Easy. Snelling was wrong to claim the samples were not contaminated.
Consider if Snelling’s young Earth / Noah’s Flood claim were correct then EVERY fossil on the whole planet should show the same 14C date of less than 6000 years. That obviously isn’t the case. Also consider 14C dating has been calibrated by at least a dozen independent yearly dating proxies (tree rings, lake varves, ice core samples, ocean core samples, coral growth bands, speleothems, etc.) back to well over 50,000 years.
Yes, thanks for pointing that out. It seems clear that Snelling has at least attempted to account for contamination, but it’s also clear that his attempts were insufficient. It’s also clear that at least some of the claims he makes in his paper are demonstrably incorrect (for example, claiming that the wood and associated ammonite samples had “nearly identical” radiocarbon ages when quite clearly they did not) so it wouldn’t surprise me in the slightest if there are several other factual inaccuracies in there. Experts with hands-on experience such as @davidson would no doubt be able to give you more details than I can here.
For what it’s worth, I’d put down up to 0.5pMC of contamination to sample chemistry and instrument background. For the remainder, I’d still say groundwater contamination is most likely your prime suspect. Without actually having access to the samples themselves it’s impossible to be sure, but I expect that he’s underestimating just how much they could be permeated by groundwater, humic acid, microbial action and so on, especially over timescales of a few thousand years. Several questions spring to mind for starters: how porous were the samples in reality? How completely were they permineralised? Did they have any microscopic cracks in them? And so on and so forth.
The easiest answer is contamination, especially in light of the thousands of other measurements that show otherwise. It’s great he tried to avoid contamination but one thing I learned with peer-review is many times they will catch potential explanations for your results that you’ve missed. He needs to do this in a real science journal with experts on radiocarbon.
Perhaps I am getting tripped up by the terminology here, but the fossilized wood I am familiar with has most of the organic material replaced by minerals. It’s pretty obvious to me that organic material can be replaced by non-organic carbon.
Did they do an analysis of 12C/13C ratios to see if the sample was organic?
From my brief interactions with scientists who do 14C dating on a regular basis, this is one of the most important analyses to do. Carbon from a living source will have higher 12C due to photosynthesis favoring the lighter isotope. This allows the scientist to determine if there is contamination from abiotic carbon.
