The Upper Cretaceous Eagle Sandstone (Campanian) and underlying Telegraph Creek Formation (Santonian) as exposed at Billings, Montana, were deposited along the margin of the Western Interior Seaway. These formations contain several stratigraphic sequences which have previously been described as three members by Hancock (1918). The sequences are recognized along outcrops and can be traced into the subsurface using oil & gas electric logs.

The lower two sequences represent two periods of landward-growing submarine shelf-bar sands. A stratigraphically-higher sequence is recognized as containing tidal channel point-bar deposits. Awareness of these varied depositional environments in the Eagle should aid in identification of stratigraphic traps in the nearby Crazy Mountain Basin.