Ioannis Liritzis

Portable XRF of Archaeological Artifacts: Current Research, Potentials and Limitations

Portable X-ray fluorescence (PXRF) serves as an effective, rapid and non-destructive, method for determining the elemental composition of natural and man-made materials, such as ceramic, glaze, glass, obsidian, pigments, paint, and metal artifacts; based on the analysis, the determination of their origin, technological and production issues, comparative studies, and more knowledge in the field of cultural heritage can be aimed at. The wavelengths of the released energy, known as fluorescent X-rays, are detected and measured by spectrograph in the energy dispersive and wavelength manner of detection. Since only the surface of an object is studied, in dimensions that typically range within some millimeters, care needs to be taken that corrosion and decay do not affect the analysis. A world survey of the major applications of PXRF in the analysis of various cultural material types is reported, and the available PXRF setups are described. A review of the results of obsidian characterization and clustering is included, and the advantages, reliability, and limitations are discussed, with particular emphasis on the calibration procedures.

Surface dating by luminescence: an overview

Daylight radiation resets luminescence ‘clock’ to zero on rock surfaces, but transmission depends on the transparency of the rock. On burial, surfaces are no longer exposed to daylight and accumulation of trapped electrons takes place till the excavation. This reduction of luminescence as a function of depth fulfils the prerequisite criterion of daylight bleaching. Thus rock artefacts and monuments follow similar bleaching rationale as those for sediments. In limestone and marble, daylight can reach depths of 0.5–1 mm and up to 16 mm respectively, while for other igneous rocks e.g. quartz in granites, partial bleaching occurs up to 5mm depth under several hours of daylight exposures and almost complete beaching is achieved in the first 1 mm within about 1 min daylight exposure. The ‘quartz technique’ for limestone monuments containing traces of quartz enables their dating with Optically Stimulated Luminescence (OSL) techniques. The surface luminescence (thermoluminescence, TL or OSL) dating has been developed and further refined on various aspects of equivalent dose determination, complex radiation geometry, incomplete bleaching etc. A historical review of the development including important applications, along with some methodological aspects are discussed.

Luminescence dating in archaeology, anthropology and geoarchaeology: an overview

Introduction.- Luminescence Dating Protocols and Dating Range.- Dose Rate.- Luminescence Dating of Archaeological Materials.- Luminescence-Based Authenticity Testing.- Luminescence Dating in Geomorphological and Geoarchaeological Research in Europe: Application Examples.- Meteoritic Impacts, Tsunamis.- Conclusions.

Dating implications from solar bleaching of thermoluminescence of ancient marble

We present measurements of Thermoluminescence (TL) from Greek marble quarried at Paros, Naxos, Pendeli, Hymitos, Thassos, which have been known since ancient times. The results concern i) the solar bleaching of TL, ii) the solar transmission through marble thicknesses up to 16 mm, and iii) the implications for potential dating of ancient carved marble monuments/objects. The bleaching rate for marbles is very fast during the first hour of exposure. The solar penetration is at least 35 mm for long exposures. Beyond the 2 mm marble slab for exposure times 90–120 hours of sunshine, the residual bleached TL level is not reached. The bleached TL reaches a plateau which serves as the “zero time” upon which the archaeological TL dose subsequently builds up and gives the age of a marble monument.

Thermoluminescence dating of ceramics revisited: Optical stimulated luminescence of quartz single aliquot with green light-emitting diodes

Two archeological ceramic sherds in a single quartz aliquot form have been dated success-fully for the first time, by the newly developed method of optical stimulated luminescence (OSL) with green light-emitting diodes (LED). Comparison with the conventional thermoluminescence (TL) method provided ages of the same order of magnitude. The ceramics come from two recently excavated sites at “Hellenikon” and “Ligourio” in Argolid, Peloponnese, Greece. One sherd dates from the end of 4th millenium B.C., while the other is classified around 7th c. B.C.. The new method of nuclear dating is described in the paper and appropriately evaluated.

Dating of hydrated obsidian surfaces by SIMS-SS

A new approach to dating ancient obsidian artifacts based on the modeling of water diffusion profiles is evaluated using multiple archaeological test cases of known age. Hydrogen profiles from hydrated obsidian surfaces have been collected by secondary ion mass spectrometry (SIMS). The H2O concentration versus depth profiles are modeled and diffusion ages have been produced. SIMS based dates for fourteen obsidian specimens of well-known age, ranging from 300-7000 years old, have been compared with radiocarbon ages. The convergence between the two dating methods is excellent and validates the new dating approach.

Geophysical prospection, archaeological excavation, and dating in two Hellenic pyramids

Geophysical prospection employing magnetometry and electromagnetic measurements has been applied in and around two small sized pyramids of Hellenikon and Ligourio in Argolid, Greece. The magnetic anomalies appropriately assessed were interpreted as possible archaeological targets. Subsequent test excavations revealed the presence of room foundations and parts of walls, as well as a plethora of ceramic ware. Typological study of the ceramics classified them to as early as the proto-Helladic period and to as late as the first centuries A.D. The earlier periods have been also confirmed by a novel application of thermoluminescence (TL) dating of ceramics and the megalithic stones themselves. The present results question earlier attempts classifying these pyramids at the Classical period and favour much earlier periods.

Time-lag of the Earthquake Energy Release Between Three Seismic Regions

Three complete data sets of strong earthquakes (M≥5.5), which occurred in the seismic regions of Chile, Mexico and Kamchatka during the time period 1899–1985, have been used to test the existence of a time-lag in the seismic energy release between these regions. These data sets were cross-correlated in order to determine whether any pair of the sets are correlated. For this purpose statistical tests, such as theT-test, the Fishers transformation and probability distribution have been applied to determine the significance of the obtained correlation coefficients. The results show that the time-lag between Chile and Kamchatka is −2, which means that Kamchatka precedes Chile by 2 years, with a correlation coefficient significant at 99.80% level, a weak correlation between Kamchatka-Mexico and noncorrelation for Mexico-Chile.

Deconvolution of optical stimulated luminescence decay curves

The Thermoluminescence (TL)-like presentation method introduced to describe the isothermal decay of a thermoluminescence glow-peak, is extended in the present work for the case of the Optical Stimulated Luminescence (OSL) decay curves. The Glow-Curve Deconvolution analysis extensively used to analyse TL glow-curves is successfully applied to find the individual components of the Optical stimulated decay curves. The method is successfully applied to both synthetic and experimental OSL decay curves of quartz, feldspar and mixed quartz plus feldspar aliquots. The potential use of the Peak Shaped (PS) TL-like presentation to extract qualitative and quantitative information from an OSL decay curves is also discussed.

Probable evidence for periodicities in global seismic energy release

A complete data set of globally distributed shallow (h ≤, 60 Km) earthquakes have been used for first time to test the possible existence of periodicities in the seismic energy release. Only main shocks of magnitude,M ≥ 7.0 were considered, which occurred in the whole Earth during 1898–1985. These magnitudes are converted in seismic energy, which is released during the occurrence of earthquakes, through Baths formula. The detection of such kind of periodicities is important in seismology, because these patterns may lead to the prediction of large earthquakes. Statistical techniques, such as Maximum Entropy (ME), and two Fourier approaches, the Fast Fourier Transform (FFT) and Power Spectrum (PS) of truncated subrecords of the whole time series have been applied to examine the possible existence of such periodicities in seismic energy release. Furthermore, the even-spacing technique is used to validate our results and a type-curve has been constructed for the data set.The results exhibit a network of periodicities with predominant periods at 3(±0.5), 4.5, 6.5, 8–9, 14–20, and 31–34 years. Some periods were occasionally interrupted. The latter implies that our time-series is not stationary, in that, the spectral peaks drift when the data are viewed through different time windows. The fact that the signal is weak and embedded in less accurate older data could contribute to this effect. The question of stability/validity of the apparently cyclic behaviour of the annual global seismic energy release, is one which requires further investigation.