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Structural and paleo-stress analyses of Muroto formation,
the Tertiary Shimanto Complex, Shikoku

*ῌ*ῌ !**ῌ"#$%*
Satomi Minamizawa*, Kazuhiko Kuwano*, Arito Sakaguchi**and Yoshitaka Hashimoto*
Abstract : Structural and paleo-stress analyses were conducted on the Muroto formation, the Tertiary Shimanto Complex, Shikoku to understand the tectonics of coherent
accretionary complex. The Muroto formation is the Tertiary accretionary complex
composed mainly of sandstone and mudstone. The study area located at the Muroto
Peninsula is composed of Coherent Zone and Deformation Zone. Coherent Zone
represents homoclinic alternation of sandstone and mudstone. Deformation Zone
shows strongly deformed structures such as tight folds and minor faults. Strikes anddips of bedding in Deformation Zone indicate that the Deformation Zone is folded withfold axis of S.0W, +/. Meso-scale fold in Deformation Zone and cleavages pervasively
observed in the study area are considered to be formed by NW-SE compression.
Paleo-stress analysis was conducted by multiple inverse method using micro faults
in Deformation Zone. This result indicates wide variation in compressive stressdirection from NW to NNE and stress ratio from * to +.
Key words : accretionary complex, paleo-stress, multiple inverse method, Shimanto belt&'() 
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PQ Kimura and Mukai, +33+ ; Murata, +33+ ;Onishi and Kimura, +33/ ; Ohmori et al., +331 ;Ujiie, +331 ; Sakaguchi, A., +333 ; Hashimoto andKimura, +333 ; Matsumura et al., ,**- ; Shibata,**/ F 3 « 3 ¬@ ,**/ F +, « +- ¬* ­®jSS{¯°±f²S²
Department of Natural Environmental Science, Faculty of
Science, Kochi Unitersity, Akebonocho ,ῌ/ῌ+, Kochi 12*ῌ
2/,*, Japan** ³ UV´gµ!¶·{ ¸UV¹,º*Japan Agency for Marine-Earth Science and Technology,,ῌ+/ Natsushima-Cho, Yokosuka-city, Kanagawa ,-1ῌ**0+and Hashimoto, ,**/:;  Kd e+*-fJ>? gh
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=>? @79A BC70 DEFG8
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?T q-.l?%&q<'79 Taira et al., +322
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LM 94N+O9= Sakaguchi, +333
,0,CD%E& N; A* 'F/-02 ./.0 9P/4Q0!R$S1
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;`a X <b*c3de$RKS #$
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=f c3g$> 94 h*?i4)@3j@; A4)@ <  ,  AB
C D4 kl mEF(;#GH c?ih4 X Deformation Zone
 -  A j@;A4 X Coherent Zone   B 3no?33 Deformation Zone Coherent Zone IJp3qrKg LM4  , 
Deformation Zone N Coherent Zone NNs %4 2 Coherent Zone
Ns 9PN)  +* cm t(;< G Deformation Zone j +* cm tu;<Deformation Zone ;  C[LOvw$"P -  AxQy
R*ST33N
 NzU, {| %}~J'K
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3qr<$"( @Z  -  C
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! ;bCNR* jq4C&[p3&Kv ^d@v!;< rv ! Norris and Barron,+303 3sC &Kv tuv 

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cm 2 m ;£¤ closed7tight Px
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>ῌ%bcd65+G :;<%GH 123
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 89:;<%iU>ῌj;Gkῌl῎m
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 1 G g23456% -  A Deformation Zone # d5%) / m B Coherent zone # d5%
) / m C Defromation Zone 3l ¡¢£¤¥LM¦LM §¨u©%I$JKLMGª«¬5­®
S.0&W +/& G D Coherent Zone 3l ¡¢£¤¥LM¦LM /ῌῌ+ῌ area % +ῌ area 0456¯° /ῌ±²¯°¨³ g ¼ 91 ¼

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 (9:;'H$%&'())*+N,*0W /*0 $4&'())*+ S/0W -/0
'H a B('H $%&'(I))*+ N+*0W -*0$4&'( S/0E 0*0 'Hb (9<='H$%&'(I))*+ N+/0E +*0 $4&'(I))*+ S+*0W 2*0'H g +@J@ K 1 Lῌ῍

Deformation Zone " M N-N(NE-SE O.PQR N(STU1 K/ L B, C 234
VN(STW
IXY  K . L B Z[" \VN(ST1 K 0 L C, D 3I ]^ *a7_7 Deformation Zone -N`!\- 6I NW-SE .-:;HbcZ@
3d9Ief ghWi"*jkZ@3l'$%&'(-.I N,*0W m[ N+/0E n"a
o"p3 'VqkZ@m3 'r"s!"t uv-*D"'w
3 K 1"xy a b g - - G"'
L C@-z{|}IghWi"*
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2 L"+-EF  zZ@3-/- z 3V-1 I4ZS
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 i-VV[ZST1CI
m K 2 L"Z@3 ¡¢£¤
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N./0E -O.QRI 1*0,2*0N }I*fC G2 '-¦"*}I
Z@3p§f} "VV['HIao"¨m@ f©"q~[@m3C

DiTullio and Byrne +33*  -O.QR¼ 92 ¼

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 +  

93

± ²³ῌ´ *µῌ¶·¸ῌ¹º»
 Deformation Zone    !"# Deformation Zone$%&'#( Deformation Zone )*+,-. !" */  Deformation Zone 012# 3456
789 :;<:;/=>?#@(ABCD / EF +<G# H:;IJ7KL
M ! N O P $ > ? 7  CD - E DF Deformation
Zone Q$:;RSTUVW+XY(Z[\# W+:]
^_,-
`\ Deformation Zone 
\abc# Deformation Zone  Coherent Zone ]de\)f Lewis et al. C,***F #W+$ge$]8hijkbl 1*m+** MPa nop%3 -W+q:r+^_,-
#st$(\ uP #(vwxyzw_{ Deformation Zone |^12^_,-}~\st
Deformation Zone Q|^ge$]8hi 1* m +** MPa jn'$ ,+/ m,// \a RS)j
,- \ CLewis et al., ,***F 
Deformation Zone ^_#+ K$st- +# O$ T
st-
H Deformation Zone ^_op
7$+<T$@a$7

D / E AF :¡¢ £!O# ,* cm BF :;¤¥¦§¨©ª«zx¬zx ,῍ῌ+῍ area # +῍ area B !"
g ,῍ ­®g¯r°\\ CF :;<G¤¥¦§¨©ª«zx¬zx

¼ 94 ¼

°±²³  .3 ´µ¶·¸¹µ#º»}~.°±I\·? @I\ Deformation Zone  Coherent Zone     !"# $DiTullio and Byrne, +33*% Deformation Zone &'()
*+&'()*,-  ./0123
4 $S./5W -/5%  Coherent
Zone . $N./5E 2*5N% /* 167849:;/0  
4 </4.=>/01 1
? @a
ABCD? 4& S/35E ,05 B
ED? 4& S.05W -,5 ? @ b BCD? 4& S-15E -/5 BED? 4& S1/5W ,25 ? @g BCD? 4& S/5E ,+5 BED? 4& N3*5
W +-56*

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OP
FGHI / J*  KLCMN
Q RSTUV CWXV YZVE[.
I\]^_`ab)c *d* efg6]^_`h FiOj/*d* Ak)*E[.I\lm9n/o)c *d* p* E[.I\qr/s1th uYvwVfg6Oj/*d*
xyz{|h}~)c *d* |  YPQ $
CM% OPQ $CCM% 
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¡¢_£¤
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"/¯ D% Coherent Zone 
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!"  #$%&'()*+,-. /$0123456 356 789:;<=" $%&'()*+,-.0# 345
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Angelier, J., +313, Determination of the mean principal direction of stresses for a given fault
population. Tectonophysics, /0, +1ῌ,0.
DiTullio, L. and Byrne, T., +33*, Deformation pathsin the shallow levels of an accretionary prism :The Eocene Shimanto Belt of southwest
Japan. Geol. Soc. Amer. Bull., +*,, +.,*ῌ+.-2.
DiTullio, L., Laughland, M.M. and Byrne, T., +33-,
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