IV. Research in geology of Manchuria i.e. Northeast China was commenced with RICHTHOFEN's trip in its southern part in 1869. In 1895 AHNERT's life work on the geology of Central and North Manchuria was started, and KOCHIBE carried out a preliminary survey in South Manchuria. Since 1923 geological papers of Manchuria were published by Y. C. SUN and others in Bull. Geol. Soc. China from 1923. Geological survey founded in South Manchurian Railway Company published Geological Map of South Manchuria, 1918 and Geology and Mineral Resources of the region, 1929. There are many papers in the regional geology written by Japanese geologists and palaeontologists. Besides late Permian naiads Silurian-Permian marine fossils were discovered in Central and North Manchuria and the Manmo group was proposed for the whole sequence of the Palaeozoic rocks accumulated in the Mongolian geosyncline. It was strongly disturbed by the Permo-Triassic orogeny accompanied by the Mongolian granite with the result that the area was consolidated and united with South Manchuria. Small basins were later brought about there and the large Liao-Sungari basin was produced in the late Mesozoic age. Recent studies by Chinese geologists reveal that the Manmo group comprises Cambrian and Ordovician fossils in its lower part and that it is rich in volcanic materials of different ages. Permian plants and lower and middle Triassic non-marine animals were discovered at some places. Further it is known that sea entered into the eastern part of Heilongjiang province temporarily in the late Triassic, middle-upper Jurassic and Cretaceous ages. V. PUMPELLY's geological reconnaissance in 1863-65 was the first in China, followed by RICHTHOFEN and others including Japanese geologists. The Tokyo Geographic Society published Geological Maps of South and North China and then of Eastern Asia all in 1 by 2 mills, scale in 1920, 1922 and 1929 respectively. According to E. T. CHANG (1922) mining was started in China already in prehistoric age. Chinese classics on stone medicine and related knowledge were imported to Korea and Japan. Among Chinese geologists CHANG was first to write geology of Chekiang, 1911. The Central Geological Survey at Nanking, Department of Geology in the National University of Peking and the Geological Society of China were successively founded in 1916, 1920 and 1922. Since then her geology advanced considerably except for some years from 1966. The research activity, however, became quite explosive from about 1973. The Geological Map of China in scale of 1/4 mills. was compiled in 1976 by the Chinese Academy of Geological Science An outline of Tectonic characteristics of China and the Tectonic Map of China were published by T. K. HUANG and his cooperators in 1977 and 1979 respectively. Supplementary notes are given on the Pentsao and world map (1) and the growth of Asia documented in the expansion of the non-marine facies in the continent (2).
Abundant wave ripples are found in the Pleistocene Shimosa Group distributed in Chiba and Ibaraki Prefectures, central Japan. Wave ripples in the Shimosa Group, which were deposited in the Paleo-Tokyo Bay, are intercalated in the following facies : the upper part of the point bar deposit of fluvial channel facies, distributary bay or lagoonal facies, tidal flat facies, tidal inlet facies, beach facies, shoreface to offshore facies, and deltaic facies. In this paper, it is introduced wave ripples in the distributary bay facies, tidal inlet facies, beach facies, and shoreface facies, which especially contain many typical wave ripples; and their paleo-environmental settings. Most of wave ripples were constructed under several meters deep in the Pleistocene Paleo-Tokyo Bay. Wave ripples in the distributary bay facies were constructed under the 'post-storm condition '. These in the shoreface facies were under both of the fair weather ' and post-storm ' conditions. These in the tidal inlet facies were mainly under the fair weather condition ' and in part under the post-storm condition '. Wave ripples are generally preserved by deposition of the overlying clay. Clay was supplied by floodwater of rivers running into the Paleo-Tokyo Bay.
The aspects of the development of isotopic methods that are pertinent to the origin of volcanic rocks are introduced. This paper deals with studies on strontium isotopes and related elements which have provide their usefulness in the field of isotope geology. In the Northeast Japan arc, a number of Quaternary volcanoes form a long, narrow belt, parallel to the Japan Trench. Decreasing 87Sr/86Sr ratios across the arc were confirmed over a wide area of Northeast Japan. In the southwest Japan, the 87Sr/86Sr ratios of Cenozoic basaltic rocks are clearly different between the San-in and the northwest Kyushu regions. The higher 87Sr/86Sr ratios of basalts from the San-in region than that of basalts from the northwest Kyushu region also reflect the different properties of the upper mantle, which means there is regional heterogeneity of Sr isotopic ratios under the southwest Japan arcs. Furthermore, the relatively high and variable 87Sr/86 ratios of volcanic rocks are partticularly concentrated in the southwestern Japan arcs which have probably more continental properties than the northeastern Japan arcs. Arc volcanism is characterized by prevalence of calc-alkaline rock suites as well as island-arc tholeiites. Various models have been proposed to interpret its genesis of the calcalkaline rocks. 87Sr/86Sr ratios vary remarkably within individual rock sultes as well as volcano and volcano. In some volcanic suites, the date points in 87Sr/86Sr ratios vs. SO2, SI and Rb/Sr plot accord with a model to produce more silisic differentiates by combined processes of crystal fractionation and wall rock assimilation in Mount St. Helens volcano. Adatara and Kirishima volcanoes in the Japanese island arcs, both the tholeiite series (pigeonitic rock series, P-series) and the calc-alkaline rock series (hypersthenic rock series, H-series) have been shown to have erupted from one volcano and difference in 87Sr/86Sr ratios shows that the H-series has lower 87Sr/86Sr rotios than the P-series, and also that each series had a separate crystal fractionation process. The results reveal that the nature of the primitive magmas of the H-series and the P-series seems to generate from individual source materials. Many Tertiary volcanic rocks from the northeastern Japan were determined for strontium isotopic ratios for the purpose of examining the genesis among the volcanic rocks. Two distinct suites of volcanic rocks occur in the northeastern Japan : the rocks older than 16 Ma of predominantly intermediate composition volcanics and the rocks younger than 16 Ma with bimodal suite of mafic and felsic rocks. Initial values of 87Sr/86Sr in the Tertiary volcanic rocks from the northeastern Japan, lie in the range from 0.7033 to 0.7068. High (87Sr/86Sr) I ratios are observed for the rocks older than 16 Ma from the Japan Sea side (H zone). It is noteworthly lower (87Sr/86Sr) I ratios in the Dewa Hill, Japan Sea coast and North Akita areas (L zone). The rocks younger than 16 Ma from the L zone can also be interpreted as having been originated as a mantle-diapir associated with the spreading of the Japan Sea basin.