It was first recognized in the central near side of the Moon in 1965, by the Astrogeology group of the United States Geological Survey.
During the Apollo era, the formation was mapped in many other parts of the Moon including the far side (e.g., Mendeleev basin.)
[2] Thus, the Cayley Formation predates the mare but postdates sculpturing by the Imbrian event.
[4] Most scientists predicted that volcanic rocks would be obtained from the Cayley Formation, but the astronauts (Charles Duke and John Young) found almost nothing but breccias.
The lack of volcanic rocks returned from the Cayley forced a reinterpretation of its origin.