Studies on Depositional History of Jinju Formation in Jinju - Sacheon Area, Korea -Sedimentological and Paleontological Studies-
한국 진주 - 사천지역 진주층(晋州層)의 퇴적발달사 연구 : 퇴적암석학적과 고생물학적 연구를 중심으로
This study is directed to study of the stratigraphy, sedimentary rocks and depostitional environment of the Jinju Formation in the Jinju-Sacheon area. The Jinju Formation in the area is subdivided into the lower member, middle member and upper member by their lithologic characteristics. Each member of the Jinju Formation is composed mianly of grey arkose sandstone, sandy shale and dark grey shale. A few thin layers of limestone and calcareous shale are intercalated in the upper parts. As in most places, sand shale of the formation shows onionJstructures and contains many nodules. The grain particle analysis of the sandstone samples were obtained moderately sorted, positive skewness and meso-kurtic. The significant sedimentary structures such as the pillow, cone-in-cone, large scale suncrack, ridge-type cross-bedding, cylindrical muddy lime concretion and stromatolites are sampled from the non-marine Cretaceous Jinju Formation in the Kyeongsang basin, Korea. The fades fossils of the Cretaceous snakeflies, freshwater fishes, cyzicuses, cladophlebis spp., and plant stems were excavated from the black shale of the formation. The paleocurrent study, was carried out by means of the statistical analysis of the cross-stratification, ripple mark, slump structure, and parting lineation, which are palecocurrent structure. The investigator presents his own computer programming process for the calculation of statistical parameters. The paleocurrent direction, depositional strike, source area, and the depositional center of the basin of the Jinju Formation are judged to be southeast, northeast, northwest, and southeast, respectively. The depositional environment on the formation in the studied area is determined definitely the fluvial environment in view of the interdisciplinary assessment of the analysis results of paleocurrent structures listed above.