However, the index is potentially subject to bias resulting from variation in the form of tool blanks: In spite of these constraints, experimental data suggest that the index constitutes' a reliable measure of the extent of tool reduction. A geometric index of reduction for unifacial stone tools.
N2 - Issues relating to the maintenance and renewal of stone tools have become increasingly important in studies of prehistoric technologies. AB - Issues relating to the maintenance and renewal of stone tools have become increasingly important in studies of prehistoric technologies.
Overview Fingerprint. Abstract Issues relating to the maintenance and renewal of stone tools have become increasingly important in studies of prehistoric technologies.
Access to Document Retouching of the point blank began on the distal and right margin of the dorsal surface of the lancet flake Figure 6. Some ventral retouch was added early in the sequence if points were destined for bifacial stages, whereas unifacial points continued to be retouched around the perimeter until the entire dorsal surface was entirely invasively flaked Figure 6.
Generally, it seems that only larger points were selected for bifacial working, whereas smaller flakes were more likely to remain unifacial. Truly bifacial points began to take on quite thick cross-sections due to reductions in width and length Figure 6.
Only late in the reduction sequence did bifacial points receive substantial thinning on both faces, with length:thickness ratios climbing again Figure 6. As the sequence continued, points were more likely to receive thinning and shaping of the proximal end, resulting in a bifacially trimmed base with a pronounced curve Figure 6.
Reduction model for points, showing the flexibility in the system to either take points into a bifacial stage if large enough, or continue with unifacial reduction generally if small. This reduction model allows us to talk of a first and a second sequence.
The first sequence is purely unifacial, while the second diverges at various points into sequence II bifacial point manufacture. No cases have yet been identified in Wardaman Country of the manufacture of bifacial points from blocks of stone rather than flakes as seen for instance in the Camooweal district of north Queensland [Moore ]. There is some evidence for the existence of a potential third sequence involving alternative bifacial reduction from the very earliest stages, although this strategy is very rare only 8.
Chapter 7 explores alterations in the frequency with which sequences I and II were used through time. While lancets appear to have commonly been used in point production, these regular flakes were often retouched into other forms as well. For instance, a large number of lancet and Leilira blades were retouched on the distal end to form a steep edge Figure 6.
Some of these show signs of having snapped transversely prior to retouching the broken distal end. Leilira blades in particular also often possess steep, convex retouching along the lateral margins. Additionally, lancet flakes sometimes had their proximal ends smashed off using bipolar percussion directed onto opposed lateral margins.
Examples of non-point retouch on leiliras and lancets. A distinctive characteristic of the Wardaman assemblages is the high prevalence of burinate retouch - or retouch that has removed one or more of the lateral margins of a flake by directing blows along the margins rather than away from them.
Burins are known throughout much of Australia Cundy ; Dortch ; Hiscock , a; McCarthy ; McCarthy , but are generally poorly reported and their technological relationship to other classes of artefacts is not well understood but see Hiscock [a] for a detailed reduction model for the Hunter Valley.
The reduction process for burins is modelled here using a sample of burins and spalls. Blank Type Burinate retouch appears to have been delivered to a wide variety of flake forms, as shown in Figure 6. Among these, flakes are most common, followed by unifacial points, then lancet flakes, then bifacial points, then scrapers and finally a single example of burinate retouch was found on a tula. The nature of burinate reduction.
A: frequency of burinate retouch on different artefact classes, B: frequency of different initiation surfaces, and C: the frequency of rotation. Burinate Initiation. An important step in understanding the nature of burinate reduction is to examine the point of initiation for burin spalls. The frequency with which spalls are initiated from different types of surfaces is shown in Figure 6.
Burin blows are most commonly initiated from the scars left by previous spalls with a different orientation i. This means that spalls were often struck from burins in more than one direction, and that the scars left by the first series of detachments were often used as a platform for the next series.
Despite the frequency of multiple burin platforms on flakes, single-platform spalling is most common in the sample of burins from rockshelters Figure 6. The second most common initiation surface is retouched edges — essentially just sections of usually steep retouch close to the junction of two margins. A third common platform type for burinate retouch is a transverse break. Platforms are also often created by faceting a section of the end of one margin to form a flat surface suitable for use as a platform for striking blows along the adjacent margin.
Original surfaces and step terminations are the next most common platform surfaces, while transverse breaks that have been retouched to provide a platform better suited to burination are the least common.
Clearly, this set of platform surfaces suggests that burination was a common way of reusing flakes once they had broken, or of transforming plain and retouched edges for some specific purpose. This may have been to create a robust scraping implement, to make long thin spalls for a specific purpose, or simply to create fresh flakes with sharp edges when little other raw material was available.
Number of Spalls. Turning to the spalls themselves, Figure 6. As the number of spalls increases, the platform angle left after the last scar also gradually increases Figure 6. Spall Length. As burinate reduction continues, as measured by the number of spalls removed from burins, the length of burin spall scars decreases markedly as shown in Figure 6.
The Reduction Sequence for Burins. The analysis of the nature of burinate reduction as well as changes in the morphology of burins and the resulting spalls, allows a simple reduction model to be built for burins, as shown in Figure 6.
Burin reduction appears to be principally focused on otherwise unretouched flakes, but unifacial points, lancets and other implement classes have all had burin spalls removed to varying degrees. The vast majority of spalls are oriented from the distal end, and initial spalls are struck either from retouched edges, breaks, plain or faceted margins.
As the number of spalls struck from the burin increases, the chance of ending reduction from a specific platform also increases as platform angle and the frequency of step and hinge terminations increase. Knappers often responded by starting burinate flake production again on a new platform, most commonly the flat surfaces left by previous spall removals, sometimes creating classic dihedral burins on the distal margins of lancets Figure 6.
Rotation of flaking around the margin continued in some cases until up to 12 spalls have been removed from all four margins Figure 6. ANOVA tests for significant changes in burin morphology as reduction continues. Changes in burin morphology as the number of platforms and scars increases.
A: number of orientations, B: changes in mean platform angle, and C: changes in the frequency of step and hinge terminations. Changes to the length of burin scars as reduction continues. Tulas are predominantly distally retouched flakes with a pronounced bulb of percussion where dorsal retouch has removed all excess ventral area, leaving only the bulb intact.
Ethnographically they are known as specialized tools for adzing hard woods. Alongside points, tulas are perhaps the best recognized retouched implement form in Australia, and their reduction sequence has been well documented by early commentators such as Horne and Aiston , and later by Cooper , McCarthy et al.
In consequence of continued use and the resultant symmetrical re-sharpening of the working edge to compensate for it, the Tula is gradually but evenly diminished in size and shape in the direction of its base… until it finally attains that state of diminution where it is no longer practical to embed it firmly in the gum or continue its employment economically.
They suggest that tulas are predominantly retouched in a succession of flake removals across the distal end, retaining the symmetry of the artefact, and ending when the flake is so shortened that it can no longer be reliably hafted.
The sequence of changes to tula morphology is explored in this section using a number of measures of reduction, but primarily elongation following Hiscock and Veth , for a sample of 66 tulas.
If the reduction sequence outlined by Cooper and Hiscock and Veth holds for the Wardaman tulas, then changes in reduction intensity as measured by elongation should be accompanied by reductions in length, as length should show greater reductions than width.
This turns out to be the case for the Wardaman tulas as shown in Figure 6. A reduction model for burins. Two common sequences are illustrated. A: the sequence leading to dihedral burins, and B: a sequence of rotations leading to multiple orientations and the removal of substantial numbers of spalls.
Changes in the morphology of tulas over the sequence of reduction. According to ethnographic accounts of tula manufacture, an important first step is the removal of excess ventral area so that only the convex bulb of percussion is left intact. Tulas are then steadily dorsally trimmed from the distal end back toward the proximal end as use and resharpening continues. The result is a gradual loss of perimeter as reduction continues, but also a relative increase in the proportion of the unretouched edge as represented by the platform.
This pattern should be represented by a decrease in the perimeter of retouch as reduction continues. This is exactly what is found for tulas, as shown in Figure 6. However, in the final stage of reduction, perimeter of retouch increases again. This likely represents the reduction of the platform in the final stages of reduction. Turning the tula degrees in the haft and retouching the old platform edge as the new working edge was observed ethnographically, and some tula slugs show signs of working on both proximal and distal ends.
This is because the edge should be at its most curved once trimming of the bulbar area has finished, resulting in a wide arc of retouch around the bulb. As retouch continues, the edge straightens out and may finally become concave. This progression of changes in edge curvature is shown in Figure 6. Changes in edge curvature for tulas as reduction continues, measured using flake elongation length:width ratio.
Unfortunately there are next to no lightly retouched tulas in the sequence and so the dimensions of fully retouched tulas must be plotted instead, as shown in Figure 6. Perhaps not surprisingly given extensive reduction, tulas cluster together very tightly in terms of elongation, but vary extensively in cross-section and marginal angle. Variation in tula shape in comparison with unretouched flakes. This is a very long use-life, especially for such a small artefact. The Reduction Model for Tulas.
The changes to size, shape and edge morphology documented here helps build a reduction sequence model for tulas like those for burins, points and scrapers above. Tulas begin as flakes with a pronounced bulb of percussion, and are first trimmed along the distal margin to leave only the bulb of percussion. A reduction sequence for tulas.
The A sequence represents continued reduction of the distal end. The B sequence results from turning the tula around and flaking the platform. As retouch is added to tulas, length is reduced rather than width, the curvature of the distal margin straightens out and the unretouched platform represents an increasing proportion of the overall edge Figure 6.
As tulas near the end of the sequence, they are sometimes flipped over and the platform is retouched to form a new edge, thereby maximizing the reduction potential of the implement Figure 6. This process takes place with increasing frequency as reduction continues.
Finally, tulas are discarded once they have reached the point at which they can no longer be hafted. This usually takes place once tulas have been reduced to around 4 mm in length reaching a minimum weight of 1. Burrens are essentially invasively retouched scrapers with retouch located on both lateral margins. Simultaneous reduction of both margins tends to result in an elongate slug-form.
Burrens are perhaps the least well documented retouched artefact form discussed here, despite their frequent mention in the older Australian archaeological literature Johnson ; Lampert ; McCarthy ; McCarthy et al. McCarthy argued that the burren was likely to be a functional equivalent of the tula, though with the haft set at 90 degrees to the lateral margins rather than parallel to it. An adzing function for these implements seems unlikely, however, at least in the same manner as the tula, since most burrens lack the pronounced bulb of percussion that enables tulas to function as efficient adzing tools when encased in large amounts of resin.
Others have tended to group burrens with other scrapers as a form of stylized scraper Sanders While plausible, functional speculations of this kind are unhelpful in understanding the reduction process, and are not considered further here. It is possible to test whether burrens stand out in any way from scrapers by examining their place within the continuum of retouch morphologies used for scrapers earlier in this chapter. This data is presented for 14 burrens and scrapers in Figure 6.
Burrens clearly sit neatly within the range for scrapers in terms of their edge curvature, perimeter of retouch, edge angle and invasiveness of retouch in relation to the GIUR. When the range of flake shapes associated with burrens and scrapers is examined, however, as in Figure 6.
The separation of burrens and scrapers is therefore likely to be an arbitrary one based on the straightness of the lateral margins, but no other aspect of formal variation. ET miniaturization continues into combination scrapers, but ASTt are even smaller. Could miniaturization of tools reflect colder environments, a landscape that was warming slowly in ET times? LT is mainly triangular, followed by ovoid and rectangular.
Rhomboid plans become reduced throughout Taltheilei, ending in a return to wider but non-triangular hafts, possibly for hand clenching. This is reinforced by the single square Chipewyan scraper. From earliest to latest, NP is almost entirely tearshaped; SA, mainly tearshaped with rising tortoise-backed. The single Chipewyan scraper is also tortoise-backed. Tundra and forest section differences are immediately apparent. All cortex spall planoconvex scrapers are tundra.
Combined with plan above , forest scrapers are mainly flat tabular rhomboids, while tundra ET are mainly tabular triangles; i. Tortoise-backing makes scrapers thicker, stronger and longer to make and is more plentiful in the semi-sedentery forest. Ululike bifacial scrapers were found only in the tundra and raise the frequency of biconvex sections.
Serrated scraper edges are similar in both ranges. So far, the data suggest that tundra scrapers are tabular with ground triangular bases. Since ET was the earliest Taltheilei culture following the cold ASTt period, ET peoples may have had more raw material or a dislike of cortex on finished tools. The incidence of striae is similar in both ranges.
Basal grinding frequency is similar in forest and tundra. Many endscrapers have ground multifacetted bifacial bases with edge angles like those of bifacial knives. Many may have been made from knife sharpening flakes and are called thinning flake scrapers. Scrapers on biface thinning flakes or which have knife-edged striking platforms have similar frequencies in both ranges.
Spurs are lateral projections from endscraper bits. They may be sharp in Taltheilei and dull in ASTt. Spurring decreases throughout Taltheilei and may relate to the trend towards thicker rounder scrapers. Tundra material frequencies are similar generally, while no forest sandstone, basalt or copper scrapers are reported. Cultural phase-pertinent traits and variables are as follows:. In broken specimens where bit retouch ends in unretouched midsections, bases are also called unretouched.
If bits are unworn or worn, bases are assumed to be unground 1 or ground 2.
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