InGen Database Description
The Peay Sandstone Member is a sub-unit of the Frontier Formation which stretches across north-west Colorado, southeast Idaho, southern Montana, northern Utah and western Wyoming. The member is in the north-east Bighorn Basin, Wyoming. It dates back to the Late Cretaceous epoch, 100 million years ago.
The region's deposits are primarily grey sandstone, along with shale (both grey and carbonaceous) and bentonite. The sediments would have been deposited by rivers and streams feeding the Cretaceous Western Interior Seaway. Some isolated sandstone bodies surrounded by marine mudrock in the Frontier Formation reveal a series of coastal islands. Evidence of waves from this period consolidate this conclusion.
Common finds here have been trace fossils, such as Thalassinoides (burrows made from various creatures such as fish or anemones), and Zoophycos (artefacts created by moving and feeding polychaete worms), along with vertebrate teeth.