*raises hand* i have no idea what Hell Creak is. tell me more

Hell Creek is a fossil-heavy rock formation located in Montana and North Dakota! It's one of the most complete fossil sites we have of the Mezosoic (along with other standouts like the Morrison and Kem-Kem). Hell Creek gets a few extra cool points for a handful of reasons:

It has a whole host of big name dinosaurs: T.rex, Triceratops, Ankylosaurus, Pachycephalosaurus, Edmontosaurus, and even a large raptor that's a real-life Jurassic Park 'Raptors' (the book and film used oversized Deinonychus, but Dakotaraptor is actually of comparable size. Potentially. I love the species and what it'd mean for the ecosystem, but I don't trust DePalma as far as I can throw him. He accidentally included turtle remains in the holotype, which... come on, man). Another cool big name potentially associated with the formation, but not a dinosaur, is a large Mosasaur species (think a giant marine monitor lizard) that was recently found to exist off the coast, as well as the (potentially) largest creature to ever fly, Quetzalcoatlus (I have no way to describe this, search it up, it's terrifying and weird).

Actually? No. You deserve to see what a Quetz would look like.

(Photo and model credit @bluerhinostudio. Seriously, they're so lifelike.)

Hell Creek's fossils were deposited at the very tail end of the reign of dinosaurs, so you get a look at their last glory days + a good handful of million years prior. Actually, the boundary layer - the actual moment the apocalypse became real and quartz was shocked by the Chixclub impact - is present! There's another site that seems to contain the actual aftermath, with molten glass raining into the mud and debris of animals caught in tsunamis thrown together (though some elements of the site are debated, because DePalma is sketchy as hell and reported different findings to the media vs his publications).

(Credit conveniently included in the image, nice.)

We have SO much information about it! Remains of everything from megafauna and their interactions - herbivores that have healed bitemarks from T.rex, facial bitemarks between T.rexes - to the minute. Pollen and seeds from a host of plants; insects trapped in amber; tiny amphibians, and sharks. The list of species on the Wikipedia articles are absolutely insane - it's so complex and detailed.

There's also a video game in slow, slow development depicting this formation, Saurian - last I heard it's grinded to almost a standstill, and IIRC there is ~tea~ in the paleo community about it, but it was fun following the development for a few years. The concept art is also gorgeous, and you really get a feel for just how much material they have to work with to make this as accurate as possible!

TLDR, Hell Creek is fascinating - though there are plenty of other cool formations worth poking at, too! The Kem Kem Group, Dinosaur Park, Candeleros, Morrison, Jiufotang and Nemegt Formations are all favorites <3