"dig" (Developing International geoarchaeology)

A GIS-based method for determining heterogeneity of burnt-bone assemblages

Matthias Czechowskr , Susan Mentzer^t2, Christopher Miller' '³

'Institute for Archaeological Sciences, University of TObingen, Germany²

Department of Anthropology, University of Arizona, Tucson, USA

³Senckenberg Centre for Human Evolution and Paleoenvironment, University of TObingen, Germany

Using a geographic information system (GIS) for data-management, analysis, and visualization of archaeological sediment thin sections, provides a powerful and easy method for resolving spatial archaeological issues. Here, we show how the method can used for determining the heterogeneity of burnt-bone assemblages from Gravettian-aged deposits at Hohle Fels Cave, Swabian Jura, Germany and from a sacrificial ash altar at Mt. Lykaion, Peloponnese, Greece.

In situ Fourier Transform infrared microspectrometry (micro-FTIR), and Fourier Transform infrared (FTIR) spectrometry reference data from burning experiments with varying temperatures, allows us to establish parameters for the degree of bone-burning. Together with qualitative data, such as micromorphological features, bone-color-values, bone-size and spatial data like plane- and cross polarized images (scans) of the thin sections, all data are integrated in a GIS-framework. Spatial analysis and the visualization of these data provide contextual arguments for interpretation. The detailed determination of the burnt-bone assemblages on a micro scale allows differentiation of intact or re-worked combustion features and intentionally or unintentionally dumped bone deposits.

The case study attempts to show an efficient method for handling archaeological sediment thin sections. In a GIS-Environment, spatial data from different sources is organized, processed and presented in a user-friendly way. This allows easy interdisciplinary collaborative work, information exchange and publication of results. The use of open software and open file formats guarantees reproducibility of the method and long-term preservation of data.

Identifying char particles using FTIR

Lucia Leierer¹, David Friesem²

¹University of Tübingen; ² of Cambridge, McDonald Institute for Archaeological Research

Charred materials are an important as well as numerous component of archaeological sediment and are often better preserved than their unburned counterparts. In micromorphological studies one often encounters charred material in thin sections. They appear black in both polarized and cross polarized light. Whereas some charred materials, like charcoal or charred plant material, can be identified very easy, others are more difficult to clearly identify.

One of these materials is char, which can occur in two forms: bone-derived char and fat-derived char. The purpose of this work is to identify fat-derived char particles in thin section using Fourier Transform Infrared Microspectrometry (micro-FTIR). The ability to differentiate between charcoal, burned bone and fat-derived char in thin section can aid in evaluating cooking habits and fire use.

For the purpose of having a control sample, animal and vegetable fat was burned experimentally and measured with attenuated total reflection (ATR) at different temperatures of burning. Archaeological char was located in thin section from Hohle Fels, an Upper Palaeolithic cave in southern Germany. It was measured under micro-FTIR using ATR.

The spectra of the experimental char showed differences in peaks and peak ratios between animal and vegetable fat and between different degrees of burning. The archaeological char showed an overlap between the peaks of the char and the resin the sample was embedded in, but after subtraction some significant peaks stood out. Two of them were similar to peaks from the experimental char but different from the surrounding matrix and other charred particles like bone and charcoal. An identification of the archaeological char between vegetable and animal fat was not possible, since the archaeological char was likely subjected to taphonomic processes. Analyzing char with FTIR yields some obstacles, since the particles are often small and porous, making it difficult to find good areas to obtain spectra with the micro-FTIR. Additionally, the interference with the resin used for impregnating the samples mostly overlaps with the main peaks, leaving only two significant peaks to identify.

Despite these drawbacks, this method can help identifying char particles quickly, especially when one is already identifying other charred materials (such as burnt bone) with the micro-FTIR. Future work on archaeological char with the micro-FTIR will also focus on alteration and preservation of char.

Variation in morphology and composition of wood-derived ashes—an experimental approach
H. B. Martinez-Dyrzo¹, S. M. Mentzer^1,2, C. E. Miller^1,3
1 Institute for Archaeological Sciences, University of Tübingen, Rümelinstrasse 23. 72070 Tübingen, Germany

2 Department of Anthropology, University of Arizona, Tucson, USA

3 Senckenberg Centre for Human Evolution and Paleoenvironment, University of Tübingen, Germany
The identification of wood ash in archaeological contexts using soil micromorphology is largely based on the observation of rhombic, carbonate pseudomorphs of calcium oxalate crystals. The in situ preservation of this particular proxy is an important requirement for establishing the presence of certain types of combustion features in archaeological sites. However, despite numerous studies investigating the effects of post-depositional processes on the preservation of wood-derived ash, little work since Courty et al. (1989), Wattez (1988) and Canti (2003) has focused on variation in morphology of unaltered ashes. Here, we present the results of burning experiments that document variation in morphology of ashes as a function of species, plant part and burning temperature.

The present study includes a collection of 200 grain mounts of six different species of trees from the Swabian Jura, Germany (fir tree, oak, beech, ash tree , pine and birch), four species from the Trans-Volcanic Belt, Mexico (yucca, cuammochitl, violet copal and white copal), one representative from Australia (eucalyptus), a grass representative (bamboo) and an herb (spinach). All of the species are C3 plants with the exception of yucca, a CAM plant.

For each species, samples from the trunk (first meter from the base in the European species), bark, leaves and branch were taken. The samples were burnt at 400 °C, 500 °C and 600 °C for 4 hours and at 900 °C for 1 hour at room pressure (970 hPa) in an Carbolite® ELF 11/6B/E301 oven. We kept an ambient humidity measurement during the immediate cooling process. An additional extraction of calcium oxalates from the trunk was performed using tetraamminediaquacopper dihydroxide (Schweizer's reagent) and hydrogen peroxide in order to compare the ash samples with their progenitors.
In addition to grain mounts of all of the ashes, a Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy analysis was performed for each sample, using a Cary 660 (Agilent Technologies) spectrometer.

The results show the existence of charcoal and organic material (a polymer organic component) at 400 °C and preservation of charcoal at 600 °C. The samples heated to 900 °C show in some cases an incomplete combustion. For some species (Pine, eucalyptus and yucca) the ashes do not appear in the typical rhombic form, but rather appears as linear aggregates of micrite. This shape is congruent with the morphology of the original oxalate crystals in these plants. Additionally, the spinach does not form typical rhombic pseudomorphs, but spherical grains. Bamboo has an anomalous result. The infrared spectra show that the major chemical compound is calcium carbonate in all the samples at 600 °C and 900 °C with the exception of bamboo. Traces of calcium oxide and magnesium oxide can be detected at temperatures above 500°C. Meanwhile, traces of calcium carbonate are found at 900° C.

Automated detection and quantification of features in thin sections

from archaeological sites

Simone Moser¹, Barbara Brilmayer Bakti¹, Martin Kehl¹

¹Institute of Geography, University of Cologne, Albertus Magnus Platz, 50923 Cologne, Germany Contact: [e-mail]

In the past decades micromorphology has become an indispensable tool in geoarchaeological research. It provides information on mineral and organic components, their nature, spatial distribution, and possible diagenesis. This supports the identification of site formation processes. Although micromorphology traditionally is a qualitative approach, quantitative analyses add valuable information. The application of the Feature Analyst® for ArcGIS is a method to quantify micromorphological results. It is an automated feature extraction (AFE) software extension for geospatial features, usually applied for the interpretation of satellite or arial images to identify i.e. buildings, roads, land-use changes or vegetation types.

The Feature Analyst® enables the user to extract features in a short amount of time and to narrow the classification, if necessary. This quantitative approach is more precise and less time consuming as for example a manual detection. Also, standardised settings guarantee the same set of algorithms applied to the data set. The use of these standards on micromorphological thin sections increases the comparability of those, regarding mineral and organic constituents, as well as fabrics and groundmasses. To demonstrate the application the Feature Analyst® is applied to rock shelter deposits of the Iberian Peninsula and Northern Morocco. It is trained to detect and distinguish pore space, micritic and sparitic limestone, travertine, quartz grains, bones, burnt bones, and opaque particles as separate feature classes.

Through the generation of feature classes it is possible to determine total volumes and polygon sizes for each feature class and to assess feature orientation. This improves statistical analysis when investigating a large number of thin sections. Also, it is possible to combine high resolution images captured under plane polarised light or crossed polarizers using a flat-bed scanner or the polarizing microscope. This makes results more reliable and precise i.e. a differentiation between quartz and pore space is possible. In addition, an error matrix could be created to assess the accuracies of the defined classes in comparison to manual detection.

With the help of the Feature Analyst® several steps of a quantitative data acquisition method could be integrated within ArcGIS. It starts with the image acquisition and processing, followed by the identification of possible feature classes, and, as next steps, the data preparation, evaluation and visualisation.
A New Archaeomagnetic Dating Curve for Peru:

Reconstructing the Secular Variation Curve for the Middle and Late Moche
Ariana Fernandez¹, Steve Victor, Reed Morgan, Thomas Fenn, Roderick McIntosh^2
1 Yale University; Archaeomagnetism Laboratory, The Center for the Study of Ancient Pyro-Technology; 51 Hillhouse, New Haven, CT

² Yale University;

Archaeomagnetism has the potential to equal and perhaps surpass radiocarbon dating in accuracy—particularly for sites inhabited during the Hallstatt Plateau period of the radiocarbon curve (800 - 400 B.C.E.). Using remnant magnetism present in burnt soil containing magnetite or hematite collected from archaeological contexts, archaeomagnetism tracks the movement of the magnetic north pole over time. Curves plotting the movement of the pole through time are constructed with historic data and archaeological samples. The more samples that are taken, the more precise this dating method becomes.  With sufficient data, the potential exists for a resolution of plus or minus eleven to forty years.  However, it is still a developing field and therefore requires more intensive study to test its validity and achieve this accuracy. While researchers have developed several potential curves in parts of Africa and North America, little work has been done in South America. The northern coast of Peru holds the archaeological remains of complex and rapidly developing societies.  Previous dating in Peru relied heavily on relative dating using pottery.  Radiocarbon dating proved insufficient in cases as many archaeological contexts existed during the Hallstatt Plateau and others yielded insufficient organic material. In 1998, Wolfman published a partial Peruvian archaeomagnetic curve spanning from AD 675 until 1550.  This curve provided foundational insight into Peru’s magnetic past, but more dates must be added to increase its breadth and accuracy.  Building upon Wolfman's work, archaeomagnetic samples were collected by the current authors from the Moche sites of Huacas Moche and San Jose de Moro. Both had extensive Moche occupations and contain archaeological components predating the period covered by Wolfman’s curve.  Using an alternating frequency demagnetizer, these samples were demagnetized in 4mT intervals from 0mT-60mT and in 5mT intervals from 65mT-100mT; after each demagnetization step, the declinations, inclinations, and intensities of the samples were recorded.  The new dating curve for Peru between 350 and 750 AD contains 5 new points, all of which are supported by consistent data. These points appear to accurately document the movement of the magnetic north pole for both the Middle and Late Moche periods.  By combining these new results with Wolfman's data, we present the most comprehensive, if still preliminary, archaeomagnetic dating curve available for Peru.

Archaeological, palaeoecological, and pedological evidence of Holocene human-environment interaction in the Silvretta Alps

Katja Kothieringer¹, Karsten Lambers¹

¹: Digital Geoarchaeology; Institute of Archaeology, Heritage Sciences and Art History; University of Bamberg, Germany

When did people exploit natural resources available in the high-altitude zone of the Alps for the first time? When did they start to stay in this extreme environment over extended periods of time for herding purposes, and not just for short-term hunting activities? These topics have recently been discussed in various regional studies of past land-use patterns in high mountainous regions of the Alps, e.g. in Tyrol, Montafon (both Austria), and Trentino (Italy). Building on archaeological research initiated by the University of Zurich in 2007, we selected the valleys of the Silvretta Massif in the central Eastern Alps between Paznaun (Austria) and Lower Engadine (Switzerland) as an appropriate study area for analyzing the relationship between Holocene climate, settlement dynamics, and human impact on the landscape in the course of an interdisciplinary research project. Based on our findings, we present new evidence from archaeological, palaeoecological, and pedological investigations that aimed at reconstructing human-environment interaction in the Silvretta from the Early Holocene to the modern era. For this purpose, archaeological sites as well as environmental archives such as peat bogs and soils have been documented and analyzed.

A rock shelter in Val Urschai, Switzerland, at about 2300 m a.s.l. represents the oldest known archaeological site in the study area. At this site, a fire place dating to the mid-9^th millennium BC indicates early Mesolithic hunting activities. Later on, archaeological data suggest a shift in subsistence strategies in the wider study area from hunting to herding at the end of the Neolithic Period (2800-2500 BC), i.e. earlier than previously assumed. This shift is evidenced, among other finds, by the earliest ceramic fragments at another rock shelter in Val Urschai. These finds indicate that people stayed at that site over extended periods of time, preparing meals and possibly processing milk. While palaeoecological data confirm this shift at that time, they also show potentially earlier human and livestock impact through forest clearances by fire and grazing from about 4200 BC onwards.

Further evidence of early human impact can be obtained from subalpine soils. Soil formation was disturbed repeatedly by human activity like slash-and-burn. In addition to fire residues, certain characteristics of special soil types like “brown podzols” or alpine pasture cambisols situated on moraines high above the modern timberline can be ascribed to human activity, e.g. vegetation opening and subsequent long-term pastoral land-use. In our study area, soil types with podzolic features show such characteristics, e.g. charcoal fragments and eroded material that were partly reworked into fossil Bs-horizons. These widespread, podzolic soil relics were presumably formed under forest or dwarf shrub vegetation during warmer periods of the Mid-Holocene. This climatic relation is confirmed by the presence of a compaction zone during the Neolithic in the stratigraphy of a peat bog in Val Fenga, Switzerland, which is probably due to drying up of the bog and simultaneous soil formation processes. While peat bogs may be used to reconstruct the past environment on a regional scale due to their extended catchment area, human impact on the environment through fire and land-use changes can be deduced from soils on a local scale.

An extensive dating program by means of ¹⁴C and OSL is expected to provide further information on soil age and soil development in the course of a follow-up project. Based on the interdisciplinary results of this reference region, the goal is to obtain an overall view of human-environment interaction in the Central Alps in high temporal resolution.

Heat-induced alteration of glauconitic minerals in the Middle Stone Age levels of Blombos Cave, South Africa: implications for evaluating site structure and burning events

Magnus M. Haaland¹, David Friesem², Christopher Miller^3,4, Christopher S. Henshilwood¹

¹Institute for Archaeology, History, Culture and Religion, University of Bergen, Norway; ²University of Cambridge, McDonald Institute for Archaeological Research, United Kingdom; ³Institute for Archaeological Sciences, University of Tübingen, Tübingen, Germany; ⁴Senckenberg Centre for Human Evolution and Paleoenvironment, University of Tübingen, Tübingen, Germany; ⁵Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa

The identification of hearths and combustion features is a recurrent theme in the study of prehistoric site structure. In some sites, an intact, unlined open hearth can be recognized by the presence of a rubified and reddened substrate, overlain by thin layers of charcoal and ash; however, this is relatively rare. In clay-poor contexts, for example, rubification of the substrate does not always readily occur, making the identification of hearths and other combustion features more difficult. The sedimentary sequence in Blombos Cave, dated to 101 – 70 ka ago, represents such a clay-poor context, being highly calcareous and dominated by quartz-rich, aeolian sand.

However, sand-sized grains of glauconite, a green, marine clay mineral, are present throughout the well-stratified anthropogenic deposits inside the cave. The main source for the glauconite is the limestone bedrock ceiling (Pliocene aeolianites) in which the cave is formed. As with many other clay minerals, glauconite may alter its colour and chemical structure due to weathering processes. While the glauconite in the bedrock occurs as unaltered, dark green grains (PPL), some of the glauconite observed in the stratified archaeological deposits appear red. The red glauconite grains are primarily found in association with lenses rich in ash, charcoal and other burnt material.

Here we present a study on the structural properties and spatial distribution of glauconitic minerals in the Middle Stone Age levels of Blombos Cave, South Africa. We analyzed and compared the mineral properties of various glauconitic grains (i.e., green and red) by measuring them with Fourier-Transform Infrared (FTIR) Spectrometry. In addition, we analyzed in-situ glauconitic grains present in thin sections using Fourier-Transform Infrared Microspectrometry (micro-FTIR). Our results show that the differences in grain color - green versus red glauconite grains - represents a structural alteration of the mineral, following exposure to heat. The green glauconitic grains are naturally abundant in the cave deposits,and their measurements showed no signs of mineral alteration. In contrast, measurements conducted on the red glauconitic grains indicated their structural alteration. A similar pattern of alteration is known to occur in other types of clay minerals as a result of exposure to high temperatures. Furthermore, high-density clusters of red glauconite suggest strong contextual correlation with the spatial distribution of burnt material.

Using our preliminary results we were able to use optical properties of glauconite in order to identify loci of past human pyrogenic activity in Blombos Cave. Thus, we suggest that the structural property of glauconitic minerals – and their potential for heat-induced optical and structural alteration – makes them particularly informative sedimentary components in an otherwise clay-poor, stratigraphic sequence. The spatio-contextual distribution of unaltered (green) and heat-altered (red) glauconitic minerals grains within the anthropogenic deposits of Blombos Cave thus have the potential of providing us with valuable insights into Middle Stone Age site structures and burning events: site forming processes that otherwise would be difficult to recognize and evaluate.
The impact of landscape changes on the site formation processes of the Hohlenstein Stadel cave.

A. Barbieri¹, C.J. Kind², N. J. Conard³ and C.E. Miller¹

¹University of Tübingen, Institute for Archaeological Science, Rümelinstrasse 23, 72070 Tübingen, Germany; ²Regierungspräsidium Stuttgart, Landesamt für Denkmalpflege, Berliner Str. 12, D-73728 Esslingen; ³ University of Tübingen, Institute for Archaeological Science, Pre- and Protohistory and Archaeology of the Middle Ages, Burgsteige 11, 72070 Tübingen
The prehistoric cave sites of the Ach and Lone valleys in the Swabian Jura (Germany), have provided important information on the arrival of our ancestors into central Europe around 40.000 years ago, and their relation with the endemic Neanderthals. In The Ach Valley, previous micromorphological studies conducted at Geißenklösterle suggested the presence of a discontinuity at the Middle to Upper Paleolithic transition marked by an erosive surface that was subjected to phosphatization and clay translocation. This surface was overlain by a deposit of fresh calcareous löss that contained the earliest Aurignacian artifacts at the site. At Hohle Fels, also in the Ach Valley, geoarchaeologists noticed that the Middle to Upper Paleolithic transition was marked by a conformable transition from extensively phosphatized to non-phosphatized sediment.

At Hohle Fels, geoarchaeologists noted field evidence for a phase of erosion that occurred shortly after the Last Glacial Maximum and potentially affected the preservation of the Gravettian deposits. Similarly, in the Lone Valley, archaeologists have noted a lack of Gravettian-aged deposits within the caves and have hypothesized that the caves of this valley might have experienced heavier erosion than those located in The Ach Valley.

From 2008 to 2013 the State Office for Cultural Heritage Baden-Württemberg has conducted new excavations in the Hohlenstein Stadel Cave, in The Lone Valley, and in front of the cave entrance (Vorplatz) aiming at verifying the data collected during previous excavations in the first half of the twentieth century. This new field season gave us the chance to collect micromorphological samples from both Hohlenstein Stadel Cave and the Vorplatz covering the lowermost sterile layer, most of the Middle Paleolithic and the transition to the Upper Paleolithic deposit. Additionally we have performed geophysical prospecting, coring and mapping in The Lone Valley.

In the study presented here we discuss the impact of major landscape changes on the formation and preservation of the archaeological sequence deposited within Hohlenstein Stadel Cave. In particular, we focus on the results from Fourier Transform Infrared (FTIR) spectrometry and thin section analysis.

As expected from the archaeological evidence, the presence of clear anthropogenic features in the sequence is very little and it is usually related to thin surfaces associated with calcined bones. The sedimentation processes are mainly natural and are dominated by low-energy surface runoff and gravitational grain flow. As in Hohle Fels, reworked löss, clay aggregates, medium-sized quartz gravel and Bohnerz are present in almost all the Stadel cave sediments. These components were originally deposited on top of the Jura plateau and were subsequently incorporated in to the karstic system. Different depositional episodes of varying energies are present in the Middle Paleolithic deposit, in particular an erosional surface that marks the transition between the sterile layer and the Middle Paleolithic deposits. Unlike at Hohle Fels, no microstructures resulting from freeze-thaw cycles were found within the cave probably because the sampled profile was located far inside from the cave entrance. As in Hohle Fels, the Hohlenstein sediments are extensively phosphatized. Remarkably, as in Hohle Fels, the Upper Paleolithic sediments display a much lower occurrence of calcite dissolution.