Unpublished potassium-argon dating on Philippine igneous rocks suggest that the earliest diorite intrusion cycle was about 60,000,000 years ago (close of the Paleocene). Datings of andesites and diorites are scattered throughout the Eocene, Oligocene and Miocene with a concentration of datings of 9,000,000 years on diorite indicating a period of active intrusion in
Late Miocene — Early Pliocene time.