Methods of Analysis

During the last thirty years, the traceological approach to the study of the lithic industries has been defined and updated by the works of several authors (even if each one with different objectives and theoretical frameworks): Odell (1977), Keeley (1980), Anderson-Gerfaud (1981), Vaughan (1981, 1985), Plisson (1985), Beyries (1987), Gijn (1989), Moss (1983), González & Ibáñez (1994), Gassin (1996), Clemente (1997a), Rots (2005), Gibaja (2003) only to cite some of the most notorious works.

The discipline has today a well-established method shared by most of the analysts. The development of new techniques and methodologies has been a constant during the history of Traceology, since the pioneer works of Semenov, through the application of both low- and high-power approaches, until the employment, in more recent years, of software-based analysis, 3D-scanning techniques, residues analysis, etc. For a detailed ‘state of art’ of the discipline, one should look at the works of Cook & Dumont (1987), Yerkes (1993), Donahue (1994) Marreiros et al. (2014). However, apart from the methodological improvements that occur along with the appearance of new techniques and analytical tools, one can fundamentally divides the traceological work in three main steps:

i. a first evaluation of the conservation of the archaeological assemblage is done through stereoscopic microscopy (in my case Leica MZ16A, 5X-40X or Leica M80). A sample of artefacts is observed, in order to identify the presence of eventual post-depositional alterations and, thus, to evaluate the feasibility of the analysis and the possible levels of interpretation;

ii. once defined the state of conservation of the industry, a detailed analysis of each single artefact is undertaken. The first step of the analysis involves the employment of stereoscopic microscope (Leica MZ16A or Leica M80) with observation between 5X-40X. The analysis of edges and surfaces is mainly directed to the identification of possible actives zones (PUAs - Possibly Used Areas) (Gijn 1989). Moreover, the observation of such macroscopic traces not only allow the determination of the PUAs, but also allows a first level of inference; it is already possible to formulate hypotheses about the hardness of the worked materials (soft, medium, hard) and about the type of movement performed (longitudinal, transversal, circular, vertical, impact). The analysis of macro traces is also important for the recognition of possible hafted parts, for the recognition of transported implements and for the identification of post-depositional and post-excavation modifications. Several works of reference are available for the study of the so called ‘macro-traces’ among which one can cites Tringham et al. (1974), Odell & Odell-Vereecken (1980), González & Ibáñez (1994). The categories considered in this study have been mainly taken from these works, classifying the traces on the basis of semi-qualitative variables. Three main classes of macro-wears have been recognized:

 macro-fractures: edge-damage or edge-scarring is classified on the basis of its invasiveness (absent, lightly, medium or strongly damaged edges), location (ventral face, dorsal face, bifacial), position (distal, proximal, mesial, entire edge) of their pattern of distribution (isolated, continues, overlapping, single scar, chaotic) and on the basis of the preferential morphology of the fracture-termination (feather, step, hinge or snap fractures). The general morphology of the edge is recorded (straight, undulated, concave, convex, denticulate), as well the presence/absence of voluntary retouches.

 edge-roundings: edge roundings are classified on the basis of their invasiveness (absent, marginal, medium, pronounced).

 lustres, patinas, bright and friction spots: the presence of macroscopic patinas, lustres and of all types of bright surfaces is also registered, considering their position (ventral, dorsal, bifacial) and distribution (marginal, invasive, all over the surfaces).

iii. when possible used areas (PUAs) or other modified zones are detected, the artefacts is submitted to a detailed microscopic analysis of the surfaces through the employment of reflected-light microscopy (metallographic microscope) (in my case Leica DM2500M, 50X-400X or Olympus BH2). The objective of this analysis is, first of all, to prove the nature of the previously identified PUAs. If PUAs are actually used we call it AUAs (Actually Used areas) (Gijn 1989). Proved the consistency of the traces, the analysis is directed toward the interpretation of the micro-features, such as strias and polishes, through the observation of their characteristics. For the definition of the semi-qualitative variables employed for micro-wears classification one can refers to several works among which Plisson (1985), Gijn (1989) and González & Ibáñez (1994) and Gassin (1996)⁴. Thus, micro-traces have been recorded following these variables:

 Distribution: this variable represent the way in which the polished zone is distributed over the lithic surfaces (normally distribution is evaluated at magnification of 50X-100X). Borrowing some categories from Gijn (1989) one can defines it as: isolated spots, streak of polish, marginal band, extended polish, very extended, covering;

 Texture: this variable represent the grade of linkage of the polished zone (it is evaluated at magnification of 200X). Following the classification proposed by Plisson (1985) and González & Ibáñez (1994) one can defines it as: compact, closed, half-closed, open.

 Topography: this variable represent the aspect of the polished zone (it is evaluated at magnification of 200X). Following González & Ibáñez (1994) one can defines it as: flat, rough, domed;

 Invasiveness: this variable represent the extension of the polish over the edge surface (it is evaluated at magnification of 50X): low (less than 25% of the edge’s surface), medium (between 25-50%), high (more than 50%);

iv. Once the artefacts has been analysed and described both on a macroscopic and

4 Among the other works that I followed for specific types of traces/alterations:

 for the analysis of all the fire/thermal alterations (both macro- and microscopic) I followed the criteria proposed by Clemente (1995, 1997b);

 for the description of chemical alterations I mainly followed the works of Gutiérrez et al. (1988), Plisson & Mauger (1988) and Gijn (1989);

 for the analysis of impact/projectile traces I mainly followed the works of Fischer et al. (1984), Domingo (2005), Gibaja & Palomo (2004); Cristiani et al. (2010); Petillón et al. (2012).

 the so-called ‘RV2’ traces has been defined following the work of Clemente & Gibaja (1998).

 Hafting traces have been recognized and analysed mainly following the work of Rots (2005, 2010).

microscopic level, a global interpretation of the observed traces is advanced. I decided to employ variables capable to describe not only use-wear traces, but also the types of traces resulting from ‘non-functional’ activities, such as hafting traces, transportation traces or alterations, which could be equally described as any other modification of the lithic surfaces/edges. The location of wear-traces is registered in the database utilizing a System of Polar Coordinates (modified from Gijn 1989) (Fig. 2.3), to indicate the exact position and extension of the observed features (both macro- and micro-traces).

 The type of wears has been classified following the criteria proposed by Gyria (2004) which include both use, manufacturing and management wears: use-wears, technological wears; non-utilitarian wears (e.g. hafting and transportation traces); alterations. A last category, residues, has been created to group the macro- and microscopic residues observed on the lithic surfaces. However, residues have been only superficially mentioned, if easy recognizable and relevant to the interpretation of the tool, as we are not specifically working on that theme.

 The interpretation of the contact material is given using three levels of confidence, depending on the interpretability and conservation of the wear (1 - hardness: soft, medium, hard; 2 - substance: animal, vegetal, mineral, metallic; 3 - material: meat, meat/bone, fish, hide, fresh hide, dry hide, bone/antler, indeterminate herbaceous plants, dry herbaceous plants, fresh herbaceous plants, herbaceous plants with abrasive component, soft woody plants, hard wood, clay, pottery, soil, etc.).

 The kinematic of the movement is described as following: cutting/sawing, scraping,

Fig. 2.3. System of Polar Coordinates for the registration of the different types of wears.

planning, graving, boring, pounding, projectile, hafting, transportation, alteration.

 Depending on which level the interpretation is made it is considered possibly (PO) (if only the hardness is determined), probably (PR) (if both the hardness and the type of substance are determined) and certain (SG) (when traces are fully interpretable).

 A final category is established to define the relationship of the traces with other traces. The relationship between traces is defined as: adjacent traces, overlapping traces, partially overlapping traces; isolated traces.

v. Photographs have been taken systematically both macroscopically and microscopically at different magnification. In the case in which archaeological materials have been studied at the Milà i Fontanals Institution (CSIC-IMF), photographs have been realized with a Leica IC3D camera for the stereoscopic microscope and with a Leica DFC420C for the reflected-light microscope, with the aid of Leica Image Manager Software to mount together the different photos. In the case of lithic assemblages that have been studied elsewhere (e.g. museum collections) has been used a Canon 450D camera and photos have been processed with the software Helicon Focus v. 4.62.

vi. Experimental references of both macro- and micro-traces have been taken from the Traceotecha of the Institució Milà i Fontanals (CSIC-IMF) in Barcelona, where more than a thousand of experiments on different materials and with different rock-types are conserved. New experimental works have been also realized to resolve specific archaeological questions, but they will later described (cfr. Chap. 2, par 2.3.).

vii. Cleaning procedures have been applied previously to the analysis of the archaeological materials. I followed the indications published by Plisson & Mauger (1988), Gijn (1989) and Bouwman (2011):

 All the materials have been washed with water after the excavations works to wash away the sediment superficially attached to the surfaces. This first phase has been realized directly on the excavation and, thus, I did not personally control this part of the procedure.

 Previously to each microscopic observation 95% ethanol has been employed for a superficial cleaning. Ethanol is applied on the surface with a cotton bud that is changed after each use. The aim is to remove the superficial grease and the dust which derives from the conservation and handling of the artefacts.

 Chemical cleaning has been realized to remove concretions, sediments, greasy patinas or other dirty substances that are not removed with a superficial cleaning.

To remove greases and other organic materials ultrasonic cleaning for 30 minute with 10% Oxygen Peroxide solution is employed. This protocol allows cleaning the lithic surfaces without destroying use-wears, even if in this case the eventual organic residues would be lost. Acid cleaning is employed to remove calcareous concretions and other inorganic residues, such as spots of sediment or other incrustations. In this case, ultrasonic cleaning for 15 minute with a 5% Hcl solution is employed. At this concentration, and for such time interval, no damage is reported on the polishes. Alkaline cleaning is never employed as potentially dangerous for the preservation of all the silica-based polishes.