A Petrological Study of Columnar Joints with Geoheritage Value in the Cenozoic Sedimentary Basin, Korea

A comparative petrological study was conducted on the columnar joints of Guryongpo, Pohang, Yangnam, Gyeongju, and Gangdong-hwaam, Ulsan in Cenozoic Miocene sedimentary basin. Horizontal joints, these are characteristically developed, cross-sectional shape each joint is predominantly quadrilateral pentagonal Guryongpo Yangnam to hexagonal Gangdong-hwaam joint. As a result XRF analysis, it confirmed that andesite, basalt, basaltic all which sub-alkaline. They easily distinguished because contains small-sized plagioclase (1∼2 mm), while rather large phenocrysts (several mm∼1 cm) uniformly distributed both joints. The value whole rock magnetic susceptibility (WRMS) also well classified according composition. In addition, tectonic discriminant diagram, correspond orogeny zone island-arc tholeiite regions orogeny, but AFM diagram WRMS analysis show formed from different magmas.