Vester Formation

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.[1]