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Volume 33 (1994)
- Issue 5 Pages 281-
- Issue 4 Pages 213-
- Issue 3 Pages 131-
- Issue 2 Pages 67-
- Issue 1 Pages 1-
Volume 33, Issue 3
Displaying 1-5 of 5 articles from this issue
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Yi Fei Zhang, Katsuhiro Inoue, Takashi Sase1994 Volume 33 Issue 3 Pages 131-151
Published: July 31, 1994
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSPhysical, chemical, clay mineralogical, and geochemical analyses of the tephra at the foot of Mt. Iwate after the fall of the Toya Ash (90, 000-130, 000yrs BP) revealed the accumulation of a long-range transported eolian dust in the tephra layer. The tephra deposits are characterized by the predominance of allophane and imogolite or halloysite (10Å and 7Å) and by a small amount of silt-sized cristobalite. However, the soil of the Shibutami Crack horizon in the tephra is characterized by low pH (NaF) and phosphate retention values, high silt and clay contents, and high bulk densities. Their dominant clay minerals are vermiculite and vermiculite-chlorite intergrades, which are weathering products from muscovite, and kaolinite. The soil also contains a considerable amount of silt-sized quartz. The oxygen isotopic ratios of 1-10μm quartz purified from two soils of Shibutami Crack horizons are +16.2 and +17.0‰, and similar to those of quartz from loess in China, loess-derived soils in China, Korea, and Japan, and modern tropospheric eolian dust in Japan. The experimental data indicate that vermiculite, vermiculite-chlorite intergrades, kaolinite, and quartz in these soils are not weathering products from tephra deposits but originated from a long-range transported eolian dust from China. The tephra stratigraphy indicates that the eolian dust was mainly deposited 20, 000-34, 000yrs BP and 50, 000-70, 000yrs BP. This study suggests that the crack horizon in the tephra section found in northern Tohoku and southern Hokkaido districts could be a key bed indicating a long-range transport of the eolian dust from China during the Last Glacial age. The flux of eolian dust onto tephra deposits at the foot of Mt. Iwate during the late period of the Last Glacial age is estimated to be 48kg/m2/1, 000 years or 4cm/1, 000 years.View full abstractDownload PDF (2913K) -
Kazuo Terada, Sadaaki Ohta, Mitsuo Suzuki, Shuichi Noshiro, Sei-ichiro ...1994 Volume 33 Issue 3 Pages 153-164
Published: July 31, 1994
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSFossil forests (approx. 12, 650yrs BP) buried in Hachinohe tephra from Towada Volcano, Aomori Prefecture, northern Japan, were studied dendrochronologically. In the forests, 22 well-preserved wood discs from erect stumps and lying trunks (14 of Picea, 5 of Larix, 3 of Abies) were obtained, and the tree-ring widths were measured and correlated. Cross-dating of Picea and Abies succeeded both among individuals and between genera, and led to the construction of a floating chronology of the cross-dated individuals, while cross-dating of Larix failed. All of the cross-dated erect stumps (8 of Picea and 3 of Abies) revealed that their terminal rings were formed in the same year. Further observation of the terminal rings showed that their latewood formation had already ceased before death. Thus it could be assumed that Towada Volcano erupted between autumn and the following spring, and that the forests were buried by the Hachinohe tephra and died out in the same season.View full abstractDownload PDF (2930K) -
Standard Tephra ColumnsYo Uesugi, Kazunori Shinkawa, Kunihiko Kigoshi1994 Volume 33 Issue 3 Pages 165-187
Published: July 31, 1994
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSLatest Pleistocene and Holocene standard tephra columns for the Izu-Oshima volcano and its adjacent areas are presented. The type locality is along the famous sightseeing roadcuts situated 3.5km southwest of the summit crater, where fresh tephra sections can be observed at any time.
More than 160 tephra layers deposited since about 25, 000yrs BP provide a detailed time scale to the worldwidely famous triple junction areas of the Philippine Sea, North American, and Pacific tectonic plates. These tephra layers are unconformably subdivided in ascending order from the Sembazaki fifth to the first formation. Their ages are approximately assigned as: older than 20, 500yrs BP, 20, 500-13, 700yrs BP, 13, 700-5, 600yrs BP, 5, 600yrs BP-1, 700yrs BP, and 1, 720-present.
The uppermost surface layers of the fifth formation are perfectly eroded, and only 29 layers (Osb127→Osb100) have been described. The surface soil of each tephra is pale yellow brown. The fourth formation is composed of 44 layers (Osb100-O64); the soil of each tephra surface is brown. The third formation is composed of 40 tephra layers (O63-Osb36-1), and the surface soil of each tephra is dark brown or black humic. O58 and O55 which are dated by their black humic soil as 11, 580±140yrs BP (GaK-16143A) and 10, 440±380yrs BP (GaK-15049), respcctively contain white rhyolite pumice. O37-3 contains pale reddish bubble wall glass shards which are correlated to the Kikai-Akahoya ash [Ah] ejected at about 6, 300yrs BP from Kikai caldera, 1, 000km WSW of Izu-Oshima Volcano. The second formation is composed of 36 tephra layers (O35-Osb1), whose surface soils are densely black humic. Sembazaki, the first formation (S, N, Y), is composed of more than 12 tephra layers which have been identified as the ejectas of syn and post caldera stages. The surface soils are brown and less humic.View full abstractDownload PDF (2815K) -
Kazumitsu Matsuoka1994 Volume 33 Issue 3 Pages 189-203
Published: July 31, 1994
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSForreconstruction of a paleoenvironment of marine coastal areas, micropaleontological and palynological investigations have been conducted along with other geochemical and sedimentological researches. Sediments provided for that research always contain a number of organic-walled microfossils generally called marine palynomorphs as wells pollen grains and fern spores. These marine palynomorphs mainly consist of dinoflagellate cysts, phycoma of prasinophycean algae, microforaminiferal linings, and acritarch. In this article, their biological aspects are briefly explained, and some examples of biostratigraphical and paleoenvironmental studies on the basis of these fossils in the Quaternary are introduced.View full abstractDownload PDF (3943K) -
M. Yanagida1994 Volume 33 Issue 3 Pages 205-207
Published: July 31, 1994
Released on J-STAGE: August 21, 2009
JOURNAL FREE ACCESSDownload PDF (395K)
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