Willwood Formation

Willwood Formation
Stratigraphic range: Paleocene-Eocene
~55–52 Ma

PreЄ

Є

O

S

D

C

P

T

J

K

Pg

N

↓
Willwood Formation; Stratigraphic range: Paleocene-Eocene; ~55–52 Ma PreЄ Є O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Bighorn Basin
Lithology
Primary	Mudstone, shale
Other	Sandstone, conglomerate
Location
Region	Wyoming
Country	USA

The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene.[1] 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 of Big Horn, Hot Springs, Park and Washakie counties of Wyoming.[2]

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.[3]

Trace fossils have been found in the Willwood Formation.[4] Fossil birds include Gastornis, Neocathartes and Paracathartes. A fossil alligatorid, namely Orthogenysuchus, was also found in this formation.

References

Neasham, John W.; Vondra, Carl F. (1972). "Stratigraphy and Petrology of the Lower Eocene Willwood Formation, Bighorn Basin, Wyoming". doi:10.1130/0016-7606(1972)83[267:SAPOTL]2.0.CO;2. Cite journal requires |journal= (help)
"Willwood Formation". USGS.
Tauxe, L., Gee, J., Gallet, Y., Pick, T., & Bown, T. (1994). Magnetostratigraphy of the Willwood Formation, Bighorn Basin, Wyoming: new constraints on the location of Paleocene/Eocene boundary. Earth and planetary science letters, 125(1), 159-172.
Bown, Thomas M.; Kraus, Mary J. (31 July 1983). "Ichnofossils of the alluvial Willwood Formation (lower Eocene), Bighorn Basin, northwest Wyoming, U.S.A". Palaeogeography, Palaeoclimatology, Palaeoecology. 43 (1–2): 95–128. doi:10.1016/0031-0182(83)90050-0.

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.

[Neasham-1] Neasham, John W.; Vondra, Carl F. (1972). "Stratigraphy and Petrology of the Lower Eocene Willwood Formation, Bighorn Basin, Wyoming". doi:10.1130/0016-7606(1972)83[267:SAPOTL]2.0.CO;2. Cite journal requires |journal= (help)

[USGS-2] "Willwood Formation". USGS.

[3] Tauxe, L., Gee, J., Gallet, Y., Pick, T., & Bown, T. (1994). Magnetostratigraphy of the Willwood Formation, Bighorn Basin, Wyoming: new constraints on the location of Paleocene/Eocene boundary. Earth and planetary science letters, 125(1), 159-172.

[Bown_1983-4] Bown, Thomas M.; Kraus, Mary J. (31 July 1983). "Ichnofossils of the alluvial Willwood Formation (lower Eocene), Bighorn Basin, northwest Wyoming, U.S.A". Palaeogeography, Palaeoclimatology, Palaeoecology. 43 (1–2): 95–128. doi:10.1016/0031-0182(83)90050-0.