Carbon‐bearing substances (charcoal and oxalate minerals) contained in rock surface mineral accretions obscuring pictographs (rock paintings) provide an indirect way of radiocarbon dating the rock art. This article describes the chronological sequence of mineralogical laminations in rock crusts at an Aboriginal site in northern Australia and establishes conformable relationships between distinct compositional bands and past evidence of rock painting. Carbon in the mineral whewellite (CaC2O4. H2O), in a layer stratigraphically equivalent to evidence of an hematite paint, was dated by accelerator mass spectrometry 14C at 24,600 ± 220 years B. P. (NZA‐2559), making this one of the oldest known pictographs in the world. Implications for the archaeology of Australia are briefly discussed. © 1993 John Wiley & Sons, Inc.