At http://westerndigs.org/stone-tool-unearthed-in-oregon-hints-at-oldest-hu… …. this excellent web site has come up with another humdinger. A multi-purpose stone tool made from an orange agate was unearthed at a rock shelter in Oregon. The site has already produced evidence of human occupation as early as 12,000 years ago – such as stone points, tools, and hearths. The new agate tool was found in a much deeper layer. It was situated in a sandy clay geology that was itself found beneath a layer of volcanic ash that has been dated at 15,800 years ago. In other words, the new tool is older than 16,000 years ago. This makes it 3000 years older than Clovis – which is what is getting American archaeologists excited.
The volcanic ash belongs to an early eruption of Mount St Helens which lad down a thick deposit of tephra. The sandy clay sediments are going to be the focus of continued research. We might wonder how those sediments were laid down – and how quickly. The point is they will not necessarily harbour evidence of human settlement at the rock shelter. The tool could have been flushed to that vicinity by water – bringing the sandy clay geology with it. Melt waters at the end of the Ice Age may have been responsible for the sediment. Hence, the tool could have come from several miles away – and may be undateable. On the other hand, if the tool was not alone and human activity is discovered within the sediment, in situ, this would imply such activity dates from after the end of the Ice Age. The more interesting, but more difficult to judge and tie down, would be if the agate tool was brought in by meltwaters – with the implication humans were already in N America during the Late Glacial Maximum.