紀伊半島四万十累帯の研究 : 本宮町・中辺路(なかへじ)町付近の牟婁(むろ)層群

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The Muro group in Hongu-cho and Nakaheji-cho was studied stratigraphically and tectonically. The Muro group is divided into the Otonashigawa Muro, the Yomurakawa-Muro and the Ukekawa-Muro subgroups in ascending order, and is overlain by the middle Miocene Kumano group with remarkable clinounconformity. As a whole, the Muro group is composed of flysch-like sediments of sandstone and shale frequently intercalated with conglomerates, attaining up to about 16,000m in total thickness. The geologic age is considered to be the Paleogene to the early Miocene from fossil evidences. The strata of the Muro group in this area constitute the northern limb of the Uchikoshi anticline, modified by nose-like Kimidani anticline and other overturned folds as shown in Figure 2. Judging from the lithologic characters of conglomerates and sandstones and the sole marks, it is inferred that the provenances of the Muro group in this district were to the north of the Shimanto Terrain. The so-called Meso-Volcanics, the Ryoke Complex, the Paleozoic in the Chichibu Terrain and the so-called Torinosu Series were the main sources. The sole marks indicate that clastic materials were supplied mainly westward or eastward, although some sole marks show the paleocurrent from the southeast. It is supposed that, firstly, most of them were transported by rivers from the north, and then supplied and settled in the sedimentary basin by westerly or easterly longitudinal turbidity currents. Igneous dykes, clastic dykes and an altered zone are also found in the area and are described in the present paper.
地学団体研究会の論文
1967-11-25

紀伊半島四万十累帯の研究 : 本宮町・中辺路(なかへじ)町付近の牟婁(むろ)層群

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