Stabilization of the Tlaltecuhtli monolith pigments

A painted monolith, as important as the Aztec Calendar or the Coyolxauhqui, has been discovered in the ritual Aztec center of Mexico City. It represents Tlaltecuhtli, the bisexual manifestation of the Earth from whom all life comes. Still, pigments, which have lost their conglomerating resins, have to be retained. In this study, the consolidation of ochre pigment on original fragments from the Aztec sculpture is presented. Several compounds were tested as consolidants, on the one hand natural polysaccharides, Funori and Slobber of Nopal exudate, on the other derivatives of cellulose, Methocel^® and Klucel^®, and also commercial consolidants as KSE 300^® and Paraloid B72^®. To simulate the ageing of consolidated samples, they were treated in an Accelerated Weathering Tester. Then, both sets of samples, fresh and aged, were characterized structural, morphological and texturally by using X-ray diffraction, electronic microscopy and nitrogen adsorption, respectively. A leaching test was performed on consolidated samples to evaluate the consolidant efficiency.     

Organic–inorganic rock–fluid interactions in stylolitic micro‐environments of carbonate rocks: a FIB‐TEM study combined with a hydrogeochemical modelling approach

Stylolites and the interfaces to the host limestone have been investigated by means of a multidisciplinary analytical approach (thin section microscopy, FIB‐TEM, organic geochemistry and petrography). Carbonate dissolution assuming different boundary conditions was simulated by applying a generic hydrogeochemical modelling approach. It is the conceptual approach to characterize and quantify traceable organic–inorganic interactions in stylolites dependent on organic matter type and its thermal maturity, and to follow stylolite formation in carbonates as result of organic matter reactivity rather than pressure solution as a main control. The investigated stylolite samples are of Upper Permian (Lopingian, Zechstein), Middle Triassic (Muschelkalk) and Late Cretaceous (Maastrichtian) age and always contain marine organic matter. The thermal maturity of the organic matter ranges from the pre‐oil generation zone (0.4–0.5% R_r) to the stage of dry gas generation (>1.3% R_r). The results of the generic hydrogeochemical modelling indicate a sharp increase of calcite dissolution and the beginning of stylolite formation at approximately 40°C, which is equivalent to a depth of less than 800 m under hydrostatic conditions considering a geothermal gradient of 30°C and a surface mean temperature of 20°C. This temperature corresponds to the pre‐oil window when kerogens release an aqueous fluid enriched in carbon dioxide and organic acids. This aqueous fluid may change the existing pore water pH or alkalinity and causes dissolution of carbonate, feldspar and quartz, and clay mineral precipitation along the stylolite. Dissolution of limestone and dolostone leads to reprecipitation of calcite or dolomite opposite of the dissolution side, which indicates only localized mass redistribution. All these integrated hydrogeochemical processes are coupled to the generation of water during organic matter maturation. In all of the calculated hydrogeochemical scenarios, H₂O is a reaction product and its formation supports the suggested hypothesis.     

MULTIANALYTICAL STUDY OF PALAEOLITHIC REINDEER ANTLER. DISCOVERY OF ANTLER TRACES IN LASCAUX PIGMENTS BY TEM*

Palaeolithic and modern reindeer antler were analysed using complementary techniques to evaluate the conservation state of bone material. X‐ray diffraction, FT‐IR spectroscopy, scanning electron microscopy (SEM–EDX) and transmission electron microscopy (TEM–EDX) as well as proton induced X‐ray and γ‐ray emission (PIXE–PIGE) at the particle accelerator AGLAE, C2RMF were applied. This study enabled us to define the chemical and structural features of ancient antler at the micro‐ and nanometre scale and compare them to those of other bone materials such as bone and ivory. Antler is richer in its organic fraction compared to bone and ivory. Its mineral fraction, carbonated hydroxylapatite, shows very specific crystal shapes at the nanometre scale. This specific property allowed us to recognize antler traces in pigment samples originating from rock art paintings in the Lascaux cave, Dordogne, southwestern France, Magdalenian period. Therefore, TEM–EDX is the technique of choice for characterizing antler traces in complex mixtures. In the paint material of Lascaux, antler seems most likely to be a pollutant introduced either by stirring the pigments in water with a piece of antler or by carving antler artefacts next to the preparation of paint material. However, it could eventually be used as a marker of paintings that were created contemporaneously.     

New trials in the consolidation of waterlogged archaeological wood with different acetone-carried products

Some acetone-carried consolidants for waterlogged archaeological wood were tested in order to evaluate treatments able to save time and energy. In details, colophony (rosin), two esterified colophonies (Rosin 100^® and Rosin 459^®), a mixture of colophony with PEG 3400 and a vinyl acetate - vinyl versate copolymer (Vinavil 8020S^®) were tested. The treatments were carried out at temperatures of 20 and 35 °C on waterlogged maritime pine, elm, oak and beech. The materials came from the archaeological site of the ancient ships of Pisa (Tuscany, Italy) and were dated back to VII cent. BC – II cent. AD. To evaluate the processes, equilibrium moisture content and dimensional stability of treated wood samples at different relative humidity, and retention of impregnating products were measured; moreover macroscopic and microscopic examination were also run to respectively assess the shape and appearance of treated wood and the way of deposition of consolidants. The results highlighted that natural and modified colophony treatments gave the most satisfactory results both in the maintenance of shape and dimensions of samples and in the stabilization with respect to RH variations. Moreover, the equilibrium moisture contents of samples treated with R100 and R459 were much reduced in comparison to the other consolidants and to untreated archaeological wood. This fact was related to the high retention values of those products that occluded most of the porosity including the microporosity of cell walls. Therefore, in terms of higroscopicity treated wood was more similar to impregnating substances rather than to decayed wood. This fact was considered helpful in contrasting the moisture-related negative effects in cases of eventual faults in the climate control during e.g. exhibition and in protecting treated wood from the risks of new fungal attacks.     

南越国宫署土遗址防风化加固材料的效果比较

南越国宫署遗址为大型土遗址类型,1996年11月国务院公布为全国重点文物保护单位,由于挖掘时间较长,遗址场地条件有限,已经出现了不同程度的风化、粉化、开裂、局部坍塌等严重病害。为此本课题组经过前期分析测试研究,采用有机硅改性丙烯酸、PS材料、有机硅改性硅酸盐、硅酸酯类和无机-有机复合材料等几种常用土遗址防风化加固材料,对南越国宫署土遗址样块进行了加固效果对比测试,研究了加固前后土样各种性能的变化情况。研究发现:硅酸酯类和无机-有机复合材料加固土体具有很好的耐水性,耐盐破坏能力,抗压强度也有提高,并且不影响土体的外观和透气性;PS材料加固土体后透气性和渗透性虽好,但耐水性能较差,加固强度低,而且容易泛白;有机硅改性丙烯酸和有机硅改性硅酸盐材料加固后土样强度适中,但透气性、耐盐性和耐水性较差。可以看出硅酸酯类和无机-有机复合材料加固南越国宫署土样的效果较好,建议可进入现场试验评估阶段。     

The Ben Lawers Historic Landscape Project: Simultaneous Multi-element Analysis of Former Settlement and Arable Soils by X-ray Fluorescence Spectrometry

X-ray fluorescence spectrometry (XRFS) was used in the analysis of A horizon soil samples collected from a former farming settlement and its associated area of infield (i.e. arable) located in the Central Highlands of Scotland. To date, XRFS has not been extensively used in geoarchaeological research, but in our study the simultaneous multi-element capabilities of this instrumental technique allowed the total concentrations of 25 major, minor, and trace elements to be fully quantified with acceptable levels of accuracy and precision. Included within this group of chemical elements are a number (e.g. Ba, Ca, P, Pb, Sr and Zn) that have proved to be of value to archaeological interpretation in earlier investigations undertaken in Scotland. In our preliminary work documented here, significant differences were found between the A horizon soils of former settlement and infield areas for 18 chemical elements. Subjecting the XRFS data—and three other measured variables: soil organic carbon (SOC), pH and A horizon depth—to discriminant analysis indicates that soils of former settlement and arable farming can be effectively classified according to their pH, SOC content and Ca, Cu, Mg, Rb, and Zn concentrations. The inference is that areas of former infield and settlement elsewhere at this study location in the Central Highlands may be able to be identified according to their soil chemical composition and use of discriminant function, even though the surface remains of pre-eighteenth century settlement sites are not readily evident today because they were constructed of perishable materials.     

Organic-walled microfossils from the Early Cambrian of South Australia

Microfossils which are hollow, possess a two-layered vesicle wall, and occur as single elements or, more rarely, as compound forms, have been recovered from the Early Cambrian Heatherdale Shale, on the Fleurieu Peninsula, South Australia. The microfossils, which range in size from 4 to 14.5 μm, are informally and tentatively assigned to the genus Sphaerocongregus Moorman 1974. Superficially they resemble forms assigned to Pyritosphaera Love 1958 and its probable junior synonym, Bavlinella Shepeleva 1962. Topotypes of these genera, however, have yet to be studied using SEM techniques, and their morphologic details remain uncertain. The organic composition of the present microfossils is supported by energy-dispersive X-ray analyses. Samples of the Heatherdale Shale were also analysed using pyrolysis techniques; the organic matter is, however, over-mature with respect to petroleum generation, and no geochemical assessment of original kerogen type is possible.     

ORGANIC RESIDUE ANALYSIS IN ARCHAEOLOGY: THE ARCHAEOLOGICAL BIOMARKER REVOLUTION*

Organic residue analysis utilizes analytical organic chemical techniques to identify the nature and origins of organic remains that cannot be characterized using traditional techniques of archaeological investigation (because they are either amorphous or invisible). The field is founded upon the principle that the biomolecular, or biochemical, components of organic materials associated with human activity survive in a wide variety of locations and deposits at archaeological sites. The archaeological information contained in organic residues is represented by the biomolecular components of the natural products that contribute to the formation of a given residue. By applying appropriate separation (chromatographic) and identification (mass spectrometric) techniques, the preserved, and altered, biomolecular components of such residues can be revealed. Once identified, the Archaeological Biomarker Concept can be applied, wherein the structure and even isotopic composition(s) of a given biomolecule or suite of biomolecules (the ‘chemical fingerprint’) can be related to the compositions of organisms exploited by humans in the past. As the organic residue field emerges from its pre‐paradigmatic phase, and the organic residue revolution gathers pace, the way is open for challenging many long‐held archaeological hypotheses and offering new perspectives on the study of human activity in the past.     

Production and use of birch bark tar at the Neolithic pile-dwelling of Palù di Livenza (North-Eastern Italy) revealed by X-ray computed micro-tomography and synchrotron Fourier-transform infrared spectroscopy

Recent excavations at Palù di Livenza (northeastern Italy) revealed a multiphase Neolithic pile dwelling dated between ca. 4,300/4200 and 3,600 cal BC. Three lumps with teeth imprints and a larger amorphous piece from the Late Neolithic layers have been studied by X-ray computed micro-tomography (microCT) and synchrotron Fourier-transform infrared spectroscopy (FTIR). FTIR spectra match well that of birch bark tar and microCT of the larger piece has revealed a rolled-up structure likely corresponding to bark rolls. The lumps of birch pitch were probably chewed to soften the tar prior to be used as hafting adhesive or therapeutic substance. The rolled-up inner structure of the larger piece and the remains of birch bark tar and abundant charcoals on its surface suggest it probably corresponds to a rare waste product from allothermic tar production.     

丙烯酸非水分散体等几种土遗址防风化加固剂的效果比较

对丙烯酸树脂非水分散体等几种土遗址防风化加固剂进行了加固效果对比检验,包括加固前后土样各种性能的变化,如：重量、颜色、孔隙率变化,抗压强度的提高,耐水、耐冻融、耐盐能力的增加等。通过检验发现,在所试材料中丙烯酸树脂非水分散体加固刑在浓度非常低的情况下对土体就有加固作用,使土体具有很好的耐水性、耐冻触能力,耐盐破坏能力也有提高,并且不影响土体的外观和透气性。而其它材料如正硅酸乙酯、丙烯酸树脂、聚氨酯、聚酯等虽在一些性能上能满足需要,但还有一些方面不能满足要求。对比表明,丙烯酸非水分散体是一类优良的土遗址防风化加固剂。     

ARCHAEOMETRIC ANALYSES ON ‘CORINTHIAN B’ TRANSPORT AMPHORAE FOUND AT GELA (SICILY,ITALY)*

The aim of this work is to throw light on the archaic production of ‘Corinthian B’ amphorae, which are widely diffused in the Western Mediterranean basin and are also present in Greece, but whose geographical provenance is still under discussion. We analysed a group of 37 samples belonging to different ceramic classes dated to the sixth and fifth centuries bc . In particular, there were 19 sherds of trade amphorae of the so‐called archaic ‘Corinthian B’ type, from archaeological excavations in Gela (Sicily, Italy). As a comparison, we also investigated 18 samples of tiles and local coarse pottery from Sibari (Calabria, Italy). The samples were analysed using different techniques, such as optical analysis with a polarized‐light microscope (OM), X‐ray diffraction (XRD), Fourier transform–infrared absorption (FT–IR) and inductively coupled plasma–optical emission spectroscopy (ICP–OES). The combination of these complementary analytical methods allowed us to characterize the samples, determine their firing temperatures and identify the probable provenance. The study of thin sections of sherds by OM allowed us to divide the investigated amphorae into two main groups: the first was characterized by a composition that suggested a Western provenance, in particular from the Calabrian–Peloritan region; the second one was very similar to the ‘Corinthian B’ amphorae that come from Corinth and have been classified as ‘fabric class 1’ by Whitbread (1995 ). The XRD and FT–IR results permitted us to determine the mineral composition of the findings and to estimate their firing temperature. The ICP–OES technique was particularly useful in identifying the production centres. In fact, in the studied pottery, this analysis revealed Ni and Cr values that were noticeably different between Greek and southern Italian production.     

ENERGY DISPERSIVE X-RAY FLUORESCENCE ANALYSIS OF ANCIENT COPPER ALLOYS: EMPIRICAL VALUES FOR PRECISION AND ACCURACY

Energy dispersive X-ray fluorescence (EDXRF) analyses are compared with neutron activation as well as atomic absorption analyses of ancient copper-based alloys in order to examine their accuracy and to estimate realistic values for precision and sensitivity of EDXRF. The results show that it is possible to obtain reliable data of the surface composition of objects non-destructively. Better results for bulk composition are usually obtained with drill samples where the sensitivity of the method is at least competitive with atomic absorption spectroscopy with flame atomization.     

露天石质文物的风化和加固保护探讨

探讨了石质物风化的诸因素,认为主要来源于石材原料、物理因素、化学因素、生物因素和人为破坏等儿个方面,阐述了目前用于石质物加固保护的无机加固剂、有机加固剂的特点、应用及其加固技术,该工作对石质物加固保护具有指导意义。     

A non-invasive study of Roman Age mosaic glass tesserae by means of Raman spectroscopy

Ancient mosaic tesserae are a range of materials of very varied and complex nature, including pottery, stone and glass. Raman spectroscopy is a powerful tool for the analysis of all these kinds of materials. In the particular case of glasses, this technique can be used both for a study of surface weathering and for the characterization of bulk structure, but it has not yet been extensively used for the characterization of mosaic glass tesserae. We carried out Raman analyses on a set of Roman and Late Antiquity period mosaic glass samples, which allowed a good characterization of both the glass matrix and the crystalline inclusions. All the samples show the typical Raman signatures of soda-lime-silicate glasses. Several crystalline phases were also identified, being relics of raw materials used during the glass manufacturing process, such as quartz and feldspars, or linked to the glass color/opacification, such as bindheimite and cuprite. The analyses also led to the identification in some blue, turquoise and green tesserae of calcium antimonate, whose Raman signature has only recently been recognized in the scientific literature on mosaic glasses. Some emphasis is given to the analysis of red lead-containing tesserae, colored with Cu⁺ ions or even Cu⁰ (or Au⁰) metal nanoparticles. Samples with peculiar compositions, as well as “modern” (and restoration) samples, could quite easily be distinguished from the ancient ones by their Raman spectra.     

Short-chain n-alkanes (C16–20) in ancient soil are useful molecular markers for prehistoric biomass burning

The incorporation of plant biomass into soil usually leads to long-chain n-alkanes with a relative predominance of odd carbon numbered homologues. Contrastingly, an increase in short-chain even carbon numbered n-alkanes was found in charred biomass with progressing temperatures. We applied lipid analysis to buried ancient topsoils that contained charred organic matter and to corresponding control soils, which were characterized by a lighter color and lower contents of charred materials. Commonly, the proportion of lipid extracts was found to be lower in the ancient soil than in the control samples, which indicated an enhanced degradation of organic matter, e.g., by thermal degradation. All samples displayed a particular pattern of short-chain and even carbon numbered n-alkanes (maximum at n-C₁₆ or n-C₁₈). The ratios CPI (carbon preference index) and ACL (average chain length) for the investigated soil samples matched the ratios found for maize and rye straw charred at 400 °C or 500 °C, respectively. These molecular ratios indicate the presence of charred biomass. The predominance of short-chain and even carbon numbered n-alkanes was a result of thermal degradation of biomass. The degradation products were preserved in ancient soils and could be applied as molecular markers in archaeological or palaeoenvironmental research.     

Chemical and mineralogical characterization of Aguada Portezuelo pottery from Catamarca,north-western Argentina: PIXE,XRD and SEM-EDS studies applied to surface pre- and post-firing paints,slips and pastes

Particle-induced X-ray emission (PIXE), X-ray diffraction (XRD), electron microprobe analysis (EDS) and scanning electron microscopy (SEM) analytical techniques were used to characterize surface paints in pre- and post-fired Aguada Portezuelo decorated pottery. Surface paintings in black, white, red, brown, burgundy and ochre were analysed. Major, minor and trace elements were detected by PIXE, whereas XRD and SEM-EDS gave information on the main mineral phases and the characteristic morphology for each analysed pigment. The results obtained indicate that the main colour groups can be easily discriminated by PIXE, and they are characterized by only one pigment for each colour: hematite (red) and manganese mineral oxides (black), respectively, whereas white pigments are characterized by calcite, ghelenite and gypsum.     

Gas breakthrough experiments on fine-grained sedimentary rocks

The capillary sealing efficiency of fine‐grained sedimentary rocks has been investigated by gas breakthrough experiments on fully water saturated claystones and siltstones (Boom Clay from Belgium, Opalinus Clay from Switzerland and Tertiary mudstone from offshore Norway) of different lithological compositions. Sand contents of the samples were consistently below 12%, major clay minerals were illite and smectite. Porosities determined by mercury injection lay between 10 and 30% while specific surface areas determined by nitrogen adsorption (BET method) ranged from 20 to 48 m² g ^{? 1}. Total organic carbon contents were below 2%. Prior to the gas breakthrough experiments the absolute (single phase) permeability (k_abs) of the samples was determined by steady state flow tests with water or NaCl brine. The k_abs values ranged between 3 and 550 nDarcy (3 × 10^?21 and 5.5 × 10^?19 m²). The maximum effective permeability to the gas‐phase (k_eff) measured after gas breakthrough on initially water‐saturated samples extended from 0.01 nDarcy (1 × 10^?23 m²) up to 1100 nDarcy (1.1 × 10^?18 m²). The residual differential pressures after re‐imbibition of the water phase, referred to as the ‘minimum capillary displacement pressures’ (P_d), ranged from 0.06 to 6.7 MPa. During the re‐imbibition process the effective permeability to the gas phase decreases with decreasing differential pressure. The recorded permeability/pressure data were used to derive the pore size distribution (mostly between 8 and 60 nm) and the transport porosity of the conducting pore system (10^‐5–10^‐2%). Correlations could be established between (i) absolute permeability coefficients and the maximum effective permeability coefficients and (ii) effective or absolute permeability coefficients and capillary sealing efficiency. No correlation was found between the capillary displacement pressures determined from gas breakthrough experiments and those derived theoretically by mercury injection.     

KIMMERIDGE JET—A POTENTIAL NEW SOURCE FOR BRITISH JET

Archaeological artefacts identified as jet are often assumed to have originated from the principal British source, which is at Whitby in Yorkshire. Geological samples of jet have also been found within the Kimmeridge Blackstone in Dorset—a seam of oil shale which has been worked since prehistoric times to produce artefacts similar to those made from jet. This paper discusses the geology and geochemistry of jet samples from both Whitby and Kimmeridge, and shows that the geological samples can be discriminated by differences in their organic components, as elucidated by Fourier transform infrared spectroscopy and pyrolysis-gas chromatography/mass spectrometry.     

土遗址防风化加固材料的研制及加固性能比较研究

本文用简单易行的方法将正硅酸乙酯进行预聚合,用盐酸作催化剂,待反应完毕后,在用乙二胺将PH值调节至微碱性,得到的预聚物呈无色透明液体。用此预聚物加固室内重塑土样,通过各种测试手段,如加固前后重量变化、渗透速度、空隙率变化、颜色变化、透气性变化、PH值以及盐蚀、冻融、高温高湿试验后的抗压强度等,并与PS材料、硅丙非水分散体、正硅酸乙酯和Remmers加固的标准土样进行各项性能的比较试验,结果表明:正硅酸乙酯预聚物加固后的土样各项性能都比较理想,能满足土遗址保护的要求。     

Technology and decay of magnesian lime plasters: the sculptures of the funerary crypt of Palenque,Mexico

The full-relief lime plaster sculptures of the funerary crypt of Palenque, Mexico, suffer from advanced decay due to the cave-like environment in which they are located. Macroscopically, the sculptures have a soft consistency, but there is a hard crust over their surface. Some of the features observed by microscopy are the neomorphism of minerals as a consequence of permanent water seepage, and the formation of wide shrinkage cracks as a result of drying. The mineral hydromagnesite Mg₅(CO₃)₄(OH)₂·4H₂O was identified by X-ray diffraction and microscopy; its relation with the shrinkage observed in the samples and its possible role in the decay of the sculptures are discussed in this paper. A short discussion is also made about the likely raw materials that were employed to manufacture the sculptures.