Post-depositional surface whitening of ceramic artifacts: alteration mechanisms and consequences

Surfaces on ceramic artifacts that are paler than the main sherd body are commonly interpreted as slips that were intentionally applied by the potter during the manufacturing process. However, due to post-depositional alteration, sherds that were not originally coated with a slip may macroscopically appear with deceptively similar pale surfaces. This paper presents a comparison of two sherds, both with pale to white surfaces, one of which is a real slip and the other a surficial corrosion that occurred during the burial stage. Observations using optical and scanning electron microscopy, as well as electron-probe image- and microanalysis, clearly illustrate the features of the two surfaces, as well as demonstrating their causes and effects. The superimposed slip is clearly delimited from the sherd body by a denser and much finer-grained fabric, in which clay minerals predominate and porosity is reduced by about 20% compared to the body. In the other sample, surface corrosion, due to invading fluids, has led to leaching of calcareous constituents and results in a remarkable increase in porosity close to the rim (ca. 25%). Sometimes called the “espresso crema effect” (Tschegg et al., 2009b), the surface becomes considerably brighter than the core and can easily be confused with intentional slips. This, as a consequence can lead to significant misinterpretations, to erroneous sherd characterizations and classifications, as well as to incorrect assignments to specific ware groups.     

Laboratory Experiments as Support for Development of In Situ Conservation Methods

Abstract

Within the EU-Project BACPOLES (EVK4-CT-2001-00043) bacterial wood degradation could be simulated in laboratory experiments to investigate the living conditions of the up to now unknown bacteria consortia, named erosion bacteria (EB), which cause considerable decay on waterlogged archaeological wood. In these Microcosm (MC) experiments the role of oxygen and chemical composition of the sediment were investigated. Therefore, the microcosms were subjected to different gassing treatments and the free dissolved oxygen was measured in different depths of the microcosms by special oxygen sensors (optodes). In further experiments the chemical composition of the sediment was verified to investigate the influence of different nutrient concentrations to the degradation process by EB.

From the findings it can be concluded that bacterial wood decay can proceed without free oxygen present but that it is more intense if oxygen is available. A water flow like streams in the sea, simulated by vertical water circulation, seems to stimulate the degradation activity and the degradation of wood by EB seems to be a result of low nutrient levels in the surrounding area.     

Holocene land-use evolution and associated soil erosion in the French Prealps inferred from Lake Paladru sediments and archaeological evidences

A source-to-sink multi-proxy approach has been performed within Lake Paladru (492 m a.s.l., French Prealps) catchment and a 6-m long sediment sequence retrieved from the central lacustrine basin. The combination of minerogenic signal, specific organic markers of autochthonous and allochthonous supply and archaeological data allows the reconstruction of a continuous record of past human disturbances. Over the last 10,000 years, the lacustrine sedimentation was dominated by autochthonous carbonates and the watershed was mostly forest-covered. However, seven phases of higher accumulation rate, soil erosion, algal productivity and landscape disturbances have been identified and dated from 8400 to 7900, 6000 to 4800, 4500 to 3200, 2700 to 2050 cal BP as well as AD 350–850, AD 1250–1850 and after AD 1970. Before 5200 cal BP, soil erosion is interpreted as resulting from climatic deterioration phases towards cooler and wetter conditions. During the Mid-Late Holocene period, erosion fluxes and landscape disturbances are always associated with prehistorical and historical human activities and amplified by climatic oscillations. Such changes in human land-used led to increasing minerogenic supply and nutrients loading that affected lacustrine trophic levels, especially during the last 1600 years. In addition, organic and molecular markers document previously unknown human settlements around Lake Paladru during the Bronze and the Iron Ages.     

Archaeological applications of polynomial texture mapping: analysis,conservation and representation

Polynomial Texture Mapping is an image capture and processing technique that was developed by HP Labs in 2000. It enables the recording and representation of subtle surface details using a standard digital camera and lighting, and software that is free for non-commercial use. Cultural heritage applications have been associated with the technology from its earliest stages, including examples in areas such as cuneiform, numismatics, rock art, lithics and Byzantine art. The paper begins by outlining the technical principles involved. It then brings together the extant work in the field. Through examples developed by the University of Southampton in partnership with a range of UK and international bodies it demonstrates the benefits of the technology in the areas of archaeological analysis, conservation and representation. Finally it considers the future possibilities of this technology and ongoing developments.     

The role of time-lapse bathymetric surveys in assessing morphological change at shipwreck sites

Data from time-lapse single-beam and multi-beam bathymetric surveys are used to assess the rate and scale of morphological change at shipwreck sites caused by anthropogenic forcing. The technique is illustrated by characterizing changes in wreck site morphology over two sites located on the east coast of Ireland – the Drogheda Boat site on the River Boyne and the Arklow Bank site in the Irish Sea. Results indicate that repeated bathymetric surveys accurately and rapidly capture morphological change, with time-lapse accretion–erosion models indicating possible erosion rates of up to 0.04 m per day and accretion rates of 0.36 m per day at dynamic riverine and marine sites in response to external triggers. These data are valuable in understanding site formation processes at fully submerged archaeological sites and in the derivation of high-resolution site formation models.     

Lake Dwellings in Baden-Württemberg. Conservation Projects In Situ at Lake Constance and the Federsee Moor

The Baden-Württemberg shoreline of Lake Constance and the lakes and moors of Upper Swabia contain important prehistoric wetland sites. From 1979, new research has brought up not only important finds and scientific results but also increasing information about bank erosion in the lakes and desiccation in the moorlands. At Lake Constance, early attempts were made in the 1980s to protect sites threatened by erosion by covering them with geo-textile and gravel. With further protective projects the know-how improved, but crucial questions still remained: What are the best practical solutions? How about ecological compatibility? Do we have other options? The INTERREG IV 2008–2011 international project ‘Erosion and Archaeological Heritage Protection in Lake Constance and Lake Zurich’ brought deeper insights and opened the field for new experiments with protective measures. At the Federsee Moor a long-term project started in 1980 with close collaboration between nature conservation and archaeological heritage management. With archaeological stocktaking, acquisition of land, establishment of new nature reserves, exchange of landholding and hydrographic engineering, the project was completed with the help of European Union funding by LIFE+in 2013.     

Site maintenance practices and settlement social organization in Iron Age Karnataka, India: Inferring settlement places and landscape from surface distributions of ceramic assemblage attributes

This paper investigates the spatial organization of social relations in settlement contexts through a quantitative and distributional analysis of surface ceramic attributes from Iron Age Period (1200–300 BC) archaeological sites in Southern India. The results discern variation in depositional contexts across each site, from which I infer a variety of basic settlement activity structures (e.g., site maintenance, trash disposal, residence, animal husbandry, metallurgy, ritual). I use these results, together with further analyses of artifact and feature distributions, to infer a basic suite of places, place-making practices and some of the social relations and organizational structures that produced these historically unique Iron Age settlement landscapes.     

榆阳区明长城典型遗址的雨蚀破坏模式分析

现有的夯土遗址雨蚀病害分类方式关注的是多次降雨后遗址破坏的静态结果,以识别病害、辨明病因为主要目的。为进一步研究水土作用方式在夯土雨蚀病害发育过程中的作用,明确雨蚀病害的动态发育过程,在现场调查的基础上对榆阳区明代夯土长城的雨蚀病害进行分类、统计、分析,综合考虑侵蚀模式、雨蚀动态响应过程和劣化程度三个方面提出雨蚀破坏模式,分别为干湿破坏、冲刷破坏和降雨导致的重力侵蚀三种,三种破坏模式的提出为研究夯土遗址雨蚀和降雨间的响应关系提供新思路。     

土遗址病害的评估体系研究

土遗址病害评估是对土遗址进行科学保护、管理、利用的一项基础性工作,但土遗址病害评估的体系还没有建立。为此,通过对土遗址病害的分析,借鉴地质工程、岩土工程的相关理论和方法,采用逐次分析的方法评估土遗址的载体和本体病害,探讨了土遗址病害评估体系。通过研究认为,可以从地质灾害、稳定性、表面风化三方面对土遗址病害程度进行评估。地质灾害和稳定性有其它学科相对成熟的理论和方法可以借鉴和采用。表面风化评估应考虑到风化剥蚀速率、遗址保存程度和文物价值三个方面,引进风化度和文物价值权重系数的概念,利用模糊数学原理对表面风化的危险程度进行综合评估是一种新思路。