 All are extensive sandstone sheets, but the Poleo Formation is distinguished by its great local thickness, grayish-yellow color, and lithology of micaceous litharenite and mixed-clast conglomerate.The formation is almost devoid of fossils, yielding only oxidized fragments of petrified wood and indeterminate vertebrate bone that are unusable for biostratigraphy.Huene described the unit in 1911, giving it the name "Poleo-top-sandstone" as the caprock of Mesa Montosa (which he knew as "Mesa Poleo").