| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1988: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
The studies on the geologic development of the Pre-Miyakoan (Lower Cretaceous) Mesozoic to Paleozoic formations distributed in the "Outer Kitakami Belt," northeastern margin of the Kitakami Massif, Northeast Japan were made with special reference to the relationaship between chert/limestone - green rocks and clastic sediments. The results are summarized as follows:
1. Detailed geological maps and geological sections of the western half ( Lwaizumi belt ) and the eastern half ( Taro belt ) of the Outer Kitakami Belt were investigated and the rock-stratigraphy, geologic structure and geologic age were interpreted. The Outer Kitakami Belt is characterized by the irregular mixture of exotic blocks of ocean-derived chert, limestone and green rocks of Permian to Triassic? age and land-derived clastic sediments of Jurassic? age. The same features were observed in the northern extension (Shiriyazaki district) of the Outer Kitakami Belt.
2. Nappe structures of limestone/chert of the Akka Formation
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( Triassic ) were recognized in the southern margin of the western half ( Lwaizumi belt ) in large scale suggesting, tectonically, the complex rock-bodies of green rocks - limestone/chert ( Sawayamagawa Formation - Akka Formation) were exotic blocks or sheets.
3. Some features of "melange" were recognized in the strata of the Takayashiki Formation ( Jurassic?) in the western half ( Lwaizumi belt)). So these strata are presumably emplaced in a trench, where land-derived clastic sediments and ocean-derived chert and limestone which covers the seamount constituents can encountered and mixed together.
4. The location and mode of occurrences of the Taro fault-line which divides the Outer Kitakami Belt into the Lwaizumi and Taro belts were traced in detail.
5. A synthetic interpretation was made on the geologic development of the Outer Kitakami Belt, on the basis of the results above-mentioned and other works adopting the "accretion tectonics", instead of the previous "geosynclinal-orogenic theory". Less
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