It may be a landmark discovery.

Scientists have found a stone tool at an ancient rock shelter in the high desert of eastern Oregon – that may turn out to be older than any known site of human occupation – in western North America.

University of Oregon archaeologist Patrick O’Grady says the tool was chipped from a piece of orange agate.

It was found below a layer of volcanic ash from an eruption of Mount St. Helens – almost 16,000 years ago.

If the 15,800 year old date is confirmed it would pre-date the so-called Clovis Culture, who were once generally believed to be the first people to migrate from Asia into North America.