Abstract
Mineral assemblages pelites of sandstones support the stratigraphic division of the Pyeongan Group. In the Upper Member of Gobangsan Formation, sandstones are characterized by acidic volcanic rock fragments (17% on average of total constituents). The Nogam Formation contains abundant potash feldspar ranging from 2 to 22% (11% on average). The Hongjeom, and Sadong Formations and the Lower and Middle Members of the Gobangsan Formation comprise quartzose arenite/wacke. The result of heavy mineral constituents are coincident with the results of mineral assemblages of the sandstones of Pyeongan Group in differentiating the stratigraphic division. Tourmalines in the Pyeongan Group were derived from Li-poor granitoids, pegmatites and aplites, or Ca-poor metapelite and metapsammites. The garnets in the Nogam Formation were derived from medium- to high-grade metamorphic rocks.
The provenance of sandstones in the Hongjeom Formation, Sadong Formation, and in the Lower and Middle Members of Gobangsan Formation is supposed to be mainly quartzite and quartzose sandstone. The provenance of sandstones in the Upper Member of Gobangsan Formation was probably andesite and granodiorite which could supply plagioclase and acidic volcanic rocks as well as quartzite and quartzose sandstone. The provenance of sandstones in the Nogam Formation was granite, granitic gneiss, pegmatite and amphibolite which supplied potash feldspar as well as quartzite and quartzose sandstone.
