The cave environment is actually quite favorable for the preservation of surface deposits of this kind.

Caves lack the wind, rain, UV radiation, and biological activity that rapidly degrade surface deposits in open environments.

A smudge mark left on a cave wall by an ancient torch may persist largely unchanged for thousands of years if the cave’s conditions remain stable.

This persistence makes cave wall deposits potentially valuable as evidence of ancient activity.

In principle, if the organic carbon in a torch smudge mark has survived in sufficient quantity and quality, it can be radiocarbon dated — providing a date for the specific episode of torch use that left the mark, not just for the organic remains found elsewhere in the cave.

In practice, this kind of dating is technically challenging because the deposits are typically very thin, the amount of carbon available is small, and contamination from more recent sources must be carefully excluded.