논문 / 한반도 중서부 지각구조와 물성 연구 : 경기도 화성군 남양 및 안산시 탄도지역에 분포하는 퇴적분지의 분석

Two Cretaceous(80-90 Ma) non-marine sedimentary basins, Namyang and Tando Basins, are distributed in the Namyang area, Hwaseonggun and in the Tando area, Ansanshi, Kyungki Province, Korea. The Namyang and Tando Basins are composed of 10 fades, which are grouped into 5 facies associations(FA). FA I consists of massive conglomerate fades, normally graded conglomerate facies and reversely graded conglomerate facies, which is interpreted to have been formed by debris and sheet flows in the alluvial fan environment. FA II consists of massive mudstone fades, massive sandstone fades, laminated sandstone fades, massive conglomerate facies(channelized), which is thought to have been formed by sheet flow, stream flow and suspension sedimentation in an alluvial/braided plain environment. FA III consists of massive mudstone(pebbly) facies, laminated mudstone fades, massive sandstone facies and is interbedded by channel-fill conglomerate. It is interpreted to have been deposited by suspension settling during flooding and channel-fill deposition in a tloodplain environment. FA IV consists of massive conglomerate facies, normally graded conglomerate fades, massive sandstone facies, normally graded sandstone fades, and laminated sandstone fades and is interbedded with mudstone facies. It is thought to have been deposited by debris flow and turbidity current in a fan-delta environment. FA V consists of massive mudstone facies, laminated mudstone fades, laminated sandstone facies and is interbedded by massive conglomerate bed. It is thought to Have been formed by suspension sedimentation and low-density turbidity current in a lake. In the Namyang Basin FA I is distributed in the eastern and southern margin of the basin, FA II in the middle part of the basin as north-south trending band, and FA III in the western part. 1n the Tando Basin FA II is distributed in the middle part of eastern margin and in the northwestern margin, FA IV in the southwestern part, and FA V in the central part. Correlation of the fades associations shows that FA I and II in the Namyang Basin are distributed in the lower to middle part of stratigraphic sequence and FA III in the upper part of the sequence whereas FA II and IV in the Tando Basin are in the lower to middle part and FA V in the upper part of the sequence. These patterns of facies associations distribution suggest that the Nanryang Basin was developed as an alluvial fan and alluvial/braided plain at first and then evolved into a floodplain whereas the Tando Basin was developed as a fan-delta and alluvial/braided plain at first and then evolved into a lake environment.