地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
96 巻 , 1 号
選択された号の論文の7件中1~7を表示しています
  • 大森 博雄, 遠藤 邦彦, 上杉 陽, 堀越 増興
    1987 年 96 巻 1 号 p. 1-22
    発行日: 1987/02/25
    公開日: 2009/11/12
    ジャーナル フリー
    Much of the coast of Australian Continent is fringed by Holocene dunefields. The coastal dunefield near Millicent, southeast of South Australia, is one of the long and broad Holocene dunefields of Australia. It occupies the outer edge of broad Quaternary barrier plain expanding about 100 km inland. The outermost barrier called Robe range (barrier) consists of 3 units of barriers whose uppermost unit is Holocene sediments covering lower 2 units of Pleistocene barriers (beach ridge-dune units). The arangement of coastal landforms expressed by the barrier and interbarrier lowland was established during the late Pleistocene. It is located in the Westerly zone characterized by the winter rainfall in the same manner as the southern parts both of east and west coasts of the continent. But the annual rainfall of 500 mm to 800 mm is less than those of the latter two coasts with annual rainfall greater than 800 mm. The authors discuss the history of dune building based on the stratigraphy of the Holocene sediments and compare it with those of some other coastal dunefields of Australia.
    The Holocene dune sediments near Millicent are divided into four units, such as the early Holocene dune sand (from 8, 000 B. P. to 5, 500 B. P.), the mid-Holocene dune sand (5, 500 B.P. to 2, 700 B.P.), the late Holocene dune sand (2, 700 B.P. to 500 B.P.) and the Present drifting sand (since 500 B.P.). Each of them consists of calcareous sand and organic layers, being subdivided into layers. The marine sediments containing shell beds of 4 m or 5 m above the present sea level show the dates between 6, 000 B.P. and 4, 000 B.P.
    Along the west coast of Lake Bonney, the early Holocene dune sand made a long-walled dune covering the flat interbarrier lowland, behind the outermost Pleistocene barrier which is now distributed in the sea as offshore submerged rocks. It suggests that the wave erosion destructing the Pleistocene barrier into submerged rocks supplied much of sand inland during the period of sea level rising. During the period from 6, 000 B.P. to 4, 000 B.P., the postgalcial marine transgression attained its maximun, and invaded behind the Pleistocene barrier at Rivoli Bay and the west coast of Lake Bonney. A number of small barriers (beach ridge-dunes) were formed around Rivoli Bay and Lake George. Wave cut benches were formed at the foot of Holocene long-walled dune which was precedingly made up inland along the west coast of Lake Bonney.
    The mid-Holocene dune sand is divided into two subunits of dates from 5, 500 B.P. to 3, 500 B.P. and from 3, 500 B.P. to 2, 700 B.P., the latter of which intercalates many organic layers, showing frequent changes in mobility and stability. Both subunits show the older phase of parabolic dunes having established the framework of dune landforms of the study area. The dunes were formed during the period from end of the most humid phase in Holocene to the driest phase. Individual dunes are wider and higher than those of the younger phase of parabolic dunes and the dunefield of this phase is the most extensive as much as 5 km inland, showing strong wind and much supply of sand.
    The late Holocene dune sand is also divided into two subunits of dates from 2, 700 B.P. to 1, 500 B.P. and from 1, 500 B.P. to 500 B.P., the latter of which intercalates many organic layers containing standing dead trees. Both subunits show the younger phase of parabolic dunes, built up during the period containing the dry phase around 3, 000 B.P., the humid phase around 2, 000B.P. and the following dry phase. They form narrow-body parabolic dunes similar to hairpin dunes on those of the older phase and are less than those of the older phase in width and height. Standing stumps of dead Casuarina trees buried in organic layers of the latter subunit show that the dunefield had been covered with Casuarina woodland before the accumulation of the latter subunit.
  • 増田 富士雄, 牧野 泰彦
    1987 年 96 巻 1 号 p. 23-45
    発行日: 1987/02/25
    公開日: 2009/11/12
    ジャーナル フリー
    Paleo-wave conditions during the Shimosueyoshi Transgression (130, 000-100, 000 years B.P.) are estimated from oscillatory ripples preserved in prodelta, shoreface and tidal flat deposits of the Paleo-Tokyo Bay. Possible combinations of wave conditions and water depths that could have generated the observed ripples are determined by ripple spacing and grain size of ripple forming sediments using the method of Komar (1974) and others, which are based mainly on Airy wave theory. In addition, paleo-depths are calculated independently by the following two methods using stratigraphic thickness from the ripples to the above foreshore deposits and the height of longshore bars containing some of the ripples in shoreface deposits. Therefore, combinations of wave height and wave period under the water depth, which was estimated by the above method, can be determined.
    Waves with a height of lower than 2.3 m and a period of 2-8 s are obtained from the ripples in prodelta deposits. Such waves represen “storm waves” of the present Tokyo Bay. This wave condition may have been formed by relatively small waves of post-storm stage, because the ripples occur in the upper part of storm-generated sheet sand and are covered by a clay layer deposited from suspended matter in flood fluvial water into the Paleo-Tokyo Bay. Waves with lower than 2.5 m in height and 1.5 to more than 10 s in period are reconstructed from the ripples in shoreface deposits. These waves can generally represent “storm waves” of the Tokyo Bay and “fairweather waves” of the Kashima beach facing the Pacific Ocean. Waves of smaller 1 m high and less than 5.5 seconds are reconstructed from the ripples in tidal flat deposits. These small waves are approximately equal to “fairweather waves” of the Tokyo Bay. No ripples representing more big waves, such as winter waves and typhoon-generated storm waves on the present Pacific coast, are preserved in the Paleo-Tokyo Bay sediments. This may be caused by the shallow seawater-depth, less than 10 m, of the Paleo-Tokyo Bay where big wave motion during storm event may have changed most of the bottom sediments to flat bed rather than ripples.
  • 小林 貞一
    1987 年 96 巻 1 号 p. 46-63
    発行日: 1987/02/25
    公開日: 2009/11/12
    ジャーナル フリー
    This Article consists of fifteen chapters as follows :
    1. Introduction.
    2. The Beginning of the Research.
    3. Systematic Research in China until 1945.
    4. Research in Koreo-Manchuria.
    5. The Tsinan Basin and the Tsinling-Keijo (Seoul) Line.
    6. Ribeirioids, Ozarkian, Plectronoceras, Agnostida and Corynexochida.
    7. The Chosen (Joseon) Supergroup in the Yokusen (Ogcheon) Zone.
    8. New Data in Korea.
    9. The Development in the Studies in China (1946-).
    10. The Great Development in the Studies in China in Recent Years.
    11. The Standard Sequence of the Cambro-Ordovician Formations in China.
    12. The Basal Part of the Cambrian System and the Pre-Trilobite Stage.
    13. The Lower Limits of the Ordovician and Silurian Systems in China.
    14. Palaeogeography of China in the Cambro-Ordovician Period.
    15. Summary.
    The History of Research in China is here divided into the initial stage started about 1856, the second stage from 1922 to 1945, the third stage of about 20 years from 1946 and the fourth stage started after an interval of about ten years. The researh developed in Koreo-Manchuria is also summarized, and the present status outlined.
  • 青山 高義
    1987 年 96 巻 1 号 p. 64-71
    発行日: 1987/02/25
    公開日: 2009/11/12
    ジャーナル フリー
    In the present study, the distribution maps of climatic water balance components were provided by climatic year method. The water balance was evaluated by “bookkeeping procedures” for each year based on the Thornthwaite's system (1948) as shown in Table 1. The data used here were monthly precipitation amount and monthly mean temperature recorded at 321 stations over the northeastern part of Japan during the period 1967-1982.
    The distribution of the mean annual total of potential evapotranspiration (PET) is shown in Figure 1. The local differences of PET can be seen among basins and plains. The amount of PET is greater than 720 mm in the Kanto Plain and the Echigo Plain, Central Japan, and less than 540 mm in the southeastern part of Hokkaido.
    Figure 2, Figure 3 and Figure 4 show the distribution of mean annual water surplus, mean annual water deficit and mean annual number of dry months, respectively. The distribution pattern of water surplus (Fig. 2) shows orographic effects of mountain ranges facing the Japan Sea ; the large amounts are observed along the mountains and the small amounts are observed over basins and plains on the Pacific side of the mountains. As shown in Figure 3 and Figure 4, the distribution pattern of water deficit and dry month is almost the same. The dry month is defined here as the month in which the monthly potential evapotranspiration exceeds the monthly precipitation. The features of these distribution are more complicated than that of water surplus. Large amounts of water deficit are appeared in some basins and plains blocked by mountains to the south.
    We would like to study the significance of water balance components as environmental elements in the future. In this study, an interpretation was given for the geographical distribution of beech trees (Fagus crenata) in Hokkaido. AOYAMA (1986b) showed that the PET indicates a similar thermal indicator for vegetation to Kira's warmth index (1945). The border between cool-temperate deciduous forest and subarctic coniferous forests runs along the western foot of the central mountains in Hokkaido, where annual amount of PET is about 560 mm. The northern limit of beech trees is located further south, in the Kuromatunai lowland, where the PET is about 600 mm. KIRA (1971 a, 1976) interpreted that the difference of location of these borders was caused by the advance of beech trees from south during th period since the last retreat of the ice. In addition to this interpretation, we can indicate climatic reasons to set the northern limit of the beech trees. At the root of the Oshima Penninsula, north of the Kuromatunai lowland, region with the amount of PET less than 560 mm spreads and reaches to the Pacific coast. Moreover, a large amount of water deficit is recognized along the coast of the Japan Sea. In general, the beech trees dominate in the cool-temperate deciduous forest under the condition of wetter maritime climate. Consequently, it can de considered that the thermal condition as indicated by PET on the coast of the Pacific side and the moisture condition as indicated by water deficit on the Japan Sea coast make a barrier for the advance of beech trees toward the north.
  • 山口 岳志
    1987 年 96 巻 1 号 p. 72-73
    発行日: 1987/02/25
    公開日: 2009/11/12
    ジャーナル フリー
  • 佐藤 正
    1987 年 96 巻 1 号 p. 73
    発行日: 1987/02/25
    公開日: 2009/11/12
    ジャーナル フリー
  • 大森 博雄
    1987 年 96 巻 1 号 p. Plate1-Plate2
    発行日: 1987/02/25
    公開日: 2009/11/12
    ジャーナル フリー
feedback
Top