Graham's books have been a big inspiration to me - Talisman for The Harrowed Garden, Supernatural for Crow of Thorns, The Sign and the Seal for Enoch's Vault - and I've met him a few times over the years.
I've not yet managed to find a good story that imagines an advanced civilisation before the end of the last Ice Age (~12,000 years ago). And by advanced, we could mean simply that they had excellent knowledge of astronomy, and could navigate the oceans in ships. I do find it compelling, if very scary, the idea that a comet brought an end to their civilisation and the warming of the planet, and then a few thousand years later, after the 'nuclear winter', further impacts brought about a return to a warmer climate.
What is chilling is the idea that there is a 30km chunk of black ice in the Taurid debris the planet passes through twice a year. Twice a year the planet runs across a busy six-lane motorway and so far hasn't hit a big truck. So far.