How are Rock Images Dated?

When dating an artifact such as rock imagery, scientists can either give it:

  • An absolute date (e.g. 1800 BCE) based on scientific dating techniques,
  • Or they can give it a relative date (i.e. this object is older than this other object)

Most rock images are given a relative date or time period of when they could have been made based on the design motifs in the images. These designs can sometimes be traced to pottery or known sites of specific cultures. Archaeologists can sometimes relatively date rock images by seeing which images are superimposed, or placed on top of others; the image on top is younger than the image underneath. Archaeologists can also determine which images have more weathering compared to other images on the same panel; typically, the more weathered or faded the image, the older it is.

These red pictographs from site WACA 503 overlap parts of the orange pictographs, indicating that they were drawn later. The orange pictographs may also show signs of weathering, further proof that they were drawn earlier.

It is extremely hard to give an absolute date to rock images. Sometimes, if pictographs contain organic pigments, they can be given an absolute age using Carbon-14 dating – but none of the pictographs at Walnut Canyon have been dated this way.  Similar attempts have been made to date petroglyphs using organic materials embedded in them, but these results are highly controversial.