1. The Río Abajo, Pitahaya, and Daguao Formations in eastern Puerto Rico : a description of three largely volcaniclastic units, which are assigned an early Cretaceous age Author/Creator: M'Gonigle, John W. Publication/Creation: Washington : U.S. Govt. Print. Off, 1977 Resource Type: Book Is Part Of: U.S. Geological Survey bulletin, no. 1434-1439. Access & Availability: Loading