Just realized that carbon dating isn't always reliable for organic material in caves

Spent three weeks trying to date a bone fragment from a dig in Tennessee before someone pointed out the cave's limestone was contaminating the sample with older carbon. Anybody else run into issues with geological seeps messing with their site's timeline?

2 comments

2 Comments

lewis.drew1mo ago

Yeah I ran into this exact mess in a cave system in West Virginia back in 2019. We were getting dates that were like 5,000 years too old on some charcoal because the groundwater was carrying dissolved carbon from the surrounding limestone directly into the deposit. Ended up having to send samples out for compound-specific radiocarbon dating on individual lipids which costs a fortune. If your site has any visible travertine or flowstone nearby, that's a dead giveaway. Best quick check is to run a stable isotope analysis first to see if the carbon signature matches the local geology.

olivia_webb1mo ago

Did I spend two solid weeks convincing myself a deer bone was from the Pleistocene before my advisor casually asked if I'd checked for limestone contamination? Yes. Yes I did. Felt real smart holding that 40,000 year old "priceless artifact" that was probably just a regular deer from like 1500 AD with a bad case of old carbon poisoning. We ended up having to collagen extract everything from that site, which is basically like trying to pick the meat out of a bone broth after you've already boiled it for 12 hours. My lab notebook from that month is basically just me drawing sad faces next to each sample number.