アンデス中部地域の古・中生界の生物層序学的研究 : 予報

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This field work was undertaken during late September to early November, 1980, and was financially supported by the Overseas Scientific Research Fund in 1980 of the Ministry of Education, Japanese Government. Members of the party include: S. SAKAGAMI (Leader of the Project): Paleozoic and Mesozoic bryozoans. J. YANAGIDA: Paleozoic and Mesozoic brachiopods. T. KASE: Paleozoic and Mesozoic molluscs. K. NAGAI: Sedimentology of Paleozoic and Mesozoic Groups in the Central Andes. C. RANGEL: Stratigraphy of Paleozoic and Mesozoic Groups in Peru. M. URDININEA: Stratigraphy of Paleozoic and Mesozoic Groups in Bolivia. The purpose of the study is to provide a more detailed biostratigraphy for the region covered in “Upper Paleozoic of Peru” by NEWELL, CHRONIC and ROBERTS (1949, 1953), and to compare the Upper Paleozoic and Mesozoic faunas in Central Andes with those of the Asian region. Knowledge of the Paleozoic bryozoan fauna in South America is especially poor. Although the Upper Paleozoic fauna of South America has been correlated mainly with that of North America, closer paleogeographic relationships can be anticipated between the South America and Eurasian regions in the Upper Paleozoic based on the Continental Drift Theory by Plate Tectonics. A more detailed paleontological study in South America is necessary to evaluate those relationships. The journeys in Peru and Bolivia are shown in Fig. 1. In Peru, the route between Lihuirco (ca. 11km north from Abancáy) and Quisuar (northern foot of Mt. Ampáy), where the Permian Copacabana Group is well developed, was measured and collected in detail. We also made a route map of this area at a scale of 1:2, 500. Many kinds of fossils such as fusulinaceans, bryozoans, brachiopods, molluscs and others were collected from 34 outcrops. Rock samples for sedimentary petrography were taken from 150 points along the route. As shown in the route map (Fig. 2), the outcrops were not seen in succession because of the strongly curved road and steep topography (Photo. 1). The columnar section will be compiled after the detailed study of the fossils and lithology. At present, it is considered that the Copacabana Group developed in the Lihuirco-Quisuar route forms the synclinal structure having an axis of WNW-ESE trend at the median part of this route. The shale facies is dominant near to the axis (upper part) and the limestone facies is rich far from the axis (lower part), namely: Upper: Mostly shale Middle: Alternation of shale and limestone facies (Qu-1-Qu-10; Qu-11-Qu-18) Lower: Mostly limestone (Qu-19-Qu-34) In Bolivia, we had the field trips to Yaurichambi and Tiquina, both situated near Lago Titicaca. Abundant fossils of the Copacabana Group occur, especially at Yaurichambi, not only fusulinaceans and corals, but also bryozoans, brachiopods, gastropods and others in many horizons. These faunas have yet to be studied. The results of paleontological and sedimentological studies will be published successively as soon as they are ready by each partakers. More field work is planned. Problems include: 1) choice of the best season, 2) proper field methods, 3) transportation of samples to Japan, and 4) permission of local governments.
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アンデス中部地域の古・中生界の生物層序学的研究 : 予報

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