Around Umsong-Jeungpyeong, the Cretaceous sedimentary basin is located along NNE direction which can be associated with Kongju basin. These basins are studied in terms of field geology, stratigraphy, paleontology, geological structure and geophysical prospecting. Chopyung Groups were deposited in the Cretaceous period : Baegyari Formation conformably over Chopyung Formtion in fault-generated tan and river basin with lake characteristics in the central part. The fossils found for the first time in this study area are Onychiopsis elongata and Euestheria, and they suggest the Chopyung Groups may be identified with the Naktong Subgroups of Kyungsang Basin. After depositon of Chopyung Groups, igneous activity became vigorous : granite intrusion in westside, andesite and basalt in east fault line and tuffaceous deposits. The gravity survey shows high Bouguer anomaly over andesites and metamorphic rocks, and low in granite area. The mean depth of density discontinuity boundary seems to be 1200∼1400m. The electric resistivity survey suggests that the cast boundary of the basin be a vertical fault.

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