HoIOCene Stratigraphy and Paleoenvironments in the Kanto Plain, in relation to the Jomon Transgression*

Kunihiko ENno**. Katsuhisa SEKIMOTO** and Tsukasa TAKANO**

(Received November 7, 1981)

1 Introduct,ion

The Kanto Plain, the biggest sedimentary basin in Japanese Islands, is situated in the middle Honshu Island, having very thick and almost continuous deposits ranging from Pliocene to Holocene time. Geomorphologically, several marine and fluvial terraces formed during the last interglacial and the last glacial ages, occupy the most extensive area in the Plain. Moreover, deep valleys dissecting these topographies are buried with deposits of the latest Pleistocene to the Holocene to become flat and broad alluvial lowl ands. Two transgressions, in the latest Pleistoce-ne and in the early to middle Holocene, played great roles in rapid accumulation and forming extensive alluvial surfaces. Especially in the early Holocene, a great number of dissected valleys, including the main valleys such as the Paleo-Ara , the Paleo-Kinu river, and these tributaries, and small valleys in the Kanto Plain, got drowned by the sea water invasion, which is called the Jomon Transgression (Holocene Transgression) in . This transgression in the Kanto Plain was proposed first on the basis of archaeological evidences of marine shell-midden and its distribution (ESAKA, 1972 ; et al.). The authors have investigated the stratigraphy of the deposits filling the drowned valleys, especially in the southern Kanto Plain characterized by rernarkable seismic upheavals, and in the central Kanto Plain, rather stable tectonically. On the basis cf these stratigraphical data, they discuss, in this paper, the processes of the Jomon Transgression and its environments, Ievels of the shoreline and its deformation, and sea- level changes in Holocene time, in the whole area of the Kanto Plain.

Proceedings of the Institute of Natural Sciences. College of Humanities and Sciences, Nihon University, Earth Sciences, No. 17, p. l-16, March, 1982. ** Department of Earth Sciences, Nihon University ; Sakurajousui 3-25-40, , , l 56, Japan. -1- Proceedmgs of the Institute of Natural Sciences（1982）

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R．Tqmo 野號・ Kb Kq K KC F 滲R，Sσ9αmi Oiso S∂9∂m’ H β∂y D E

c 5101520km

Fgi。1 Map showing the invest玉gated areas a． Distribut圭on of the alluvial plains in the Iくanto Plain b． Investigated areas A：Paleo－OshikiriBay，B＝Paleo－OfunaBay，CIPaleo－TateyamaBay，D：Paleo・Sanuki Bay，E：Paleo－lsumi Bay，F二Tsubaki－umi Lowland，G： Lowland・H；Area around ，1：Tokyo Lowland，J二〇ku－Tokyo Bay（Ja：Ara River Lowland， Jb；Naka River Lowland），K：Paleo－Kinu Bay（Ka：Kokai River Lowland，Kb：Sakura River Lowland，Kc：Tega－numa and Inba・numa Lowland） 1．alluvial plain（includlng Holocene terraces）2・terraces and hills3・mountain Iands

2． Outlines of the stratigTaphy

Drowned valley丘11ings in the Kanto Plain have been investigated by many geologists and geomorphologists（OTsuKA，19341SuGIMuRA and NARusE，1954－551HAToRI et ＆1．，196211KEDA，19641AoKI and SHIBAsAKI，19661KAlzuKAαnd MORIYAMA，19691 NIIGATA QuATERNARY REsEARcH GRoup，19721MATsuDA，1973and1974）．Among them，SHIBAsAKI，AoKI and KuwANo（1971）studied the stratigraphy in the Tokyo Lowland using a great number of borehole records，and proposed且rst that the drowned valley deposits are divided into two formations，the lower the Nanagochi Formation of

2 Holocene Stratigraphy and Paleoenvironments in the Kanto Plain

Table 1. Correlation table of the Latest Pleistocene and the Holocene stratigraphy in the Kanto Plain. figures : 14C age, lvl : marine facies. F : f.uvial Lacies, UA : upper alluvial deposits, US : upper sand, UC : upper clay, MS : middle sand, LC : Iower clay, LS : Iower sand. 1) : ENDO, SEKIMOTO and TSUJI (1979), 2) : SEKIMOTO and ENDO (1980), 3) : SHIBASAKI, AOKI and KUWANO (1971), 4) : KAIZUKA, NARUSE and MATSUDA (1977). the latest Pleistocene, and the upper the Yurakucho Formation of Holocene time. They, also, mentioned that there exists a unconformity which is shown by the presence of a valley (Prehoreal valley) between two formations. Moreover, the ages of a peaty silt layer overlying directly the unconformity were dated by i4C method to 9,820 ~ 230 y. BP (GaK-1936) and 9,500~-~60 y. BP (GaK-1937). Lately. KAIZUKA, NARUSE and MATSUDA (1977) summarized these formations and buried topographies in and around Tokyo Bay, using borehole data. ar Prcu t' ar I y,I abasal gravel bed (BG) of the drowned valley was clearly reccnstructed as a channel floor of the Paleo-Tokyo River over the area. Thus, the area in and around Tokyo Bay including the Tokyo Lowland is where the most abundant informations have been accumulated. During the last ten years, on the other hand, small drowned valley fillings in the southern Kanto Plain have been studied vigorously. This area is characterized by active upheavals and rich in cutcrops of fossiliferous valley fillings. Especially, based on the molluscan, foraminiferal, and pollen assemblages and a great number of 14C dates, the -3~ Proceedings of the Institute of Natural Sciences (1982) detailed Holocene stratigraphy is established and tectonics, climatic changes and sea level changes have been also investigated (Paleo-Ofuna Bay : MATSUSHIMA and OHSHIMA, 1974 ; Paleo-Tateyama Bay : YONEKURA, 1975 ; YOKOTA, 1978 ; MATSUSHIMA, 1979 ; NAKATA et al., 1980 ; Paleo-Oshikiri Bay : YONEKURA et al. 1968 ; ENDO et al., 1979 ; MATSUSHIMA,1979 ; SEKIMOTO and ENDo, 1980 ; Sanuki Bay : ENDO and SEKIMOTO, 1981 ; Paleo-Isumi Bay: SEKIMOTO and ENDo, in preparation ; Tsubakiumi Lowland : TSUJI and SUZUKI, 1979). In Paleo-Oshikiri Bay, the Shimobara Formation equivalent to the Yurakucho For- mation is divided into two members. Lower one, Kawaa Member, is mainly composed of manne silt wrth sandy gra~el and peaty silt of the basal honzon Its 14C ages range from 8, 800 to 7, 700 y. BP. This duration is corresponding to that of rapid rising of the Jomon Transgression. Upper on.e, Obune Member, consists of gravelly sand, marine silt, marine sand, brackish sandy silt, and fluvial sandy gravel and peaty silt, in ascending order. Its 14C ages range frcm 7, 600 to 6, OCO y. BP. This duration is corresponding to

l{] 30~ K.~a .e 20 10 Fig. 2 Longitudinal geologic section O along the Ara River and Kokai -]O River Lowlands - 20 NiizoF. (1) : Ara River Lowland - 30 (2) : Kokai River Lowland - 40 a : marine silt or sand bear- - 50 ing molluscan L0ssils, - 60 Toda F. b : fresh or brackish water - 70 BG silt or sand, c : fuvial sand - 80 - 90 and gravel O 20krn10 m 70 60 Shimodate 50 40 30 Ishige 20 Kawachi F. Fuji5hiro F. 10 :~:r~~:_ ~:~ ~_ r~ O ~:;h..;L ~ ~f ~ _1~:c'~~ - lO ~e j :i~~. ~S{S 'is~ - 20 ~ :-*-~-_s ~.~f;i~ - 30 --1~E - 40 ~e}:~ }~~_o__~1] {-:~:!~ _: -~~; le:_: Kokaigawa F. ~~ ~Jt:~*-~- - -'sol -._!~~~ - 50 BG. ' tL~~},~l,;~~ - 60 -70 Yawara F.(HBG) O 20lO km - 4 - Holocene Stratigraphy and Paleoenvironments in the Kanto Plain that of the maximum phase of the Transgression. Paleo-Oshikiri Bay emerged about 5, 500 -5, OOO y. BP to form the Holccene highest marine terraces. During late Holocene time, a few younger marine and fluvial terraces were formed. Lithostratigraphical features as mentioned above are common throughout tho southem Kanto drowned valleys. In contrast to those in the southern Kanto Plain and the Tokyo Lowland, stratigraphical works of the latest Pleistocene and the Holocene in the central and eastern ~(anto Plain have scarcely done. The authors obtained about thirty thousands horehole records and several hundreds boring cores in the central (Oku'Tokyo Bay) and the eastern Kanto Plain (Paleo-Kinu Bay) in order to clarify the stratigraphy and paleoenvironments during latest Pleistocene and Holocene time. Furthermore, they attempted to correlate the stratigraphy in the above-mentioned area with those in the southern Kanto and around Tokyo Bay, and, on the basis of the above results, to discuss the paleoenvironments and sea level changes in relation to the tectonics in the whole area 0L the Kanto Plain. Outlines of the stratigraphy in the central and eastern Kanto Plain are as follows. a) In Paleo-Kinu Bay, there exists a sand and gravel bed with the 14C ages of 9, OOO to 11.000 y. BP which divides the drowned valley fillings into two formations. It is the basal gravel of the Holocene deposits and named HBG. b) In Oku-Tokyo Bay, a basal sandy gravel or sand bed of the Holocene (HBG) is also found clearly. Its depth below the surface ranges from 15 meters in the upper stream area, to 35 meters in the present coastal area as is obvious in Fig. 2. c) In the both Bays, marine facies of the Holocene deposits are distributed extensively, but in some places, the upper horizon is cut clearly by fluvial and marshy deposits dated 3, OOO to 4, OOO y. BP by 14C method. To summarize these, the stratigraphy of each drowned valley is correlative as shown

in Table 1.

3. Holocene stratigraphy and paleoenvironments from the viewpoint of benthomc foraminiferal assemblages

In the southern Kanto Plain, Holocene stratigraphy and its environments have becn discussed on the basis of benthonic foraminiferal assemblages (SEKIMOTO and ENDo, 1980 ; ENDO and SEKIMOTO, 1981). Foraminiferal analyses for a number of boring cores obtained from the central and the eastern Kanto Plain, have been performed. In this chapter, comparing with the results and discussion in the southern Kanto Plain, benthonic foraminiferal assemblages from the central Kanto Plain are examined ~5- Proceedings of the Institute of Natural Sciences (1982)

,,,O'.LILP. Fig. 3 Geochronological changes of Fora-

2] miniferal Number (FN) and Plank- o pF d'5a~o~) tonic ratio (PF) for the drowned t. valley deposits in the southern and ,, ::'..*t" the central Kanto Plain. PF 3peh ,D (1) : Paleo-Isumi Bay (Kuniyoshi ,. PF I~lL) , Formation) (2) : Paleo-Sanuki Bay(Yawata For- ~. a.5FN 1lo21 1.5 ~ mation), after ENDO and SE- , KIMOTO (1981) (3) : Paleo-Oshikiri bay (Shimob- o FN2 4al02 6 o FN1 l,,a22 3 ' ara Formation), after SEKIM- OTO and ENDO (1980) ~-･: FN (4) : Ara River Lowland (Toda and

t･-*･ : PF Niizo Formations equivalent to

FN: Foramfn,ferat nurpber Nanagochi and Yurakucho For- mations) PR Ra,,ktonic rat,o Age of each sample in Paleo- Isumi and Paleo-Oshikiri Bays was determined by 14C dating. Age in Paleo-Sanuki Bay and Ara River Lowland was extra- O O,5 1 1 J5 2 polated by 14C dates, Iithostra- ,tlO tigraphical correlation and se- dimentation rate. stratigraphically, and discussed in relation to the transgression. Boring cores used for the examples shown in Figs. 3 and 4, are located about 7 km northwest (Loc. 1) and 5 km north (Loc. 2) of Kawaguchi. Both cores of Locs. I and 2 about 40 m in length, are composed of sandy silt of the lowest (Tokyo Formation) , gravel and organic matter- and shell-bearing silt of the lower (Toda F.), shell-bearing silt of the middle (Niizo F.), and organic matter-bearing sandy deposits of the upper horizon (Hikawa F. ) . The results of the analyses are summarized as follows. a. Foraminiferal Number (FN) (Fig. 3) : FN values are the highest in the middle, very low in the lower and fairly higher in the lowest. b. Planktonic ratio (PF) : Though the ratio is very low through the cores, it becomes higher in the middle (Niizo F.). c. Benthonic foraminiferal assemblage : The assemblage from the lowest h ' ' onzon rs characterized by dominant occurrences of Ammonia japonica and Buccella frigida with a considerable occurrence of Ammonia beccarii. Ammonia japonica characteri- stically occurs in bay center to bay mouth (MATOBA, 1970) and Buccella frigida is important species of thanatocoenosis in northern Japanese open coast and inner bay such as off (ISHIWADA, 1964) and Matsushima bay (MATOBA, 1970). Dominant species from the lower (Toda F.) are Ammonia beccarii and Crtbrononlon

- 6 - Holocene Stratigraphy and Paleoenvironments in the Kanto Plain

Loc.1 Loc. 2 o ~Dlm} toil I peat ~} silt ~l or9inlc materl81 5 ~1 sand ~] 'hell ~] 9ravel 10

IE 15 ID E , IC *aa, 20 a ･B

25 IA

30

35

40 O '20 e 2o*10 'ro-5 t5-2 02-1 0'1rlh'

Fig. 4 Foraminiferal asserrrblages from the drowned valley deposits in the Ara River Lowland and the columnar sections showing the sampling horizons. Loc. I : 7 km NNW of Kawaguchi, Loc. 2 : 5 km N of Kawaguchi. T : Tokyo Formation, N : Toda Formation (Nanagochi Formation), Y : Niizo Forma- tion (Yurakucho Formation), H : Hikawa Formation.

somaense, accompanying Cribrononion cf. subgranulosum or Nonionella stella as subdo- minant species. Those species are found commonly innermost hay to bay center environment. Thus, in contrast of the Tokyo Formation, the Toda Formation was characterized by dominance of mesohaline water and remarkably inner bay environment. The middle (Niizo F. ) contains dominant species of Cribrononion cf, subgranulosum, Quinqueloculina spp., and/or Cribrononion sovraense and subdominant species of Crib- rononion advenum or Ammonia beccarii. Similar assemblages have been reported in many recent inner bays, Hamana Lake (ISHIWADA, 1958 ; IKEYA, 1977) and other Japanese bays (UJIIE~ and KUSUKAWA, 1969 ; MATOBA, 1970 ; et al.). Furthermore, Holocene marine deposits of Paleo-Oshikiri Bay (SEKIMOTO and ENDO, 1980) and the - 7 - Proceedings of the Institute of Natural Sciences (1982)

Tokyo Lowland (UJIl~, 1962, 1963) in the Kanto Plain and Osaka Plain (NAKASEKO and CHIJI 1956), yield also similar foraminiferal assemblages. All these assemblages indicate middle to innermost bay environments. Facies of the upper Niizo Formation become sandy, and this horizon is characterized by abundant occurrence of Quinqueloculina spp. and common occurrence of Cibicides spp. On the other hand, Upper Kuniyoshi and upper Yawata Formations in southern Kanto Plain, are dominated by sandy facies, having Cibicides spp., Elphidiul71 crispwn and Rosalina spp. as dominant or characteristic species (SEKIMOTO and ENno, in preparation ; EN'Do and SEKIMOTO, 1981). As described above, each horizon of Loc. I and 2 has peculiar character in fossil foraminiferal assemblages. It is summarized as follows ; (1) Tokyo Formation : Iess abundant in FN, open coast to bay center assemblage, occurrence of cold water species. (2) Toda Formation : FN values are smallest among four formations, innermost to middle bay environment. (3) Niizo Formation : characterized by highest FN, values, occurrence of planktonic foraminifera, high species diversity, middle to innermost bay environment, upper horizon is subdominated by assemblage prefering to sandy bottom. (4) Hikawa Formation : no foraminifers, rich in organic matter, often intercalated by

peaty silt. These features are recognized also in the other valley fillings of the Kanto Plain and are useful for determining stratigraphic division of boring cores.

4. Paleoenvironments and Jomon Transgression

On the basis of the Holocene stratigr'aphical data as mentioned precedingly, positional changes of the shoreline during the Jom-on Transgression and environments of each phase of the Transgression have been elucidated in the whole area of the Kanto Plain. The Jomon Transgression ranges in age from 9, 500-10,000 to about 5, OOO y. BP. T1le earlier half of the duration is characterized by rapid rising of the sea level, and the later half by gradual rising and the high stand of sea level. And finally it was replaced by small regression about 5, OOO y. BP. Distribution of marine or non-marine sediment during the Jomon Transgression in the Kanto Plain is shown in Fig. 5. A solid circle in Fig. 5 means the locality where the presence of marine horizon in the valley flllings formed during the Jomon Transgres- sion is reco*'nized. An asterisk means the locality where only non-marine horizon (peat, peaty silt, fluvial gravel, etc.) exists. The presence of marine horizon vvas partially -8- Holocene Stratigraphy and Paleoenvironments in the Kanto Plain recognized by direct observation of marine molluscan fossils at outcrops and for core samples, and by foraminiferal analyses for core samples. In many cases, however, it was done by interpretation of borehole records. In any rate, Fig. 5 shows generally the distribution of land and sea around the maximum phase of the Jomon Transgression in the Kanto Plain. Preceding the Transgression, fluvial deposits of HBG advanced downwards about 9, 500 to 11,000 y. BP. Their facies vary from gravelly in the upper stream to organic matter-bearing sand or sandy silt in the lowest stream. Following their advancing, sea water invaded into the present lowland area, in resulting that the Tokyo Lowland was already submerged 9, OOO to 9, 500 y. BP. This is contrary to the archaeological view that the lowland area had not been submerged yet at

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Fig. 5 Map showing the distribution for the presence of marine or non-marine horizon during the period of the Jomon Trans- gression' Illustrated using the data partly from WAJIMA et al. (1968), MATSUSHIMA and OHSHIMA (1974), MATSU- SHIMA (1979), and NAKATA et al. (1980). l : marine, 2 : non-marine. 9- Proceedings of the Instltute of Natural Sciences (1982) that time (ESAKA, 1972). Deduced shorelines in 8. OO0-8, 500 and 6, OO0-7, OOO y. BP. are shown in Fig. 6. In the former duration, sea level was rising rapidly and reached to - 4- - 12 meters above sea level. Horizontally the shorelines in the drowned valley moved generally inwards up to near the maximum positions. In Paleo-Kinu Bay, the shoreline of this duration attained to the innermost position through the transgression. In the latter duration, sea level, in general, rose up to 2 or 3 meters above sea level, sea water invaded into numerous small tributaries of the bay, and the shoreline was situated at the innermost part of the bay, ¥vith a exception of Paleo-Kinu Bay where fuvial action was dominated. Fig. 6-b resembles the shoreline map reconstructed by the distributicn of shell middens of the early Jomon Cultural Period (ESAKA, 1972).

~

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O 10 20km O 10 20km

Fig. 6 Map showing the shoreline during the Jomon Transgression in the Kanto Plain. Illustrated using the data partly from KAIZUKA and MORlYAMA (1969), MATSU- SHIMA and OHSHIMA (1974), KAIZUKA et al. (1977), MATSUSHIMA (1979), ENDO et al. (1979), NAKATA et al. (1980), and ENDO and SEKIMOTO (1981). a : Shoreline during 8, OOO-8, 500 y. BP b : Shoreline during 6, OO0-7, OOO y. BP Dashed lines show former shoreline.

- 10 - Holocene Stratigraphy and Paleoenvironments in the Kanto Plain

5. Displacements of the shore levels and sea level changes in Holocene time

Fig. 7 shows altitudinal distribution for the highest r'nma I horizone in each bore hole and outcrop of the Holocene deposit in the Kanto Plain. This horizon is approximately corresponding to the maximum phase of the Jomon Transgression, 5, 500 to 6, 500 y. BP. The altitude depends originally on the highest level of the Jomon Transgression with a small discrepancy due to the situation in the bay, beach, river mouth, bay center, etc. It has been deformed during the last 6, OOO years, 110wever, by crustal movement, trunca- tion of fluvial processes, and recent land subsidence. In the southern Kanto Plain, it is very clear in Fig. 7 that the nearer the Sagami Tectonic Line situated southwest of the Kanto Plain, the higher the altitude of the highest marine horizon becomes. This active tilting is attributed to the frequent seismic upheavals such as associated with 1923 Kanto Earthquake (SUGIMURA and NARUSE, 1955 ; YONEKURA et al., 1968 : YONEKURA., 1975 ;

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10 ¥¥ ¥ 17.e 2o km ¥¥ 22.5 Fig. 7 Altitudinal distribution of the highest marine horizon during the maximum phase of the Jomon Transgression

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ム あ ● ノ 0 ジノ～、 ● ● 0 0 一一－ ●も●7●6●o 、

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、 m同 ＼ oω Φ 圃50 口 o 一50 一50 o 5 10 5 コ0 0 5 10 Φ ×103y・B・P・ ×1・3y・B・P・ ×103y．B．P．

oGO Fig。8 Shore level displacement curves aud revised sea Ievel change curves 腫 （1）：Paleo－Oshikiri Bay，（1）一a：Shore level d藍splacement curve，（1）一b l Revised curve．＊1 ） （2）＝Paleo・lsumi Bay・（2）一a：Shore level displacement curve，（2）一b：Revised curve．＊2 （3）：Shore Ievel displacement curve in Paleo・Kinu Bay．＊3 （4）：Shore level displacement curve around the Tokyo Low豆and．＊4 1：peat and wood from non－marine deposits，2：wood and peaty silt from marine and brackish deposits，3；molluscan shell from marine deposits。 ＊1 IIlustrated using the data partly from YoNEKuRA et aL（1969）and ENDO et aL（1979）． ＊2 IIlustratedusingthedatapardyfr・mOHARAandTAIRA（1974），NIRElandYADA（1977），andNAGAsAwA（1979）． ＊3 Illustrated using the data partly from OYA（1969）． ＊4 Illustratedusingthedatamainlyfr・mMATsusHIMA（1976and1981），KAlzuKAetal．（1977），andUMITsu（1977）． Holocene Stratigraphy and Paleoenvironments in the Kanto Plain

NAKATA et al., 1980). On the other hand, in the central Kanto Plain, the altitude seems to be rather constant, around 2.5 meters ahove sea level. At the same time, it shows a small and 10cal variation ranging from 3 to - O. 5 meters. There is, however, no regional trend such as upheaving unidirectionally towards the south, the north, or the center. A few local center showing low value are situated near Kazo, in the central Kanto Plain, around Tokyo Bay and the Tokyo Delta, and along the Ara River. These are corresponding to the land subsidence centers in recent ages. Consequently, from the viewpoint of subsurface geology and geomorphology, the central Kanto Plain has not been effected by tilting

having been active in the southern Kanto Plain. In Fig. 8, shore level displacement curves in Holocene time are shown. Broken lines in Figs. 8-(1) and (2) mean average upheaving rate which is based on the following

assumptions. (1) Sea level about 6. OOO years BP reached to 3 meters ahove sea level which are common level of the highest marine hcrizcn in the central Kanto Plain. (2) Seismic upheaving rate has been approximately uniform throughout Holocene time. Figs. 8-(1)b and (2)b show curves revised by each average upheaving rate. These revised curves are similar to the shore level curves as shown in Figs. 8-(3) and (4). It suggests that the revised curves [8-(1)b and (2)b] or the shore level cuves [8-(3) and (4)] indicate sea level change curves (eustatic curve) , to first approximation, if some regional

tectonic movement can be neglected.

6. Concluding Remarks

Drowned valley deposits of the latest Quaternary, distributed along the main and their tributaries in the Kanto Plain are divided into two. The both units of the lower and the upper, having gravel to gravelly sand bed in their basal horizon, are cor- related with the Nanagochi Formation of the latest Pleistocene and the Yurakucho For- mation of the early to middle Holocene in the Tokyo Lowland (SHIBASAKI, AOKI and

KuwANO, 1971), respectively. Foraminiferal assemblages from the Nanagochi and the Yurakucho equivalent forma- tions show commonly inner bay environments, ranging from bay center to innermost bay. Reflecting advancement of the Jomon Transgression, values of Foraminiferal Number and planktonic ratio are increasing in the Yurakucho equivalent formations. The highest level of the sea attained to 2-3 meters above sea level about 6, OOO- 6, 500 y. BP in the central portion where the seismic upheaval is negligible. Jomon

- 13 - Proceedings of the Inst…tute of Natural Sciences（1982）

shorelines during the early and the maximum phase of the Jomon Transgresslon were reconstructed mainly on the bas1s of borehole data．Those indicate that in early Ho1㏄ene age，the shoreline was situated nearly in the imermost portion of the drowned valley，

Revised shore level displacement curves of the southern Kanto are similar to the shore level displacement curves of the central and eastem Kanto Plain．It suggests th＆t

the revised curves approximate the sea level change curve．

Referenees

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