[F] Horsethief Sandstone - Montana - US
Montana - US
The Horsethief Formation is gray to gray-brown, fine- to medium-grained marine sandstone, commonly crossbedded. Titaniferous magnetite sandstone locally is present in the upper 20 - 40 feet of the formation (Mudge and Earhart, 1983). Large calcareous concretions locally are present in the middle part. The Horsethief Formation is as thick as 165 feet and it forms prominent bluffs and ridges.
The Horsethief-Bearpaw transition unit is dark-gray marine mudstone, interbedded with thin, fine- to medium-grained sandstone (Cobban, 1955). The sandstone beds are thicker and more abundant in the upper part. The unit is as thick as 400 feet in northern areas and it thins southward (Cannon, 1996). Source: Berg (2002) Geologic Map of the Cut Bank 30\\\' x 60\\\' Quadrangle Norhwestern Montana.
Hadrosaurid indet. - Ornithopoda - Cretaceous Late Maastrichtian