Microfacies Analysis of Limestones from Batan, Sabtang, Itbayat and
Ivuhos Islands, Batanes Province, Philippines
John Warner M. Carag, Justine Perry T. Domingo,
Raymond G. Leuterio, Sandra G. Catane, Allan Gil S. Fernando,
Alyssa M. Peleo-Alampay
National Institute of Geological Sciences,
University of the Philippines, Diliman, Quezon City 1101
Preliminary results of the microfacies analysis of limestone samples collected from Batan, Sabtang, Itbayat and Ivuhos Islands show that the limestones belong to at least three (3) Facies Zones (FZ): (a) Shelf Lagoon, (b) Back-reef and (c) Organic Build-up. The Shelf Lagoon FZ is characterized by wackestones and floatstones, with occasional grainstones containing abundant planktonic and (small and large) benthic foraminifera. The Back-reef FZ is distinguished by the presence of rudstones and grainstones with a diverse assemblage of bioclasts consisting of large benthic foraminifera, echinoid spines, mollusks and coral fragments. The Organic Build-up FZ consists of bindstones and framestones. This facies contains algal mats and corals in living position. Occurrence of lithic volcanic fragments and detrital minerals in some limestones in Batan Island indicates proximity of the reef environment to the volcanic source.