Juana Lopez refers to both the uppermost member of the Carlile Shale formation and to the environment that caused it to form.

The Juana Lopez Member is calcareous sandstone dated to the Turonian age of the Upper Cretaceous and is exposed in the southern and western Colorado, northern and central New Mexico,[1] and northeastern Utah.

It formed on wide, shallow marine shelf, with strong wave action, but with little sediment coming in from land.

As currently defined, the unit includes the entire sequence of calcarenite beds separated by mudstone intervals, and is up to about 140 feet (43 m) thick.

Fossils identified in the unit are primarily marine molluscs, including Prinocyclus, Inoceramus,[8] Ostrea,[9] Lopha lugubris, Coilopoceras, Hourcquia, and Scaphites.