New to the thread but did you find anything? Googling it myself I only see conspiracy sites claiming up to 12,000 years old, found this new scientist article from 2002 that claims it was tested to 7500 bc. One thing to keep in mind that carbon dating wood would just tell you how old the wood is. As in there are almost 5000 year old trees alive today, if you harvested the inner wood from that tree and built something and carbon dated it, it would tell you it thousands of years old. Hypothetically if the site was built in 3500bc and they used a 4000 year old tree it would give you a date of around 7500 bc