Early Cretaceous (Aptian) radiolarians from the Gumizaki Formation in northwestern Kagoshima Prefecture, Japan and their significance in stratigraphic correlation of Lower Cretaceous formations

Abstract

This study is the first report of radiolarians from the Early Cretaceous Gumizaki Formation in the northwestern part of Kagoshima Prefecture, Japan. Diverse radiolarian assemblages (including 16 genera and 25 species) were found in five mudstone samples collected from two localities in the B member of the Gumizaki Formation. These assemblages indicate the late Early Cretaceous (late early to middle Aptian) in age. Based on the age of these radiolarian assemblages, the B member of the Gumizaki Formation is correlated to the lower to middle members of the Hinagu Formation or the lower member of the Imaizumigawa Formation in the Yatsushiro area.