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Explaining point variability in the eastern Victoria River Region, Northern Territory.

Article Excerpt
Abstract

This paper constructs a reduction sequence model for north Australian points from the eastern Victoria River region, and identifies a single continuum linking unifacial and bifacial point forms, with some divergence from this single reduction trajectory dependent upon artefact size. Chronological changes in reduction intensity between 5,000BP and the present are found to coincide with typological variation in points as well as changing emphasis on the extendibility of point reduction. It is suggested that changes in the extendibility of point reduction can be linked to intensified ENSO-driven climatic variability in the late Holocene that likely increased economic risk and warranted a substantial technological response, including the use of retouched toolkits with potential for longer use-lives.

Keywords: Stone points, reduction trajectory, Victoria River

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North Australian prehistory is largely built on stone typologies, yet the relationships between the various implement forms is poorly understood, as are the changes in morphology they undergo throughout their use-lives. One way to resolve these problems is to build reduction sequence models for retouched implements for various regions, and thereby identify the relationships within and between 'types' across space and time. This paper builds such a reduction sequence for points from one region of the Northern Territory with the aim of determining whether unifacial and bifacial points share a common reduction trajectory, or whether these two forms diverge at various points along the way from unretouched blanks to heavily reduced forms.

The classification of Australian retouched implement forms has been a focus of archaeological inquiry since archaeology began in Australia. In particular the uncertain relationship between unifacial and bifacial points has occupied much attention in the literature with various archaeologists arguing for or against a continuum linking these implement forms (Allen and Barton 1989; Flood 1970; Hiscock 1994; Jones and Johnson 1985; Roddam 1997; Schrire 1982). Their relationship to the pressure flaked Kimberley points of northwestern Australia and to the pressure and percussion flaked 'pirri' points of South Australia has also remained ambiguous (Akerman and Bindon 1995; Elkin 1948; Tindale 1985). It is difficult to see how these problems can be adequately resolved without undertaking detailed studies of artefact production and the effects of resharpening on implement morphology in a number of regions where points are common.

A number of forms of evidence have been presented in favour of a divergent model of unifacial and bifacial point manufacture. For example, differences in the types of raw material used in the manufacture of unifacial and bifacial points was cited by Schrire (1982) as evidence for divergence in point production in Arnhem Land, with unifacial points more commonly made from quartz and bifacial points from quartzite. Size differences were also advanced as evidence for the existence of a divergent model by Flood (1970), who argued that the smaller size of bifacial points at Yarrar shelter southwest of Darwin proved the existence of two separate types. Allen and Barton (1989) found the opposite pattern, with bifacial points from Ngarradj Warde Djobkeng in Kakadu tending to be larger than unifacial points, and likewise inferred that two discrete forms were represented. Flenniken and White (1985) argued on technological grounds founded in replicative experiments that true bifacial point reduction always commences on the ventral face first, in order to move "the margins of the preform toward the middle of its mass so that flakes could be removed successfully from both faces" (Flenniken and White 1985:148). As unifacial points are typically reduced on the dorsal surface only, they reasoned that unifacial and bifacial points must be separate, as each entails a distinctive and mutually exclusive reduction sequence.

In a review of this literature, Hiscock (1994) pointed to a number of flaws in the logic of those arguments in favour of the divergence model. He also offered evidence from point assemblages from Kakadu and Lawn Hill in support of a sequential model of the gradual transformation of unifacial points into bifacial points. For example, he found Schrire's (1982) case for the separation of point types on the basis of raw material useage unconvincing, citing a number of studies that have shown both kinds of points to be made from a wide range of materials throughout Arnhem Land and Kakadu National Park (Allen and Barton 1989; Brockwell 1989). The size differences noted by Flood also offered poor proof of the typological divergence model, and in fact conformed better to a reduction sequence model in which larger unifacial points were worked down into smaller bifacial ones. At Ngarradj Warde Djobkeng, where unifacial points were on average smaller than bifacial points, Hiscock found the results not to be statistically significant.

Hiscock's own analysis focused on the patterns of scar superimposition, found on the ventral and dorsal surfaces of individual specimens as they were transported away from a stone source, to determine the sequence of flake removals from each surface and hence the nature of progression from unifacial to bifacial points. The results showed that flaking began on the dorsal surface in the vast majority of cases for both unifacial and bifacial points, that points tended to decrease in size with distance from a stone source, and that bifacial forms became increasingly abundant in more distant assemblages. Hiscock interpreted this pattern to mean that unifacial points were often reworked into bifacial forms to extend their use-life as replacement stone became more difficult to obtain.

Roddam (1997) has also advanced evidence in support of a reduction continuum model using a sample of unifacial and bifacial points from sites across the Northern Territory. Roddam examined changes in the morphological characteristics of unifacial and bifacial points in relation to a number of indices of reduction, including size, frequency of invasive scar removals, and the frequency with which dominant dorsal surface scar patterns shifted from an alignment parallel to the percussion axis to one that was perpendicular to it, thereby tracking the gradual removal of pre-existing dorsal scars through...

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