CHAPTER FIVE

EXPERIMENTAL PROGRAM FOR THE DETECTION OF USE WEAR

IN QUARTZITE

VICTORIA ARANDA*1,2,3, ANTONI CANALS1,2,3

AND ANDREU OLLÉ1,2 1IPHES, Institut Català de Paleoecologia Humana i Evolució Social

43007, Tarragona, Spain. 2Àrea de Prehistòria, Universitat Rovira i Virgili (URV)

Av. Catalunya 35, 43002. Tarragona, Spain.

3Equipo de Investigación Primeros Pobladores de Extremadura. Casa de Cultura Rodríguez Moñino, Avd. de Cervantes s/n, 10003

Cáceres, Spain. victoriaarandasanchez@gmail.com

Abstract

This paper presents preliminary results obtained from a series of butchery and woodworking experiments aimed at identifying use-wear traces on quartzite. Sequential SEM observation of wear on tool edges allowed us to document slight development and conservation of wear features. Wear results mostly from the essentially fragile behaviour of quartz grains, which tend to fracture with applied effort, generating a loss of microrelief. Our results demonstrate the potential of establishing experimental wear patterns on quartzite objects, which aid interpretation of features observed on archaeological materials.

Keywords: Quartzite, experimental program, Scanning Electron Microscopy.

Chapter Five 46

1. Introduction

The paucity of experimental studies of use-wear on quartzite tools constrains the study of quartzite archaeological assemblages. Previous studies have demonstrated the difficulties encountered when comparing use-wear traces produced on flint with those on quartzite, and have shown that both types of rocks have their own wear characteristics (Beyries 1982; Plisson 1985; Mansur and Alonso 1990; Utrilla and Mazo 1996).

At a macroscopic level, the surface topography of quartzite is irregular which seems to explain why use-wear develops on much smaller and discontinuous areas than on other rocks such as flint (Clemente 1997; Mansur 1999; Gibaja et al. 2002, Ollé 2003; Vergès 2003; Leipus and Mansur 2007). A further problem noted is the loss of traces accumulated during the first moments of use due to destruction of microrelief caused by microflaking of the edge. This destruction is produced during the first stage of fracture with a loss of crystals caused by attrition. At the second stage of edge stabilization fracture decreases and the presence of friction phenomena rises (Ollé 2003).

The present study aims to present the results of a preliminary experimental program devoted to the monitoring of wear formation on experimental quartzite tools.

2. Materials and methods

Eight experimental tools were used in this study: 4 were used for woodworking and 4 were used in butchery processes. The butchery tools comprised 2 large shaped tools (handaxes) (CSAC1-CSAC2), and 2 medium-sized flakes (CSAC4-CSAC5). Wood working tools consisted of 2 large shaped tools (handaxe (CSAM2) and cleaver (CSAM4)), and 2 medium-sized flakes (CSAM3-CSAM5) (Table 5-1). As the experimental program was conceived to aid future study of the Acheulean assemblage from Santa Ana cave (Cáceres, Spain), all replicas were made from local quartzite slabs (Ordovician Armorican, from Salor Valley). The choice and combination of tool types respond to specific questions posed by a preliminary use-wear study of the assemblage (Ollé et al. this volume).

The program included sequential experiments, which aimed to monitor wear process during the actions performed (Ollé and Vergés 2008). Choice of activities was restricted to butchery and woodworking to begin with as these are activities commonly assumed to be related with Acheulean large cutting tools (Clark and Haynes 1969; Clark 1975; Jones 1981; Villa 1990;

Experimental Program for the Detection of Use Wear in Quartzite 47

Schick and Toth 1993; Ashton and McNabb 1994; Mitchell 1995; Domínguez-Rodrígo et al. 2001; Ollé 2003).

In order to control variables, we grouped actions into a limited number of categories (Table 5-1). Butchery activities (Ovis aries and Cervus elaphus) included skinning, disarticulation and defleshing. Although all experiments were planned to be sequential, to date only 2 cases (CSAC1 and CSAC5) have been observed through two stages of use. Woodworking consisted of cutting, scraping and planing fresh Holm oak (Quercus ilex) branches.

Experimental tools were analysed under the SEM (JEOL JSM-6400), a technique of analysis that offers some advantages with respect to conventional light optical microscopy, essentially in terms of image resolution, depth of field and the potential of associated elementary microanalysis (EDS) (Ollé 2003; Vergès 2003).

To accurately observe deformations on tool surfaces caused by use, we followed a cleaning procedure proposed by Ollé and Vergès (2008). For SEM observation we made high-resolution moulds of tool edges using the dental silicone Provil® novo Light (Heraeus Kulzer, Inc.). For casts or replicas we used a bicomponent polyurethane rapid setting resin (Feropur PR-55, Synthesia Española S.A.). Replicas allow us to record the morphological features of the fresh cutting edge and thus compare a given point of the edge before and after use.

Edge visualization was carried out by locating points of interest defined by areas where use-wear traces were observable. These points were systematically recorded by taking images at different magnifications (50, 100, 250, 500 and 1000x), after which they were located on the fresh edge of the replica. These series of micrographs were crucial in order to properly locate points of interest, record the distribution of traces, and analyse minute details of features individualized at different magnifications. In some cases, we were able to take images of the same point of the edge and thus note the development of microrelief at three different stages: before use and after two episodes of use.

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Chapter Five 50

3. Results

3.1. Butchery processes

After 15 minutes of cutting meat (CSAC4) minor microrelief modifications were observed along the active edge (64 mm) of the tool that are restricted to the crystals close to the edge, and do not extend towards the inner area of the tool surface. A slight microfracture and slight smoothing of the crystal ridges can be observed.

During disarticulation (CSAC2) the point of the tool broke, which involved the loss of any previous modification, as well as making it impossible to compare the same points on the edge before and after rupture.

The skinning activity (CSAC1) produced continuous wear of crystals close to the edge that was particularly developed on the dorsal face that had sustained greater contact with the worked material. Deformations observed after 30 and 60 minutes of use include edge rounding (Fig. 1 B-C), friction features in the form of linear grooves, and a slight polish from plastic deformation. Microfracture of crystal ridges and loss of material are evident, and sometimes the only feature recorded (Fig. 5-1 E-F).

Evisceration, disarticulation of ribs and meat cutting (CSAC5), produced deformations that are distributed along the active edge, but which are more intense at the distal end. Crystal microfracture close to the edge became more intense as time of use increased, leading to more rounded ridges and smoothed surfaces after four minutes of use (Fig. 5-2 B-C).

In those cases where two stages of use are documented, the same wear pattern can be observed. After the first period of use almost no visible deformation, and only a loss of material due to the fracture of crystals close to the edge, can be observed. When use is extended, crystal ridges begin to round off and some friction features appear (Fig. 5-1 F). In the case of the tool that was subjected to harder contact material (CSAC5, cutting ribs), fractures are dominant during the entire process (Fig. 5-2) and plastic deformation, although visible during the second period of use is poorly developed.

Experimental Program for the Detection of Use Wear in Quartzite 51

Fig 1: CSAC1. Skinning action, 2 stages of use (30 minutes +30 minutes). A: Fresh edge of control point 1. B: after 30minutes use; rounded edge and loss of material. C: after 60 minutes use, edge rounding, smoothing and initial polish. D: Fresh edge ocçf control point 2. E: after 30 minutes use, quartz crystals microfracture. F: after 60 minutes use, loss of material because of intense quartz crystals micro-fracture and initial surface regularisation.

Fig 2: CSAC5. Evisceration, rib cutting and meat cutting actions, 2 stages of use (20 minutes +20 minutes) A: Fresh edge. B: after 30minutes use, loss of material due to crystal microfracture and slight smoothing of the surface. C: after 60 minutes use, accentuation of the loss of the quartz crystals and smoothing, with no clear wear features visible.

Chapter Five 52

3.2. Fresh wood working

During the first 3 minutes of striking (in an axe-like manner) (CSAM2-CSAM3), both pieces used were fractured and their points showed heavy chipping. After a few minutes of use, the edge began to stabilize and smoothing and slight rounding of crystals closer to the edge were visible.

During wood scraping (CSAM4), wear developed continuously along the used edge. A great loss of material due to the microfracture of crystals close to the edge was observed. Crystal ridges became rounded and the surface smoothed. In many cases, an incipient polishing and rounding of the stabilized active edge occurred after fracture (Fig. 5-3).

Fig 3: CSAM4. Fresh wood scrapping action. A: Fresh edge. B: after 15 minutes use. Intensive microfracture of the quartz crystals of edge (clearly transverse oriented), surface smoothening and marked edge rounding.

Finally, wood-cutting (CSAM5) resulted in very slight deformations that are restricted to the microfracture of crystals close to the edge and distributed intermittently along the first third of the tool, smoothing of the surface, and the beginning of edge rounding.

4. Discussion and conclusions

In this study we have presented a methodological procedure that includes sequential experiments and microscopic analysis based on observations at different magnifications using scanning electron microscopy. Although the preparation process of samples is more demanding than with traditional

Experimental Program for the Detection of Use Wear in Quartzite 53

optical microscopes, the SEM offers significant advantages over traditional optical microscopes, especially in terms of magnification power, image resolution and depth of field.

The experimental program allowed a preliminary approach to the development of wear induced by butchery and woodworking activities on a set of tools made of a specific variety of quartzite. In order to evaluate precisely the effects of use on the experimental tool edges, monitoring of the wear process from the fresh edge (for which replicas were used) through different stages of use is considered crucial. This procedure has reinforced the idea that functional studies of raw materials other than flint are possible, although not all raw materials offer the same potential to identify actions undertaken and materials worked.

Wear features discernable from butchery actions are very weak and appear only on the rim of the edge, whereas they are more developed and extended in woodworking actions. But forceful actions produce more edge microfracturing that causes the loss of portions of the edge (and so, loss of wear features). This can explain why longitudinal motions on soft materials tend to leave wear features along the entire edge and transversal motions on harder materials leave main microfractures (that make a detailed comparison between fresh and used edges difficult to do).

Quartzite crystallographic properties explain the essentially fragile behaviour of this rock when submitted to force. The continuous fracture of its quartz crystals obstructs both the appearance and the conservation of wear features (striations, plastic deformations…). Nevertheless, the two-time sequential experiments have shown how this low intensity process of wear includes a first stage of fracture that involves abrasion of crystal ridges, after which there is a stage of edge stabilization when plastic deformation (rounding, polish…) begins to appear.

This study is a methodological approach for the analysis of large

shaped quartzite tools. As well as the need to extend the experimental program by the inclusion of a wider range of activities, other surface modifications such as those produced by postdepositional processes must be considered in future research.

Acknowledgements

We would like to thank all our colleagues from the Eauipo Primeros Pobladores de Extremadura, as well as the institutions that supported research in the Calerizo de Cáceres. This study was developed in the framework the MICINN project CGL2009-12703-C03-02 and the

Chapter Five 54

AGAUR projects 2009SGR-188 and 2009PBR-00033. We also thank Antonio Rodriguez and Lucía Bermejo for making corrections and Norah Moloney for her assistance with the English version of the manuscript.

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