Testing the accuracy of portable X-ray fluorescence to study Aztec and Colonial obsidian supply at Xaltocan,Mexico

This article demonstrates the accuracy of non-destructive portable X-ray fluorescence (pXRF) for the study of obsidian in central Mexico. Obsidian sources were identified for a sample of 103 artifacts from the site of Xaltocan, which spanned the rise and fall of the Aztec empire and the first centuries of Spanish colonial rule (AD 900–1700). Sources were assigned by comparing pXRF measurements with previously published source data and were verified using the standard techniques of laboratory XRF (lXRF) and instrumental neutron activation analysis (INAA). Additional tests of potentially confounding factors show that neither length of read time, presence of surface residue, nor incomplete detector coverage due to small artifact size compromised our ability to attribute sources to artifacts. Concave surfaces did decrease the accuracy of readings because of the greater distance between the artifact and the detector. Our results provide new insight into the stability of supply networks and markets well into the Colonial period as well as the homogenizing tendencies of the Aztec market system.     

Patterning in procurement of obsidian in Chaco Canyon and in Chaco-era communities in New Mexico as revealed by X-ray fluorescence

X-ray fluorescence analysis of obsidian artifacts from sites located in Chaco Canyon and from three Chaco-era communities in New Mexico permits determination of their geological origin. These source data are used to describe patterning in obsidian procurement in sites located in Chaco Canyon dating from A.D. 500–1150, and in a three non-Canyon communities occupied during the period of Chaco Canyon's regional prominence (ca. A.D. 875–1150). These data demonstrate that the most proximate sources generally dominate the sourced obsidian assemblages from sites of all periods, but also suggest differences in procurement patterning both over time and across space. Within Chaco Canyon, there is a notable shift from Mount Taylor obsidian to use of Jemez Mountains sources over time. These data also suggest that earlier analyses of obsidian from sites in Chaco Canyon misidentified some obsidian artifact sources; these new data indicate the central areas of disagreement and provide a revision of procurement patterning. In the Chaco-era communities located outside Chaco Canyon, procurement patterning diverges. The Blue J community shows an increase in use of the nearby Mount Taylor source over time. Two communities located toward the southern extent of the Chaco great house distribution reveal a markedly distinct procurement pattern, obtaining nearly all of their obsidian from southern sources largely unrepresented at Chaco Canyon. Combined, these data provide new insights into raw material procurement and artifact production at sites in Chaco Canyon, and in communities occupied during the Chaco Phenomenon, the period of the Canyon's greatest regional influence.     

Evidence for volcanic ash fall in the Maya Lowlands from a reservoir at Tikal,Guatemala

Powder X-ray diffraction and petrographic analyses of reservoir sediments from Tikal, Guatemala have identified significant quantities of decomposed volcanic ash in the form of smectite and euhedral bipyramidal quartz crystals. X-ray fluorescence trace element content analysis was used to eliminate distant Sahara-Sahel and Antilles sources. The Zr/Y and Ni/Cr ratios of reservoir sediment from Tikal are consistent with a source from Central American volcanism (e.g., Guatemalan and Salvadoran). AMS radiocarbon dating of the smectite and crystalline quartz-rich reservoir sediments show that volcanic ash fell during the Preclassic, Classic, and Postclassic Maya cultural periods. It may now be possible to develop an effective chronology of ash fall at Tikal and the greater Peten.     

Evaluating effects of chemical weathering and surface contamination on the in situ provenance analysis of building stones in the Cuzco region of Peru with portable XRF

As the only type of instrument capable of determining artifact geochemistry in a wide variety of settings, portable X-Ray Fluorescence (PXRF) may be frequently utilized as probably the best option for collecting data when removal of objects in part or in whole is unfeasible. However, using PXRF in circumstances where sample selection and preparation diverge from standards developed for lab-based instrumentation requires assessing the impact of new and potentially limiting factors to establish the validity of the method in these new contexts. Here we examine the effects of surface contamination and chemical weathering on the ability to assess provenance of igneous building stones used in the Cuzco region of Peru. Surface contamination was assessed through comparing low-impact cleaning methods on diorite and andesite blocks, and weathering was examined by comparing weathered vs. fresh surfaces of samples from two andesite quarries. In general, the lightest elements were most impacted by contamination and weathering while measurements of many of the heavier elements commonly used in provenance studies were relatively unaffected. Concentrations of Pb and Zn were problematic in the urban context of Cuzco because of pollution. Ability to determine provenance of building stones within those limitations (i.e., the validity of this application of PXRF) was demonstrated in a preliminary study by comparing measurements from uncleaned, exposed building stones in the region to fresh quarry samples.     

便携式X射线荧光现场分析壁画颜料适用性研究——以西藏拉萨大昭寺壁画为例

便携式X射线荧光光谱仪作为快捷的无损分析技术,广泛应用于壁画文物的现场分析中.本文利用便携式X射线荧光光谱仪分析了西藏拉萨大昭寺转经廊壁画,选取部分样品,利用实验室X射线荧光分析,发现所分析颜料的主要显色元素具有一致性,并利用拉曼光谱确定了壁画颜料的成分.通过比较研究,发现便携式X射线荧光光谱仪可确定大部分色彩较为纯正的颜料的成分,同时,由于西藏拉萨大昭寺壁画颜料的杂多性,对于含砷的橙色颜料、含砷或含铅与含铁的黄色颜料、含铜砷的绿色颜料、含钙硫的白色颜料、群青与孔雀石的混合颜料则需结合拉曼光谱确定之.本研究工作显示,利用便携式X射线荧光光谱仪开展现场检测,可极大地减少实验室分析样品的取样数量,有利于壁画颜料的无损分析与微损分析.     

Precision in the X-ray fluorescence analysis of sixty-one Augustan quadrantes

Sixty-one Augustan quadrantes were analysed for calcium, iron, nickel, copper, silver, tin, antimony, and lead by X-ray fluorescence. Most coins contained about 99·7% copper with the other seven elements present as trace impurities. Significant differences in composition were found for the three different issues of quadrantes minted in c. 9 BC indicating that these issues were not minted exactly contemporaneously. Quadrantes minted in c. 4 BC have trace element concentrations in ranges that differ from those of the 9 BC quadrantes. The precision is very good for all trace elements (the precision of calcium was not calculated): average standard deviations are 0·0021% for Fe, 0·0026% for Ni, 0·0038% for Ag, 0·0014% for Sn, 0·0031% for Sb, and 0·015 for Pb.     

Geochemical provenance analyses of Roman lava millstones north of the Alps: a study of their distribution and implications for the beginning of Roman lava quarrying in the Eifel region (Germany)

In Roman times, rotary querns and different types of millstones, driven either by horse-capstan or water power, were produced in the lava quarries of the quaternary volcanic Eifel region and exported to many parts of the Empire. The geographic distribution of Roman lava millstones from the Eifel region provides important information about trade patterns and, in cases of well dated millstones, also allows an estimate as to when the Roman lava quarrying in the Eifel region began. Sixty-two millstones from Germany, France and Austria were sampled and analyzed for major and trace elements by X-ray fluorescence. To determine their provenance, the millstone data was evaluated by a combination of geochemical discrimination and cluster and discriminant analyses using an extensive and detailed database of all Roman lava quarries in the Eifel region. An Eifel provenance could be confirmed for forty-four artefacts and, furthermore, determined down to the exact lava flow. The affiliation of the other artefacts to other possible regions where millstones of comparable lava were extracted was carried out on the basis of geochemical data from the literature. However, because of insufficient data, only assumptions about the regional provenance can be made. The origins of the other finds are assumed to be the Vogelsberg region, the Massif Central, Orvieto, and, possibly, the Pannonian Basin. A preliminary map of the distribution of Eifel millstones in Roman times based on these data is presented; the beginning of Roman lava quarrying can be constrained to 8–7 BC.     

Geochemical discrimination of basaltic sources as a tool for provenance analyses of bifacial tools in the southern Levant: first results from the Jezreel Valley,Israel

The determination of groundstone tool sources bears the potential to examine aspects like raw material selection and preference, mobility, trade and exchange patterns, control over resources and long term use of raw material sources. The discovery of the Neolithic/Chalcolithic basanite bifacial quarry of Giv'at Kipod in the Jezreel Valley, Israel, provides the opportunity of raw material centred provenance studies of bifacials in the southern Levant. The basis for reliable provenance analyses is a clear geochemical characterization of the extraction site and its discrimination from other potential sources. To achieve this, the Miocene magmatic rocks of the Jezreel Valley were sampled and analysed by XRF and La-ICP-MS. The geochemical evaluation, combined with cluster analyses, resulted in a clear discrimination of the Giv'at Kipod lava from other basaltic sources in the area. Based on the geochemical field data, a Giv'at Kipod provenance for six bifacial tools found in three archaeological sites dated to the Neolithic and the Chalcolithic periods was established. The results suggest that the quarry was in use for several millennia. This pilot study demonstrates that for provenance analyses lava outcrops in the southern Levant can be geochemically discriminated from each other on a very small spatial scale, on the basis of a detailed field sampling and the application of multivariate methods.     

The use of SEM-EDS,PIXE and EDXRF for obsidian provenance studies in the Near East: a case study from Neolithic Çatalhöyük (central Anatolia)

In this paper we evaluate the relative analytical capabilities of SEM-EDS, PIXE and EDXRF for characterizing archaeologically significant Anatolian obsidians on the basis of their elemental compositions. The study involves 54 geological samples from various sources, together with an archaeological case study involving 100 artifacts from Neolithic Çatalhöyük (central Anatolia). With each technique the artifacts formed two compositional groups that correlated with the East Göllü Da? and Nenezi Da? sources. The non-destructive capabilities of these methods are emphasized (albeit with certain analytical limitations in the case of SEM-EDS), suggesting important new techniques for Near Eastern obsidian provenance studies.     

Obsidian provenance analyses at Göytepe,Azerbaijan: Implications for understanding Neolithic socioeconomies in the southern Caucasus

This study presents a provenance analysis of the Neolithic obsidian assemblages from the early to mid‐sixth millennium bc settlement at Göytepe, Azerbaijan. The study is unique in that (1) it involves a complete, non‐selected obsidian assemblage (901 artefacts) from one particular area of the site; (2) the material is derived from a well‐stratified sequence of 10 securely radiocarbon‐dated architectural levels; and (3) the use of an extraordinarily wide range of sources (more than 20) was identified by provenance analysis using energy‐dispersive X‐ray fluorescence. The results reveal a previously unknown diachronic change in obsidian use in the region, suggesting the occurrence of significant socioeconomic changes during the Late Neolithic of the southern Caucasus.     

中华民国三十四年中央银行纸币印刷颜料无损研究

法币在中国货币史特别是近代货币史上有着重要地位。1935年11月至1948年8月间,先后发行了15种从"壹分"到"壹萬圆"不同面额的法币,由中外十六家不同印刷公司承印,版别多达百余种。本研究利用超景深三维视频显微镜、激光显微共聚焦拉曼光谱仪和便携式X射线荧光光谱仪,对11枚1945年(中华民国三十四年)中央银行发行的壹仟圆法币的印刷颜料进行了无损研究。结果表明,红色部分(印章、冠字号、纹饰等)普遍使用了有机合成染料系列颜料红PR,而蓝色、绿色、棕色部分普遍使用了普鲁士蓝、铅铬黄和炭黑等颜料进行调配呈色。这些信息能够为纸币类文物的鉴别、保护修复以及相关研究提供依据。