| Vester Formation | |
| Type: | Formation |
| Age: | Ladinian - Norian |
| Region: | Oregon |
| Country: | United States |
| Coordinates: | 44.118° N, 119.483° W |
| Unitof: | Olds Ferry Terrane |
| Subunits: | Brisbois Member |
| Area: | Central Oregon |
| Period: | Triassic |
The Vester Formation is a geologic formation in Oregon which preserves fossils dating back to the Triassic period. The partial skeleton of a new genus of basal thalattosaur has been recovered from the Brisbois Member of this formation.[1] The Brisbois Member, which dates to between the Carnian and Norian, is a marine sequence primarily composed of fine-grained clastic sedimentary rocks with fissile mudstones of black, green or gray variety broken up by widely spaced intervals of calcirudite beds and calcareous conglomerate.[2] The formation formed between two parallel island arcs, that of the Baker Terrane and the Olds Ferry Terrane. The formation mostly consists of reworked chert grains from the Baker Terrane.[3] In addition to the remains of the basal thalattosaur, fragmentary and undescribed remains exist of an ichthyosaur, archosaur, and a hybodontid shark as well as many invertebrate fossils.