Minami-Shitaura fault is an almost vertical fault and 60km south of Tokyo, trending WNW to ESE across the Miura Peninsula. The upper Miocene Hatsuse formation shows a flexure along the fault, in which the southern side of the fault subsided about 500m relatively and a fault plane, along which the same side was uplifted about 250m relatively to the northern side. If we give appropriate absolute ages to four horizons in the middle and upper Pleistocene formations, we can obtain the rates of displacements as 10 to 30cm/103 years, in which the southern side has been uplifted relatively. If we assume the uniform rate back to the time when the faulting changed from subsidence to uplift of the southern side, the time should be one or two million years ago. The rate of right-lateral displacement seems to have become to predominate far over the rate of vertical one at least since the late Pleistocene, on the basis of the offset of stream courses, ridges, and terrace scarps.
In March of 1971, the writers had an opportunity to find and excavate the skull of the fossil elepahnt at Saruyama, Shimohusa-machi, Katori-gun, Chiba Prefecture. That skull was unearthed to be in the state of lacking the lower jaw bone and the most part of both tusks, but it could be identified that the material belonged to Elephas namadicus naumanni MAKIYAMA. The material was lain under overturned position in fine-gained sandstone which was assignable to the upper part of the Yabu formation of Upper Pleistocene. Immediately above the location of the fossil skull, about 20cm high, there was overlying fossil enclosure composed of abundant molluscan fossils which belong to the Lower part of the Narita formation of the younger. The details of the paleontological and the paleoecological studies are keeping up now.
Although many serveys and studies on the distribution and stratigraphy of tephras in Hokkaido have been done during last 50 years or more, the chronology on these tephras has not yet been correctly established. The authors have carried out the absolute chronology by dating with 14C on humified tephras in Hokkaido and made the correlation between each tephra. Moreover, they have tried to estimate the geological age of humus formation in these humified tephras. The chronology and the correlation of tephra layers in Hokkaido are as shown in Table 3, based on the 13C ages for humified tephra layers, as well as on some archeological data. Results obtained are summarized as follows; (1) In Hokkaido it seems that the age in which the remarkable humus have accumulated on tephras is not older than the earliest stage of the Holocene-about 8000 years ago. (2) Especially abundant accumulation of humus on tephras may have occured during 5000y.B.P. and 3000y, B.P. Perhaps the climate would have been rather humid and suitable for humus accumulation during this period. So called“Rodo”(humic volcanic ash soil) in Hokkaido is thought to have been farmed in this period. (3) The reddish-brown color of weathered pumices in Ta-d, Ma-k, Ma-d1 and Ko-f tephras may be due to the weathering under the past warmer climate than present. These periods are estimated about 7000 years ago for the former two and 3000-2500 years ago for the latter two.
This paper consists of a historical review on the formation of sand dunes and some considerations on the relationship between the dune formation and the intercalated humus layers in several districts. The following results were obtained; (1) Buried dunes beneath the surface of Tatebayashi upland in Tochigi Prefecture. Sand layers constituting the buried dunes are divided in two, both having been deposited under stable circumstances. And volcanic ash layers are found in this district, divided into three; upper, middle and lower. There is every reason to believe that these dunes were formed at the beginning of the fall of the middle ash, or at the end of that of the lower ash. (2) Sand dunes on Sanrihama and Kaetsu uplands. The formation of some of Sanrihama dunes were due to a relative rising of sea level in early Holocene epoch. At the bottom of shallow valleys in Kaetsu upland, humus accumulation occured in stagnant water prior to the formation of dunes. (3) Kashima dunes in Ibaragi Prefecture. In the Kashima peninsula are found sand dunes with three intercalated humus layers, which are thought to have been formed after the formation of sand bars caused by a rise of sea level during the Jomon culture period, early Holocene. (4) Genkai dunes in Fukuoka Prefecture. Sand dunes of this area were formed during the time of high sea level in Pleistocene epoch. Aeolian sand layers are thin in depth and cover uplifted sand bars of marine deposits forming coastal terrace topography. Furthermore, five buried humus layers called Kurosuna are found among sand beds of Holocene dunes, which indicate the ages of dune formation and the stable period.
Palynological, stratigraphical and chronological investigations were made on the Holocene buried humus soils intercalated in the coastal sand dunes developed along the Japan Sea in the Hokuriku district, Central Japan. The purpose of the present investigations is to determine a definite age of the formation of the humus soils, palaeoclimatic condition under which they were formed, their topographical environments and the relationship between the formation of their humus soils and coastal sand dune and the cahnge of sea-level. Most of the studied humus soils and peat deposits are considered to have formed during the close of the Middle Jomonian to the Early Old Tomb periods. The conclusion are based on 14C dating, the stratigraphy, topographical setting and archaeological remains found in the humus soils. The palaeoclimatic condition at those periods was cool temperate, judging from such macroplant remains as erect tree stumps, leaves and seeds, and microplants as pollen grains and spores. The annual mean temperature was estimated at some 11°C, and the flora which was developed on the Inner and Middle or Old sand dunes was composed mainly of either a riparian or a mixedslope type, being closely similar to the present lowland vegetation in the northern Honshu. A relative minor rise of the sea-level and migration of the coastal sand dunes seem to have caused the formation of most of the buried humus soils and peat which is called Sotan in Japanese, and submerged and buried forests in the coastal areas of the Japan Sea, Hokuriku district, Central Japan.
The humus contents and the Ch/Cf ratios of fifteen Humic Allophane soils were very high and the humus composition was characterized by the predominance of fraction 1 and low contents of fraction 2 and humins. The Ch/Cf ratios of Humic Allophane soils have certain geographical regularities. In Japan the ratios generally increase from the north to the south. Though the former contains a considerable amount of amorphous aluminosilicates dissolved by the Tamm's reagent, Altered Humic Allophane soils should be distinguished from Humic Allophane soils by the predominance of 14Å minerals and kaolin minerals. The Ch/Cf ratios of nine Altered Humic Allophane soils are higher than those of Humic Allophane soils, but the aromatic nature of the humic acids is almost the same as that of Humic Allophane soils. If Altered Humic Allophane soils were of the hydromorphic origin, their humic acids would not have such a high degree of aromaticity. The humic acids of normal and Altered Humic Allophane soils can be distinshished from those of Red-Yellow soils by their high Ch/Cf ratios and aromatic nature. Therefore, the forming process of the humus of Altered Humic Allophane soils is different from that of geographically associated Red-Yellow soils, but closely resembles that of Humic Allophane soils. This is the reason why Altered Humic Allophane soils should be regarded as a subtype of Humic Allophane soils.