Laser scanning for conservation and research of African cultural heritage sites: the case study of Wonderwerk Cave,South Africa

The ‘African Cultural Heritage and Landscape Database’ project, initiated and directed by the senior author and administered by Aluka (www.aluka.org), is aimed at the creation of a digital library of spatial and non-spatial materials relating to cultural heritage sites in Africa. The archaeological site of Wonderwerk Cave (South Africa) is one of the 19 sites documented to date using laser scanning, conventional survey, digital photogrammetry and 3D modelling. To date, it is one of the few archaeological caves worldwide to be fully scanned. This paper explores the different uses to which the spatial data derived from this cave have been, or will be, put – for historical and educational purposes, scientific research and site conservation and development.     

南京堂子街太平天国壁画再保护

为了使已经经历过保护修复的14幅南京堂子街太平天国时期的壁画能够更好地保存和展览,在全面的现场调查和修复资料收集的基础上,对壁画实施了现场预保护、搬迁以及实验室保护修复。采取了比较成熟的保护材料Paraloid B72、Primal AC33对壁画进行加固回贴;并将蒸汽清洗、激光清洗引入到壁画的表面清理中;同时改善了灌浆材料;采用了贴木浆纸、预先刷涂乙醇等改良工艺。在上述措施的综合使用下,壁画再次保护修复后效果良好。此保护修复方法可对类似需要再保护的壁画提供借鉴。     

Chemical analysis of white porcelains from the Ding Kiln site, Hebei Province, China

The Ding kilns were some of the most famous early kilns of medieval China, producing huge quantities of white and cream-white porcelains of outstanding technical and aesthetic quality. Since 1949 they have been excavated three times, in 1965, in 1987, and in 2009 respectively. In this latest study 69 white porcelain sherds from assured contexts and from the 2009 excavations were analyzed using laser ablation techniques (ICP-AES). The samples date from Five Dynasties, Northern Song and Jin Dynasties respectively (early 10^th to early 13^th C CE). The results show that Ding wares of different times show different characteristics that can be demonstrated through chemical composition. During the early phase of production the Ding ware bodies consisted largely of high firing kaolinitic clays with predominantly calcareous materials as fluxes. After the early Northern Song Dynasty, some calcareous material was replaced by a more potassic material. The compositions of the glazes show a parallel evolution to the bodies. However, because the glazes are very low in titania it seems unlikely that the main clay ingredients of the bodies could have been used in the glaze recipes. For much of the kiln site’s history the glazes appear to have been made mainly from the same siliceous flux-rich materials that had been blended with the main body-clays used to make the Ding ware porcelains, plus some extra calcareous material. The P₂O₅ contents of the glazes suggest that wood ash may have been one source of CaO in the glaze recipes.     

Strontium isotope ratios in fossil teeth from South Africa: assessing laser ablation MC-ICP-MS analysis and the extent of diagenesis

This study tests the precision and accuracy of laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) for measuring strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) in fossil teeth from Swartkrans and Sterkfontein in South Africa, and explores the extent of diagenesis in these specimens. Compared to solution MC-ICP-MS or thermal ionization mass spectrometry (TIMS) methods, LA-MC-ICP-MS can be faster and less expensive, but has lower precision and accuracy. We found that ⁸⁷Sr/⁸⁶Sr ratios in fossil rodent teeth measured by LA-MC-ICP-MS were offset from solution values by a mean of 0.0005 ± 0.0010 (2σ). Because of the very wide spread of biologically available ⁸⁷Sr/⁸⁶Sr ratios (∼0.710 to ∼0.790) in the region, LA-MC-ICP-MS is more than sufficient for assessing the geographic origins of the fossil rodents. The concentration of strontium in modern and fossil enamel from the area is statistically indistinguishable, as is the range of ⁸⁷Sr/⁸⁶Sr ratios in modern rodents and fossil rodents from Swartkrans. Thus, there is little evidence of diagenetic Sr in the fossil enamel. In contrast, the fossil dentine may contain up to ∼50% diagenetic strontium, although many dentine ⁸⁷Sr/⁸⁶Sr ratios are still far removed from the background cave value of 0.729. We propose that LA-MC-ICP-MS will also be of use for investigating the geographic origins of other, non-rodent fossil teeth from the Sterkfontein and Swartkrans collections, and may prove of similar utility at other suitable sites.     

Earthenware production and distribution in the prehispanic Philippine polity of Tanjay: results from laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS)

This paper presents the results of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of low-fired earthenware from the prehispanic trading polity of Tanjay (c. A.D. 500–1600) in the central Philippines. The goal of this project was to determine whether or not the compositional analysis of ceramics could be used to examine the organization of pottery production and exchange relationships in the Bais-Tanjay region of Negros Island. Results indicate that at least five distinct groups of ceramics can be differentiated based on elemental compositions and that pottery production was both a part-time, dispersed endeavor and a full-time, likely centralized, craft. In addition, a number of compositional outliers in the ceramic dataset suggest that interregional trade took place, with pottery made outside the Bais-Tanjay region being imported, especially by upland swidden farmers.     

Integrating radar and laser-based remote sensing techniques for monitoring structural deformation of archaeological monuments

Ground-Based Synthetic Aperture Radar Interferometry (GBInSAR) and Terrestrial Laser Scanning (TLS) were purposely integrated to obtain 3D interferometric radar point clouds to facilitate the spatial interpretation of displacements affecting archaeological monuments. The paper describes the procedure to implement this integrated approach in the real-world situations of surveillance of archaeological and built heritage. Targeted tests were carried out on the case study of the Domus Tiberiana sited along the northern side of the Palatino Hill in the central archaeological area of Rome, Italy, and displacements of the monument were monitored over almost one year of acquisition. The GBInSAR – TLS integration provided updated information about the condition of the archaeological structures in relation to their history of instability mechanisms, and did not highlighted a general worsening for the stability of the entire monument. Point-wise and prompt detection of displacement anomalies and/or sudden changes in displacement trends proved the suitability of the method to support early warning procedures, also to evaluate effects on the masonry due to human activities.     

Investigating compositional diversity among Fijian ceramics with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS): implications for interaction studies on geologically similar islands

This paper presents a ceramic provenance analysis of 260 Fijian sherd clays by laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS). Our analyses define three compositional groups in western Fijian ceramics distributed across the 2700 year ceramic sequence. Frequencies of compositional groups represented in the diachronic assemblages indicate an increasing spatial sphere of interaction until approximately 1500 BP. By 1000 BP interaction had spatially contracted to a significant degree. These findings suggest re-evaluation of current ideas about interaction in the southwest Pacific is necessary.     

The spiral that vanished: the application of non-contact recording techniques to an elusive rock art motif at Castlerigg stone circle in Cumbria

This article describes the recording of stone 11 of the Castlerigg stone circle in Cumbria through two different non-contact techniques: laser scanning and ground-based remote sensing. Despite the unproblematic recording of modern graffiti, neither technique was able to document the spiral photographed and rubbed in 1995. It is concluded that the spiral was most probably painted and has since faded away due to natural events. The discovery and loss of the spiral motif in Castlerigg is seen as a cautionary tale. In particular, it seems to suggest that it is time to take advantage of the novel technologies based on the digitisation of 3D surfaces with millimetre and submillimetre accuracy such as laser scanning and ground-based remote sensing. They offer many advantages to the recording of prehistoric carvings. In addition to avoiding direct contact with the rock surface eliminating the preservation concerns raised by other techniques, both produce high quality images (laser scanning offering a greater potential for this, but at higher cost) having a much higher level of objectivity, and precision and accuracy far beyond those of traditional recording methods such as wax rubbings and scale drawings.     

Comments on Richards et al., Journal of Archaeological Science 35, 2008 “Strontium isotope evidence of Neanderthal mobility at the site of Lakonis,Greece using laser-ablation PIMMS”

We present an evaluation of the laser ablation Sr isotope data reported by Richards et al. [Richards, M., Harvati, K., Grimes, V., Colin Smith, C., Smith, T., Jean-Jacques Hublin, J.J., Karkanas, P., and Panagopoulou, E., 2008. Strontium isotope evidence of Neanderthal mobility at the site of Lakonis, Greece using laser ablation PIMMS. Journal of Archaeological Science 35, 1251–1256] for a Neanderthal tooth recovered from a site in Greece. Based on an alternative and analytically more robust method of correcting for isobaric interferences present during the analysis the tooth appears to be isotopically homogenous and within uncertainty of the value for modern seawater. If this is the case then contrary to the migration model proposed by Richards et al. [Richards, M., Harvati, K., Grimes, V., Colin Smith, C., Smith, T., Jean-Jacques Hublin, J.J., Karkanas, P., and Panagopoulou, E., 2008. Strontium isotope evidence of Neanderthal mobility at the site of Lakonis, Greece using laser ablation PIMMS. Journal of Archaeological Science 35, 1251–1256] the Neanderthal individual may have actually been a coastal dweller and lived within the vicinity of the find site.     

Shell-gathering from mangroves and the seasonality of the Southeast Asian Monsoon using high-resolution stable isotopic analysis of the tropical estuarine bivalve (Geloina erosa) from the Great Cave of Niah, Sarawak: methods and reconnaissance of molluscs of early Holocene and modern times

This paper describes a reconnaissance, high-resolution, study of stable isotopes (δ¹⁸O and δ¹³C) from modern shells of the estuarine bivalve Geloina erosa, and those dated to the early Holocene that were harvested by people from mangroves near the Great Cave of Niah on the north coast of Borneo. This reconnaissance study provides high-resolution palaeoclimatic-palaeohydrological information concerning early human activity in the region and the past character of the Southeast Asian Monsoon. Laser ablation continuous flow isotope ratio mass spectrometry (LA-CF-IRMS) on modern shells of Geloina erosa revealed ‘saw-tooth’ stable isotopic profiles that bear a close resemblance to peaks and troughs of trends in recent local rainfall, including the 1998 El Niño drought, highlighting the potential of Geloina erosa for reconstructing seasonality of the Southeast Asian Palaeomonsoon. LA-CF-IRMS analysis of prehistoric shells of Geloina erosa held in the Harrisson Archives of the Sarawak Museum revealed cyclical shifts in δ¹⁸O with similar amplitudes of variation as found in modern shells of Geloina erosa. As at the present day, this probably reflects the changing seasonality of the monsoon rains with shifts to negative δ¹⁸O values during periods of high runoff. Lighter mean δ¹⁸O values of the prehistoric shells, however, may indicate a greater annual surplus of rainfall and possibly consistent with the early Holocene strengthening of the summer monsoon at that time. The similarity of the last growth increment δ¹⁸O of the prehistoric shells to their mean δ¹⁸O profile values suggests that gathering took place during times of moderate runoff.