results is complicated by superficial contaminations. Therefore, this situation was simulated by the use of powdered rhyolitic pumice to investigate its capability to adsorb several ions from aqueous solutions. Using neutron activation analysis, adsorption could be proven for Cr3+, Cr2O72- (dichromate), Fe3+, Co2+, HAsO42- (hydrogen arsenate), Rb+, Sr2+, Cs+, Ba2+, La3+, Ce3+, Ce4+, Sm3+, Th4+ and UO22+, which is a clear evidence for the interaction of those ions with the volcanic glass. In our experiments, pumice powder showed the ability to adsorb ions in the range from 1.8 mg kg-1 (in case of HAsO42-) to 5.8 wt% (in case of Fe3+). Adsorption is probably due to ion-exchange reactions. It could also be shown that a few ions are not adsorbed in detectable quantities: Na+, K+, Fe2+, Zn2+ and Nd3+. The knowledge about adsorption of ions enables us not only to examine the possible influence of contaminations where chemical fingerprinting methods are applied to volcanic material for archaeometry, but it also suggests the technical application of pumiceous materials for technical purposes, like water purification or as an adsorbent in the final storage of nuclear waste. In another series of INAA supported experiments, the influence of chemicals like ascorbic acid, acetic acid, HCl, HF, HNO3, H2O, H2O2, H3PO4, H2SO4, NaOH and NH3 on the bulk composition of pumice powder was investigated--resulting in no detectable change. We conclude that superficially contaminated tephra can be washed in diluted HF to remove contaminations without influencing the chemical fingerprint.

NAA of the "Minoan pumice" at Thera and comparison to alluvial pumice deposits in the Eastern Mediterranean Region

Neutron activation analysis was used to determine up to 30 elements in the pumice layers from the "Minoan eruption" at Thera (Santorini, Greece), Mt Pilato (Lipari, Italy) and in alluvial pumice from coasts of the Eastern Mediterranean region. The morphologically well distinguishable layers of the "Minoan pumice" were found to be of nearly similar composition in respect to the elements determined and their distribution patterns could therefore be used to identify a sample as Santorinian or not. Additionally, this method was applied to pumice lumps found during archaeological excavations in the Nile delta, Egypt. The results showed that two of the three Egyptian samples are products of the Minoan eruption at Thera and therefore chronologically useful. A second group of pumices collected at Antalya (Turkey), Crete (Greece) and also in Egypt was found to have a distinctly different composition and is therefore related to another volcanic event.

Freeze Dried Samples of Volcanic Gases - a New Method for the Determination of Trace Elements by NAA

A new routine technique for the determination of trace elements in volcanic gases by NAA is presented. For time and money saving reasons this method is applicable to samples, collected by the conventional method. This technique uses evacuated glass bottles, partly filled with NaOH solution to absorb acidic gas components and CO2, which is the main constituent of the incondensable gas fraction at ambient conditions. The application of NAA to samples collected by this method shows two main sources of difficulties: drying of NaOH without loosing volatile elements of interest (in particular Hg and Se) and the high activities of 24Na after neutron irradiation. The first can be avoided by liquid irradiation, thereby limiting the irradiation time, the second excludes the determination of short and medium lived nuclides because of the high gamma-background due to 24Na. A new freeze drying technique enables the application of long irradiation times and therefore the use of long-lived activation products for analysis. The samples of volcanic gases were collected at the fumarole fields of La Fossa volcano on the island Vulcano, Southern Italy. This technique allows very sensitive determinations of trace elements in volcanic gases and adds highly valuable information to the understanding and modeling of volcanic gas sources.

A comparison of new techniques for the determination of minor and trace elements in volcanic gases by NAA

Minor and trace elements in gaseous effluents from active volcanic areas could be useful indicators for hydrothermal activity. The knowledge of their elemental distribution contributes to a better understanding of degassing processes from various sources. Several methods for the sampling of volcanic gases for NAA are presented and discussed. Absorption by activated charcoal, alkaline solutions like ammonia solution, tetraethylammoniumhydroxide and tris(hydroxymethyl)aminomethane and 7LiOH solutions were tested in addition to the conventionally applied NaOH solution. The tests were performed mainly at the fumarole fields of La Fossa volcano on the island Vulcano, Southern Italy. Diluted ammonia solution gave the best results.

INAA of Aegean pumices for the classification of archaeological findings

Instrumental neutron activation analysis (INAA) was used to determine 29 elements in pumice from several volcanic sources (Milos, Nisyros, Yali, Kos and Thera) in the Aegean Sea, Greece, to establish a data basis for the identification of pumice and tephra layers found in archaeological context. The widespread products of the "Minoan Eruption" of the Thera volcano can now be distinguished clearly from all other sources and will be used to establish a datumline in the Eastern Mediterranean Region in the second millenium B.C. The elements Al, As, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Ti, Th, U, V, Yb and Zr were determined in 14 samples from Milos, 25 samples from Nisyros, 7 samples from Yali, 7 samples from Kos and 17 samples from Thera. Two cycles of irradiation and four measurement runs were applied. The results were compared and suitable groups, typical for each island, were classified. Due to insufficiently comparable data sets, the criteria for distinguishing the different sources have not been revealed by previous studies. This basic knowledge was used to relate pumice from excavations in Tell-el-Daba (Egypt) and Bronze Age Knossos to their specific volcanic origin.

Separation and Analysis of Theran Volcanic Glass by INAA, XRF and EPMA

Pumice from the "Minoan eruption" on Thera (Cyclades, Greece) was investigated to reveal the differences between the composition of the bulk material, which contains a certain percentage of crystallites, and the pure glass phase. This is important for the identification of vitric tephra layers found in the Eastern Mediterranean region in archaeological context and in deep sea drilling cores. Eruption products, deposited at some distance, have usually lost their crystalline fraction due to gravity separation and consist only of glass shards. Only major element distributions in such layers and in pumiceous glass phases have been published up to now, but these data are not sufficient for a reliable identification of the volcanic source, as several other eruptions are known to have produced chemically very similar layers in this region (Milos, Nisyros, Yali, Kos). Therefore, a technique has been developed to separate the glass phase from the primary pumice to reveal differences in the trace element distributions obtained by instrumental neutron activation analysis (INAA). X-ray diffractometry and microscopical techniques were applied to check the purity of this fraction. The concentrations of the major constituents, in particular Al, Ca, Fe, K, Mg, Mn, Na, Si, and Ti were determined by X-ray fluorescence (XRF) and electron probe microanalysis (EPMA), those of Al, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Ti, Th, U, Yb and Zr by instrumental neutron activation analysis and partly also by X-ray fluorescence. Subtle differences between the compositions of the glass phase and the bulk material are explained by differentiation during partial crystallization and their applicability to the classification of tephra layers is demonstrated.

South Aegean Volcanic Glass: Separation and Analysis by INAA and EPMA

Pumice from the major volcanic sources (Milos, Nisyros, Yali, Kos and Santorini) in the South Aegean region was investigated to reveal the differences between the composition of the bulk material, which contains a certain percentage of crystallites, and the pure glass phase, which is the main constituent. The knowledge of these differences is important for the identification of vitric tephra layers found in the Eastern Mediterranean region in archaeological context, in deep sea drilling cores and lake sediments. Eruption products, deposited at some distance, show not only a decrease in their grain size, but also have usually lost their crystalline fraction due to gravity separation and consist only of glass shards. Major element distributions in such layers and in pumiceous glass are not sufficient for a reliable identification of the volcanic source, as several eruptions are known to have produced chemically very similar tephra layers in this region. Trace element data, especially of the rather immobile rare earth elements (REEs), can provide greater information on tephra originating from different volcanic eruptions. Therefore, a technique has been developed to separate the glass phase from different primary pumices to reveal differences in their trace element distributions. The concentrations of the major constituents, in particular Al, Ca, Fe, Mg, Mn, Na, Si, and Ti were determined by electron probe microanalysis (EPMA), those of Al, As, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Th, Ti, U, V, Yb and Zr by instrumental neutron activation analysis. Subtle differences between the compositions of the glass phase and the bulk material are explained by differentiation during partial crystallization. Their applicability to the classification of tephra layers is demonstrated.

Classification of archaeologically stratified pumice by INAA

In the framework of the major research scheme "Synchronization of Civilizations in the Eastern Mediterranean Region in the 2nd Millenium B.C." instrumental neutron activation analysis (INAA) was used to determine 30 elements in pumice from archaeological excavations to reveal their specific volcanic origin. The widespread pumiceous products of several eruptions in the Aegean region were used as abrasive tools and were therefore popular trade objects. A remarkable quantity of pumice and pumiceous tephra (several km3) was produced by the "Minoan eruption" of Thera (Santorini), which is assumed to have happened between 1450 and 1650 B.C. Thus the discovery of the primary fallout of "Minoan" tephra in archaeologically stratified locations can be used as a relative time mark. Additionally, pumice lumps used as abrasive can serve for dating by first appearance. Essential to an identification of the primary volcanic source is the knowledge that pumices from the Aegean region can easily be distinguished by their trace element distribution patterns, as previous work has shown. The elements Al, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, Ti, U, V, Yb, Zn and Zr were determined in 16 samples of pumice lumps from excavations in Tell-el-Dab'a and Tell-el-Herr (Egypt). Two irradiation cycles and five measurement runs were applied. A reliable identification of the samples is achieved by comparing these results to the database compiled in previous studies.

An Early Bronze Age Necklace from Tell Abu al-Kharaz, Jordan Valley

The aim of this study is the investigation of an Early Bronze Age necklace, which was unearthed at Tell Abu al-Kharaz, Jordan Valley, by the Swedish Jordan Excavation under the direction of the co-author in 1991 (see i.a. the basic reports in Fischer 1991, 1993-1996, 1997a, 2000). The necklace consists of beads of both man-made and shaped natural materials including parts of molluscs. The context in which the necklace was discovered and which also showed an Egyptian connection will be described. The relative and absolute dates, the latter of which is based on radiocarbon AMS-datings, will be presented. The scientific methods used in the characterization of the beads include X-ray Diffractometry, KUV and LUV Fluorescence and Instrumental Neutron Activation Analysis (INAA). The molluscs were also classified.

Classification of prehistorical artefacts of obsidian by INAA

During archaeological excavations in Miletos (Turkey) under the direction of Prof. Dr. W.D. Niemeier (University of Heidelberg) four obsidian (volcanic glass) artefacts have been found in strata of an age of 3500 to 5500 years. Since no deposit of obsidian exists in the direct vicinity of this settlement, the question about the origin of this material arose. Samples of obsidian from Milos, Giali (both Aegean islands, Greece) and Lipari (Italy) were compared to the four artefacts from Miletos. Instrumental neutron activation analysis (INAA) was applied to determine a suitable set of elements, in particular Al, As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, U, Yb, Zn, and Zr. Differences in the element distributions were observed and used for the identification. Possible Anatolian sources are excluded by comparison to analytical data from the literature. Additional X-ray powder diffraction measurements were carried out to check the samples for significant crystalline phases in the glassy matrix. According to the elemental distribution, the material of the artefacts is from Milos, three of them belonging to the sources at Agia Nychia and one to Demenegakion.

Geochemical correlation of archaeological sites using Tephra from the Minoan eruption

Pumice and volcanic ash from different localities in the Middle East region were analysed for major and trace element contents using instrumental neutron activation analysis (INAA). Samples of alluvial pumice found in archaeological excavations of Early to Middle Bronze age (~3500 y. B.P.) from Egypt, Palestine and Israel could be correlated to the different possible volcanic eruption events in the Aegean Sea. Volcanic ash beds as primary deposits of the Minoan eruption of the Santorini volcano between 1650 ­ 1450 B.C. were traced throughout the Aegean islands, drill cores from the Mediterranean and the Black sea and in Anatolia. This study lead to a new interpretation of the main distribution of volcanic ash falls from this eruption. Therefore, primary ash beds can be used as direct chronological tracers, whereas pumice found in excavations can only be used for dating by first appearance.

182Hf, a new isotope for AMS

The neutron-rich isotope 182Hf with its half-life of 9±2 million years [1] was alive in the early solar system and has been used to study the early development of the Earth and the Moon through isotopic anomalies of its stable decay product 182W. In addition, 182Hf may also complement a few other radionuclides in the million-year half-life range to trace relatively recent stellar events with high neutron fluxes in the vicinity of the Earth. This may be accomplished by finding measurable traces of live 182Hf in suitable terrestrial archives. With accelerator mass spectrometry (AMS) it should be possible to detect minute amounts of 182Hf. We will show that the main interference for the detection, the stable isobar 182W, can be significantly reduced by using HfF ions. The AMS detection method of 182Hf and first results from Hf control rods of a recently retired research reactor are presented, which encourage us to search for naturally produced traces of 182Hf on Earth.

Identification of pumice and volcanic ash from archaeological sites in the Eastern Mediterranean Region using chemical fingerprinting

The volcanic layer of the ³Minoan² eruption of the Thera volcano between 1450 and 1650 B.C. is a clear time marker in the stratigraphy of the surrounding area. Therefore, the general idea of this study was to settle the volcanic products of this major eruption, which lasted only a few days, within the relative archaeological chronologies of the Eastern Mediterranean region in correlation to its different time frames. Although the date of the eruption is still object of intense debates , the eruption products can be used as tangible evidence for contemporaneity or at least post-eruption dating of the respective strata wherever found within well-defined stratigraphies of an archaeological site. The majority of the erupted material consists of chemically rather homogeneous pumice and pumiceous flow deposits, the so-called ³Minoan tuff² or ³Oberer Bimsstein² (Bo, upper pumice ). Generally, the term tephra designates all fragmental volcanic ejecta produced during an eruption. The volume estimations for the tephra output of the Minoan eruption range from 16 to 35 km3 of dense rock equivalent . The impact on the contemporary civilizations is evident and alluvial pumice as well as direct fallout from the eruption cloud is reported from several sites on Greek islands and Asia Minor (see e.g., and references therein). The fallout formed a synchronous layer of volcanic ash (tephra with grain size £ 2 mm) that can be used directly as a datum line. Provided a reliable identification, it can be used for chronology wherever found in primary deposits. Pumice, on the contrary, floats on water and was transported over large distances all over the Eastern Mediterranean region due to marine currents and wind . It can be assumed that within weeks after the eruption large amounts of pumice were accumulated along the shorelines. Pumice is a quite useful abrasive which has been collected and traded since prehistoric times. The applicability for chronological purposes has been checked in earlier studies by demonstrating that the ³Minoan³ pumice is sufficiently homogeneous and can be distinguished from the numerous other Aegean pumice sources by comparing normalized trace element distribution patterns (³chemical fingerprinting²) . Additionally, these studies have shown that instrumental neutron activation analysis (INAA) is a perfectly suitable technique to identify such material. Nevertheless, for the identification of tephra deposits in greater distance to the volcano a chemically relevant effect has to be considered. The erupted material consists mainly of highly vesicular silicate glass (pumice) with a certain percentage of crystals having formed during melt ascent (e.g., pyroxene, quartz, feldspar, titanomagnetite). Several elements are enriched in these mostly sub-mm sized crystals, which numerically decrease with growing distance from the volcano due to separation by gravity . Previous studies from our working group showed significant differences in the compositions between bulk pumice and the pure glass fraction. The occurrence of Minoan tephra deposited directly from the eruption cloud is not restricted to the Aegean region. It has also been found in lake sediments from Köycegiz, Gölcük Gölü, Gölhisar Gölü (Turkey) and even in deep-sea cores from the Black Sea . The estimated orientation and extent of the tephra layer differs greatly depending which types of deposits (e.g. lacustrine and continental deposits, deep-sea drill cores) are considered. This is due to the difficulty to decide whether deep-sea tephra layers have been produced by fallout from the eruption cloud or if there is a major contribution by sunken, fragmented, and compacted pumice. The amount of this contribution is governed by the direction of the marine currents and the time span until the pumice starts to sink. Experiments and observations have shown that this can last for months and therefore a significant amount can be expected even in areas where actually no eruption cloud fallout has been deposited.

Search for Live 182Hf in Deep-Sea Sediments

The presence of live 182Hf (half-life 9 Ma) in the early solar system is well established but the understanding of its abundance is still challenging. Live 182Hf is expected to be present in the interstellar medium (ISM) as a result of recent nucleosynthesis activity. We are attempting a search for live 182Hf possibly deposited on Earth. The search focuses on deep-ocean sediments and a method for chemical extraction of the Zr-Hf fraction from sediments has been developed. The detection of 182Hf is performed at the Vienna Environmental Research Accelerator (VERA). Measurements of Hf and W isotopic abundances for the Zr-Hf fraction extracted from deep-sea sediment samples were performed. Present limits for the 182Hf abundance derived from the measured isotopic abundances are discussed.

Application of INAA to reveal the chemical evolution of selected volcanic eruptiva from Santorini, Greece

The pumiceous products of the large-scale explosive eruptions at Santorini show a high grade of similarity in their optical appearance as well as in their chemical composition. The demand for a clear classification of these eruption products raised from archaeological research, where pumice can be interpreted as a ³post-eruption² time marker. The aim of this work was to find elements that underwent significant changes because of geochemical processes and that could be indicative for a distinction of pumice produced by the five major explosive eruptions. INAA of 25 elements allows a clear classification and contributes new information to the chemical evolution of Santorini volcano.

New half-life measurement of 182Hf: Improved chronometer for the early solar system

The decay of 182Hf, now extinct, into stable 182W has developed into an important chronometer for studying early solar system processes such as the accretion and differentiation of planetesimals and the formation of the Earth and the Moon. The only 182Hf half-life measurements available were performed 40 years ago and resulted in an imprecise half-life of (9 ± 2) x 106 y. We redetermined the half-life by measuring the specific activity of 182Hf based on two independent methods, resulting in a value of t1/2(182Hf) = (8,90 ± 0,09) x 106 y, in good agreement with the previous value, but with a 20 times smaller uncertainty. The greatly improved precision of this half-life now permits very precise intercalibration of the 182Hf / 182W isotopic system with other chronometers.

182Hf ­ From Geophysics to Astrophysics

182Hf is a so-called ³extinct² radionuclide interesting for both geophysical and astrophysical studies. The discovery of live 182Hf in the early solar system through isotopic anomalies of stable 182Win meteorites opened up an important application as a chronometer for the formation of the Earth and Moon. In addition, 182Hf plays an important role for the understanding of nucleosynthesis of heavy elements in stellar environments, since both r- and s-processes can be responsible for the high abundance in the early solar system. In contrast to most other extinct radionuclides there is no significant natural or anthropogenic production of 182Hf on Earth. Thus finding live 182Hf on Earth today would be a strong indication for introduction of material from recent nucleosynthesis, e.g. from nearby supernovae. This paper gives a short overview of applications and summarizes recent and ongoing experimental nuclear physics measurements of 182Hf.

Neutron Activation Analysis of Pumice from Lipari, Italy, and Identification of a Pumice Find from the Excavation at Tel Megadim, Israel

16 pumice samples produced by the youngest eruption sequences of Mt. Pelato (Island of Lipari, Italy) were analyzed with Instrumental Neutron Activation Analysis (INAA) for their major and trace element contents, in particular Al, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sm, Ta, Tb, Th, Ti, U, V, Yb, Zn, and Zr. A pumice from the archaeological excavation in Tel Megadim, Israel, could be correlated to this volcanic source, using its chemical fingerprint. This result, together with the background information about the well dated eruption cycles of this volcano lead to the assumption that trade connections between cultures in Palestine and the Tyrrhenian region existed during the Persian Period (approx. between the 6th and 3rd century B.C.), in spite of the long distance of over 2000 km.

Zur Identifikation von Bimssteinfunden aus Grabungen in Tel Megadim und Aegina Kolonna

Im Rahmen des internationalen Forschungsprogramms SCIEM2000 (Synchronisation von Zivilisationen im östlichen Mittelmeerraum im 2. Jahrtausend v.Chr.) wurde eine analytisch-geochemische Datenbank für die Identifizierung von vulkanischem Gestein aus archäologischen Grabungen erstellt. Diese Datenbank beinhaltet die Konzentrationen von 25 für den jeweiligen Ausbruch charakteristischen Haupt- und Spurenelementen in den Produkten von 22 explosiven Eruptionen im mediterranen Raum. Erfasst sind die Vulkaninseln Lipari (Italien), Milos, Santorini, Nisyros, Giali, Kos (Griechenland) und 5 Zentren in Kappadokien (Türkei). Unter bestimmten geochemischen Bedingungen (vor allem hohe SiO2 - Konzentrationen), die zu Eruptionen mit stark explosivem Charakter führen, wird überwiegend Bimsstein unterschiedlicher Korngröße erzeugt. Dieser besteht hauptsächlich aus aufgeschäumtem Silikatglas, schwimmt auf Wasser und wird als Treibgut weit verfrachtet. Zusätzlich zu dieser natürlichen Verbreitung macht ihn seine Verwendbarkeit als Schleifmittel und Baustoff auch heute noch zu einer begehrten Handelsware. Aber auch kultische Verwendung ist nachgewiesen worden. Die Instrumentelle Neutronenaktivierungsanalyse (INAA) hat sich als geeignete Methode erwiesen, Bimssteinfunde aus archäologischen Grabungen mit der entsprechenden Eruption zu korrelieren. Sowohl das komplette Verteilungsmuster der bestimmten Elementkonzentrationen (³chemischer Fingerabdruck³) als auch die Auswahl einiger besonders geeigneter Elemente können zur Klassifikation herangezogen werden. Im Zuge dieser Arbeiten wurden bisher 388 Bimssteinproben aus archäologischen Grabungen identifiziert. In jüngster Vergangenheit untersuchte Proben aus Tel Megadim und Ägina Kolonna lieferten überraschende Ergebnisse, werden hier exemplarisch vorgestellt und demonstrieren die hervorragende Eignung der INAA für derartige Anwendungen.