Miocene sandstone of 'continental' origin on Iriomote Island, southwest Ryukyu Arc, Eastern Asia

We evaluated the major mineral composition of 100 sandstone samples from the Iriomote Formation of the Yaeyama Group located at the southwestern end of the Ryukyu Islands, eastern Asia. These sandstones are feldspathic arenites. Paleocurrents inferred from these sandstones are generally from north to south. Compared with other Tertiary sandstones of the Japanese Islands arc, the Iriomote sandstones are enriched in quartz and contain less lithic fragments. The roundness and sorting of the sand grains are high, suggesting long transport distances. We interpret these compositional and textural data as indicating that the provenance of the Iriomote Formation was the Eurasian Continent.