Calcareous nannofossil biostratigraphic study of the Pugo River section of Amlang Formation in the Luzon Central Valley Basin, Philippines

摘要

The study aims to establish the calcareous nannofossil biostratigraphy of an outcrop consisting of turbiditic sandstones and shales located along Pugo River, La Union in the Luzon Central Valley Basin, Philippines. Examination of the samples reveals a moderately- to well-preserved assemblage dominated by Discoaster and Sphenolithus. Based on the occurrence of Discoaster berggrenii in all of the samples, the nannofossil NN11A Zone is recognized. This suggests a late Tortonian (late Miocene) age for the investigated section. Biostratigraphic and lithologic correlation suggest that the Pugo River section is part of the Amlang Formation. The result of the present study, in addition, extends the base of the Amlang Formation to middle late Miocene.