阿讃山脈東部板野-引田地域の和泉層群

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Upper Cretaceous strata Izumi Group which is distributed in the Kami ita cho-Hiketa cho area, located in the eastern part of the Asan Mountains (fig. 1) is stratigraphically divided into the following six formations inascending order as shown in fig. 7 : Gosho Formation (900m+ in thickness), Kawamata F. (330-450m), Izumitani F. (150-800), Miyagatani F. (130-350 m), Ohyamahata F. (110 m-420 m) and Osaka F. (1500m+).<BR>The total thickness of these formations exceeds 4420 m. The present strata is lithologically subdivided into three units, namely the northern, central (axial part of the sedimentary basin) and southern parts (figs. 2, 3, 4 and 5).<BR>Turbidited facies are prevalent in the central part. The turbidites consist mostly of 20-300 cm of stratified sandstone and of 10-50 cm of alternating bedded sandstone and mudstone. On the contrary, the northern and southern parts mainly consist of mudstone which interfingers with turbidites along the boundary between the central part of the sedimentary basin.<BR>The sole marks which were measured at 118 points in the present area show mainly an east to west orientation (figs. 8, 9 and 10). Other orientations, e. g. from north to south or from south to north, were hardly found. The orientations of sole marks suggest that turbidity currents run in the direction of the axis of the sedimentary basin.<BR>Pyroclastic materials (fig. 6), which are well-stratified in the strata, are rhyolitic in composition. These were transported from the easternareas by the bottom currents and deposited normally in the present area.
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阿讃山脈東部板野-引田地域の和泉層群

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