  //  (,*+*)
 /  ,+/ῌ,+2      » ¼  = Q ½,*+*/ 3 -+ 4 ,*+*+* 3 0 4+.

C ages for the Kitanoyama and Itonashi cores in Izu-Oshima volcano, JapanTakahiro YAMAMOTO and Yoshihisa KAWANABE

Izu-Oshima volcano is one of the most active basaltic volcanoes in Japan, and consists of the pre-caldera older
and younger ediﬁces, the syn-caldera ejecta, and the post-caldera ediﬁce. The Japan Metrological Agency madenew boreholes on this volcano in ,**3. We dated two carbon samples from the Kitanoyama core in thenorthwestern foot and the Ithonashi core in the northeastern ﬂank. OSKT*+ at /2.1* m of the Kitanoyama
core and OSIT*+ at 03.-/ m of the Ithonashi core, which represent the upper part and the middle part of thepre-caldera younger ediﬁce, are dated as ,*.*1* y BP and 300*1* y BP by AMS +.C method, respectively.
Key words : Izu-Oshima volcano, borehole, +.C age+    56789 ,+ (Fig. ,)
:;<=>?@ABC7DEFGHI .1

J;K7%,

 L7BFGJ;MNOῌ>=PQRSTU VAF WXS Y .+., m.

(N -..0῍.,.1 E +-3,+῍-3.1)

Z[\]!"#S^_FG , J; ῌ $%`Za ..+, m S  `Z]&J; `ZDEFGb , K'cd(e a -.*3 m 7 fF , mm )ghij

k *+lm7% no J;*/J;   Nakamura (+30.)

ipqir=7,sFtu TUQ*/J;v

-wxt8y./x701z {|>}i~23+j=jSVAzG J;e0TU xlSm7% 45 56`Z nX 6F+S]!"#x7% `Z|>}ia ..+, m `Za ..,* m S 

%78`Zeu |>}i9~9x S,x3:;23S  ,**0R|>}i9  {|>}i7 < Sa ..,* m `Za ..21 m S Nakamura, +30*, +30. ; g +32. ; = +332 7eu |>}i~> 701o|>}i7O5?63@`Za ..21 m `Za //.0* m S 1 ¡¢=£¤¥o¦~>RO@ o~>7<F§¨AB;`Ze ¡¢=£¤¥§©7;   g +32. ;  = +332   ¦ ~ R  ~ ;ªr«|=`ZeCNakamura (+30.) ­Ex®R¦~"#x®701o£¤¥§B; *3`F¯p°«

QS J;]!"#±G ]&§*3` J;H²@³´`ZIJSeJ;KS^_FGQS (Fig. +) µ0`¶GS7¬NFG]!"#xRO¹ze

QR´Z 0P+RIJF º!-*/ῌ2/01 "#$%&'( +ῌ+ῌ+ ) 1*+,-./01 2 /0
Geological Survey of Japan, AIST, Higashi +ῌ+ῌ+Central 1, Tsukuba -*/ῌ2/01, Japan.

¬DS Z 1

L7 ±GM·®`Z¸zG

Corresponding author : Takahiro Yamamoto
e-mail : t-yamamoto@aist.go.jp

*+,-./0216

12 22.2* m 12 3,.12 m789:;<=>? 3 4565 @ABCDE>*FG*H IJKL >? MN O P='Q% R*HST "UVW OM
12 3,.12 m XY12 +**.1* m[\

3 Z  ] "^^_`aCb$cdef3g - 

ῌhi(N -..0ῌ,3.* E +-3,.ῌ-2.-) jk,-+.- m.
ῌ] 12 ..-3 m

opq>*lr

3 4>*l$mn

 12 -./+ m " st - mm

uvwExq>*lQ pq>*lr Nakamura (+30.) yzKO{|K"A}W
~CDEG 3g 12 ..-3 m 12 /..* m

3 >*lqq$q>*  CDE TGK S, K>? 2 3g

*+ ,**0

12 /..* m 12 3./1 m

3 x`^<=>? p$mnopq>*l  BC
DE>*G*Hd"A} 3 Z [\12 3./1 m 12 +2.,3 m @P=12 +2.,3 m 12 +2.30 m"x`^<=>? g 12 +2.,3 m 12 --.-2 md=3 7 

3 "k212 -0.11 m 12 03.+/ m
Location for the boring sites.

[\

12 --.-2 m 12 -0.11 m

Fig. +.

3 Z

 &oW qq3

"s Z 

3 [\W Y_`aCb 12 01.+, m 12 02.*3 m "$W UV"~ 3
12 //.0* m 12 /1.2* m3 ^¡ 12 /1.2* m 12 /3.** m3 4p  ¨©$Qn3
12 /1.2* m 12 22.2* m¡¢M

O@M¦§$STW3 ¬­"^¶ A$£e 3  ¡^12¸¹º =+... m¥"¨q Q&'()


3 "k212 03.+/ m 12 03.1. m ª«¢¡t &p§^"'®¯°±²aµ

12 03.+/ m 12 23./. m7   ¥"<=>? $mn3

¢M A£e¤3g ·!" #  $% &'()

g 

 dpK"& 12 2-.02 m 

12 2..// m ">*³$Q´4565789:;<=>? m



12 23./. m XY12 +**.*3 m3 4.1./ m 3g 3 O@M@AºYef565789:;<=>? »¼pK3 m

DE>*FG*H IJKL >? MN O ½3g # R*HST "UVW OM

 @ABC



Fig. ,.

 

217

Lithofacies for the Kitanoyama and Itonashi cores.

.ῌ ῒΐῐ῕῍῔ῑ῏῎   /2.1* m ( !")*+,
'-=>/0?@ABCD5EF 12G - cm,
O2G 0 mm 7PQ; IJKLM;N (OSKT*+)   03.-/ m  !"#$%&'-./

012 / mm 3456789:;<

H / mg 7IJKLM;N (OSIT*+)
IJ BETA ANALYTIC R?ST;N 56

!"#$%218

Table +.

&'ῌ()*+ῌ',-./2

34  AMS+3/**0

Results of +.C dating.

 1 56  78 RCYBP AD  d +-C   Stuiver et al. (+322) A2 7EF Talma and Vogel (+33-) 4A2 OSKT *+ OPQR7 ,*.* 9+:;<(=>?@A B2C56D
GGHI<(J3;)KLM NST<(UVWU+XYZ [\2]

1* y BP OSIT*+ OPQR7 300*1* y BP 5

2 12 ^_T`a.bc<(def65ghi2 jklm2n1 (Table +)   /t*)UG ±v w uv w2$% (+332) opG ^q[ G ^q[ +*^qrsa +ῌ2dy (+32.) p^z^q ^z^qT`{ / + ^q[! ^qrsa +ῌ+-Nakamura, K. (+30*) Stratigraphic Studies of the
Pyroclastics of Oshima Volcano, Izu, deposited during
the Last Fifteen Centuries. I. Cyclic Activity of “MainCraters” and the Absolute Chronology of the PyroclasticSediments. Sci. Pap. Coll. General Educ., Univ. Tokyo,+*, +,/ῌ+./Nakamura, K. (+30.) Volcano-stratigraphic study ofOshima Volcano, Izu. Bull. Earthq. Res. Inst., Univ.
Tokyo, .,, 0.3ῌ1,2.
Stuiver, M., Reimer, P. J., Bard, E., et al. (+332) INTCAL
32 Radiocarbon Age Calibration, ,.,***ῌ* cal BP.
Radiocarbon, .*, +*.+ῌ+*2-.
Talma, A.S. and Vogel, J.C. (+33-) A simpliﬁed approachto calibrating +.C dates. Radiocarbon, -/, -+1ῌ-,,.
!"# (,**0) opG  *)UvG§:;$«¬: : ­<^ S,   ®  7¯°= G  /+ ,/1ῌ,1+.

C5 ^@A?@5·}C AY

>²X ³´µ¶<(b  /2.1* m @A  A2 OSKT *+  

7 (,*.*1* y BP) t*)UG uv wxk7 n|}C56D b ..21 m @Ab//.0* m 15~"G@A#$%}  C&n} p'~( , .@A +.1 .*)U15#$F5)%*+n2C A12 b 3,.12 m @A,b +**.1* m 15#$- . 0* m .56 5 #$/v0.v Fn2C A o12<(b 03.-/ m @AA2 OSIT*+ 7(300*1* y BP)  b -0.11 m @Ab 03.+/ m  3#$ F7 }¡ ¢£^4^t*)UG uv( +#$5. 3 ¢£.¤6¥A¦u2}7¨56  #$8©92ª^p·}^%}¸¹ºK»n2

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