That chat with a geologist made me question everything about carbon dating

I was at a dig site in Oregon last month. This geologist walked over and said "you guys just assume the layers are undisturbed but floods mess that up more than people admit." He showed me a core sample where a 2000 year old tool was sitting below a 5000 year old bone. Flood deposits can flip the timeline completely. So how do we actually trust our dating sequences when water can just rearrange everything down there?

2 comments

2 Comments

troythompson21d ago

Has anyone looked at how flooding can actually concentrate older material on top of younger stuff in specific spots? I read a paper last year about how turbulence in floodwaters can pick up an ancient bone, carry it uphill, and drop it on a newer floodplain layer. So those reversed dates might not mean the whole timeline is wrong, just that you're looking at a local mixing zone rather than a clean stratigraphic column.

loganthompson20d ago

That 2,000 year old tool under a 5,000 year old bone thing is wild but not as rare as people think. What @troythompson mentioned about turbulence is key, but I've seen something even trickier in the Pacific Northwest. After big floods, the heavy stuff like stone tools and big bones actually sink down through the soft mud and sand, landing way below where they get dated from. So you can have a 200 year old axe head sitting on top of a 10,000 year old layer just because it settled down through the muck from a recent flood. The dates themselves are usually fine, it's the layers that lie to us.