Distinguishing between calcites formed by different mechanisms using infrared spectrometry: archaeological applications

Infrared spectrometry is a well-established method for the identification of minerals. Due to its simplicity and the short time required to obtain a result, it can be practiced on-site during excavation using portable infrared spectrometers. However, the identification of a mineral may not be sufficient. For example, a lime plaster floor and a crushed chalk surface have a similar appearance and are composed of the same mineral – calcite. Here we exploit differences in the infrared spectra of geogenic, biogenic and pyrogenic calcites for the identification of each calcite type. The infrared calcite spectrum has three characteristic peaks in the region of 400–4000 cm⁻¹, designated ν₂, ν₃, and ν₄. When a calcite sample is ground, as part of the measurement preparation procedure, some grinding dependent changes will be revealed in the infrared spectrum. With additional grinding, the ν₃ peak narrows and the heights of the ν₂ and ν₄ peaks decrease, when both are normalized to the ν₃ height. By plotting the normalized heights of the ν₂versus the ν₄ of several grindings of the same sample, a characteristic trend line is formed for each calcite type. The trend lines of geogenic calcites have the shallowest slopes and highest ν₄ values when compared to pyrogenic calcites, which can be further divided to ash and plaster/mortar samples. This method can assist in distinguishing between the various calcites, and provide insights into homogeneity and preservation state of the calcitic materials in question.     

陕西高陵杨官寨遗址H85发掘报告

2010年以来,陕西省考古研究院、中美国际田野考古学校在杨官寨遗址环壕东北角联合进行了数次考古发掘,发掘遗迹中包含一座堆积复杂、遗物丰富的庙底沟文化中晚期灰坑(H85)。根据遗迹结构、堆积状况,推测该灰坑应为一处具有居住性质的新石器时代遗存。     

Icelandic volcanic ash from the Late-glacial open-air archaeological site of Ahrenshöft LA 58 D, North Germany

Cryptotephra of Icelandic origin from the open-air archaeological site of Ahrenshöft LA 58 D (Kr. Nordfriesland, Schleswig-Holstein), northern Germany overlies a Late-glacial Havelte lithic assemblage, hitherto dated by ¹⁴C and biostratigraphy to the earliest part of the Late-glacial interstadial (GI-1e to GI-1c₃). Peaks in ash shards are observed in two profiles. Major and minor element geochemistry indicates volcanic ash originating in the Katla system. Precise correlation to previously described tephra is uncertain due to overlapping chemical characteristics. The Ahrenshöft ¹⁴C determinations, litho- and bio-stratigraphy encompass a broad age-span for the cryptotephra bearing sediments, from the end of the Allerød to the Preboreal. The most plausible volcanic eruption correlates are the Vedde Ash (∼Younger Dryas), already known from the European mainland, tephra AF555 (late Younger Dryas) and the Suduroy tephra (∼Preboreal/Boreal), hitherto recorded only in the North Atlantic region. These three ash horizons have been dated to, respectively, 12,171 ± 57 yr b2k in the NGRIP ice-core, c.11,500 cal BP, in Scotland and c.8000 cal BP, by radiocarbon from the Faroe Isles. Ongoing research on deposits from the type sites for the tephra layers may in the future differentiate these markers leading to better discrimination of the chemistries and a resolution of this question.     

Fuel, Fire and Heat: an experimental approach to highlight the potential of studying ash and char remains from archaeological contexts

As in traditional societies today ancient societies probably selected different fuels to meet specific heat requirements. Char and ash, the end products of fire, are often found in abundance in archaeological contexts. These end products can provide information regarding (i) the original fuel resource and type, (ii) the characteristics of the fire and (iii) combined with other archaeological evidence shed further light on possible socio-economic activity(-ies) associated with that fire. The three main fuel resources would have been (i) modern vegetation, (ii) fossil fuel and (iii) animal by-products. Local availability and abundance would have influenced the choice made.In this study an experimental approach was adopted to try and distinguish between the three different fuel resources that are known to have been used by ancient societies (and continue to be used by traditional societies today) from their char and ash remains to help determine original fuel-type and understand the relative heating properties. For this end one fuel-type from each fuel resource listed above, namely wood, peat and cow dung, was chosen.     

河南三门峡市庙底沟遗址仰韶文化H9发掘简报

2002年,河南省文物考古研究所等对庙底沟遗址进行了抢救性发掘,H9是这次发掘中较为重要的遗迹之一。H9结构规整,出土遗物丰富,主要是陶器,另有少量石器和骨器,并有石块和兽骨等。H9的发掘,对研究庙底沟类型文化具有重要意义,对探讨此类遗迹的性质具有科学价值。     

An Experimental Investigation into the Accidental Invention of Ceramic Glazes

Glazed objects, mainly in the form of glazed quartz and steatite solid stones, first appeared during the fifth millennium bc . At the present time, it is generally accepted that the accidental discovery of glazing was associated with ancient copper production. However, the replication experiments already conducted on glazed stones were unable to provide a convincing explanation for the accidental invention of ceramic glazes. This paper attempts to suggest a possible explanation for the accidental invention of glazes on solid stones (i.e., steatite and quartz) during the Chalcolithic period. A series of replication experiments were undertaken and the resulting objects were examined using SEM–EDS.     

A Study of the Techniques Used to Make Laohudong Guan Ware in China in the Southern Song Dynasty

Through a combination of analysis and synthesis of Laohudong Guan ware shards from Hangzhou City in southern China, some new hypotheses concerning Guan ware manufacture can be proposed. These suggest that the complex microstructures seen in Guan ware glazes, and which contribute significantly to their jade‐like qualities, may owe much to layers of fine bubbles trapped during the glazing process. It is also proposed that the multi‐layer glazing methods used at the Guan ware kilns at Hangzhou may have helped initially to disguise the relatively coarse and ferruginous clays used for Guan ware manufacture. Once established, the layered glazing technique was used for its own sake—eventually yielding wares that could comprise more glaze than clay. Raw materials and firing temperatures were also explored for this study, and these suggest the use of porcelain‐stone/wood ash mixtures for glaze‐making, with 20–30% calcareous wood ash being the usual amounts. The average heat‐work for the glaze firing seems to have been equivalent to Orton Cone 7, giving a typical finishing temperature of ～1215°C. A single biscuit firing and a single glaze firing seem likely for most Laohudong Guan wares. Studies of the losses that occur in the preparation of calcareous wood ashes suggest that very large quantities of botanic material must have been burned to provide ash for glaze‐making at the Laohudong kiln. From the environmental perspective, a combination of thick glazes and heavy wood‐ash usage would have placed great demands on local fuel supplies.     

An ethnoarchaeological study of cooking installations in rural Uzbekistan: development of a new method for identification of fuel sources

Mud constructed cooking installations such as ovens and hearths are common in modern, pre-modern and archaeological domestic contexts in West and Central Asia. Archaeological cooking installations are primarily identified using analogy of shape and size to ethnographic installations. The study presented here establishes direct evidence to the use of fire within mud constructed cooking installations, thus providing means for reducing ambiguity in identification of archaeological cooking installations. In addition, we present here a newly developed method that enables a clear-cut distinction between wood and dung ashes used as fuel materials in many modern and archaeological domestic contexts. The study is based on an ethnoarchaeological research in rural households at the Republic of Uzbekistan that was followed by geoarchaeological analyses of installation walls, wood ash, dung ash and wood and dung standards collected in the study area. Field work included ethnographic observations, interviews with informants and temperature measurements during cooking experiments. We show that changes in the clay mineral structure due to exposure to high temperatures on the interior walls of cooking installations can be detected using FTIR (Fourier Transform Infrared) spectroscopy, providing for the first time direct evidence to the use of fire within such installations. We demonstrate that the temperature recorded by clay alteration on installation walls as well as in the ashes left on installation bottoms does not correspond to baking or cooking temperatures. We also show that the newly developed method, based on the ratio of wood ash pseudomorphs to dung spherulites, separates between wood and dung ashes with very high certainty. Yet, we identify a range of values where differentiation between wood and dung ashes is uncertain, and suggest it results from intensive mixing processes. Lastly, we show that phytolith morphotype analysis is an insufficient tool, if used alone, for distinguishing wood from dung ashes in the study area. The newly developed tools for temperature estimation within mud constructed installations and for fuel origin determination contribute to better understanding of cooking-related practices, and can be applied to archaeological contexts worldwide.     

Ashes to ashes, charcoal to dust: micromorphological evidence for ash-induced disintegration of charcoal in Early Neolithic (LBK) soil features in Elsloo (The Netherlands)

Charcoal and other forms of charred organic material - an important part of the archaeological record - consist of benzenoids. Such components are unstable in basic or alkaline conditions. Since ashes are alkaline, this means that archaeological charcoal may have been disintegrated and lost if they were buried together with ashes, e.g. as in fireplaces. Ash may also cause clay translocation in decalcified loess because of the disaggregating effect of K⁺ ions in the soil solutions. We investigated the interplay of these two processes, using micromorphological samples from the Early Neolithic site at the Joannes Riviusstraat in Elsloo. Evidence for charcoal disintegration was found in the form of cavities in charcoal fragments, most commonly filled in with thick reddish limpid clay coatings. The combination of cavities and clay coatings are evidence for the disintegration of charcoal under the influence of ash. Ash may also have been instrumental in preserving small bone fragments in these decalcified well-drained loess soils. The evidence of ash-induced charcoal disintegration implies that charcoal preservation in the archaeological record is dependent on (1) whether or not is was buried alongside with ashes, and (2) on various soil characteristics that determine that determine how quickly the ash-derived alkalinity and potassium ions are leached.