The Lookingglass Formation is a geologic formation in Oregon. 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 in ...

dating back to the

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

period. Geologically, it spans a time frame from the Tertiary period to the middle Eocene. It was named for the Lookingglass Valley. It overlies the Roseburg Formation, and is divided into three geologic members: the Bushnell Rock Member, the Tenmile Member, and the Olalla Creek Member. The Bushnell Rock Member is a basal conglomerate, mostly made of 1-2 inch diameter pebbles embedded in a sandstone matrix, deposited by an onlapping (advancing) sea. The Tenmile Member is composed of rhymthically bedded layers of sandstone and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

, indicating deposition in quiet water not close to the shore. The Olalla Creek member is composed in some places of conglomerate and pebbly sandstone, and in other places of thinner bedded sandstone and silt, and, where the silt layer is absent, is hard to distinguish from the Bushnell Rock Member.

References

Paleogene geology of Oregon Formations {{Paleogene-stub

See also

References