What Kind of Geological Formations Are Best for Preserving Fossils?

Chris i was just interested in thinking about, we've been talking about terrestrial rock. Now that we're beginning to venture further out beyond the planet earth, what about the geology? I mean, it's not long ago when you now, the pictures of dinosaurs i grew up with were kind of lizard like things, green or grey. And now we have the high quality fossils that can allow us to see that they were colored, and see pigments and so on. What kind of geological formations are best for preserving fossils?"