Throughout the world coals occur in scattered localities in each of the major post-Silurian stratigraphic subdivision. The workable coal seams are, however, principally included in the sediments of three ages, (1) the Upper Carboniferous-Permian, (2) the Upper Triassic-Jurassic, and (3) the Upper Cretaceous-Middle Miocene. These considerable coal formation in the world were coincident with the development of the land plants. Coal deposits exist in many countries of the earth. However, the largest coal deposits are concentrated in some countries on the northern hemisphere, viz. the Union of Soviet Socialist Republics, the United States of America, the People's Republic of China as well as a few European countries. On the southern hemisphere, only two countries have important coal deposits, viz. Australia and Republic of South Africa.
The eolian dust comes from China to Japan, flying frequently in spring. The eolian contribution to surface sediments cannot be ignored, because Japan is exposed to the westerly wind from China. The magnitude of the quantities of eolian dust that had been transported to Japan in the last glacial period may be greater than that in the Holocene. The purposes of this paper are to elucidate the depositional sequences, chemical properties, clay minerals of loesses, and to point out the significant contribution of eolian dust to accumulate on the surface sediments in Japan in the late Pleistocene. The results from our research are summarized as follows : 1) The twenty Japanese samples were collected from the outcrops of Karatsu city, Genkai town, Iki Island, Yonaguni Island. The analyses of three Chinese loess samples are quoted from Inoue and YOSHIDA (1978) and RYU and CHAN (1962) in China, the analyses of two eolian dust samples are quoted from Jyoetsu in 1966 (HASEGAWA 1967) and MORIOKA in 1977 (INOUE and YOSHIDA 1978) in Japan. The loess deposits consist of mixture of two component parts : silt and clay fractions and sand fraction. Most of silt and clay fractions is considered to be eolian materials which were originated in eolian dust from China, while sand fraction is eolian sand which was blown out from dried sea bottom in the W&uum l;rm glacial age. A judgement based on analyses of size distribution, we can conclude that eolian dust is mixed much in paleosol horizons in Karatsu city. 2) Loess including paleosol is considerably subjected to a weathering action. They are weakly acidified in soil reaction, and the amount of their exchangeable bases is relatively low except Mg2+. Loess and eolian sand beds are characterized by low fluoride pH and low phosphate adsorption. They are distinguished from volcanic ash beds, which are characterized by high fluoride pH and high phosphate adsorption. According to the amount of SiO2, Al2O3 and ±H2O in the < 0.02mm fraction of twenty five samples, they are distinctly divided into four groups ; Chinese loess, eolian dust and loess including paleosol, eolian sand, and volcanic ash. The relative orders of the SiO2, Al2O3 and H2O contents are in the following order on the basis of the diagram of three components distribution : SiO2 : Chinese loess> eolian dust, loess including paleosol> eolian sand> volcanic ash Al2O3 : eolian sand, volcanic ash> eolian dust, loess including paleosol>Chinese loess H2O : volcanic ash> eolian sand> eolian dust, loess including paleosol> Chinese loess An eolian dust in the late Pleistocene, which is originated from the arid regions in China, had gradually accumulated on the paleosol more than the eolian sand bed. 3) The clay fraction of loess including paleosol is characterized by predominance of 14 Å minerals, illite, kaolinite, and quartz. The 14 Å minerals are composed mainly by vermiculite, chlorite, and their intergrades. On the contrary, volcanic ash beds are characterized by predominance of allophane, imogolite, and amount of layer silicates, and they also contain a great amount of gibbsite concretion. The eolian contribution is primarily reflected in the distribution of illite, kaolinite and quartz in the loess deposits. The clay mineral composition of loess including paleosol resembles nearly to that of Chinese loess in China and eolian dust which failed in Japan in 1966 and 1977. 4) Depositional rate of loess is calculated 2.1-3.3g / cm2 / 1, 000 years by the analyses of thickness and silt and clay contents of the loess including paleosols in Karatsu in Würm glacial age. The results of the study in Karatsu may indicate the important contribution of eolian dust to the last glacial period sediments.
Open joints are paticular concern for engineering geologists, since they deteriorate elasticity and impermiability of rock mass. Their genesis has not been discussed in detail up to the present, presumably due to a limited number of the outcrops. In this study, the open joints are investigated in tunnels at mainly four dam project sites, with regards to topography and geology. The reached conclusions are as follows. 1) Open joints are oriented nearly parallel to the ground surface and exist only at shallow depth, so that they can be regarded as a variety of sheeting joints. 2) Open joints occur in the rock mass when the chemical weathering induces remarkable volume increase, and release of confining pressure at alternating beds causes differential rebound. 3) As far as “Green tuff region” in Japan is concerned, open joints, i.e. sheeting joints are of general occurence. 4) The rock mass with open joints is accompanied by landslide topography, although the rock mass without open joints is not, therefore the open joints are assumed to be prerequisite condition for landslide. 5) Vertical open joint at ridge top is presumably the origin of “ridge top depression”.
This is a recent revision of the Geology of the Kitakami region (1956, 1969, 1981) by Yoshio ONUKI who discovered Silurian fossils at Hikoroichi about 50 years ago. His description of the Kitakami mountains occupies two-thirds of this text and the Tertiary and Quarternary chapters are contributed respectively by S. KITAMURA and H. NAKAGAWA. It is quite astonishing that ONUKI abolishes the Shizu phase of disturbance which is the principal event of MINATO's Abean orogeny. According to YAZAWA and KITAYAMA's recent geological survey (1979) no discordance exists at the base of the upper Visean Yukizawa formation and the boundary at the type-exposure of Kotsubosawa is warranted to be a fault, instead of an orogenic discordance as emphasized by MINATO. ONUKI considers that the Kesen orogeny must be pre-Tobigamori i.e. early Upper Devonian in age and the Setamai orogeny is Upper Carboniferous. These orogenies are recognized in Japan only within the southern Kitakami mountains. On the other hand the pre-Carnic Akiyoshi orogeny was a strong one widely known in Northeast as well as Southwest Japan. The late Lower Cretaceous, or Aptian Oshima orogeny is the strongest one in the Kitakami region through which the folded mountains were completed. Now the early Cretaceous igneous activity from basic to acidic is clarified there in detail. Later the folded mountains were largely undulated and suffered from faulting in early Palaeogene, middle Tertiary and middle Neogene. Of the ancient igneous and metamorphic rocks their correlation is provisionally made with the pre-Cambrian history of China, but its decision is said to depend upon future investigation.