Latest Jurassic to earlier Early Cretaceous foraminifers from the Torinosu-type limestone blocks in Southwest Japan: Constraints on chrolonogic calibration of the Torinosu-type limestones

Abstract

Thirty-six taxa of foraminifers were recognized from 31 samples of the Torinosu-type limestone blocks in South of Yatsushiro, Azamui (Kyushu), Nomura (Shikoku), and Yura (Kii) areas, Southwest Japan. Those identified in species level are confined to five: Nautiloculina broennimanni, Freixialina planispiralis, Charentia cuvillieri, Melathrokerion spirialis, and Pseudocyclammina lituus. Such genera as Kurnubia and Alveosepta showing the pre-Kimmeridgian, and orbitolinids characteristic in the post-late Hauterivian are completely absent in them. The Torinosu-type limestones studied are assigned to the latest Jurassic to earlier Early Cretaceous based on the biostratigraphic distribution of the identified five species in the western Tethyan region and chronologic constraints on the studied material excluding the pre-Kimmeridgian and post-late Hauterivian faunal elements.