Stratigraphic correlation of Cretaceous non-marine sedimentary basins of Southeast Korea and Southwest Japan

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Cretaceous non-marine sedimentary rocks called the Kyongsang Group are widespread in the southeastern Korean Peninsula. The following results were obtained from this research.(1) The Kyongsang Group in the Yongyang area that occupies the northern part of the Kyongsang Basin consists mainly of sandstone, conglomerate and red siltstone. The conglomerate, although very rare, contains chert clasts in some horizons. Several chocolate brown chert clasts yielded well-preserved permian radiolarians of the Follicucullus group.(2) The matrix sandstone of the above Cretaceous conglomerate contains such heavy minerals of tourmaline, opaques, zircon and monazite. The detrital monazites yielded CHIME ages of ca.1500 Ma of middle Proterozoic age and ca.250 Ma of Permian-Triassic boundary age.(3) Black phyllite and schist in the Okchon Belt to the southeast of Chunju sporadically contain clasts of quartzite, granitoid, marl and limestone. The granitic gneiss clasts yielded CHIME monazite ages of 1450 Ma, suggesting that middle Proterozoic granite and gneiss were present in the provenance of Okchon clastic rocks.(4) The Okchon metamorphic rocks exposed near the Chunju dam consist of metabasite, dolomite, quartzite and metapelite. Garnet-bearing actinolite-epidote schist of basaltic tuff origin contains allanite that yields CHIME ages of ca.250 Ma. This age probably represents the time of regional metamorphism of the Okchon schists.