Mesoscopic structures produced by Plio-Pleistocene wrench faulting in (Brerry.,).pdf

8/20/2019 Mesoscopic structures produced by Plio-Pleistocene wrench faulting in (Brerry.,).pdf

1/11

Journal of Structural Geology,Vol. 9, No. 5/6, pp. 563 to 571, 1987 0191-8141/87 $03.00 + 0.130

Printed in Great Britain © 1987 Pergamon Journals Ltd.

M esoscopic s tructures produ ced by P l io -P le i s tocene wrenc h fau l t ing in

S o u t h S u l a we s i , I n d o n e s i a

R. F. BERRY

Depart ment of Geology, University of Tasmania, Hobart, Australia

and

A. E. GRADY

School of Earth Sciences, Flinders University, Adelaide, Australia

Received

23

May

1986;

accepted in revised orm

27

February

1987)

Abstr act-- The Bantimala Complex and overlying Cretaceous sediments of South Sulawesi, Indonesia, were

intensely faulted in the Plio-Pleistoce ne as a result of the northwa rd move ment of the Banda Sea microplate with

respect to Wes tern Indone sia. The area is dominated by NNW-striking sinistral wrench faults. The structures in

these faults formed at less than 250 C. Zones of intense rotation and faulting, 200 m wide, parallel the major

faults. They consist of lenses of a wide range of sedimenta ry and metamor phic rocks separat ed by narrow zones

of foliated cataclasite. Within the lenses, folding is non-cylindrical and there is a weak stretching lineation parallel

to the sh ear directi on. Exte nsion fractures and veins occur at 70* to the stretching lineation. Sinistral and dextral

faults within the lenses are symmetrical to the major faults. The fabric within these lenses suggests moderate

horizontal extension rather than strong simple shear. Within the cataclasite, the foliation is composed of

anastomosing microfaults. The sense of shear is demonstrated by offset on these microfaults and on smaller

fractures within the microlithons. Elongate clasts are horizontally aligned within the cleavage and have

symmetrical drag patterns . Many o f the equidimens ional clasts have asymmetrical drag patterns consistent with

sinistral shear.

INTRODUCTION

THE NORTHWARD movement of the Australian Plate has

produced a collision margin in Timor. Since this Late

Miocene collision (Berry & Grady 1981, Berry & Mac-

Dougall 1987), the continued movement of the Austra-

lian plate has driven the Banda Sea northward with

respect to continental South East Asia (Fig. 1) (Hamil-

ton 1979, Berry & Grady 1981, McCaffrey e t a l 1985).

Much of this relative movement has occurred on a

system of sinistral wrench faults exposed in Sulawesi

(Katili 1970, Sukamto 1978, Tjia 1981). In North and

East Sulawesi the tectonics are complicated by the E-

striking wrench faults associated with sinistral shearing

between the Australian and Pacific plates (Hamilton

1979, Silver 1981, Silver e t a l 1985). There is no direct

evidence of these E-striking wrench faults in South

Sulawesi.

The pattern of Late Tertiary and Quaternary faulting

in South Sulawesi is relatively simple. The dominant

structure is the Walanae Fault Zone, a major N-S

depression bounded on the east and west by major

sinistral wrench faults (Fig. 2) (Van Leeuwen 1981). The

East Walanae Fault apparently continues southwards

into a deep oceanic trough interpreted as a Neogene

trench by Hamilton (1979). In the north the Walanae

Fault Zone is truncated by a major group of NW-striking

sinistral faults which form the boundary of the Central

Highlands of Sulawesi.

To the west of the Walanae Fault Zone is an uplifted

area, dominated by a mountainous belt of Late Tertiary

volcanic rocks. Calderas are still visible in this sequence

and a Pleistocene stratovolcano in the south, Mt Lom-

pobatang, lies on an active fault zone (Fig. 2). Older

rocks are exposed in a low-lying strip 25-75 km nor th of

Ujung Pandang. Within these older rocks, two fault-

bounded blocks of Cretaceous basement are exposed.

The crystalline basement rocks and overlying sediments

contain excellent examples of mesoscopic structures

produced by the Plio-Pleistocene wrench faulting in

South Sulawesi. This study is restricted to faults

observed within this 50 km strip of Mesozoic rocks. A

brief summary of the structure within an area o f Tertiary

sediments has been pre sented by Van Leeuwen (1981).

GEOLOGY

The crystalline basement rocks, Ban timala Complex,

consist of thrust-bounded slices of L / S schists and phyl-

lites. The most common lithologies are glaucophane

schist, eclogite, chlorite feldspar phyllite, serpent inite,

graphitic phyllite and piemontite-bearing quartzites.

Pelitic rocks are rare. Overlying the metamorphic rocks

is a clastic sequence of Cretaceous age (Sukamto 1978,

Van Leeuwen 1981). This includes a basal breccia,

siliceous red mudstone, and a sequence of feldspathic

greywacke and siltstone (Marada Sandstone). The

563


2/11

5 6 4 R . 1 J. B E R R Y a n d A . [i+ G R A D ' ,

C e l e b e s S e a

- j ~ •

o

+

2 ; 0 ; , + 7

P h i l i p p i n ~

~ e i J

s B a x ~

~ /

i ~re sin

- : > - o < ] . . . . j _ " , , " ~ + . + ; ~ . ~ \ ' ~

~L O ~ , , .+~ -~ t ~ .

" " \ {shelf

- ~ - ~ + ~ ~ • , A . > ~ + > - - ~ o o ° , , ° + ° +

' ° ' °

- + 4

-- .+ -. _ +7> ~ ~ .....

F i g . 1 . L o c a t i o n m a p s h o w i n g m a j o r f a u l ts a t t h e i n t e r s e c t i o n o f t h e S o u t h E a s t A s i a n , P a c i f i c a n d A u s t r a l i a n P l a t e s . T h e

f a u l ts , s h o w n i n t h i c k li n e s , w e r e c o m p i l e d f r o m H a m i l t o n ( 1 9 7 8 ) , S u k a m t o ( 1 9 7 8 ) a n d S il v e r e t aL 1985 ) . T h r u s t s a r e s h o w n

w i t h t e e t h t o w a r d s t h e o ve r r i d i n g b l o c k . T h e c o l l i s io n z o n e o n t h e N W m a r g i n o f A u s t r a l i a is s h o w n a s d i a g o n a l l i n e s .

"k

] \

\~ . ....

,

B /

A

t t + i t

X

U J U N G P ~ \

t

0 30 k m

. . . . . . . . . . . . . . . . . . . I I I i

C r e t a c e o u s s e q u e n c e i s t n t ) rc + t h a n 7 5 0 m t h i c k a n d i s

o v e r l a i n u n c o n f o r m a b l y b y a 2 k m t h i c k T e r t i a r y

s e q u e n c e o f l i m e s t o n e a n d v o l c a n i c ro c k s ( V a n L e e u w e n

1 9 8 1 ) . M i o - P l i o c e n e g r a n o d i o r i t e s a nd la m p r o p h y r e s

i n t r u d e t h e s e q u e n c e . A d e t a i l e d s u m m a r y o f t h e s t r at i -

g r a p h y i s g i v e n b y V a n L e e u w e n ( 1 9 8 1 ) . T h e c a t a ct a s it e s

i n t h e s e z o n e s c o n t a i n q u a r t z , i l l i t e a n d F e - r i c h c h l o r i t e .

T h e i l l i t e c r y s t a l l i n i t y s u g g e s t s a m e t a m o r p h i c t e m p e r a -

t u re o f 2 0 0 - 2 5 0 ° C w h i l e th e F e 2 0 3 / M g O r a ti o a n d

c r y st a l li n i ty o f c h l o r it e s u g g e s t a m a x i m u m t e m p e r a t u r e

o f 1 5 0 - 2 0 0 ° C u s i n g t h e c al i b ra t i o ns o f W e a v e r ( 1 9 8 4 ,

p . 1 9 8 ) . T h e s t r a t ig r a p h i c e v i d e n c e s u g g e s t s t h i s t e m p e r -

a t u r e w a s r e a c h e d a t a b o u t 3 k m d e p t h .

S T R U C T U R E

E x t e n s i v e a r e as o f c r y st a l li n e b a s e m e n t r o c k s a re

e x p o s e d a t B a n t i m a l a a n d B a r r u o n t h e w e s t c o a s t o f

S o u t h S u l a w e s i . B o t h a r e b o u n d e d t o t h e w e s t b y a

c o m p l e x a s s o ci a t io n o f E - d i p p i n g t h ru s ts a n d N N W -

s t ri k i n g w r e n c h f a u lt s . E v e r y w h e r e t h e w r e n c h f a u l ts

o f f s e t t h e t h r us t s • I n a f e w l o c a l i t i e s , N N W - s t r i k i n g

f a u l t s o f f s e t p o o r l y c o n s o l i d a t e d r i v e r g r a v e l s .

T h e n o r t h an d s o u t h b o u n d a r i e s o f th e b a s e m e n t

c o m p l e x e s a r e si n is t ra l w r e n c h f a u lt z o n e s s t ri k i n g N W .

T h e s e z o n e s w e r e p r o b a b l y a c t iv e d u r i n g b o t h p h a s e s o f

F i g . 2 . F a u l t p a t t e r n i n S o u t h S u l a w e s i . l ' h e p r e - F e r t i a r y r o c k s a r c

s h o w n i n s t ip p l e . F a u l t s c o m p i l e d f r om D j u r i S u d j a t m i k o ( 1 9 7 4 ) ,

S u k a m t o ( 1 9 8 2 ) a n d S u k a m t o S u p r i a t n a ( 1 9 8 2 ) .


3/11

Structures produced by wrench faulting in S. Sulawesi 565

P O L E S T O B E D D IN G

P O L E S T O S C H I S T O S I T Y M E T A M O R P H I C L I N E A T I O N

N N N

t~

o

N

I-

%1

u.

z

F i g . 3 . L o w e r - h e m i s p h e r e e q u a l - a r e a s t e r eo g r a p h i c p r o j e c ti o n s o f s tr u ct ur es f r o m t h e B a r r u a n d B a n t i m a l a b lo c k s : ( a ) - ( c )

a r e fr o m a r e a s d is t a n t fr o m m a j o r f au l t z o n e s ; ( d ) - ( f ) a r e fr o m t h e s o u t h e r n m a r g i n o f t h e B a n t i m a l a B l o c k , i n a n d n e a r

m a j o r f a u l t z o n e s .

... =========================""...

~ Q U A R T Z I T E A N D : : :: - "" " ' - , 8 / : ~ 3 N

G RE EN P H Y L L IT E . :, ;: :; :; ;; ::~: .. ;; .. ;; ..

. o s c o v , T . O O . . T Z

S:::

S C H I S T j ~ , ~ 0

i:

[ ] S E R P E N T IN I T E A N D

. . . . . I /

2 5 0 m

I

....;:.

"'..-'1

..., .

. . . . . . •

..: -...-

f

} I L , ' ' - - '

F i g . 4 . G e o l o g i c a l m a p o f a s e c ti o n o f t h e B a n t i m a l a C o m p l e x n e a r t h e c en t r e o f th e B a r r u B l o c k .


4/11

56 6 R . F . B ER R Y a n d A , E . (.~RA I)~r

I , ~ i i t l l i l i , , i , ~ 4

. ~ t j / / i i / i l i / 7 . . i l l :

~ . # . l . ~ l l . 7 ~ / t / i 7 ' ~ / / 1 1 1 t@ 1 # ' i ' ' - -

I I , ,i l t t t : i - - I ~ . ~ : ~ : / { i ~

, , . f f i < [ . , . . , o t l ~ ~ ~ ~

\

\

0

-r

0

m ~ r , j

a r

i

0 r z . . .i O 0

( 3 ( 3 ~ I I l i . ~

m

W

0

D @ D

I i

w 'h

i -

~ >

E

0

O -

~ E

~ e

< - ~ ,

~-~ ~>

~ F~

z ~

a ~

,=


5/11

S t r u c t u r e s p r o d u c e d b y w r e n c h f a u l t in g i n S . S u l a w e s i

a

f

I l m m j

i ~ ' ~

/ . . . 2 , . . , , , , , . , , , , , , - : . , , m ~ . • , , _ . , ~ . - - : . : :

I i ,., ~ ' ~ ~ - : : i

I / /

I j ' • / . - . - . : . :-~, ,~-: . : .: - : . : .: - : . : . :. ; .~e:. . :- : . ; . :- : : . : . : - : - : . : . : . : -~ : . : ,eT.

l :-

::::

• i ~ . . ~ : : ~ i : ~ : ~ : i : i : ] 8 ~ ] : ] : ~ : ~ . : i : ] : ~ : i S ~ : i ~ ? : ? : ~ r . : . : i : i : i : . : ~ : ~ : i : : ~ : ~ i . : i : i : i : i : : : : : : ~ : : : : ~ : : : : : : : % : : : : . : . : i : i : ? : i :

~' i I

~ s / / ,, ==================== ===================== ==================== ==================== ===================== ==================== =======

/ , ' ~ ~ / / , ,. . . ::::i:i:~:i:~:i: : : :~:~ :~]:~:i:i:i:i:~:~:~:i:~i:i~: :~: : :i:i:i:~:]:i:i:i:i:i:i:i:i:i:i: :i:i: :i: :~:i:~:i:~:i:i:i:~:i:~:~:i: :i:i: :~:i:i:i:i:]:i:~i: ' i i ~ i ~ i i ~ i ~ : :

- : . : : : : : : : 8 ~ : ~ : i ~ i : : i : : i : S i ~ : : : ~ : ~ : ] : i ] i : i 8 : : i : ~ : i : [ ~ i : i ~ : ? : i: : ? : : i: i : ~ : i i : i [ : i : : i : ~ : : i i : ] : i: i : i :i 1 :1 i i : : ~ :

i : : i : i : i: ~ : ~ i : i : ~ : ~ : i : ] : i : i :~ : ~ : i : ~ : : : : ~ : : : : 1 8 1 : 1 : i 8 ~ : : : : : i: ~ : ] : ~ : ~ : i : ~ i : i ~ i : ~ : ~ 8 : : : : : :i : ~ : ~ : i : ~ : ~ : ~ : : i : ~ : i : ~ : ~ : i ~ : ~ : ] : : : : : : :i : i : ~ : i : i: 7 : : : i : ~ i : ~ ] : i ~ : : : : :: : : ~ : ~ :. . . . . . . . .

I . . . - . - . . . . . ._ - • - .. .- i ,~ . - . ,~ @ . . . . . . . . . . . . . . . . - . . . ~ , . . . -

.............. O " 0 5 m m I

F i g . 6 . D e t a i l e d s t r u c t u r a l r e l a t io n s h i p in t h e f o l i a te d c a t a d a s i t e . ( a ) a n d ( b ) a r e l i n e d r a w i n g s f r o m S E M p h o t o g r a p h s , ( c )

a n d ( d ) , r e s p e c t i v e l y . T h i c k l i n e s a r e m i c r o f r a c t u r e s d e f i n i n g t h e s p a c e d c l e a v a g e , t h i n f i n e s a r e c o m p o s i t i o n a l l a y e r i n g ,

d a s h e d l i n e s a r e t h e b a s a l c l e a v a g e o f c l a y m i n e r a l s a n d t h e s t i p p l e d a r e a s a r e s i li c a -r ic h t u f f. ( a ) & ( c ) : p h a c o i d o f t u ff , ( b )

& ( d ) : s h e a r e d m a r g i n o f p h a c o i d .

5 6 7


6/11


7/11

S t r u c t u r e s p r o d u c e d b y w r e n c h f a u l t in g i n S . S u l a w e s i 5 6 9

f a u l ti n g . I n c e n t r a l S u l a w e s i , N W - s t r i k i n g w r e n c h f a u l t s

a r e c l o s e ly a s s o c ia t e d w i t h E - d i p p i n g t h r u s t s ( D j u r i &

S u d j a t m i k o 1 9 74 ) w h i c h a r e i n t e r p r e t e d a s M i o c e n e

s t r u c t u r e s ( S u k a m t o 1 9 7 8 , S il ve r & M a c C a f f r e y 1 98 3) .

A s h a l l o w ly d i p p i n g ( F i g . 3 a ) s e q u e n c e o f C r e t a c e o u s

s e d i m e n t s c r o ps o u t a l o n g t h e e a s t e r n m a r g i n o f t h e

b a s e m e n t c om p le x e s . T h e s e s e d i m e n t s u n c o n f o r m a b l y

o v e rl ie t h e b a s e m e n t r o c k s a n d t h e u n c o n f o r m i t y d i ps

g e n t l y w h e r e i t i s e x p o s e d o u t s i d e t h e m a j o r f a u l t zo n e s .

T h e g r o s s s t r u c t u r e i s r e la t i v e l y r i g i d b lo c k s t i l t e d t o t h e

E a n d b o u n d e d o n t h r e e s i d e s b y l a r g e fa u l ts . T h e r i g i d

b l oc k s a r e 0 . 5 - 2 k m w i d e a n d u p t o 1 0 k m l on g . T h e

f a u l t s a r e u p t o 5 0 0 m w i d e . T h e s t r u c t u r e s o b s e r v e d

w i t h i n t h e b l o c k s a r e d i f f e r e n t f r o m t h o s e w i t h i n t h e

f a u l t z o n e s .

A n e x a m p l e o f t h e s t r u c t u r e w i t h i n t h e c o r e o f th e

B a r r u B l o c k i s s h o w n i n F i g . 4. T h e a r e a i s c o m p o s e d o f

a s e r i e s o f L/ S s c h i s t s w i t h a S E - d i p p i n g f o l i a t i o n a n d a S -

t o S W - t r e n d i n g l i n e a t i o n ( F i g . 3b & c ). T h e s e q u e n c e o f

r o c k t y p e s i s s e r p e n t i n i t e , t h e l o w e s t e x p o s e d u n i t ,

t h r o u g h q u a r t z - m i c a s c h i s t t o q u a r t z i t e a n d c h l o r i t i c

p h y l li t e . T h e s m a l l r a n g e i n t h e o r i e n t a t i o n o f t h e s c h is -

t o s i t y a n d t h e s h a l l o w d i p o f b e d d i n g i n t h e C r e t a c e o u s

s e d i m e n t a r y r o c k s d e m o n s t r a t e t h e l i m i t e d T e r t i a r y

f o l d i n g i n t h e s e a r e a s . I n c o n t r a s t t h e s a m e f a b r i c e le -

m e n t s a t B a n t i m a l a , i n a n d n e a r t h e m a j o r w r e n c h

f a u l t s, a r e s t r o n g l y r o t a t e d ( F i g . 3 d , e & f ) . T h e m o s t

c o m m o n s t ri k e d i r e c t i o n o f th e s c h i st os i ty a t B a n t i m a l a

i s N W , r o u g h l y p a r a l l e l t o t h e f a u l t s ( F i g . 3 e ) . N W - t o

N - s t r i k i n g f a u l ts a t B a r r u a r e s i n i s t ra l w h i l e t h e r e a r e a

l a r g e n u m b e r o f N E - s t r i k i n g d e x t r a l fa u l t s a n d l e s s

c o m m o n S E - d i p p i n g t h r u s t s . C a t a c l a s i t e z o n e s , u p t o 1

m w i d e , o c c u r a l o n g N N W - s t r i k i n g w r e n c h f a u lt s a n d

S E - d i p p in g t h r u s t s . T h e D e n g e n g e F a u l t Z o n e ( F ig . 4 ) is

c o m p o s e d o f s tr o n g ly d e f o r m e d s e d i m e n t b u t n o s e d i-

m e n t s a r e e x p o s e d e i t h e r s i d e o f t h i s s t r u c t u r e . I t m a y

h a v e b e e n f o r m e d a s a n i n t e n s e ly s h e a r e d s y n c li n a l c o r e

w h i c h h a s b e e n r e a c t i v a t e d a s a d e x t r a l f a u l t. T h e s t r u c -

t u r a l s t y le i n th e c o r e o f th e B a r r u B l o c k i n v o l v e s

e x t e n s i v e f a u l t i n g w i t h m i n o r f o l d i n g .

A P l i o - P l e i s t o c e n e s i n i s t r a l f a u l t z o n e i s e x p o s e d a t

t h e j u n c t i o n o f t h e P a n g k a j e n e a n d P a t t e t e j a n g R i v e r s

( F i g . 5 ). W i t h i n t h e f a u l t z o n e , t h e s t r a i n is c o n c e n t r a t e d

i n t o d i s c r e t e z o n e s o f c a ta c l a s i t e f r o m 2 0 c m t o 8 m w i d e .

T h e c a t a c l a s i te s h a v e a s t r o n g a n a s t o m o s i n g c l e a v a g e

w i t h a s p a c i n g o f 1 - 2 m m . T h e c a t a c l a s i t e s p l i t s v e r y

e a s i l y a l o n g t h i s s p a c e d c l e a v a g e i n t o m i c r o l i t h o n s w i t h

a n i r r e g u l a r e l o n g a t e s h a p e , a b o u t 2 c m l o n g h o r i z o n t a l l y

a n d 1 c m h i g h . T h e c l e a v a g e s u r f a c e s a r e m i c r o f a u l t s

( F i g . 6 a ) . W i t h i n t h e m i c r o l i t h o n s a r e r e li c ts o f c o m p o s i -

t i o n a l l a y e r i n g w i t h p h a c o i d a l s h a p e s . A w e a k s l a t y

c l e a v a g e d e f i n e d b y t h e p r e f e r r e d o r i e n t a t i o n o f i ll it e i s

s u b p a r a l l e l to t h i s la y e r i n g . B o t h t h e l a y e r i n g a n d t h e

i ll it e f o li a t i o n a r e m o s t c o m m o n l y o r i e n t e d a t 1 6 0 - 1 7 5 °

t o th e m i c r o f a u l t s , u s i n g t h e a n g u l a r c o n v e n t i o n o f

C h e s t e r

et al.

( 1 98 5 ). E x c e p t i o n s o c c u r i n a r e a s o f b u c k -

l i n g o f t h e i ll i te f o l i a t i o n (F i g . 6 b & d ) . T h e a n g u l a r

r e l a t i o n s o f t h e i l li t e f o l i a t i o n t o t h e m i c r o f r a c t u r e s a n d

t h e p h a c o i d s h a p e s ( F i g . 6 a & c ) s u p p o r t s i n i s tr a l s h e a r .

I n a d d i t i o n , w i t h i n t h e m i c r o l i t h o n s t h e l a y e r i n g is

c o n s i s t e n t l y o ff s e t in a s i n i s t r a l se n s e b y m i c r o f r a c t u r e s .

R e c r y s t a l l i z a t io n i s v e r y l i m i t e d i n t h e s e c a t a c la s i t e s.

C a l c i t e g r a i n s a n d p y r i t e f r a m b o i d s a c t a s r i g i d c l a s t s .

N e w g r a i n g r o w t h a l o n g t h e m i c r o f a u l t s i s l i m i t e d t o r a r e

c a l c i t e a n d i l li t e g r a i n s . T h e i l li t e f o l i a t i o n m a y b e a

m o d i f i e d b e d d i n g p l a n e f a b r i c .

C h e s t e r

et al.

( 19 85 ) h a v e d e s c r i b e d f o l i a t e d c a t a c la -

s i te s f r o m C a l i f o r n i a . D e s p i t e s u b s t a n t i a l d i f fe r e n c e s i n

m i n e r a l o g y , m o s t o f t h e f ab r ic e l e m e n t s t h e y r e p o r t e d

a r e r e c o g n i z a b l e i n t h e f o l i a t e d c a t a c l a s i t e s f r o m

S u l a w e s i. T h e y i n t e r p r e t t h e f o l i a ti o n f o r m e d a t 1 6 0 ° t o

t h e m a i n s h e a r p l a n e a s t h e r e s u l t o f f l a tt e n i n g w i t h o u t

s u b s t a n t i a l c r y s t a l p l a s ti c i t y o r d i f f u s i o n a n d t h e y c o n -

c l u d e t h a t c a t a c l a st i c m e c h a n i s m s a r e c a p a b l e o f p r o d u c -

i n g a f o l i a t e d m a t e r i a l , s u c h a s t h a t e x p o s e d i n S o u t h

S u l a w e s i .

P e b b l e -s i z e d e l o n g a t e c l as t s w i t h i n t h e c a t a c l a s i te

z o n e s h a v e a s t r o n g p r e f e r r e d o r i e n t a t i o n p l u n g i n g s h a l-

l o w ly s o u t h ( F i g . 7 a ) a n d a p p r o x i m a t e l y p a r a l le l t o t h e

l o n g a x e s o f t h e m i c r o l i th o n s . T h e y a r e p e r f e c t l y a l i g n e d

i n t h e c l e a v a g e a n d h a v e a s y m m e t r i c a l c l e a v a g e d i s t r ib u -

t i o n . H a l f o f t h e n e a r e q u i d i m e n s i o n a l pe b b l e - s iz e d

c la s t s, ( l e n g t h / w i d t h r a t i o s < 2 ) w i t h i n t h e c a t a c l a s i t e

h a v e a n a s y m m e t r i c a l c l e a v a g e d i s t r i b u t i o n (F i g . 8 ). A

s a m p l e o f 4 5 c la s t s fr o m t h r e e c a t a c l a s it e z o n e s c o n -

t a i n e d 2 2 c la s ts w h e r e t h e c l a s t w a s r o t a t e d a n t i c l o c k w i s e

w i t h r e s p e c t t o t h e c l e a v a g e . T h r e e c l as t s h a d t h e o p p o -

s i te s e n s e o f a s y m m e t r y a n d 2 0 c l a st s h a d n o d i s c e r n i b l e

a s y m m e t r y . G h o s h ( 1 97 5 , fi g . 2 2 a ) p r e d i c t e d t h i s d r a g

p a t t e r n f o r s i n i s tr a l s h e a r w h e r e t h e f o l ia t i o n is p a r a ll e l

t o t h e s h e a r d i r e c t i o n e i t h e r i n i t i a ll y o r b e c a u s e o f h i g h

s h e a r s tr a in s . G h o s h & R a m b e r g (1 97 6 ) p r op o s e d a

m o d e l f o r r o t a t i o n o f c la s ts w h i c h p r e d i c t e d a s t a b le

o r i e n t a t i o n p a r a l l e l t o t h e s h e a r d i r e c t i o n f o r a x i a l r a t i o s

g r e a t e r t h a n 2 , i f t h e s t r a i n r a t e r a t i o o f p u r e s h e a r t o

s i m p l e s h e a r w a s g r e a t e r t h a n 0 . 7 . W h i l e w e h a v e n o t

a t t e m p t e d a n e x a c t s u r v e y o f t h e a x i a l r a t i o s o f c la s ts i n

t h i s s t u d y , t h e p r e s e n c e o f a r a n g e o f c la s t s o f v a r i a b l e

a x i a l r a ti o s w i t h s y m m e t r i c a l f ol i a t io n s i n d i c a t e s a s u b -

s t a n t i a l c o m p o n e n t o f p u r e s h e a r i n t h e s t r a in . B o u l d e r -

s i z e d c l a s t s w i t h i n t h e f o l i a t e d c a t a c l a s i t e o c c u r a s

b o u d i n s a n d r o u n d e d b l o c k s w i t h th e i r l o n g a xe s a p p r ox -

i m a t e l y h o r i z o n t a l ( F i g . 7 a ) .

B e t w e e n t h e f o l i a te d c a t a c la s i t e z o n e s a r e e l o n g a t e

b l o c k s u p t o 2 00 m l o n g a n d 1 0 m w i d e ( F i g . 5 ) . T h e

t e c t o n i c f a b r ic i n t h e s e b l o c k s i s m u c h w e a k e r w i t h l o c a l

c l e av a g e d e v e l o p m e n t , e s p e c ia l ly n e a r t h e m a r g i n s . F o r

e x a m p l e , i n a s a n d s t o n e / s i l t s to n e s e q u e n c e ( F i g . 5, in s e t

c ) a w e a k c l e a v a g e s t r i k e s N E a n d i s r e s tr i c t e d t o t h e

m a r g i n o f t h e b lo c k . T h e r e i s a s h a r p c h a n g e i n f o l i a ti o n

d i r e c t i o n a t t h e c a t a c la s i t e b o u n d a r y , b u t t h e o r i e n t a t i o n

o f t h e c l e a v a g e w i t h i n i t s m a r g i n s u p p o r t s a s i n i s t r a l

c o m p o n e n t o f sh e a r . O t h e r f e a t u r e s o f t h is m a r g i n a r e

t h e n u m e r o u s d e x t r a l f a u lt s w h i c h m a y b e R 2 R e i d e l

s h e a r s ( S a n d e r s o n & M a r c h i n i 1 9 84 ). T h e s a n d s t o n e i n

t h i s a r e a h a s p i n c h - a n d - s w e l l s t r u c t u r e s w i t h b o u d i n s

s u b v e r t i c a l, in d i c a t i n g h o r i z o n t a l e x t e n s i o n . C o m m o n

f e a t u r e s w i t h i n t h e s e b l o c k s a r e c o n j u g a t e d e x t r a l a n d

s i n i s tr a l fa u l t s s y m m e t r i c a l l y r e l a t e d t o t h e l a y e r i n g ( F i g .

5 , i n s e t b ) . B o t h n o r m a l a n d r e v e r s e f a u l t s o c c u r w i t h


8/11

570 R. F BErry

and

A. E. (JrAI)~

N

• POLES TO CATACLASITE

ZONES

N N

, , . . , . .

]

• POLES TO BEDDING IN • LINE ATION IN RED MUDSTONE

SEDIMENTARY BLOCKS

• PEBBLE STRETCHING

DIRECTION

• POLES TO FOLIA TION IN

METAMORPHIC BLOCKS

¢ FOLD AXES IN RED MUDSTONE

LON G AXES OF LARGE

BLOCKS

C POLES TO EXTENSION VEINS

iN RED MUDSTONE

Fig. 7. Lower-hemisphere equal-area stereographic projection of structures within the NNW-strikmgfault zone: (a) fabric

of cataclasite zones, (b) layering within large lenses and (c) fabric n red mudstone lenses.

strikes at a high angle to the NNW-striking cataclasite

zone. The norm al faults appear to be related to boudin-

age of blocks with a pre-existing plane of weakness.

Blocks of siliceous red mudstone contain a range of

fabric elements. A weak stretchi ng lineation is subparal-

lel to the shear direction in the foliated cataclasite (Fig.

7c). Beddin g is subparallel to the cataclasite zones which

bound the block. Tight non-cylindrical folds are com-

mon with a range of steep to mode rat e plunges (Fig. 7e).

Small extension fractures and quartz veins are wide-

spread and are most com mon ly at 70 ° to the stret ching

lineation and perpendicular to the cataclasite zones.

Burg & Harris (1982) have interpreted these types of

extension fractures as Luders Bands.

In combination, all the fabric elements within these

large blocks support a moder ate N -S extension but there

. . . . . . . _ i ~ . . _ _ ; ; . . . .

, S - :

e

Fig. 8. Asymmetric cleavage distribution around near equidimen-

sional clast in the foliated cataelasite. Inset shows cleavage relation

predicted by Ghosh (1975) for this case~

is limited evidence of rotational strain (non-cylindrical

folds, lineated fabric) and no strong evidence for the

sense of simple shear. However, the gross orientation of

the large blocks is at 160-170 ° to the fault z one (Fig. 5).

This asymmet ry matches the orient ation of relict layer-

ing in the cataclasites and is compatible with sinistral

shear.

The boundaries ol the NNW-striking fault zone are

transitional. Towards the blueschists to the E there is a

gradual increase in the width of relatively undeformed

material and a decrease in the width of foliated catacla-

site zones. The deformation within the blocks is reduced

and the orientation of layering and bedding is more

variable.

The NW-striking shear zones have a similar style of

deformation. For example, along the River Pattetejang

there is a series of fault bounded blocks with strong

extensional fabrics. Small blocks show conjugate sinist-

ral and dextral faults, and have near horizontal fold

axes. The blocks are separated by cataclasite zones in

which elongate clasts have a subhorizontal preferred

orientation. A feature common in this zone but not

obser ved in the NNW-stri king fault zones is the presen ce

of blocks with curved antithetic faults. This difference

may be related to lithological variation.

CONCLUSIONS

Sinistral wrench laulting has occurred at very low

glades of metamorphism in South Sulawesi. The early

stage of faulting was dominated by NW-striking wrench

faults and E dipping thrusts. The s econd phase of fault-

ing was dominated by NNW-striking wrench faults with

the NW-striking wrcnch faults probably reactiwlted dur-

ing this phase. T he area is now compose d of blocks up to

10 × 2 km separated by maior fault zones 100-500 m

w-ide.


9/11

S t r u c t u r e s p r o d u c e d b y w r e n c h f a u lt i n g i n S . S u l a w e si 5 7 1

W i t h i n t h e f a u lt z o n e s , th e s h e a r s t r a in w a s c o n c e n -

t r a t e d i n t o f o li a t e d c a t a c la s i t e z o n e s w h i c h a n a s t o m o s e

a r o u n d s t r on g l y r o t a t e d b l o c k s o f le s s d e f o r m e d c o u n t r y

r o c k a b o u t 1 0 m w i d e . W i t h i n t h e c a t a c l a s i t e , a s tr o n g

s p a c e d c l e a v a g e p a r a ll e ls t h e s h e a r d i r e c t i o n . T h e d i r e c -

t i o n o f s h e a r is i n d i c a t e d b y t h e l o n g a x e s o f m i c r o l i t h o n s

a n d t h e l o n g a x e s o f p e b b l e t o b o u l d e r s iz e cl as ts . T h e

s e n s e o f m o v e m e n t is in d i c a t e d b y c o n s i s t e n t m i c r o f a u l ts

a n d p h a c o i d s w i th i n t h e m i c r o l i t h o n s , t h e a s y m m e t r y o f

t h e c l e a v a g e a r o u n d e q u i d i m e n s i o n a l c l a s t s a n d l o c a l l y

t h e r e f r a c t i o n o f t h e f o l i a ti o n i n t o a d j a c e n t l es s d e f o r m e d

b l oc k s . A s u b s t a n t ia l p u r e s h e a r c o m p o n e n t o f t h e s tr a i n

is s u g g e s t e d b y t h e s y m m e t r i c a l c le a v a g e d i s t r i b u t io n

a r o u n d c l a s ts w i t h a x i a l r a t io s a s s m a l l as 2 .

I n l a r g e r b l o c k s w i th i n t h e s h e a r z o n e t h e d i r e c t i o n o f

s h e a r i s in d i c a t e d b y a r a n g e o f s tr u c t u r e s b u t n o

u n e q u i v o c a l e v i d e n c e f o r t h e s e n s e o f s h e a r w a s

o b s e r v e d . A l i n e a t i o n i n s i li c e ou s m u d s t o n e , e x t e n s i o n a l

v e i n s a n d f r a c t u r e s , c o n j u g a t e d e x t r a l a n d s i n i s tr a l

f a u lt s , a n d s u b v e r t i c a l b o u d i n a x e s a ll s u p p o r t h o r i z o n t a l

e x t e n s i o n . T h e e v i d e n c e o f a r o t a t i o n a l s t r a in h i s t o r y

w i t h i n t h e l a r g e r b l o c k s , i s l i m i t e d t o n o n - c y l i n d r i c a l

f o ld i n g a n d t h e l i n e a t e d f a b r i c i n t h e m u d s t o n e . T h e

o b l i q u i t y o f t h e s e b l o c k s t o t h e c a t a c l a s i te z o n e s s u p p o r t s

t h e e v i d e n c e f o r s i n i s tr a l s h e a r w i t h i n t h e c a t a c l a s i t e s .

Acknowledgements--Our

t h a n k s a r e g i v e n t o t h e G e o l o g i c a l R e s e a r c h

a n d D e v e l o p m e n t C e n t r e , B a n d u n g , I n d o n e s i a a n d e s pe c i a ll y M r R .

S u k a m t o f o r pr o v i d i n g a c c e ss to m a p s , a e r i a l p h o t o g r a p h s a n d u n p u b -

l i s h e d m a t e r i a l o n S o u t h S u l a w e s i . T h i s p r o j e c t w a s s u p p o r t e d b y t h e

A u s t r a l i a n R e s e a r c h G r a n t s S c h e m e . T h e a n o n y m o u s r e v i e w e r s p r o -

v i d e d u s e f u l a n d c o n s t r u c t i v e c r i ti c i sm .

R E F E R E N C E S

B e r r y , R . F . & G r a d y , A . E . 1 98 1. T h e a g e o f t h e m a j o r o r o g e n e s i s i n

T i m o r . I n :

Geology and Tectonics of Eastern Indonesia

( e d i t e d b y

B a r b e r , A . J . & W i r y s u j o n o , S .) .

Geol. Res. Dev . Centre, Bandung,

Spec. Pubis

2 , 1 7 1 - 1 8 1 .

B e r r y , R . F . & M a c D o u g a l l , I . 1 98 7 . I n t e r p r e t a t i o n o f 4 ° A r /3 9A r ~ a n d

K / A r d a t i n g e v id e n c e f r o m t h e A i le u F o r m a t i o n , E a s t T i m o r .

Chem. Geol. lsot. Geosci. Sect.)

5 9 , 4 3 - 5 8 .

B u r g , J . P . & H a r r i s , L . B . 1 98 2. T e n s i o n f r a c t u r e s a n d b o u d i n a g e

o b l i q u e t o t h e m a x i m u m e x t e n s i o n d i r e c t io n : a n a n a l o g y w i t h

L u d e r s ' b a n d s .

Tectonophysics

8 3 , 3 4 7 - 3 6 3 .

C h e s t e r , F . M . , F r i e d m a n , M . & L o g a n , J . M . 1 98 5. F o l i a t e d c a t a c l a -

s i t e s .

Tectonophysics

1 1 1 , 1 3 9 - 1 4 6 .

D j u r i & S u d j a t m i k o 1 97 4 . G e o l o g i c m a p o f t h e M a j e n e a n d w e s t e r n

p a r t o f t h e P a l o p o Q u a d r a n g l e s , S o u t h S u l a w e s i 1 : 2 5 0 , 0 0 0 S e r i e s.

G e o l . R e s . D e v . C e n t r e , B a n d u n g .

G h o s h , S . K . 1 9 75 . D i s t o r t i o n o f pl a n a r s t r u c t u r e s a r o u n d r i g id

s p h e r i c a l b o d i e s .

Tectonophysics

2 8 , 1 8 5 - 2 0 8 .

G h o s h , S . K . & R a m b e r g , H . 1 97 6 . R e o r i e n t a t i o n o f i n c l u s i on s b y

c o m b i n a t i o n o f p u r e s h e a r a n d s i m p l e s h e a r .

Tectonophysics

3 4 ,

1 - 7 0 .

H a m i l t o n , W . 1 97 8. T e c t o n i c m a p o f th e I n d o n e s i a n r e g i o n . M i s c .

I n v e s t . S e r . M a p 1 - 87 5 -D , U . S . G e o l . S u r v .

H a m i l t o n , W . 1 97 9. T e c t o n i c s o f t h e I n d o n e s i a n r e g i o n , U . S . G e o l .

S u r v . P r o f . P a p . 1 0 7 8 .

K a t i li , J . A . 1 97 0 . L a r g e t r a n s c u r r e n t f a u l ts in S o u t h e a s t A s i a w i t h

s p e c i a l r e f e r e n c e t o I n d o n e s i a .

Geol. Rdsch.

5 9 , 5 8 1 - - 6 0 0 .

M a c C a f f r e y , R , M o l n a r , P . , R o e c h e r , S . W . & J oy o d i w i r y o, Y . S .

1 98 5. M i c r o e a r t h q u a k e s e i s m i c i ty a n d f a u l t p l a n e s o l u t i on s r e l a t e d

t o a r c c o n t i n e n t c ol li s io n in t h e E a s t e r n S u n d a A r c , I n d o n e s i a . J .

geophys. Res.

9 0 , 4 5 1 1 - 4 5 2 8 .

S a n d e r s o n , D . J . & M a r c h i n i , W . R . D . 1 98 4. T r a n s p r e s s i o n .

J. Struct.

Geol.

6 , 4 4 9 - 4 5 8 .

S i lv e r , E . A . 1 98 1. A n e w t e c t o n i c m a p o f t h e M o l u c c a S e a a n d E a s t

S u l a w e s i, I n d o n e s i a w i t h i m p l i c a t i on s f or h y d r o c a r b o n p o t e n t i a l

a n d m e t a l lo g e n e s i s . I n :


( e d i t e d b y B a r b e r , A . J . & W i r y s u j o n o , S . ) .

Geol. Res. Dev. Centre,

Bandung, Spec. Pubis

2 , 3 4 3 - 3 4 6 .

S i lv e r , E . A . & M a c C a f f r e y , R . 1 9 83 . O p h i o li t e e m p l a c e m e n t b y

c o l li s io n b e t w e e n t h e S u l a P l a t f or m a n d t h e S u l a w e s i Is l a n d A r c ,

I n d o n e s i a .

J. geophys. Res.

8 8 , 9 4 1 9 - 9 4 3 5 .

S i lv e r , E . A . , G i ll , J . B . , S c h w a r t z , D . , P r a s e t y o , H & D u n c a n , R . A .

1 98 5. E v i d e n c e f o r a s u b m e r g e d a n d d i s p la c e d c o n t i n e n t a l b o r d e r -

l a n d , n o r t h B a n d a S e a , I n d o n e s i a .

Geology

1 3 , 6 8 7 - - 6 9 1 .

S u k a m t o , R . 1 97 8. T h e s t r u c t u r e o f S u l a w e s i in t h e l i g h t o f p la t e

t e c t o n i c s .

Proc. Reg. Conf. Geol. Min . Res. S.E. Asia,

1975 ,

J a k a r t a , 1 2 1 - 1 4 1 .

S u k a m t o , R . 1 98 2. G e o l o g ic m a p o f t h e P a n g k a j e n e a n d w e s t e r n p a r t

o f W a t a m p o n e Q u a d r a n g l e s , S u l a w e s i. 1 : 2 5 0 , 0 0 0 S e r ie s . G e o l .

R e s . D e v . C e n t r e , B a n d u n g .

S u k a m t o , R . & S u p r i a t n a , S . 1 98 2. G e o l o g i c m a p o f t h e U j a n g p a n -

d u n g , B e n t e n g a n d S i n j a i Q u a d r a n g l e s , S u l a w e s i. 1 : 2 5 0 , 0 0 0 S e r ie s .

G e o l . R e s . D e v . C e n t r e , B a n d u n g .

T j i a , H . D . 1 98 1. E x a m p l e s o f y o u n g t e c t o n i s m i n E a s t e r n I n d o n e s i a .

I n :


( e d i te d b y B a r b e r ,

A . J . & W i r y s u j o n o , S . ) .

Geol. Res. Dev. Centre, Bandung Spec.

Pubis

2 , 8 9 - 1 0 4 .

V a n L e e u w e n , T . M . 1 98 1. T h e g e o l og y o f s o u t h - w e s t S u la w e s i w i th

s p e c i a l r e f e r e n c e t o t h e B i r u a r e a . I n : Geology and Tectonics of

Eastern Indonesia

( e d i t e d b y B a r b e r , A . J . & W i r y s u j o n o , S . ) .

Geol.

Res. Dev. Centre, Bandung, Spec. Pubis

2 , 2 7 7 - 3 0 4 .

W e a v e r , C . E . 1 9 8 4 .

Shale-Slate Metamorphism in the Southern

Appalachians.

E l s e vi e r , A m s t e r d a m .

S G 9 : 5 / 6 D


10/11

SHEAR CRITERIA IN ROCKS

Section II

Sense of slip on faults


11/11

Documents

Mesoscopic structures produced by Plio-Pleistocene wrench faulting in (Brerry.,).pdf