Hell-Creek-Formation

The Hell Creek Formation is a sequence of continental sedimentary rocks of Late Cretaceous and early Paleocene in the north- western United States and a major store of dinosaur fossils. This formation (geology) is open in the badlands of eastern Montana and parts of North Dakota, South Dakota and Wyoming, from their originating popular dinosaurs such as Tyrannosaurus, Triceratops, Ankylosaurus and Edmontosaurus. Furthermore, it shows at its upper end enriched with iridium Cretaceous-Tertiary boundary, a thin, discontinuous running but characteristic layer comprising the Mesozoic ( Mesozoic ) from the subsequent Cenozoic ( Cenozoic ) separates.

The Hell Creek Formation is well studied and is named after Hell Creek at Jordan (Montana). It is composed of clay minerals, shales and sandstones, which have formed mainly during the Maastrichtian, the last stage of the Cretaceous period, 67-65 million years, from the deposits of rivers ( fluvial ). The rivers flowed at the time of the deposits on the eastern edge of the Western Interior Seaway in the formation, a sea in North America during the Late Cretaceous, which stretched from northern Canada to the Gulf of Mexico. Therefore, the easternmost deposits of the formation originate occasionally from swamps. The climate at the time of deposition was mild, the presence of crocodiles can also connect to a subtropical climate without pronounced annual periods of cold weather.

Similar formations of the same age are the south of the Hell Creek Formation located Lance Formation and the Frenchman Formation and the Scollard Formation of Canada. About the Hell Creek Formation is the Tullock Formation and, in North and South Dakota, the Ludlow formation. Under the Hell Creek Formation is found the older Fox Hills formation. Commercial excavations market fossils of the formation, usually dinosaur teeth, fragments of armor plates of fossil crocodiles and fish. A representative collection of fossils of this formation is to visit the Museum of the Rockies in Bozeman (Montana).

Fossils

From the Hell Creek Formation dates back an impressive amount of invertebrates, plants, mammals, fish, reptiles and amphibians. In 2000, the most complete skeleton of a dinosaur was discovered Hadrosauriden that has ever been found. In addition to dinosaurs and the fossils of some birds and pterosaurs ( flying dinosaurs ) were found. Also teeth of sharks and rays are occasionally found in these river sediments, suggesting that some of these taxa were more tolerant to freshwater, as they are today.

The dinosaurs found include various theropods do with how the frequent genera Paronychodon and Ricardoestesia, the tyrannosaur Tyrannosaurus rex and Nanotyrannus lancensis, the Ornithomimosaurier Ornithomimus sp., The Caenagnathiden Chirostenotes sp. and Elmisaurus elegans, and other Maniraptoren as Troodon sp., cf Dromaeosaurus, Avisaurus archibaldi as well as remains of Velociraptorinen.

The Ornithischia ( bird Beck dinosaurs) are represented with Ankylosaurus magniventris, Edmontonia sp., Pachycephalosauriden as Dracorex hogwartsia, Pachycephalosaurus wyomingensis, Sphaerotholus bucholtzae and Stygimoloch spinifer, Ceratopsia as cf Leptoceratops sp., Torosaurus latus, the very frequent Triceratops horridus and Triceratops prorsus, and finally ornithopods as Bugenasaura infernalis, Thescelosaurus neglectus, Anatotitan COPEI and the very frequent Edmontosaurus annectens Edmontosaurus regalis and.

External links and sources

• Cretaceous Hell Creek Faunal Facies, with a fauna list.
• Phillip Bigelow: Hell Creek life: Fossil Flora & Fauna, a Paleoecosysten
• Paleobiology Database: MPM locality 3850 ( Hell Creek Formation): Maastrichtian, Montana

• Fossil deposit
• Lithostratigraphy
• Geology America
• Rock unit of the Cretaceous
• Rock unit of the Paleogene