Vol.3 No.1 2010

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Research paper : The advanced geological researches and fundamental national land information (M. Saito)−22−Synthesiology - English edition Vol.3 No.1 (2010) 7 Value and uses of the GMJ Tomochi 1:50,000 sheetThe published GMJ Tomochi 1:50,000 sheet provides geological research results for an area that is geographically difficult to survey and geologically complex. We created an accurate geological map based on up-to-date geological theory and other current published information. This map will set the standard for determining the geology of this area and the surrounding region. On the basis of our work on the Tomochi sheet, we are now creating a regional-scale GMJ 1:200,000 map covering the Yatsushiro and a part of the Nomo Zaki sheet[19]. Our evidence-based interpretation of the geological structure and evolution of southwestern Japan advances the broader understanding of Japanese geology.The published Tomochi sheet is not simply the result of basic research on individual rock units. It represents the synthesis of information from several geoscientific disciplines to create a geological map. Further, it is one individual published map of many that constitute the entire GMJ, for which there are many important uses in Japanese society.The Tomochi 1:50,000 sheet, and the GMJ as a whole, are used not only immediately after publication. They will be valid for several decades and will continue to be used to satisfy basic societal information needs. Thus, the GMJ provides research results with a longer lifespan than, for instance, engineering research. However, some uses are expected at this point as follows.7.1 The Tomochi sheet as a mapping standardAn example of the use of the Tomochi sheet as a standard is provided by the 1:200,000 GMJ of the Yatsushiro and part of the Nomo Zaki sheets[19]. In compilation of this map, the rock classifications of the Tomochi[12] and the GMJ Shiibamura 1:50,000 sheets[20] were used. Within this 1:200,000 sheet area, the geological classification of the Tomochi sheet was the most complex, and its completion was a prerequisite for compilation of the entire 1:200,000 sheet, which filled the last blank area of the GMJ 1:200,000 series in Kyushu.7.2 Industrial locationsThe Tomochi sheet clarified the relationship of the Jurassic accretionary complex with the rocks of the “Kurosegawa Belt” (that the “Kurosegawa Belt” rocks overlie the Jurassic accretionary complex above a low-angle thrust fault) (Fig. 7).This understanding can be transferred to improve understanding of industrial locations in areas of similar geology (e.g., the location of the Sendai Nuclear Power Station in Kagoshima Prefecture).7.3 Disaster preventionWe believe the Tomochi sheet can contribute to the prediction of landslides, because it has clarified the structural relationships in areas of serpentinite rocks, where landslides are known to occur. Further, there are frequent failures of road embankments in the Tomochi area, for roads ranging from National highways to forest roads. These failures are commonly related to the local geology. Thus, the Tomochi map can provide basic information that can be used to develop measures to prevent these failures.In the report that accompanies the Tomochi sheet, we have described both faults that have been repeatedly active since the late Pleistocene (125,000 years ago), and which are expected to cause future earthquakes, and faults that were not identified as active because there were no formations younger than the late Pleistocene to provide evidence of their activity. The map and report can therefore be used for investigation of regional crustal movement during the period from the late Pleistocene to the present.7.4 Mining resourcesMapping of the Tomochi sheet indicated that the prospects for metal resources in the area are poor. It showed that limestone rocks are abundant in the mountainous regions, but that further development of these resources is unlikely, except in the northern area where there is current mining and transport infrastructure available. The prospects for other mineral resources and crushed stone are also poor. On the other hand, a hot spring developer indicated that the Tomochi sheet will be used extensively for hot spring development projects in the area.7.5 TourismNew uses of the Tomochi sheet include regional promotional activities and tourism. The research report that accompanies the map describes previously known sites of general interest, such as stalactite caves, and a natural stone bridge formed by welded pyroclastic rocks deposited about 90,000 years ago. There are natural features within the Tomochi sheet area that are potential national monuments, and others suitable for geo-sites or geoparks. These include previously known Cretaceous ammonite fossils, recently discovered Devonian fern fossils[15], megacrystalline clinopyroxenite[17], and deposits of jadeite[18]. These are described in the accompanying report. Also, the geology of the mountains used for the mountain events of the National Athletic Meet as well as the mountains that comprise the unique landscape of the region are clarified, and this can be used as material to explain the natural environment of the district.7.6 Utility value of the GMJThe GMJ Tomochi 1:50,000 sheet will have many uses for decades after its publication. In addition to conventional uses of geological maps, new uses may arise in response to changes in society, or to the occurrence of natural disasters.

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