Hell Creek Formation

Hell Creek Formation
Location
Supercontinent	Laurasia
Continent	North America
Country	USA
Unit of	Montana Group
Region	Montana, North Dakota, South Dakota, Wyoming
Underlies	Hell Creek and Lance Formations Fort Union Formation Scollard Formation Paskapoo Formation
Overlies	Hell Creek Formation Fox Hills Formation Lance Formation Meeteetse Formation Scollard Formation Battle Formation
Temporal Range	Hell Creek Formation 68 - 66 million years ago, Maastrichtian Stage, Late Cretaceous Period Lance Formation 69 - 66 million years ago, Maastrichtian Stage, Late Cretaceous Period Scollard Formation 70 - 65 million years ago, Maastrichtian - Danian Stage, Late Cretaceous - Early Paleogene Period
Episodes	Coasts (Segment 1) Freshwater (Segment 2) Forests (Segment 2) Swamps (Segments 4 and 5) North America (Segments 3 and 4)
Filmed In	Hell Creek Formation Bog Pond, Waterford, Oxford County, Maine, USA (Swamps, Segment 5) Lance Formation Winterfold Forest, western Greensand Ridge, Surrey, England (North America, Segment 5) Scollard Formation Lake Morena County Park, San Diego, California, USA (Swamps, Segment 4)
Characteristics
Climate	Subtropical
Environment	Coastal, Estuarine, Floodplain, Fluvial, Forest, Lacustrine, Swamp
Notable Areas	Tanis Fossil Site

The Hell Creek Formation, named for exposures studied along Hell Creek by Jordan, Montana, is a formation that stretches across parts of Montana, North and South Dakota, and Wyoming. Due to being very heavily studied, it is one of the most known Late Cretaceous formations of North America.

Along with the Lance Formation (named after Lance Creek, Wyoming) and the Scollard Formation (named after the Scollard Canyon at Dry Island Buffalo Jump Provincial Park) of southwest Alberta, Canada, Hell Creek Formation forms a section of the eastern side of Laramidia, as part of it made up one of the western coasts of the shrinking inland sea that split North America in half during the Late Cretaceous Period.

Paleoenvironment

During the Maastrichtian stage of the Late Cretaceous Period, Hell Creek and its neighboring formations were full of estuaries, floodplains, forests, lakes, rivers, swampy lowlands, and coastal plains, kept constantly humid by ample rainfall and a subtropical climate warmer than the region today (hence, there was no cold season in those areas back then).

These conditions climate helped support conifers, ferns, flowering plants, palmettos, and ferns in swamps, as well as ash trees, conifers, canopy and understory plants, oaks, and shrubs in forests. The area by northwestern South Dakota is a coal-rich wetland environment fit for supporting angiosperms, but also (to a lesser degree) conifers, cycads, cypresses, and ferns. Several sites also preserve fossilized leaves that indicate a forest of small trees

One area of Hell Creek, known as the "Tanis Fossil Site", is believed to preserve a catastrophic moment that occurred 66.043 million years ago, in the wake of the Chixiclub asteroid impact that wiped three quarters of all life on Earth, including all non-avian dinosaurs. Preserved traces of the disaster include millions of mikrotektites (molten debris generated by the asteroid impact) that weren't reworked into different layers, a turtle impaled on a tree branch, large primitive feathers, compacted plants, fish that suffocated during the impact, with their skeletons indicating that the impact occured during spring, drowned ants, eggs and hatchlings, and broken remains of almost all known dinosaur groups in the Hell Creek Formation, among them the partially-mummified foot of a Thescelosaurus with the skin still intact.

While rich in dinosaurs and other terrestrial creatures, surprisingly, a mosasaurine measuring at least 11 meters (36 feet) long was found in the area. It is possible that this animal is a sub-adult form of Mosasaurus itself, given its status as a cosmopolitan species (being found on all seven continents). It is likely that this is meant to be the animal portrayed going after the T. rex family in the first segment of Coasts, explaining why it is identical to the fifty-foot "Hoffmann's Mosasaur" found in the fourth segment of Coasts and the fourth segment of Oceans. Hell Creek Formation also has at least one azhdarchid, Infernodrakon, similar in size to Quetzalcoatlus lawsoni, which is, in turn, half as large as the more well-known Quetzalcoatlus northropi.

Paleofauna

A selection of non-avian dinosaurs that lived in the Hell Creek, Lance, and Scollard Formations

Edmontosaurus annectens

Mosasaurus hoffmannii

Pachycephalosaurus wyomingensis (Pachycephalosaurus spinifer?)

Pectinodon bakkeri

Protostegid

"Styginetta lofgreni"

Triceratops horridus

Tyrannosaurus rex

Appearances

“ Across this vast continent, there are over a hundred thousand square miles of swamplands. And most of them remain flooded all year-round. ”

― David Attenborough, Swamps

The Hell Creek Formation is the setting of the fifth and final segment of Swamps, which shows a pair of T. rexes ambushing an Edmontosaurus at night. It also appears to be the likely setting of the first segment of Coasts, where a T. rex leads his hatchlings to an offshore island. It may possibly be the setting of the second segment of Freshwater, though it's also possible that this is set in the neighboring Lance Formation.

“ Further north, the Rocky Mountains are still slowly rising. And as they do, they create higher, cooler landscapes where vast pine forests flourish. ”

― David Attenborough, North America

The Lance Formation is the setting of the fourth segment of North America, where male Triceratops show off and fight rivals to impress females during the mating season. It might also be the likely setting of the second segment of Freshwater and the second segment of Forests, both of which show thick forests inhabited by Triceratops, one of which got hunted down by a T. rex in Freshwater.

“ A devil toad can only survive here because every year, the land is flooded by seasonal rains. However, there are places where changing climate means the rains are less-certain. This inland basin in North America was, in the past, several feet deep in water. But after a decade of drought, it's now bone-dry. Nonetheless, some dinosaurs still linger here. ”

― David Attenborough, Swamps

The Scollard Formation is the setting of the fourth segment of Swamps, which depicts an inland basin that used to be several feet deep in water, dried up by a decade-long drought, where an old Pachycephalosaurus defends his leadership over the herd against a young challenger. Of the three formations, it is the only one that lasted past the Cretaceous Period (and therefore the Mesozoic Era).

Trivia

• Dr. Darren Naish, Prehistoric Planet's lead consultant, heavily opposed the setting chosen for the fourth segment of Swamps, since not only does the arid basin of that story poorly fit the "swamps" theme of the episode (even considering the fact that it was once covered in water), it is also an inappropriate habitat for Pachycephalosaurus, which is known for living in wetter, more heavily forested lowlands like the one shown in the fifth and final segment of Swamps.