Saturday, June 27, 2020
KEYHOLE SINK, KAIBAB NATIONAL FOREST, AZ. - ANOTHER RESTORATION:
Saturday, June 20, 2020
DATING AUSTRALIAN ROCK ART WITH MUD WASP NESTS:
Australian mud wasp, Sceliphron laetum.
And while we have been on the subject of rock art in Australia - mud daubers (wasps) have long been a friend to potters as a guide to good deposits of local clays they can use to produce their pottery, now they are becoming recognized as friends to Australian rock art researchers as a source of potential dating for rock art panels.
Not so much a new technique, but a new source of datable material has been found in rock art panels in Australia - mud wasp nests. Made from mud found locally by "mud dauber" wasps, the nests are assembled with cells for the incubation of the offspring, then filled with stung and paralyzed insects for food and a single egg by the female wasp. A mud wasp nest on top of a painted rock art panel will have to have been made after the rock art was created, and if paint is found on top of the remains of an earlier mud wasp nest that nest is older than the painting. If there are a number of nests, and they can be dated, the oldest date from on top of the paint will establish a minimum age range for the rock art (this could be true for petroglyphs as well). A range of maximum and minimum dates can be determined if there are nests found both over and under the painted image. If found in a protected location such as a rock shelter, a mud wasp nest can last a very long time indeed.
How can a mud wasp nest provide dating you ask? There are currently two possibilities; AMS 14C dating, and optically-stimulated luminescence (OSL). For AMS 14C dating small bits of organic matter in the dried mud are extracted and dated with an accelerator mass spectrometer (AMS), and the OSL dating is done on small grains of quartz sand included in the dried mud.
"OSL is a light sensitive signal that builds up over time during a period of 'burial' or cover. Provided the samples are not exposed to light during collection the signal can be stimulated in laboratory conditions and measured. When divided by the natural radioactivity of the soil or substrate, the amount of light (luminescence) produced is proportional to the period of burial time. OSL is the main method used for establishing chronologies for excavated occupation deposits that pre-date the maximum AMS 14C boundary, or in deposits that lack ample carbon samples. Samples of sediments found within the cave environment have no direct association with the art, but sediments may be collected by wasps and then 'buried' within mudwasp nests found on top of the art. Dating of mudwasp nests using OSL was first introduced by Roberts et al. They initially worked with large nests and sampled each layer to determine the extent to which light no longer penetrated the nests and the quartz was effectively 'buried' and supported their OSL age estimates with AMS 14C or organics found within two nests (Roberts et al)".
As mud dauber wasps are found pretty much all over the world this tool may provide valuable information in many instances where rock art is otherwise undatable.
NOTE: Some images in this posting were retrieved from the internet with a search for public domain photographs. If any of these images are not intended to be public domain, I apologize, and will happily provide the picture credits if the owner will contact me with them. For further information on these reports you should read the original reports at the sites listed below.
REFERENCES:
Roberts
RG, Walsh GL, Murray A, Olley J, Jones R, Morwood MJ, et al.
1997 Luminescence
dating of rock art and past environments using mud-wasp nests in northern
Australia, Nature, 1997; 387 (6634): 696-699.
Ross, June, Kira Westaway, Meg Travers, Michael J. Morwood, and John Hayward,
2016 Into the
Past: A Step Towards a Robust Kimberley Rock Art Chronology, August 31,
2016, Plosone,
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0161726
Saturday, June 13, 2020
ROCK ART MADE WITH STENCILS
Stenciled crab, Photo Brady et. al., 2020, p. 7, Fig. 4-9 |
The creation of rock art images with pigment and stenciling is fairly common in panels of handprints. There are also instances in Australian rock art of images made by holding an object against the rock face and spraying paint around it. These are often images of boomerangs or throwing clubs. Now, a new type of stenciled image has been discovered in Australia. Small images of animals, boomerangs, and humans have been discovered at a rock shelter named Yilbilinji 1, in Limmen National Park in the southwest Gulf of Carpentaria region in northern Australia. "Traditionally owned by the Marra Aboriginal people, the site was documented by the research team in 2017 and instantly stood out as unique, according to the researchers from Flinders University and the Monash Indigenous Centre." (phys.org 2020)
The authors of the study described it in their published report. "In 2017, as part of an ongoing rock art recording project in northern Australia's south-west Gulf of Carpentaria, a unique and distinctive assemblage of miniature and small-scale stenciled motifs consisting of anthropomorphs, boomerangs, macropod tracks, and geometric and linear designs was recorded from the Yilbilnji rockshelter, traditionally owned by the Marra Aboriginal people, in Limmen National Park." (Brady et al. 2020:2)
Stenciled long-necked turtle, Photo Brady et. al., 2020, p. 7, Fig. 4-10.
The real question is what material and techniques were used to make the stencil. We traditionally think of stencils as particular shaped openings in a sheet of some material that paint can be applied through. This sort of stencil used on a rock face would show considerable edge bleed at rough spots on the edges of the image, yet these particular small motifs show generally sharp and clear edges. The assumption has to be that they used a flexible material that somehow adhered to the surface while paint was being applied.
As the authors described it - "Morphologically, most of the assemblage comprises motifs with well-rounded or curved edges. These attributes suggest that a malleable substance, such as wax, resin or clay, was used to sculpt the templates, and also to allow the creation of curved but also sharper edges and points, where required. . . . Additionally, with a malleable raw material, a shaped object can be placed flush against an uneven rock wall surface resulting in a more complete reproduction through stenciling. In addition, an adhesive, malleable material would not require support to hold it against the rock wall." (Brady et al. 2020:8-9)
The authors concluded that the malleable material in question was probably beeswax, commonly used by Aboriginal peoples for a large number of purposes. Procuring an actual sample of the native beeswax from Aboriginal sources they tested its efficacy. Small (miniature) shapes were replicated and used as stencils on a sandstone surface using kaolin mixed with water to a paint consistency and then flicked onto the surface from a brush. The beeswax was then removed leaving the negative images.
"In each case, the sculpted beeswax templates allowed for a direct or close replication of the original motifs. Both the sharply defined edges and the curving and angular shapes were easily reproduced in our experiment. The heating and shaping of the beeswax required minimal time or effort, and was an effective and expedient way to create miniature or small-scale stencil motifs on a sandstone rock surface. In addition, the variable rock surface, both smooth and rough, played no role in the model's ability to adhere, suggesting that this technique would be suitable in a variety of different contexts." (Brady et al. 2020:12)
Although no analysis of the rock surface for wax residue was attempted the authors hope to be able to conduct that study in the future. This interesting paper provides useful information Australian Aboriginal rock art as well as introducing a relatively unknown technique they used to create stenciled rock art. Perhaps other parts of the world should also be examined for traces of such techniques.
NOTE: Images in this posting were retrieved from the internet with a search for public domain photographs. If any of these images are not intended to be public domain, I apologize, and will happily provide the picture credits if the owner will contact me with them. For further information on these reports you should read the original reports at the sites listed below.
REFERENCES:
Brady, Liam M., John J. Bradley, Amanda Kearney and Daryl Wesley,
2020 A Rare Miniature and Small-Scale Stencil Assemblage from the Gulf of Carpentaria: Replication and Meaning in Australian Rock Art, Antiquity, https://doi.org/10.15184/aqy.2020.48
phys.org,
2020 Miniature
rock art expands horizons,
https://phys.org/news/2020-05-miniature-art-horizons.html