The (super 14) C ages obtained on charcoal were, in most of the cases, in agreement with the humin fraction considering the experimental errors, or 20% older in average.The dates obtained from total SOM showed significantly younger ages than the humin fraction indicating contamination by younger carbon.Lab manager Dr Christine Prior already has bad news for another client – an art authenticator in Hong Kong.The drinking vessels made from rhino horn she sent for radiocarbon dating turned out to be modern fakes.And so it's kind of a record of the atmosphere up to 10,000 years. Those are the speleothems that are coming from the top of the cave.If you want to go even further back, you can look at cave deposits, and the fancy word for these cave deposits are speleothems. But the reason why these are useful is these are formed by calcium carbonate, so they have carbon in them, and slowly over, really, tens of thousands of years, the water in the cave deposits that calcium carbonate.
However, the humin fraction ages could be assumed as the minimum ages for carbon in soils.
And you can look at their tree rings, and I think most of us are familiar with this idea that every year that a tree grows, it forms another layer of bark.
And so you can look back to that layer of bark just for the half life of carbon-14, and then figure out how much carbon-14 was there in the atmosphere at that period in time. Those are those speleothems that are kind of coming out of the bottom of the cave, or stalactites.
And if it isn't constant, how do you calibrate your measurement so you can actually figure out how much carbon-14 there is relative to living plants and animals at that time?
And the way that you can make that calibration, because it turns out it isn't perfectly constant, the way that you can make that calibration, there's two ways, and I have pictures here of both of them, one is to look at tree things. And I'm told this will work up to about 10,000 years. I don't know of any 10,000 year old trees, I don't think anyone does, but maybe there's some remains of old trees.