- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
The Changuinola Formation of Late Cretaceous age consists of light-colored foraminiferal limestones and andesitic and dacitic volcanic flows and clastics. Deposition of the limestones occurred in moderately deep to bathyl waters adjacent to an eastward extension of the 'Guanarivas' volcanic island chain. Another section of probable early Tertiary age along the Rio Lari in southeastern Costa Rica is described.