1996 Fiscal Year Final Research Report Summary
SEDIMENTATION AND ENVIRONMENTAL CHANGE FROM SEDIMENTOLOGICAL ANALYSIS OF BOTTOM SEDIMENT OF LAKE KAMO,SADO ISLAND
| Project/Area Number |
07640598
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | NIIGATA UNIVERSITY |
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Principal Investigator |
TAKEISHI Masaaki DEPARTMENT OF GEOLOGY,NIIGATA UNIVERSITY PROFESSOR, 理学部, 教授 (00126426)
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| Project Period (FY) |
1995 – 1996
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| Keywords | coastal lagoon / echo sounding / sand bar / diatom / pollen / Alluvium / transgression |
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| Research Abstract |
Lake Kamo is a coastal lagoon separated from Ryotsu Bay by a sand bar formed at the transgressional stage after the last. To make clear the sedimentation and environmental change of Lake Kamo, echo sounding profiles by SH20 and uniboom were firstly investigated, and diatom and pollen in core dorring samples were secondarily analyzed.
The lake is divided into two parts from the geomorphological feature, that is, the southern and northern part. The geomorphology of the southern lake shows the form like a bottom of the ship, which is a broad plain with steep margin. The plain bottom is 7 to 8m in depth. A long and narrow depression with 2 m depth is observed along the eastern margin. On the other hand, the northern bottom slopes gentlly from north to south.
The southern bottom is covered by broad dispersive layrs. A sounding basement is cropped out on the lake bottom along the lake coast. In the northern lake the sounding basement is extended to the central part from the eastern margin. The echo sounding profiles by uniboom and boring cores showsthat the sounding basement was formed by progradation of sand bar, which developed after last glacial stage.
The base of alluvium sediments is observed at 37 m in depth under the lake bottom. Terrestrial sediment underlying the alluvium sediment is considered to be Upper Pleistocene terrace deposits. The analysis of diatom assemblage about the alluvium sediments show the environmental change of the lake from brackish/fresh through marine to brackish.
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[Publications] TATEISHI,M., KANZO,K., TAMURA,Y., NGUYEN L.V., KOBAYASHI,I., TANAKA,S., MATSUE,M.: "Geomorphology and sediments of Lake Kamo, Sado Island (Prediction)" Proc.6th Symposium on Geo-Environments and Geo-Technics.183-186 (1996)
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