One Colour, (at Least) Two Minerals: A Study of Mulberry Rock Art Pigment and a Mulberry Pigment 'Quarry' from the Kimberley, Northern Australia
Distinctive mulberry paintings found in northern Australia, particularly those of the Kimberley region, have been argued to represent some of the oldest surviving rock art on the continent. Significant research efforts continue to focus on resolving the age of these motifs, but comparatively little attention has been given to understanding their physical composition and potential source(s). In a pilot investigation, we conclude that (at least) two mineralogically distinct mulberry pigments occur in 'Gwion' motifs and demonstrate that their major components can be indicatively chemically differentiated, non-invasively. Characterization of a 'quarried' mulberry ochre source demonstrates that these pigments occur locally as natural minerals.
Changing art in a shifting landscape: A comparative study of rock art sequences in northwest Australia using headdress depictions as a principal method of identification
The age of much Aboriginal rock art in northwest Australia is unknown. Concentrating on headdress depictions and some specific motifs in these paintings, an experiment has been undertaken to establish the feasibility of using perceived similarities and differences in their styles to compare the relative ages of art in two major locations. The order of established chronological sequences for the paintings in the core study area, Arnhem Land, in the Northern Territory has been used to establish comparative order matches with the Kimberley rock art sequences. The sequences seen in the Aboriginal rock art defined in previous research by well established authors in this topic do not appear to have been matched with the art in the two major locations, specifically using headdress depictions. In my thesis Grahame Walsh's sequence for the Kimberley has been compared with that of George Chaloupka's order for Arnhem Land (Chaloupka, 1993:47; Walsh, 2000). I felt that comparing the changes in headdress depiction over time would allow a method of wider investigation to be undertaken. It was therefore worthwhile to try a new way of comparison over a wider range of art styles than previously attempted. Using depictions of headdresses, as well as portrayals of the specific custom of circumcision, I analysed published reproductions of paintings and personal photographs from Arnhem Land (n=777) and the Kimberley (n=1066), using a database to record each headdress type and region, and then compare numbers of each type, according to the study area. Headdress types were defined by obvious shape. Observing the frequency of the most common Arnhem Land and Kimberley headdresses, I saw that in Arnhem Land, Vertical and Inclined Cones, Swept-Back hair styles and Round heads dominated with frequencies between 15% and 11%. In the Kimberley, Vertical, Inclined and Hanging cones on headdresses lead the counts (between 16% and 10%), along with Bun head shapes (10%) and Round Heads (17%). The resemblance between these particular headdress designs was notable in the Early, Intermediate and Late sequences for both Arnhem Land (AL) and the Kimberley (K). As well, a likeness in circumcision representation was noticed in both the core (AL) and the comparative study area (K), particularly relating to the more recent paintings. This suggested possible parallels in Early and Late sequences. Smaller counts of many different headdress types were also seen during the recording. Observations of paintings with approximately 5-7 headdress types seen only in either Arnhem Land or the Kimberley showed that diversity and local preferences also existed. I found that a visual and quantitative relationship was seen to exist between popular and wide-spread depictions of similar headdress motifs and circumcision motifs which may indicate communication of ideas between the people of Arnhem Land and the Kimberley regions and suggest a comparable time of painting.
Untangling time-averaging in shell middens: Defining temporal units using amino acid racemisation
Time-averaging is a process that affects almost every form of archaeological deposit. The conflation of two or more units from different time periods masks the true temporal span of units which is hidden by postdepositional processes. The implications of this are obvious as archaeological material found in close stratigraphic association may differ in age by hundreds or thousands of years. Some sites have a greater tendency towards the effects of time-averaging, with shell middens being one of the more susceptible. Conventional approaches to midden excavation or analysis, however, do little to tackle the issue of time-averaging. Using amino acid racemisation (AAR), an intensive relative dating programme was undertaken on shell midden excavated from a potentially time-averaged midden deposit. This approach revealed temporally distinct units that had been con flated into one deposit resulting in shell specimens temporally separated by up to 6000 years being found in close stratigraphic association. The application of AAR allowed us to define the temporal parameters of the various comingled deposits, and in doing so isolate temporal units which showed very different depositional patterns. These contrasting units imply different depositional behaviours and in turn changes in site use through time. This new application of AAR offers a way to approach shell midden archaeology to expose instances and repercussions of time-averaging that were previously hidden.
Isolating downward displacement: The solutions and challenges of amino acid racemisation in shell midden archaeology
Shell middens are particularly susceptible to post-depositional processes that can rework and redistribute material through a deposit. As archaeological material is moved from its original primary context, the assumption that a temporal connection exists with spatially associated material becomes tenuous. It therefore becomes critical to identify displaced archaeological material within a deposit to ensure correct chronologies are being built. Radiometric dating techniques can identify individual displaced materials, but are sometimes prohibitively costly to utilise on a large scale. This study presents a new application of amino acid racemisation (AAR) dating that identifies stratigraphically displaced midden shell from within a deposit from the northwest Kimberley, Western Australia. Low-cost AAR analysis of 72 samples identified a sample of downwardly-displaced midden shell. Upon close inspection, comparison of AAR and AMS radiocarbon determinations identified fine-grained inconsistencies. Possible processes generating these discrepancies are considered with future avenues for research presented. While an enormous amount of potential is contained within AAR, more work is required to bring the method to the same level of precision as other commonly utilised dating techniques in archaeological research.