An early Carboniferous (late Visean) brachiopod fauna from the Arakigawa Formation of Hongo, Hida Gaien Belt, central Japan, and its tectonic significance

Abstract

Here we describe an early Carboniferous brachiopod fauna from the middle part of the Arakigawa Formation in the Hongo area, Hida Gaien Belt, central Japan. The Hongo fauna consists of six species in five genera: Pugilis sp., Marginatia sp., Fluctuaria undata (Defrance), Fluctuaria sp., Actinoconchus sp., and Imbrexia sp. The fauna is identified as late Visean in age, thus correlating the middle part of the Arakigawa Formation with the upper Visean. Palaeo-biogeographically, the Hongo fauna exhibits affinities with early Carboniferous brachiopod faunas of northwestern China (Xinjiang) and northeastern Japan (South Kitakami Belt). The fauna probably belonged to the North China Province, which covered a broad area between the North China Block and the Siberian Block (i.e., the Central Asian Orogenic Belt, CAOB) during the late Visean. The Hida Gaien Belt, including the Hongo area, was likely located in the CAOB during the late Visean. Similarities between the lithology and fauna of the Arakigawa Formation and those of the Carboniferous formations of the South Kitakami Belt provide positive evidence of a tectonic connection between the Hida Gaien and South Kitakami belts.