AGES OF SILURIAN RADIOLARIANS FROM THE KUROSEGAWA TERRANE, SOUTHWEST JAPAN CONSTRAINED BY U PB SHRIMP DATA/

Radiolarians are abundant in mid-Paleozoic tuffs of the Kurosegawa ter rane of southwest Japan. Well preserved Silurian radiolarian faunas re covered from several localities are described herein and include four new species: Ceratoikiscum kurosegum n. sp., Fusalfanus? konomoriensis n. sp., Futobari? jingamoriensis n. sp., and Futobari? tosaensis n. s p. The absence, within the same strata, of fossils belonging to other taxonomic groups has presented difficulties in determining the precise ages of the Kurosegawa radiolarian faunas. U/Pb SHRIMP ages of pyrocl astic zircons from tuff units within the succession indicate Wenlockia n [427.2 +/- 7.6] and Pridolian [408.9 +/- 7.6] ages and remove ambigu ity regarding the Silurian age of tuffaceous rocks in the Kurosegawa s equence. Copyright (C) 1996 Elsevier Science Ltd