Carbon 14 dating used to be reliable back to about 35,000-40,000 years, but advances in shielding and now AMS dating have extended it to about 50,000 years. They are also working on advances which may make 80,000 years possible, but that is still a few years away most likely.
This is one of my fields, so let me know if you have any other questions.
Thanks. Always learn something on here.