Geological, petrological, and biostratigraphical studies of Mineoka ophiolite and related rocks, Hayama and Mineoka Belts, central Japan, were reviewed, and the origin of ophiolite is summarized as follows. 1) Pelagic to hemipelagic sedimentary rocks occur from late Paleocene to middle Miocene. 2) Basaltic rocks in the Hayama Belt are mostly alkali basalts of hotspot origin, whereas those in the Mineoka Belt are mostly tholeiite of mid-ocean ridge origin. 3) Chemical compositions of gabbros and diorites indicate island arc origin. 4) Peridotites are residues after a medium degree of partial melting. These facts arenot consistent with previous ideas that the ophiolite is island arc or back arc originonly. “It is concluded that ophiolite is part of the Mineoka plate” in the Pacific Ocean side, not in the Philippine Sea as previously proposed. Reconstruction of plate motions of the Mineoka plate is proposed, as it was formed at mid-ocean ridge, was subducted by the Pacific plate, and obducted to the Honshu arc during Miocene age after the eastward motion of the triple junction.
Marine terraces are well preserved in the coastal region facing the Pacific Ocean of northeast Japan. Their geomorphic development has been studied to clarify the history of sea-level changes and crustal movements. The Tsukabara coast located in the southeast part of Haramachi City, Fukushima Prefecture, has a marine terrace named the Kobama surface. Previous studies concluded that this terrace was formed in the last interglacial period. In the basal part of the Tsukabara Formation, which is marine sediment stratigraphically just below the terrace deposit of the Kobama surface, an air fall tephra consists of fine pumice lapilli was discovered. This study clarifies that this tephra contains mainly a well-vesiculated fiber type of glass shard with distinctive low indices (n=1.495-1.499) and small mounts of phenocrysts (orthopyroxene, hornblende, biotite, quartz, plagioclase). These characteristic properties and the chemical composition of the glass shards show that this tephra is correlated to the Tagashira Tephra (TG), which is distributed in the area from southern Fukushima Pref. to north Tochigi Pref., and also to Yokomori Volcanic Ash (YkA) distributed on the easten base of Adatara Volcano. Fission track dating and stratigraphic positions of TG and its related tephra suggest that the Tsukabara Formation and the terrace deposit of Kobama surface were formed during marine isotope stage 5.5. The Tsukabara Formation is most likely to be marine bay sediment, which buried a dissecting valley formed in the low stand of sea-level of MIS 6. Judging from the stratigraphic position of TG in the Tsukabara Formation, TG deposited between the low sea-level period when the Tsukabara coast was dry land and higher sea-level period when this area was submerged in the bottom of the bay with a depth of less than 20m, was associated with the transgression from MIS 6 to MIS 5.5. It is most likely that the present altitude of sea-level at the deposition of TG is about 2 m. This estimate and the elevation of the former strandline of MIS 5.5 indicate that the sea level at the deposition of TG was 28m lower than that at the culmination of MIS 5.5. On the basis of highresolution chronostratigraphy of Martinson et al.(1987), the age of TG is estimated to be135-125ka. After the deposition of TG, the sea invaded landward, resulting in the formation of a bay, with continuous deposition of fine marine silt of the Tsukabara Formation. The regression from MIS 5.5 to MIS 5.4 took place after the culmination of MIS 5.5, associated with the emergence of the Kobama surface. Subsequently, Ad-D tephra estimated to be 125-100ka was deposited. At that time sea-level was at least 17m lower than that of the MIS 5.5 culmination. Paleosealevel of MIS 5.3 is estimated to be less than-8m from the present altitude.
Meteorological observations have been made since 1881 by a weather station in Kyoto, Japan. Therefore, some approach must be considered to know about tempe ratures before 1881. This paper gives quantitative estimates of the monthly mean of the lowest daily temperature in winter in Kyoto. A long record of dates Lake Suwa, in central Japan, 36°N138°E, 250km from Kyoto, was frozen has been found in the Suwa Shrine Documents by S. Fujiwara and collected by H. Arakawa. A long record of dates of snowfalls was extracted by the author from many old diaries kept in Kyoto. The dates Lake Suwa froze and the first and the last dates of snowfalls in Kyoto bet ween 1881 and 1953 are correlated with the monthly mean of the lowest daily temperature in winter observed in Kyoto. The correlations obtained are applied to estimate winter temperatures in Kyoto before 1881. As a result, two series of winter temperatures are obtained: one deduced from the freezing dates and the other from the dates of snowfalls. The former covers 430 years (1450-1880) and the latter 880 years (1001-1880). The two series give almost identical winter temperatures considering the error involved in the correlation used and the volume of available snowfalling data. The sequence of the 50-year means of temperature obtained from the dates the lake was frozen shows that the mean lowest daily winter (December-March) temperature has been rising incrementally from-0.7°C in 1551 to-0.2°C in 1880. The sequence of the 100-year means of temperature obtained from the dates of snowfalls shows that the mean of the lowest daily winter (December-March) temperature from the year 1101 to 1200 was higher by 0.8°C than one from the year 1001 to 1880.
The average growth rate of energy consumption in China has been 5.2 percent per annum for the last five years. Energy demand is closely related to economic growth, and a stable energy supply is one of the key strategic policy goals of China. Coal is the major energy supply source with a seventy-five percent share. Oil production may not increase significantly in spite of planned exploration and production. China has abundant coal reserves, however, transportation and environmental issues could become bottlenecks to the expanded use of coal. Under such circumstances, increases in supplies of natural gas are desirable. China is promoting natural gas exploration and production, however, the share of natural gas to total energy supply is only two percent at present. Coalbed Methane (CBM) is regarded as an unconventional natural gas resource with reserves contained in coal seams. The volume of CBM in China is estimated to be over 1, 000TCF, and the area of CBM reserves is identical to that of coal. Although a small amount of CBM has been used adjacent to coal mines, most CBM have been ventilated and released into the air as a safety control measure in coal mines. To use CBM as natural gas energy, MOCI (Ministry of Coal Industry) and MGMR (Ministry of Geology and Mineral Resources) have performed a survey of CBM reserves in China. Based upon available data, a preliminary screening was carried out in this study on areas suitable for CBM development from the viewpoint of the volume of CBM reserves and productivity. Fushun, Fuxin, and Baotou coal mines may have great potential for CBM development with higher productivity of CBM per well. From a business development point of view, various pre-conditions need to be cleared, such as a proper gas market price mechanism, construction of gas supply pipelines, incentives to business enterprises such as tax credits and clarification of the scope of governmental administration for mining rights, for China to use the abundant CBM as a new energy resource.