The Puget Group is a

geologic group In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into superg ...

Washington (state) Washington, officially the State of Washington, is a U.S. state, state in the Pacific Northwest region of the United States. It is often referred to as Washington State to distinguish it from Washington, D.C., the national capital, both n ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

. In the northern area of group around

Renton, Washington Renton is a city in King County, Washington, United States, and an inner-ring suburb of Seattle. Situated southeast of downtown Seattle, Renton straddles the southeast shore of Lake Washington, at the mouth of the Cedar River. As of the 202 ...

, the Group has been divided into three formations (from oldest to youngest), the Tiger Mountain Formation, the Tukwila Formation, and Renton Formation. Robin Burnham (1994) specifies that these formations have not been defined and extended to Puget Group outcrops to the south within the Green River gorge and all of the Tukwila formation rocks are missing. The Puget Group has been mapped across a total of six western Washington geographic quadrangles.

Age

The total deposition time has been estimated to be as short as approximately 7.7 million years, from around based on isotopic data reported in 1993 or as long as based on the paleofloristic data of Wolfe (1968, 1977)

Western North American floral stages

The Western North American floras of the Eocene were divided into four floral "stages" by Jack Wolfe (

1968 Events January–February * January 1968, January – The I'm Backing Britain, I'm Backing Britain campaign starts spontaneously. * January 5 – Prague Spring: Alexander Dubček is chosen as leader of the Communist Party of Cze ...

) based on work with the Puget Group plant fossils. The four stages, Franklinian, Fultonian, Ravenian, and Kummerian covered the Early Eocene through early Oligocene, and three of the four were given informal early/late substages. Wolfe tentatively deemed the Franklinian as Early Eocene, the Fultonian as Middle Eocene, the Ravenian as Late, and the Kummerian as Early Oligocene. The beginning of the Kummerian was refined by

Gregory Retallack Gregory John Retallack (born 8 November 1951) is an Australian paleontologist, geologist, and author who specializes in the study of fossil soils ( paleopedology). His research has examined the fossil record of soils though major events in Earth ...

''et al'' (2004) as 40 mya, with a refined end at the Eocene-Oligocene boundary where the younger Angoonian floral stage starts.

References

Geologic groups of Washington (state) Paleogene stratigraphic units of North America {{Paleogene-stub

Age

Western North American floral stages

See also

References