[1] The Arroyo Penasco Group consists of marine sedimentary formations, primarily massive limestone but with some sandstone.

Together with the presence of paleosilcretes in the Manuelitas Member, the middle part of the Tererro Formation, this suggests a history of at least four episodes of sea level fluctuation during the Mississippian in northern New Mexico.

Diagenetic fabrics can be traced across the region, demonstrating that the group was deposited across an extensive surface of low relief.

[5] The massive limestone beds of the Arroyo Penasco Group were originally included as the base of the Pennsylvanian Sandia Formation.

The discovery of Endothyra and Plectogyra in 1951 showed that the beds were actually Mississippian in age, and they were split off as the Arroyo Penasco Formation.