Data related to the Geology and petrography of the Late Cretaceous Nagato–Hōhoku caldera

Fig. A1. Field photographs of the Awano Conglomerate and Sandstone Member. (a) Conglomerate facies to the east of Awano in Hōhoku-Chō. (b) Interbedded tuffaceous sandstone, siltstone, and shale near the locality of (a). (c) Photomicrograph of an accretionary lapilli from the forestry  road east of the Awano River. Note the coarsegrained core with mafic crystals and fine-grained concentrically laminated rim.

Fig. A2. Representative photomicrographs of (a) the Hōzōyama Lapilli Tuff Member, which contains biotite crystals formed by contact metamorphism, and (b) the Ōtōyama Tuff Member. Kfs: K-feldspar, Bt: biotite, Pum: pumice, Lf: lithic fragment.

Fig. A3. Field photograph of the Asōgawa Shale and Tuff Member at Ōhiraba, Ōmishima Island, Nagato City: wellstratified shale and tuff that dip gently to the south. Photograph by Shinichi Nagayama, using a drone.

Fig. A4. Photomicrographs of (a) the Daibōgawa Rhyolite Tuff Member, (b) a representative sample of the Kumanodake Rhyolite Tuff Member, (c) densely welded tuffs of the Kumanodake Rhyolite Tuff Member, and (d) an andesite of the Kunihiro Andesite Member containing biotite clots formed by contact metamorphism caused by the intrusion of the Okuhata Granite and the Kusazoeyama Granodiorite. Qtz: quartz, Kfs: K-feldspar, Pl: plagioclase, Bt: biotite, Opq: opaque mineral.

Fig. A5. Photograph of the Funakoshi Rhyolite Tuff Member.

Fig. A6. Photomicrographs of the Kitakohara Felsic Intrusive Rock. (a) Felsite, (b) granite porphyry, (c) finegrained granite containing tourmaline, and (d) micrographic texture in the groundmass of the granite porphyry. Qtz: quartz, Kfs: K-feldspar, Pl: plagioclase, Tur: tourmaline.

Fig. A7. Field photographs from Heikedai on Ōmishima Island. (a) Roof pendant (RP) of the Asōgawa Shale and Tuff Member on the Ōmishima Granite (Gr). (b) Ōmishima Granite with a miarolitic texture. (c) Contact between the tonalite (To) and quartz porphyry (Qp). (d) Fine-grained granite dike (“Shirahataiwa”, white flag rock). (e) Swarm of mafic microgranular enclaves (MMEs) in the Ōmishima Granite at Fūfudo, Ōmishima Island. (f) MMEs with various shapes in the Ōmishima Granite.

Fig. A8. Photomicrographs of (a) the Sakane Granodiorite Porphyry, (b, c) the Agawa Diorite Porphyry, and (d) dolerite. Qtz: quartz, Kfs: K-feldspar, Pl: plagioclase, Hbl: hornblende, Cpx: clinopyroxene, Opx: orthopyroxene, Opq: opaque mineral.

Fig. A9. Field photograph of a clastic dike (Cd) intruding into the Awano Conglomerate and Sandstone Member (Awa) at Ōura, Shimonoseki City. The Agawa Diorite Porphyry dike (Po), which intrudes into Awa, is cut by the clastic dike.

Table A1. Representative whole-rock chemical compositions of the Abu Group in the Nagato–Hōhoku area.