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Home > Digsite Zones > Morrison Formation
MORRISON FORMATION. Extending from approximately 145 million to 200 million years ago, the Jurassic Period marks the middle of the Mesozoic Era and the great Age of the Dinosaurs.In North America, Jurassic dinosaur remains are found in the Morrison Formation, a geological layer of mudstone, sandstone, siltstone and other conglomerates that runs through parts of Canada, the Dakotas, Montana, Wyoming, Colorado, Utah, Arizona and New Mexico.

The Morrison Formation on the ranch is approximately 300 ft. thick and consists of multi-layered sandstones, siltstones, clay stones and limey units. It is conformably underlain by the early Jurassic Period Sundance Formation, which was deposited in a vast inland waterway and consists of thick fossiliferous marine deposits.

Overlain by the relatively fossil-poor Cloverly Formation, the actual Morrison/Cloverly contact at the digsite is indistinct and varies depending on which boundary conditions are utilized (smectite layer, conglomerate, reworked zones, etc). Current interpretation puts the dinosaur bone-bearing layers in the middle to upper Morrison units. In these layers, more than 15 species of Jurassic Period dinosaurs have been found.

Wyoming ranches often rim or inter-finger BLM land Limited Private Land. Jurassic dinosaur bones and teeth are seldom available for excavation or private purchase because much of the visible or accessible Morrison Formation layer is found on Federal or Bureau of Land Management (BLM) property. That leaves little private land for individuals or private companies to dig and excavate Jurassic fossils.
Difficult, Costly Excavation. While 'younger' Cretaceous fossils can often be found close to the surface – even lying right on the ground in front of you - the deeper, bone-bearing layers of the Morrison Formation consist of hard, dig-resistant rock. Costly heavy equipment is often required.
Careful Preparation. Unless found relatively near the surface (which is rare) and in excellent condition, Jurassic bones and teeth demand many hours of work by our prep team. The durable matrix encasing the bones is removed. Bones are reassembled and stabilized. Fractures are filled with ground bone material. If reconstruction is done, rebuilt areas are always indicated in images in the Bones & Teeth Gallery

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