Silurian and Devonian radiolarian biostratigraphy was studied for tuffaceous clastic rocks developed in the Fukuji - Hitoegane and Kuzuryu Lake - Upper Ise River areas of the Hida Gaien belt, central Japan. The objective of the study was to improve chronostratigraphic calibration of these intervals and to discuss local correlation among the Middle Paleozoic strata in Japan. Radiolarian zones characterized by eight distinctive assemblages have been defined in the seven measured sections, as follows:
Haplotaeniatum tegimentum -
Syntagentactinia excelsa (middle to upper Llandovery),
Fusalfanus osobudaniensis -
Secuicollacta itoigawai (lower Ludlow),
Zadrappolus spinosus -
Praespongocoelia parva (lower or middle Ludlow),
Stylosphaera (?)
magnaspina (upper Ludlow),
Pseudospongoprunum (?)
tauversi (lower to middle Pridoli),
Futobari solidus - Zadrappolus tenuis (lower or middle Pridoli to Lower Devonian),
Palaeoscenidium ishigai -
Deflantrica furutanii (Lochkovian or Pragian to lower Emsian), and
Pactarentinia intermedia -
Pactarentinia igoi (lower Emsian) Assemblage Zones. Age control is based on the stratigraphic relationship between the zones, other fossils, and correlation with other radiolarian zones established in the southern Urals, west Texas, and the Kurosegawa belt, Southwest Japan.
Biostratigraphic correlations clearly show that Ludlow to Emsian tuffaceous clastic rocks of deep-water origin in the Hida Gaien belt are exceedingly similar to those in the Kurosegawa and South Kitakami belts in depositional age. It provides a constraining link between these terranes during the early evolutionary stage of their geologic history.
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