백악기 음성분지는 북동-남서 방향으로 발달한 공주 주향이동 단층대를 따라 생성된 인리형 분지이다. 분지 남서부의 구곡리 농다리-미르 숲에는 두꺼운 자색 이암 퇴적층이 분포하며, 역암, 역질 사암, 녹색 이암 등이 자색 이암층에 협재한다. 퇴적층은 7개의 퇴적상으로 구성된다: 층리를 보이는 역암(C2), 실트암 내 역암(CE), 실트암 내 층리를 보이는 역질 사암(PSE2), 자색 사질 실트암(Zp), 녹색 사질 실트암(Zg), 자색 이암(Mp), 녹색 이암(Mg). 퇴적환경은 분지 남서부에서 발달하였던 충적-호소 퇴적계에서 충적 평원이 우세한 환경으로 해석된다. 구곡리 퇴적계의 퇴적층을 1:5000 축척 지형도를 이용하여 조사하였고, 도로 지질도로 작성하였다. 본 연구는 이 숲의 새로운 노두에서 측정한 고수류 방향 자료와 퇴적층의 특징에 근거하여, 동북동과 북북동 방향으로 발달한 하천 퇴적계를 새로이 제안하였다. 또한 기존에 보고된 구곡리 퇴적계의 모델을 개선하였다.

본 연구의 목적은 학생들로 하여금 실제 야외지질조사를 효과적으로 수행하기 위한 교육 자료를 개발하는 것이다. 이를 위하여 시대를 달리하는 다양한 암석과 지질구조를 가지고 있고 지리적으로 접근하기 편리한 음성분지의 남동부 두타산 일대를 대상으로 선정하였다. 음성분지의 야외지질 실습코스에는 13개의 관찰지점이 있으며 실제 현장에서 각 관찰 지점별로 학생들이 활동할 수 있도록 야외학습자료를 제시하였다. 이를 위해 일반 지형도나 수치 지형도를 이용하여 스스로 노선지질도를 작성하도록 하였으며 큰 구조나 서로 다른 암상과의 관계를 광역적으로 알 수 있도록 항공사진을 첨가하였다. 또한 각 관찰 지점마다 노두 및 편광 현미경 사진을 제시하여 야외학습에서 경험할 수 있는 환경으로 설계하여 실제로 야외에서 겪게 되는 갈등 요인을 최소화 할 수 있도록 하였다. 이렇게 구현된 야외지질조사자료는 충북대학교 사범대학 지구과학 수강자를 대상으로 학생들의 태도를 조사하였으며, 그 결과 정의적 측면에서 학생들이 야외학습을 수행하는데 도움이 된다는 긍정적인 변화를 보였으며, 특히 지구과학에 관한 구체적인 개념 형성에 많은 도움이 되는 것으로 분석되었다.

The Kongju basin of Cretaceous sedimentary rocks, which is located in the area between Ogcheon fold belt and Gyeonggi massif, is developed by the strike-slip fault and shows elongated rhombic shape trending roughly NE and SW with about 4㎞ in width and 25㎞ in length. Two stripes of ductile shear zone are traced in basement rocks along the boundary of basin. The shear sense of ductile shear zone is suggested to be sinistral. The Cretaceous sedimentary rocks within the Kongju Basin also exhibit deformed state in terms of developments of en-echelon arrayed folds, faults and various kinds of joint systems. The majority of joints is occupied by the fractures whose strikes are approximately normal to the directions of en-echelon arrayed fold axes. The shortening(α^(-1)) of fold system is most pronounced at the central part of the basin and gradually decreases toward both ends of the basin. Both of the strikes of fold axial planes and the azimuths of fold axes change discontinuously to form sigmoidal style of en-echelon arrayed folds. The en-echelon arrayed folds, all plunged towards SW direction, indicate that upper layers of the sedimentary rocks are more distributed in the SW area of the basin than in its NE area. The gravity anomaly around the Kongju basin shows 12∼17 mgal in the outer metamorphic zone and 8∼10 mgal in the basin; and its minimum value occurs in NE-SW direction along the western boundary of the sedimentary basin. The electric resistivity study on both boundaries of the basin shows 200∼300Ω-m in the boundary zone, 500∼600Ω-m in sedimentary rocks, and 1000Ω-m or more in the granite-gneiss region. These values indicate that the east boundary be gentle slope and the west one be steep fracture zone. 'These patterns of geophysical data implicates that the Kongju sedimentary basin should be dipping down to the west.

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.

In order to investigate the relationship between the distribution pattern of subsurface geological features and the Bouguer anomaly in the Eumseong area, Chungbuk Province, gravity values were measured from 290sites using Worden gravity meter. The study area consists of (1) Pre-Cambrian metamorphic rocks which were intruded by the Jurassic igneous rocks, (2) the Mesozoic Chopyeong and Baegyari Formation, and (3) the Basalt and Andesite which intruded the Cfiopyeong Formation. Terrain correction value using 0.5km X 0.5km blocks is an average of 0.9mgal (max. 1.8mgal, min. 0.1mgal). The depth of density boundary in the study area were calculated by power spectrum analysis with double Fourier transform and FFT. Downward continuation of gravity was performed using the sinχ/χ convolution method. To minimize the Gibbs phenomenon associated with the downward continuation, Hamming filter was used. The value of Bouguer anomaly is-8mgal to 4mga1. Direction of the regional anomaly is the NEW whose trend is parallel with regional structural features. Residual anomaly is low in sedimentary rocks of middle part and igneous rocks regions of eastern and western parts of the study area, whereas it is high in metamophic rocks and andesite vein of middle part. Mean depth of the density boundary is 1420m, and undulation aspect of the subterrain was highest in andesite region. The boundary depth is increasing from Chopyeong Formation to Baegyari Formation.