Quartz luminescence dating
Archaeologist Sue O'Connor at the Australian National University has found a buried fragment of rock painting preserved in the limestone rock-shelter of Carpenter's Gap in the Kimberley (near Windjana Gorge National Park) in a layer dated to 40 000 years old.
The red pigment seems to be the remains of paint on a rock art fragment fallen from the ceiling above.
Probably Australia's earliest known artistic system is the rock engravings in the Olary region of South Australia.
Most have been radiocarbon dated and the dates range from 10 000 to 40 000 years. As well as rock art, ochre has many other uses in modern Aboriginal ceremony, and is repeatedly found in association with burial not only in Australia but also in other parts of the world.
In Arnhem Land, there is no certainty either that ochre was used for painting from the beginning; or that painting with ochre was on rock surfaces (rather than on perishable subjects); or that the first paintings on rock are amongst the ones that survive.
Many of these have been used for camping and their floors are layered with charcoal and ash from camp fires, the remains of food such as shells and animal bones, stone tools and, very often, pieces of ochre.
Ochre comes from soft varieties of iron oxide minerals (such as haematite - a fine-grained iron oxide which produces a strong red colour with a purple tint) and from rocks containing ferric oxide.
The layer containing the painted fragment yielded ochre, burnt bone, stone artefacts and charcoal with an accelerator mass spectrometry (AMS) radiocarbon date of 39,700 1,000 BP (BP means Before the Present, which in this context is 1950, when the radiocarbon dating technique was developed).
Another AMS date on charcoal from 20 centimetres below this gave statistically the same date.
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Australian rock art shows some of the oldest-known artistic images by modern humans.
However, the hardness of much of the ochre found in deposits strongly suggests that it was used on rock or other hard surfaces and the pattern of wear is totally consistent with use of the ochre in art.
The oldest dates so far found by direct dating of art were obtained by geologist Alan Watchman for layers of pigment in two rock-shelters on Cape York in north Queensland, one of 25 000 years and one of almost 30000 years.
These dates give a minimum age for the fragment and for the occupation of the shelter.