Subdivision of the Upper Paleozoic Taean Formation in the Anmyeondo-Boryeong area, west Korea: a preliminary approach to the sedimentary organization and structural features

A preliminary analysis of sedimentary organization and detailed geological mapping of the Upper Paleozoic Taean Formation have been conducted in the Anmyeondo-Boryeong area. The Taean Formation comprises the 'sandy unit' and 'sandy-muddy unit'. The former unit consists of massive or bedded sandstone beds often with scoured base, and the latter unit consists of sandstone beds graded from the massive sandstone to laminated siltstone or pelagic mudstone, representing the Bouma sequence. Based on the differing patterns of facies stacking, the Taean Formation is informally divided into the Sinni, Sinon, Kkotji, Seungeon, Jungjang and Nudong units in ascending order. The lower four units show largely N-S trending paleoflow, while the upper two ones show NE-SW to E-W trending paleoflows. Such a change in sedimentary supply directions could be resulted from changes in depositional regime and/or allogenic controls including tectonics.