The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or
Clarkforkian
The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting .
Considered t ...
,
Wasatchian
The Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 55,400,000 to 50,300,000 years BP lasting .
It is usually ...
and
Bridgerian
The Bridgerian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 50,300,000 to 46,200,000 years BP lasting .
It is usually c ...
Fossilworks
Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world.
History
Fossilworks was crea ...
.orgNeasham & Vondra, 1972
Description
It consists of fine grained clastic rocks ( mudstone and shale) interbedded with medium grained clastic rocks ( sandstone) and sporadic conglomerates. The formation underlies portions of the
Bighorn Basin
The Bighorn Basin is a plateau region and intermontane basin, approximately 100 miles (160 km) wide, in north-central Wyoming in the United States. It is bounded by the Absaroka Range on the west, the Pryor Mountains on the north, the Big ...
Hot Springs
A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by ci ...
Washakie
Washakie (1804/1810 – February 20, 1900) was a prominent leader of the Shoshone people during the mid-19th century. He was first mentioned in 1840 in the written record of the American fur trapper, Osborne Russell. In 1851, at the urging ...
Radiometric dating of volcanic tuffs, combined with comparisons with other formations using magnetostratigraphy, using numerous samples from various levels of the formation suggest an age range of 55 – 52 million years ago, placing the Paleocene-Eocene boundary near the base of the formation.Tauxe et al., 1994
Fossil content
Trace fossils have been found in the Willwood Formation.Bown & Kraus, 1982 Fossil birds include ''
Gastornis
''Gastornis'' is an extinct genus of large flightless birds that lived during the mid Paleocene to mid Eocene epochs of the Paleogene period. Fossils have been found in Europe, Asia and North America, with the remains from North America origina ...
Paracathartes
''Paracathartes'' is a genus of extinct bird from the Wasachtian horizon of lower Eocene Wyoming. One species, ''Paracathartes howardae'' has been described.
It is a paleognathous bird, turkey-like in stature and size, that probably resembled ...
''. A fossil
alligatorid
The family Alligatoridae of crocodylians includes alligators, caimans and their extinct relatives.
Phylogeny
The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the American alligator t ...
, namely '' Orthogenysuchus'', was also found in this formation.
Mammals
Afrotheres
Apatotheres
Bats
Cimolestans
Eulipotyphlans
Ferae
Leptictids
Marsupials
Multituberculates
Primatomorphs
Rodents
Ungulates
Reptiles
Birds
Crocodilians
Squamates
Testudines
Amphibians
Fish
Invertebrates
Invertebrate ichnotaxa
Gastropods
Plants
Wasatchian correlations
See also
*
List of fossiliferous stratigraphic units in Wyoming
This article contains a list of fossil-bearing stratigraphic units in the state of Wyoming, U.S.
Sites
See also
* Paleontology in Wyoming
Paleontology in Wyoming includes research into the prehistoric life of the U.S. state of Wyoming a ...
*
Paleontology in Wyoming
Paleontology in Wyoming includes research into the prehistoric life of the U.S. state of Wyoming as well as investigations conducted by Wyomingite researchers and institutions into ancient life occurring elsewhere. The fossil record of the US s ...