No.43 2008 pp.337 345 Holocene Deposits and the Paleoenvironments in the Tokyo International Airport Haneda Northwest part of Tokyo Bay, Central Japan Katsuhisa SEKIMOTO, Kunihiko ENDO and Keisuke SHIMIZU Received September 30, 2007 Paleoenvironmental change in Tokyo Bay area in the latest Pleistocene and Holocene was investigated using the cores of Chuseki-so at Tokyo International Airport near the northwest Tokyo Bay. Foraminifer analysis clarified the changing processes of environment in Haneda Area. During the later stage of the Nanagochi Formation, the boundary of sea / fresh water might be situated near the center of Tokyo Bay, and the environment was river mouth to brackish water area. In the early to middle stage of the Yurakucho Formation, sequential changes in foraminiferal assemblages and wide occurrence of oyster reefs indicate quick sea-level rise and transgression occurred from 10,000 to 9,000 ca. years ago. Sea level of 10,000 ca. years ago must be -40 m. In the early to middle stage of the Yurakucho Formation, around 8,000 ca. years ago, inner bay environment extended and transgression advanced to the northern or inner part. Such trend in environmental changes mainly from 10,000 to 8,000 years ago, is nearly consistent with those in the previous studies such as Ishiwata 2004 and Endo in press in Tokyo coastal areas and Endo et al. 1983 in Nakagawa Lowland. Keywords: Chuseki-so, Yurakucho Formation, Nanagochi Formation, Holocene, Paleoenvironment, Foraminifera, Oyster reef, Tokyo Bay 1972 2001 19841972 1 1988 1988 1987 2004 2006 1 336-0015 1284-4-305 156-8550 3-25-40 175-0082 3-11-1-1323 Geological Science Research; 1284-4-305, Daitakubo, Minami-ku Saitama City, Saitama Prefec., 336-0015 Japan Department of Geosystem Sciences, College of Humanities and Sciences, Nihon University; 3-25-40, Sakurajosui, Setagaya-ku, Tokyo, 156-8550 Japan Former Bureau of Port and Harbor, Tokyo Metropolitan Government; 3-11-1-1323, Takashimadaira, Itabashi-ku, Tokyo, 175-0082 Japan 337 251
56 59 2006 40m 1 A-A, B-B,C-C 2 4 Fig. 1 Location map A-A, B-B and C-C show location of schematic geological section Figs.2 4 19831993 2001 2004 1 2 3 4 A-A B-B C-C A-A - 1 Table 1 Stratigraphy and paleoenvironmental changes of Haneda offshore area 252 338
2 A-A Fig. 2 Schematic geological section of A-A Line 4 C-C Fig. 4 Schematic geological section of C-C Line 3 B-B Fig. 3 Schematic geological section of B-B Line 30m 55m 60m BG B-B 3 10 15m 50m BG 4 C-C A-A B-B 500m 1 A-A 60m 70m 2001 2004 339 253
5 Fig. 5 Typical columnar sections showing the ostrea bed. 7 Fig. 7 Contour map showing the base of Chuseki-so (Holocene and Latest Pleistocene) in northwest area of Tokyo Bay. 6 14 Fig. 6 Distribution of the ostrea bed and 14 C ages. 50 60m 10 40mm 2 4m BG 1983 10 50mm BG 10 15m 254 340
15m 37m 43m A-A 50 100m100 200m2 3m 14 C 8,800 9,300yrs. BP 6 26m 7,300yrs. BP K-Ah 8 1983 7 A-A 5 6 2 14 C 46.0m 10,490 180 12072 1 37m 42m 8,800 9,300yrs. BP cal.10084 cal.10656yrs 2 2005 14 C 1982 8 Fig. 8 Diagram of fossil foraminifers from the analyzed core. 341 255
2 14 C 2005 Table 2 List of 14 C ages from the ostrea bed and peat Cal. ages are calculated based on Endo 2005 14 C m GaK-11501 8,820 220-39.3 10,084 GaK-11502 9,300 200-37.1 10,656 GaK-12528 10,490 180-46.0 12,072 GaK-12746 9,180 170-42.8 10,513 GaK-12745 12,380 360-66.0 14,321 GaK-12747 14,650 220-43.1 17,022 1 40m 14 9,220 140yrs. BP 2005 10,560yrs 300m 37.5m 14 9900 200yrs. BP 2005 11390 160yrs. BP 1966 1995 2006 42 38m 2006 1 32.0m TP-42.0m 12 20g 80 24 1 20mesh 0.075mm 200mesh 200 20 40 100 160 8 1 2 1 Fissurina cucurbitasema bispinata 2 Ammonia beccarii 3 4 Ammonia beccarii, Elphidium somaense, Elphidium clavatum 256 342
3 Elphidium subarcticum 4 Elphidium excavatum, Miliolinid 5 7 Ammonia japonica, Pseudorotalia gaimardii, Nonionella stella Elphidium excavatum Quinqueloculina Massilina Miliolinid 1g 60 142 8 10 Ammonia japonica, Nonionella stella, Miliolinid Pseudorotalia gaimardii Ammonia beccarii, Elphidium somaense, Elphidium excavatum, Epistominella tamana, Fissurina cucurbitasema bispinata 20 40 8 9 K-Ah Ca7,300yrs 11 Fissurina cucurbitasema bispinata, Miliolinid Ammonia beccarii, Ammonia japonica, Elphidium somaense 12 1mTrochammina hadai B-B 43.1m 14 C 14,650 220 1 2 1 46.0m2 41.5m Ammonia beccarii, Fissurina cucurbitasema bispinata 2006 42.65m 42m 9000 10000-40 -36m Ammonia beccarii, Elphidium somaense, Elphidium clavatum 5 7 35.5m 32.5m Ammonia japonica, Pseudorotalia gaimardii Nonionella stella, Miliolinid 8 10 31.5 20.5m Pseudorotalia gaimardii Ammonia japonica, Nonionella stella Miliolinid 2006 Fissurina cucurbitasema bispinata, Miliolinid Ammonia beccarii, Ammonia japonica, 343 257
Elphidium somaense 1987 Ujiie: 1962, 1963 Endo et.al, 1982 1979 ; Sekimoto and Endo, 1980 1981 1989 12 15.5m Trochammina hadai 1983 210 Pb 1950 Nonionella stella Trochammina hadai Morishima 1955 1 9 2005 1990 14 C 1 9000 15,000 9 2005 Fig. 9 Relative sea level change curve in the central part of Kanto Plain (Endo, 2005) peat and wood, indicating terrestrial environment molluscan shells living in intertidal zone molluscan shells living in sublittoral zone of inner bay 10,000 9,000 40m 6 258 344
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