J . G . S . M . V o l . 1 6 N o . 1 Februar i 2 0 1 5 h a l . 2 4 5 - 2 5 4 245

SISTEM MINYAK DAN GAS DI CEKUNGAN TIMOR, NUSA TENGGARA TIMUR PETROLEUM SYSTEM IN THE TIMOR BASIN, NUSA TENGGARA TIMUR

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Abstrak

B a h a s a n s i s t e m m i g a s p a d a m a k a l a h i n i d i k h u s u s k a n p a d a p e m b i c a r a a n m e n g e n a i k e b e r a d a a n b a t u a n i n d u k , b a t u a n w a d u k , b a t u a n t u d u n g a t a u p e n u t u p , s e r t a p e r a n g k a p h i d r o k a r b o n . D i k e n a l b e b e r a p a m a c a m b a t u a n i n d u k d i C e k u n g a n T i m o r , y a i t u s e r p i h h i t a m d a r i F o r m a s i A t a h o c , F o r m a s i C r i b a s , d a n F o r m a s i W a i l u l i . A n a l i s i s g e o k i m i a a t a u p u n p e t r o l o g i o r g a n i k m e n u n j u k k a n b a h w a s e r p i h h i t a m d a r i k e t i g a f o r m a s i t e r s e b u t m a s u k d a l a m k l a s i f i k a s i s a n g a t b a i k , d a n m e r u p a k a n k e r o g e n t i p e I I I . B e r d a s a r k a n a n a l i s i s p e t r o g r a f i , S E M d a n p o r o s i t a s m a k a y a n g b e r p e l u a n g m e n j a d i b a t u a n w a d u k a d a l a h b a t u p a s i r d a r i F o r m a s i C r i b a s , F o r m a s i B a b u l u d a n F o r m a s i O e b a a t , s e r t a b a t u g a m p i n g F o r m a s i A i t u t u . S e m e n t a r a b e r d a s a r d a t a p e t r o g r a f i d a n S E M m a k a s e p i h F o r m a s i C r i b a s d a n N a k f u n u b e r p o t e n s i m e n j a d i b a t u a n p e n u t u p . P e r a n g k a p s t r u k t u r y a n g b e r k e m b a n g a d a l a h s t r u k t u r b u n g a p o s i t i f , a n t i k l i n l a n d a i , a n t i k l i n t e r s e s a r n a i k k a n , d a n g r a b e n . S e d a n g k a n p e r a n g k a p s t r a t i g r a f i d a p a t b e r u p a l e n s a - l e n s a b a t u p a s i r d a n l a p i s a n b a t u g a m p i n g .

K a l a k u n c i : S i s t e m m i g a s , C e k u n g a n T i m o r , b a t u a n i n d u k , b a t u a n w a d u k , b a t u a n p e n u t u p d a n p e r a n g k a p h i d r o k a r b o n .

Abstract Discussion on petroleum system in the present paper is specialized on discussion the occurrence of hydrocarbon source rocks, reservoir rocks, seals and taps. There are several source rocks in the Timor Basin, i.e. black shales of the Atahoc, Cribas and Wailuli Formations. Geochemical and organic petrology analysis indicate that the black shale of the three formations is chatagorized into very good class and belong to kerogen type III. Based on petrographic analysis, SEM and porosity, there are four formations which may become reservoir, i.e. sandstone of the Cribas, Babulu and Oebaat Formations, and limestone of the Aitutu Formation. On the other hand, on the basis of petrogaphic and SEM analysis, shale of the Cribas and Nakfunu Formations may become cap rocks. The developing structural traps are positive flower structure, gentle anticline, thrusted anticline and graben. Moreover, sandstone lenses and limestone beds may become stratigraphic traps.

Keywords: Petroleum system, Timor basin, source rocks, reservoir rocks, seals and hydrocarbon traps.

Pendahuluan

Latar Befakang

F a k t o r p e n t i n g d a l a m m e n g i d e n t i f i k a s i s u a t u p o t e n s i h i d r o k a r b o n a d a l a h a d a a t a u t i d a k n y a s u m b e r d a r i h i d r o k a r b o n t e r s e b u t . H a l i n i d a p a t d i i d e n t i f i k a s i d a r i k e b e r a d a a n r e m b e s a n m i n y a k d a n g a s b u m i d i c e k u n g a n y a n g d i t e l i t i . D a r i h a s i l p e n g a m a t a n d i l a p a n g a n d i t e m u i s a t u l o k a s i r e m b e s a n g a s d i d e k a t S u n g a i O e b a n a k , B l o k K o l b a n o . S e l a i n i t u , m e n u r u t p e n e l i t i a n t e r d a h u l u , j u g a d i j u m p a i r e m b e s a n m i n y a k d a n g a s b u m i d i b e b e r a p a t e m p a t l a i n n y a ( G a m b a r 1 ) . H a l i n i i n i m e m b u k t i k a n b a h w a c e k u n g a n y a n g d i t e l i t i m e m i l i k i s u m b e r h i d r o k a r b o n . S e l a i n d a r i r e m b e s a n m i n y a k d a n g a s b u m i p o t e n s i

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

F a k t o r b e r i k u t n y a y a n g t a k k a l a h p e n t i n g a d a l a h k e b e r a d a a n b a t u a n w a d u k d a n p e r a n g k a p , b a i k p e r a n g k a p s t r a t i g r a f i , s t r u k t u r , m a u p u n k o m b i n a s i k e d u a n y a . D i s a m p i n g i t u j u g a h a r u s d i t e m u k a n b a t u a n t u d u n g (cap rock).

F a k t o r s e l a n j u t n y a y a n g j u g a s a n g a t p e n t i n g a d a l a h a d a n y a p r o s e s p e m a t a n g a n d a n m i g r a s i , s e h i n g g a m i g a s a k a n b e r m i g r a s i k e t e m p a t d i m a n a t e r d a p a t b a t u a n w a d u k d a n p e r a n g k a p . N a m u n p a d a m a k a l a h i n i b e l u m m e m b a h a s m a s a l a h p e m a t a n g a n d a n m i g r a s i h i d r o k a r b o n .

N a s k a h d i t e r i m a : 2 5 O k t o b e r 2 0 1 4 R e v i s i t e r a k h i r ; 0 4 J a n u a r i 2 0 1 5

246 J . G . S . M . V o l . 1G N o . 1 Februari 2 0 1 5 hal . 2 4 5 - 2 5 4

Lokasi dan tipe cekungan Maksud dan tujuan serta metodologi

C e k u n g a n T i m o r t e r l e t a k d i b a g i a n t i m u r P u l a u T i m o r y a n g m a s u k w i l a y a h I n d o n e s i a , a t a u t e r l e t a k d i P r o p i n s i N u s a T e n g g a r a T i m u r ( G a m b a r 1 ) . B e r d a s a r k a n p o s i s i t e r h a d a p k e r a n g k a t e k t o n i k d i I n d o n e s i a , c e k u n g a n i n i t e r l e t a k d i b u s u r - l u a r B a n d a . B e r d a s a r k a n g e n e s i s n y a c e k u n g a n i n i d i k l a s i f i k a s i k a n s e b a g a i c e k u n g a n t i p e passive margin - trench ( B a d a n G e o l o g i , 2 0 0 9 ) . D i k a t a k a n t i p e p a s s i v e m a r g i n k a r e n a d a l a m c e k u n g a n i n i d i j u m p a i b a t u a n - b a t u a n b e r u m u r P r a - T e r s i e r y a n g s e m u l a t e r b e n t u k d i passive margin A u s t r a l i a . A d a p u n d i k a t a k a n t i p e trench, k a r e n a d a l a m c e k u n g a n i n i d i j u m p a i b a t u a n - b a t u a n b e r u m u r T e r s i e r d i m a n a p a d a s a a t i t u c e k u n g a n s u d a h t e r b a w a k e I n d o n e s i a d a n b e r a s o s i a s i d e n g a n Timor Trench.

M a k s u d m a k a l a h i n i a d a l a h m e r a n g k u m b e b a g a i d a t a d a r i p e n e l i t i a n t e r d a h u l u s e r t a p e n e l i t i a n s e n d i r i o l e h t i m d a r i P u s a t S u r v e i G e o l o g i , d e n g a n t u j u a n m e m a h a m i l e b i h t e r i n c i s i s t e m m i g a s d i C e k u n g a n T i m o r . M e t o d e y a n g d i g u n a k a n a d a l a h m e r a n g k u m d a t a l a p a n g a n b e r u p a s t r u k t u r g e o l o g i d a n s t r a t i g r a f i , d i b a n t u d e n g a n b e b e r a p a a n a l i s i s l a b o r a t o r i u m t e r u t a m a a n a l i s i s g e o k i m i a p a d a b a t u a n i n d u k , s e r t a a n a l i s i s S E M d a r i p e n e l i t i t e r d a h u l u .

Tataan tektonik

B u s u r B a n d a t e r d i r i a t a s s e p a s a n g b u s u r k e p u l a u a n , y a i t u b u s u r - l u a r ( n o n - g u n u n g a p i ) d a n b u s u r - d a l a m ( g u n u n g a p i ) . B u s u r l u a r { T i m o r , T a n i m b a r , S e r a m d a n p u l a u - p u l a u l a i n n y a ) s a a t i n i m e r u p a k a n b a t a s u t a r a l e m p e n g b e n u a A u s t r a l i a y a n g m e n u n j a m d i b a w a h b u s u r - l u a r B a n d a .

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Gambar 1 . Peta t e k t o n i k Busur Banda dan lokasi C e k u n g a n T imor.

S i s t e m M i g a s d i C e k u n g a n T imor, Nusa Tenggara T i m u r 247

K o n f i g u r a s i l i t o s f e r y a n g m e n u n j a m t e r s e b u t t e r c e r r n i n k a n o l e h p o l a g a r i s k o n t u r k e d a l a m a n z o n a s e i s r n i k ( z o n a B e n i o f f ) , y a n g d a l a m h a l i n i a d a p e r b e d a a n p e n d a p a t a n t a r a H a m i l t o n ( 1 9 7 9 ) d a n C a r d w e l l & I s a c k s ( 1 9 7 8 ) . P e n d a p a t p e r t a m a ( H a m i l t o n , 1 9 7 9 ) m e n g a n g g a p k o n f i g u r a s i l i t o s f e r y a n g m e n u n j a m d i B u s u r B a n d a b e r b e n t u k c e k u n g s e p e r t i s e n d u k , k a r e n a z o n a B e n i o f f d a r i a r a h T i m o r m e n y a m b u n g d e n g a n y a n g d a r i a r a h S e r a m . S e d a n g k a n p e n d a p a t k e d u a ( C a r d w e l l & I s a c k , 1 9 7 8 ) m e n g a n g g a p l i t o s f e r y a n g m e n u n j a m d i b a w a h T i m o r t i d a k b e r h u b u n g a n d e n g a n l i t o s f e r y a n g m e n u n j a m d i b a w a h S e r a m .

P u l a u T i m o r d a n S e r a m , y a n g m e r u p a k a n b a g i a n d a r i B u s u r l u a r B a n d a , m e r u p a k a n z o n a t u m b u k a n a n t a r a l e m p e n g b e n u a A u s t r a l i a , a t a u t e p i a n p a s i f b a r a t -d a y a A u s t r a l i a , d i b a g i a n s e l a t a n , d a n s i s t e m s u b d u k s i y a n g b e r h u b u n g a n d e n g a n B u s u r B a n d a d i b a g i a n u t a r a ( G a m b a r 1 ) . B u s u r B a n d a m e l e n g k u n g s e t e n g a h l i n g k a r a n y a n g m a n a P u l a u T i m o r t e r l e t a k d i b a g i a n b a r a t d a y a , s e m e n t a r a P u l a u S e r a m t e r l e t a k d i b a g i a n t i m u r l a u t . D i s e b e l a h s e l a t a n T i m o r d i j u m p a i b a g i a n l u a r t e p i d a r i P a p a r a n b a r a t d a y a A u s t r a l i a , s u a t u t e p i a n p a s i f b e n u a y a n g d i h a s i l k a n d a r i p e c a h n y a G o n d w a n a p a d a J u r a ( P o w e l , 1 9 7 6 ; V e e v e r s , 1 9 8 2 ) .

T u m b u k a n y a n g t e r j a d i p a d a N e o g e n a n t a r a B u s u r B a n d a d a n A u s t r a l i a m e r u p a k a n t u m b u k a n a n t a r a b u s u r d e n g a n b e n u a y a n g m e n g h a s i l k a n d e f o r m a s i d i s e r t a i p r o s e s p e m a l i h a n d a n p e n s e s a r - n a i k a n b a t u a n b u s u r - l u a r B a n d a p r a t u m b u k a n k e a t a s b a t u a n d a r i b e n u a A u s t r a l i a . T i m o r d a n S e r a m m e r u p a k a n p u l a u - p u l a u d i b u s u r - l u a r B a n d a y a n g d i h a s i l k a n o l e h t u m b u k a n a n t a r a b u s u r d e n g a n b e n u a t e r s e b u t .

Stratigrafi Timor Bagian Barat

T e k t o n o s t r a t i g r a f i T i m o r b a g i a n b a r a t s e r u p a d e n g a n T i m o r L e s t e , y a i t u t e r d i r i a t a s s a t u a n a t a u r u n t u n a n p a r a a u t o k t o n , a l o k t o n d a n a u t o k t o n . D i P u l a u T i m o r b a g i a n b a r a t s a t u a n p a r a a u t o k t o n t e r d i r i a t a s r u n t u n a n K e k n e n o y a n g b e r u m u r d a r i p r a - P e r e m s a m p a i J u r a , s e m e n t a r a s a t u a n a l o k t o n t e r d i r i a t a s d u a r u n t u n a n , y a i t u r u n t u n a n K o l b a n o d a n K e l o m p o k P a l e l o , y a n g k e d u a n y a m e m i l i k i k o n t a k t e k t o n i k ( s e s a r n a i k ) ( S a w y e r d r r . , 1 9 9 3 ) . S e m e n t a r a i t u s a t u a n a u t o k t o n t e r d i r i a t a s r u n t u n a n V i q u e q u e y a n g b e r u m u r M i o s e n A k h i r s a m p a i P l i s t o s e n ( S a w y e r d r r . , 1 9 9 3 ) , s e r t a K o m p l e k s B o b o n a r o , k h u s u s n y a y a n g b e r g e n e t i k s e b a g a i e n d a p a n o l i s t o s t r o m y a n g fcerumur M i o s e n A k h i r s a m p a i P l i o - P l i s t o s e n .

Satuan Paraautokton

S a t u a n p a r a a u t o k t o n d i T i m o r m e r u p a k a n e n d a p a n P a p a r a n B a r a t d a y a A u s t r a l i a y a n g t e r b a w a k e A s i a b e r s a m a a t a u m e n u m p a n g d i a t a s b a t u a n a l a s n y a . D i b a g i a n b a r a t T i m o r , s a t u a n i n i t e r d i r i a t a s b a t u a n a l a s m a l i h a n b e r u m u r P e r e m y a n g d i t u t u p i o l e h r u n t u n a n K e k n e n o y a n g d i s e t a r a k a n d e n g a n Tethys margin nappe ( S a w y e r d r r . , 1 9 9 3 ) . B a t u a n a l a s m a l i h a n t i d a k t e r s i n g k a p d i C e k u n g a n T i m o r , n a m u n t e r s i n g k a p d i d a e r a h T i m o r L e s t e , d a n d i k e n a l s e b a g a i K o m p l e k s L o l o t o i . N a m a - n a m a f o r m a s i d a l a m r u n t u n a n K e k n e n o s e b a g i a n b e s a r m e n g i k u t i A u d l e y - C h a r l e s ( 1 9 6 8 ) . R u n t u n a n i n i b e r u m u r d a r i P e r e m A w a l s a m p a i J u r a T e n g a h , s e m e t a r a J u r a A k h i r t e r d a p a t k e t i d a k s e l a r a s a n {hiatus) ( G a m b a r 2 ) . B a g i a n b a w a h r u n t u n a n K e k n e n o t e r d i r i a t a s b a t u a n b e r u m u r P e r e m , y a i t u F o r m a s i A t a h o c d a n F o r m a s i C r i b a s , k e d u a n y a m e n j e m a r i d e n g a n F o r m a s i M a u b i s s e . F o r m a s i A t a h o c b e r u m u r b a g i a n b a w a h P e r e m A w a l , s e m e n t a r a F o r m a s i C r i b a s b e r u m u r b a g i a n a t a s P e r e m A w a l , d a n F o r m a s i M a u b i s s e b e r u m u r d a r i P e r e m A w a l s a m p a i P e r e m A k h i r . D i a t a s F o r m a s i M a u b i s s e d i j u m p a i h i a t u s h i n g g a a k h i r T r i a s A w a l . M u l a i a k h i r T r i a s A w a l h i n g g a T r i a s T e n g a h d i e n d a p k a n F o r m a s i N i o f . D i a t a s F o r m a s i N i o f d i e n d a p k a n F o r m a s i A i t u t u y a n g b e r u m u r b a g i a n a t a s T r i a s T e n g a h h i n g g a T r i a s A k h i r , d a n F o r m a s i B a b u l u y a n g b e r u m u r y a n g b e r u m u r T r i a s A k h i r . D i a t a s n y a l a g i d i e n d a p k a n F o r m a s i W a i l u l i y a n g b e r u m u r J u r a A w a l h i n g a J u r a T e n g a h , d a n d i a k h i r i o l e h k e t i d a k s e l a r a s a n d i b a g i a n a t a s n y a .

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248 J . G . S . M . V o l . 1 6 No. 1 Februari 2 0 1 5 h a l . 2 4 5 - 2 5 4

( 1 ) . F o r m a s i M a u b i s s e

F o r m a s i i n i b e r u m u r P e r m A w a l - J u r a A k h i r d e n g a n l i t o l o g i p e n y u s u n n y a a d a l a h b i o k a l k a r e n i t m e r a h -u n g u , p a c k s t o n e s , d a n b o u n d s t o n e s y a n g k a y a a k a n r o m b a k a n c a n g k a n g k o r a l , c r i n o i d s , b y r o z o i d s , b r a c h i p o d s , c e p h a l o p o d s d a n f u s i l i n i d s s e r t a b a t u a n b e k u e k s t r u s i f y a n g m e r u p a k a n b a t u a n t e r t u a d i T i m o r ( S a w y e r d r r . , 1 9 9 3 ) .

( 2 ) . F o r m a s i A t a h o c

F o r m a s i i n i b e r u m u r P e r m A w a l b e r d a s a r k a n u m u r d a r i f o s i l a m m o n o i d . L i t o l o g i d o m i n a n y a n g m e n y u s u n f o r m a s i i n i a d a l a h b a t u p a s i r h a l u s a r k o s e d e n g a n c i r i t e r p i l a h s e d a n g , m i n e r a l o g y t e r d i r i a t a s k u a r s a m o n o k r i s t a l i n , f e l d s p a r , p l a g i o k l a s , s e r t a t e r d a p a t f r a g m e n f i l i t y a n g b e r a s o s i a s i d e n g a n b a t u a n d a r i K o m p l e k s M u t i s / L o t o l o i .

( 3 ) . F o r m a s i C r i b a s

F o r m a s i i n i d i p e r k i r a k a n b e r u m u r P e r m A w a l d a n d a p a t d i b a g i m e n j a d i b e b e r a p a f a s i e s b a t u a n y a n g k o n t i n u s e c a r a l a t e r a l y a i t u l a p i s a n b a t u p a s i r m u l t i w a r n a , b a t u l a n a u , b a t u i e m p u n g h i t a m , d a n b a t u g a m p i n g b i o k l a s t i k . S t r u k t u r s e d i m e n s e p e r t i ripple d a n sole marks m e n u n j u k k a n b a h w a a r u s t u r b i d i t b e r p e r a n d a l a m p r o s e s p e n g e n d a p a n f o r m a s i i n i .

( 4 ) . F o r m a s i N i o f

F o r m a s i i n i b e r u m u r T r i a s A w a l - T r i a s T e n g a h y a n g d i c i r i k a n o l e h k o n t a k l a p i s a n y a n g t a j a m s e r t a m e n u n j u k k a n b a n y a k s t r u k t u r s e d i m e n . L i t o l o g i y a n g m e n y u s u n f o r m a s i i n i a d a l a h b a t u i e m p u n g b e r l a p i s t i p i s , b a t u s e r p i h w a r n a m e r a h - h i t a m - c o k l a t , b a t u p a s i r g r e y w a c / r e , n a p a l , d a n b a t u g a m p i n g m a s i f . P r o s e s p e n g e n d a p a n f o r m a s i i n i m e l a l u i m e k a n i s m e a r u s t u r b i d i t . L i n g k u n g a n p e n g e n d a p a n d a r i f o r m a s i i n i d i p e r k i r a k a n t e r d a p a t p a d a l i n g k u n g a n l a u t d a n g k a l h i n g g a l a u t d a l a m .

( 5 ) . F o r m a s i A i t u t u

F o r m a s i i n i b e r u m u r T r i a s A w a l - T r i a s A k h i r . L i t o l o g i p e n y u s u n d a r i f o r m a s i i n i a d a l a h b a t u g a m p i n g p u t i h -m e r a h m u d a d e n g a n p e r s e l i n g a n b a t u i e m p u n g k a r b o n a t a n b e r w a r n a a b u - a b u h i t a m . T e b a l l a p i s a n k o n s i s t e n y a i t u 4 5 - 6 0 c m d a n p a d a b i d a n g p e r l a p i s a n d a p a t d i t e m u k a n m a k r o f a u n a s e p e r t i H a l o b i a , D a o n e l l a , M o n o t i s , A m m o n i t , d a n f r a g m e n f o s i l l a i n n y a , L i n g k u n g a n p e n g e n d a p a n d a r i f o r m a s i i n i a d a l a h l a u t t e r b u k a y a i t u s e k i t a r p a p a r a n l u a r .

( 6 ) . F o r m a s i B a b u l u

F o r m a s i i n i d i s u s u n o l e h l i t o l o g i p e r s e l i n g a n b a t u l e m p u n g - b a t u l a n a u d a n b a t u p a s i r m a s i f . P a d a p e r m u k a a n b i d a n g p e r l a p i s a n b a n y a k d i t e m u k a n b r a c h i o p o d , a m m o n i t , f r a g m e n t u m b u h a n , s o l e m a r k s , d a n f o s i l j e j a k . L i n g k u n g a n p e n g e n d a p a n d a r i f o r m a s i i n i b e r a d a p a d a a r e a t e p i p a p a r a n .

( 7 ) . F o r m a s i W a i l u l i

L i t o l o g i y a n g m e n y u s u n f o r m a s i i n i a d a l a h b a t u l e m p u n g g e l a p d e n g a n p e r s e l i n g a n b a t u g a m p i n g o r g a n i k , k a l s i l u t i t , b a t u l a n a u , d a n b a t u p a s i r . U m u r d a r i f o r m a s i i n i a d a l a h J u r a A w a l - J u r a T e n g a h . L i n g k u n g a n p e n g e n d a p a n d a r i f o r m a s i i n i b e r k i s a r d a r i p a p a r a n d a l a m - p a p a r a n t e n g a h .

Satuan Alokton

S a t u a n a l o k t o n d i T i m o r b a g i a n b a r a t t e r d i r i a t a s R u n t u n a n K o l b a n o d a n R u n t u n a n B u s u r B a n d a p r a -t u m b u k a n y a n g k e d u a n y a m e m p u n y a i k o n t a k t e k t o n i k d i d a e r a h K o l b a n o , T i m o r b a r a t b a g i a n s e l a t a n . R u n t u n a n K o l b a n o b e r u m u r d a r i J u r a A k h i r s a m p a i P l i o s e n A w a l , d e n g a n s a t u a n d a r i b a w a h m u l a i d a r i F o r m a s i O e b a a t ( b a g i a n b a w a h K a p u r A w a l ) , F o r m a s i N a k f u n u ( K a p u r A w a l - K a p u r A k h i r ) , F o r m a s i M e n u ( K a p u r ) , d a n F o r m a s i O f u ( T e r s i e r ) . P a d a r u n t u n a n i n i d i j u m p a i b e b e r a p a k e t i d a k s e l a r a s a n , y a i t u p a d a K a p u r T e n g a h , P a l e o s e n A w a l , s e r t a O l i g o s e n y a n g s e t e m p a t s a m p a i M i o s e n A w a l . A d a p u n R u n t u n a n B u s u r B a n d a p r a - t u m b u k a n t e r d i r i a t a s b a t u a n a l a s K o m p l e k s M u t i s b e r u m u r t i d a k l e b i h t u a d a r i J u r a A k h i r , y a n g s e c a r a t i d a k s e l a r a s d i t u t u p i o l e h K e l o m p o k P a l e l o y a n g b e r u m u r K a p u r A k h i r h i n g g a M i o s e n A w a l , y a n g s e c a r a t a k s e l a r a s p u l a d i t u t u p i o l e h F o r m a s i M a n a m a s d a n b a t u a n c a m p u r - a d u k B o b o n a r o y a n g k e d u a n y a b e r u m u r a k h i r M i o s e n A k h i r s a m p a i P l i o - P l i s t o s e n .

Runtunan Kolbano:

( 1 ) . F o r m a s i O e b a a t

F o r m a s i i n i b e r u m u r J u r a A k h i r s a m p a i P l i o s e n A w a l d a n d i b a g i m e n j a d i d u a a n g g o t a f o r m a s i y a i t u :

- B a t u p a s i r m a s i f d e n g a n c i r i j a r a n g m e m i l i k i k e d u d u k a n p e r l a p i s a n , t a p i s a a t d i a m a t i t e r d i r i a t a s p e r l a p i s a n b a t u l a n a u d a n b a t u p a s i r . B a g i a n b a w a h d a r i u n i t i n i t e r d i r i d a r i b a t u l a n a u c o k l a t -h i t a m d a n b a t u i e m p u n g b e r n o d u l l i m o n i t - l a n a u . L i n g k u n g a n p e n g e n d a p a n d a r i u n i t i n i d i p e r k i r a k a n a d a l a h l a u t .

S i s l e m M i g a s di C e k u n g a n T i m o r , Nusa Tenggara T i m u r 249

- B a t u p a s i r g l a u k o n i t b e r l a p i s d e n g a n c i r i k e t e b a l a n l a p i s a n s e k i t a r 4 0 - 5 0 c m . F o s i ! a m m o n i t d a n b e l e m n i t b a n y a k d i t e m u k a n p a d a u n i t i n i . L i n g k u n g a n p e n g e n d a p a n d a r i u n i t i n i a d a l a h p a p a r a n d a n g k a l .

( 2 ) . F o r m a s i N a k f u n u

L i t o l o g i y a n g m e n y u s u n f o r m a s i i n i a d a l a h r a d i o l a r i t e , b a t u i e m p u n g , k a l s i l u t i t , b a t u l a n a u , p e r l a p i s a n b a t u i e m p u n g , k a l k a r e n i t , w a c k e s t o n e s , d a n p a c k s t o n e s . C i r i k h u s u s d a r i F o r m a s i N a k f u n u a d a l a h t e b a l l a p i s a n b a t u a n y a n g k o n s i s t e n s e k i t a r 3 -3 0 c m . K e h a d i r a n f o s i l r a d i o l a r i a s a n g a t m e l i m p a h , s e d a n g k a n f o s i l f o r a m i n i f e r a j a r a n g d i t e m u k a n . U m u r f o r m a s i i n i d i p e r k i r a k a n b e r u m u r K a p u r A w a l - K a p u r A k h i r . L i n g k u n g a n p e n g e n d a p a n d a r i f o r m a s i i n i a d a l a h l a u t d a l a m .

( 3 ) . F o r m a s i M e n u

F o r m a s i i n i b e r u m u r K a p u r d a n m e m i l i k i l i t o l o g i y a n g m i r i p d e n g a n F o r m a s i O f u y a n g b e r u m u r T e r s i e r . F o r m a s i i n i t e r s u s u n a t a s b a t u g a m p i n g d i m a n a t e r d a p a t l a p i s a n t i p i s a t a u n o d u l r i j a n g m e r a h , s e r t a m e n u n j u k k a n a d a n y a b e l a h a n y a n g i n t e n s i f . K e m i r i p a n l i t o l o g i y a n g d i m i l i k i o l e h F o r m a s i M e n u d a n F o r m a s i O f u m e n g i n d i k a s i k a n a d a n y a k o n t a k s t r a t i g r a f i . F o r m a s i i n i d i e n d a p k a n d e n g a n m e k a n i s m e t u r b i d i t p a d a l i n g k u n g a n l a u t d a l a m .

( 4 ) . F o r m a s i O f u

F o r m a s i i n i d i e n d a p k a n s e t e l a h t e r j a d i n y a h i a t u s p a d a P a l e o s e n A w a l s a m p a i M i o s e n A k h i r . L i t o l o g i p e n y u s u n d a r i f o r m a s i i n i a d a l a h b a t u g a m p i n g m a s i f b e r w a r n a p u t i h - m e r a h m u d a d e n g a n k e n a m p a k a n r e k a h a n k o n k o i d a l - s u b k o n k o i d a l . P a d a s i n g k a p a n u m u m n y a b a n y a k d i j u m p a i l a m i n a s i t i p i s , u r a t k a l s i t , s t i l o l i t , k e k a r , d a n r e k a h a n . F o r m a s i i n i d i e n d a p k a n p a d a l i n g k u n g a n l a u t d a l a m d e n g a n m e k a n i s m e t u r b i d i t .

Runtunan Busur Banda Pra-tumbukan

K e l o m p o k s a t u a n a l o k t o n i n i t e r d i r i a t a s b a t u a n y a n g b e r a s a l d a r i b u s u r m u k a d a n b u s u r g u n u n g a p i B a n d a p r a - t u m b u k a n N e o g e n a n t a r a B u s u r B a n d a d e n g a n p a p a r a n b a r a t l a u t A u s t r a l i a . P a p a r a n b a r a t l a u t A u s t r a l i a s e n d i r i t e r d i r i a t a s b a t u a n a l a s k e r a k b e n u a d a n s e d i m e n y a n g m e n u t u p i n y a . R u n t u n a n B u s u r B a n d a p r a - t u m b u k a n i n i t e r d i r i a t a s b a t u a n a l a s m a l i h a n K o m p l e k s M u t i s d a n b a t u a n y a n g m e n u t u p i n y a , y a i t u : K o m p l e k s P a l e l o ( F o r m a s i N o n i , F o r m a s i H a a u l a s i , F o r m a s i M e t a n ) , B a t u g a m p i n g C a b l a c i , d a n K o m p l e k s B o b o n a r o .

( 1 ) . K o m p l e k s M u t i s

K o m p l e k s M u t i s d i j u m p a i d i b a g i a n t e n g a h - u t a r a T i m o r b a g i a n b a r a t , t e r d i r i a t a s b a t u a n m a l i h a n y a n g b e r u m u r t i d a k l e b i h t u a d a r i J u r a A k h i r ( B r o w n d a n E a r l e , 1 9 8 3 ; S o p a h e l u w a k a n , 1 9 9 1 , s e m e n t a r a S a w y e r d r r . ( 1 9 9 3 ) m e m b e r i k a n u m u r K a p u r A w a l . S e b e l u m n y a , K o m p l e k s M u t i s d i n y a t a k a n b e r u m u r p r a - P e r e m ( R o s i d i d r r . , 1 9 9 6 ) . S a t u a n i n i d i s u s u n o l e h b a t u s a b a k , f i l i t , s e k i s , a m f i b o l i t , s e k i s a m f i b o l i t , k u a r s i t , g e n e s a m f i b o l i t d a n g r a n u l i t . K o m p l e k s M u t i s d i t u t u p i o l e h r u n t u n a n y a n g m e n d a n g k a l k e a t a s , d a r i d a s a r s a m u d e r a s a m p a i s a m p a i p a p a r a n b e n u a h i n g g a t e r u m b u . T i d a k s e l a r a s d i a t a s K o m p l e s * . M u t i s d i e n d a p k a n K o m p l e k s P a l e l o y a n g b e r u m u r d a r i K a p u r A k h i r s a m p a i M i o s e n A w a l , d a n d i a t a s n y a l a g i s e c a r a t i d a k s e l a r a s d i e n d a p k a n F o r m a s i M a n a m a s y a n g b e r u m u r M i o s e n A k h i r s a m p a i P l i o s e n A w a l ( S a w y e r d r r . , 1 9 9 3 ) .

( 2 ) . K e l o m p o k P a l e l o

K o m p l e k s P a l e l o t e r d i r i a t a s F o r m a s i N o n i , F o r m a s i H a u l a s i , F o r m a s i M e t a n d a n B a t u g a m p i n g C a b l a c i .

a . F o r m a s i N o n i

F o r m a s i N o n i b e r u m u r K a p u r A k h i r ( S a w y e r d r r . , 1 9 9 3 ) , t e r d i r i a t a s b a t u r i j a n g r a d i o l a r i a , b a t u g a m p i n g r i j a n g a n d a n r i j a n g l e m p u n g a n .

b . F o r m a s i H a u l a s i

F o r m a s i i n i b e r u m u r P a l e o s e n A k h i r - ; E o s e n T e n g a h . T e r d i r i a t a s g r e w a k e k o n g l o m e r a t a n , b a t u p a s i r , s e r p i h t u f a n d a n n a p a l .

c . F o r m a s i M e t a n

F o r m a s i i n i b e r u m u r E o s e n T e n g a h s a m p a i O l i g o s e n A k h i r , t e r d i r i a t a s a g l o m e r a t d e n g a n k o m p o n e n m e n y u d u t d a n m e n y u d u t t a n g g u n g d a l a m m a s a d a s a r t u f .

d . B a t u g a m p i n g C a b l a c i

L o k a s i t i p e s a t u a n i n i b e r a d a d i G u n u n g C a b l a c i , T i m o r L e s t e . D i l o k a s i t i p e n y a s a t u a n i n i t e r s u s u n o l e h b a t u g a m p i n g m a s i f k r i s t a l i n , s e m e n t a r a d i t e m p a t l a i n ( T i m o r b a g i a n b a r a t ) j u g a t e r s u s u n o l e h b a t u g a m p i n g k o r a l , b a t u g a m p i n g k a l k a r e n i t d a n k a l s i r u d i t . S a t u a n i n i m e r u p a k a n b a g i a n d a r i K e l o m p o k P a l e l o , s e c a r a t i d a k s e l a r a s d i t i n d i h o l e h F o r m a s i M a n a m a s .

250 J . G . S . M . V o l . 1 6 N o . 1 Februar i 2 0 1 5 Hal. 2 4 5 - 2 5 4

( 3 ) . F o r m a s i M a n a m a s

F o r m a s i i n i b e r u m u r M i o s e n A k h i r , t e r d i r i d a r i b r e k s i v u l k a n i k y a n g p e j a l d e n g a n s i s i p a n l a v a d a n t u f h a b l u r .

Satuan Autokton

S a t u a n i n i t e r u t a m a t e r s u s u n o l e h e n d a p a n - e n d a p a n p a s c a o r o g e n i k , s e b a g i a n t e r b e n t u k s e j a k o r o g e n e s i s a t a u s i n - o r o g e n i k , y a i t u b e r s a m a a n d e n g a n t u n b u k a n a n t a r a b e n u a A u s t r a l i a d e n g a n B u s u r B a n d a p r a -t u m b u k a n .

(1) . R u n t u n a n V i q u e q u e

R u n t u n a n V i q u e q u e t e r d i r i a t a s A n g g o t a B a t u p u t i h d a n A n g g o t a V i q u e q u e ( N o e l e ) , k e d u a n y a b e r u m u r M i o s e n A k h i r s a m p a i P I i s t o s e n A w a I . A n g g o t a V i q u e q u e t e r d i r i a t a s b a t u p a s i r g a m p i n g a n , b a t u p a s i r k o n g l o m e r a t a n g a m p i n g a n d a n k o n g l o m e r a t , s e m e n t a r a a n g g o t a a n g g o t a B a t u p u t i h t e r s u s u n o l e h b a t u g a m p i n g k a l s i l u t i t d a n n a p a l .

( 2 ) . K o m p l e k s B o b o n a r o

K o m p l e k s B o b o n a r o ( R o s i d i d r r . , 1 9 9 6 ; S u w i t o d i r j o d a n T j o k r o s a p o e t r o , 1 9 9 6 ) a t a u B o b o n a r o S c a l y C l a y ( A u d l e y - C h a r l e s , 1 9 6 8 ) m e r u p a k a n b a t u a n c a m p u r -a d u k {chaotic rock) y a n g t e r s u s u n o l e h m a t r i k s l e m p u n g b e r s i s i k y a n g m e n g a n d u n g b o n g k a h a n b a t u a n y a n g b e r u m u r l e b i h t u a , y a i t u b e r k i s a r d a r i P e r e m s a m p a i M i o s e n A w a l ( A u d l e y - C h a r l e s , 1 9 6 8 ) . N a m a K o m p l e k s B o b o n a r o s a a t i n i d i p a k a i u n t u k s e l u r u h b a t u a n c a m p u r - a d u k y a n g d i j u m p a i d i P u l a u T i m o r , m e n e m p a t i s e k i t a r 4 0 % d a r i l u a s p u l a u t e r s e b u t .

S a m p a i s e k a r a n g t e r d a p a t b e b e r a p a t a f s i r a n m e n g e n a i g e n e s i s K o m p l e k s B o b o n a r o , y a i t u ( 1 ) s e b a g a i o l i s t o t r o m ( A u d l e y - C h a r i e s , 1 9 6 8 ) , ( 2 ) m e r u p a k a n b a n c u h t e k t o n i k a t a u m e l a n g e ( H a m i l t o n , 1 9 7 9 ) , d a n ( 3 ) m e r u p a k a n h a s i l d a r i t e r o b o s a n d i a p i r s e r p i h ( B a r b e r d r r . , 1 9 8 6 ) . N a m u n , m e n u r u t B a c h r i ( 2 0 0 4 ) , s e b a g i a n b e s a r b a t u a n c a m p u r - a d u k d i T i m o r d i d u g a m e r u p a k a n h a s i l l o n g s o r a n b a w a h l a u t , a t a u o l i s t o t r o m , y a n g m u n g k i n b e r k a i t a n d e n g a n p r o s e s t u m b u k a n b u s u r d a n b e n u a p a d a N e o g e n . P a d a w a k t u t e r j a d i n y a t u m b u k a n t e r s e b u t d i d u g a t e r b e n t u k p u l a b a n c u h t e k t o n i k y a n g h a n y a m e m b e n t u k s e b a g i a n k e c i l d a r i K o m p l e k s B o b o n a r o . D i b e b e r a p a b a r a t , t e r u t a m a d i T i m o r b a r a t , j u g a t e r j a d i p e m b e n t u k a n b a t u a n c a m p u r - a d u k y a n g d i s e b a b k a n o l e h d i a p i r i s m e s e r p i h a t a u k e g i a t a n p o t o n . P o t o n - p o t o n t e r s e b u t m e m b a w a b e r b a g a i f r a g m e n b a t u a n y a n g d i t e r o b o s n y a , d a n m a s i h a k t i f s a m p a i s e k a r a n g .

Sistem Migas

Batuan Induk

B e b e r a p a p e n e l i t i t e r d a h u l u t e l a h m e n g i d e n t i f i k a s i f o r m a s i y a n g m e n g a n d u n g b a t u a n i n d u k d i C e k u n g a n T i m o r , y a i t u F o r m a s i A t a h o c , F o r m a s i C r i b a s , F o r m a s i A i t u t u d a n F o r m a s i W a i l u l i ( A u d l e y C h a r l e s , 1 9 6 8 ; B i r d , 1 9 8 7 ; C h a r l t o n , 2 0 0 1 ) . N a m u n d a r i b e b e r a p a p e n e l i t i b e l u m s e c a r a s p e s i f i k m e m b a h a s p o t e n s i b a t u a n i n d u k d a r i s e t i a p f o r m a s i y a n g m e n g a n d u n g b a t u a n i n d u k t e r s e b u t .

B e r i k u t i n i a k a n d i b a h a s h a s i l a n a l i s i s g e o k i m i a d a n p e t r o l o g i o r g a n i k k a i t a n n y a d e n g a n p o t e n s i b a t u a n i n d u k d a r i s e t i a p f o r m a s i y a n g d i t e l i t i , m e l i p u t i s e r p i h h i t a m d a r i F o r m a s i A t a h o c , F o r m a s i N i o f , F o r m a s i A i t u t u , d a n F o r m a s i W a i l u l i .

S e r p i h h i t a m d a r i F o r m a s i A t a h o c b e r u m u r P e r e m A w a l ( A u d l e y - C h a r l e s , 1 9 6 8 ) . H a s i l a n a l i s i s g e o k i m i a o r g a n i k t e h a d a p t o t a l k a n d u n g a n o r g a n i k m e n u n j u k k a n 8 , 8 5 % y a n g t e r m a s u k d a l a m k l a s i f i k a s i s a n g a t b a i k . H a s i l a n a l i s i s p e t r o l o g i o r g a n i k m e n u n j u k k a n s e r p i h d a r i F o r m a s i A t a h o c m e m i l i k i k o m p o s i s i m a s e r a l y a n g d i d o m i n a s i o l e h v i t r i n i t ( 6 5 % - 8 7 , 1 % ) , y a n g t e r m a s u k d a l a m k e r o g e n t i p e - I I I y a n g k e m u n g k i n a n s e b a g a i g a s p r o n e p o t e n t i a l . P e n g u k u r a n r e f l e k t a n v i t r i n i t p a d a s e r p i h d a r i F o r m a s i A t a h o c r a t a - r a t a d i a t a s 1 % , h a l i n i m e n u n j u k k a n s e r p i h i n i s u d a h t e r m a s u k k e d a l a m k a t e g o r i early peak mature.

S e r p i h h i t a m d a r i F o r m a s i N i o f b e r u m u r T r i a s A w a l -T r i a s T e n g a h . H a s i l a n a l i s i s p e t r o l o g i o r g a n i k m e n u n j u k k a n s e r p i h d a r i F o r m a s i N i o f m e m i l i k i k o m p o s i s i m a s e r a l y a n g d i d o m i n a s i o l e h v i t r i n i t ( > 8 0 % ) , y a n g t e r m a s u k d a l a m k e r o g e n t i p e - I I I y a n g k e m u n g k i n a n s e b a g a i g a s p r o n e p o t e n t i a l . P e n g u k u r a n v i t r i n i t e r e f l e k t a n p a d a s e r p i h d a r i F o r m a s i N i o f r a t a - r a t a d i a t a s 0 , 8 0 - 1 % , h a l i n i m e n u n j u k k a n s e r p i h i n i s u d a h t e r m a s u k k e d a l a m k a t e g o r i early mature.

S e r p i h h i t a m d a r i F o r m a s i A i t u t u b e r u m u r T r i a s A k h i r . H a s i l a n a l i s i s g e o k i m i a o r g a n i k t e h a d a p t o t a l k a n d u n g a n o r g a n i k m e n u n j u k k a n b e r k i s a r a n t a r a 2 , 4 7 % - 9 , 1 6 % y a n g t e r m a s u k d a l a m k l a s i f i k a s i s a n g a t b a i k s a m p a i s a n g a t b a i k s e k a l i . H a s i l a n a l i s i s p e t r o l o g i o r g a n i k m e n u n j u k k a n s e r p i h d a r i F o r m a s i A i t u t u m e m i l i k i k o m p o s i s i m a s e r a l y a n g d i d o m i n a s i o l e h v i t r i n i t ( 6 4 % - 8 5 . 1 % ) d a n l i p t i n i t ( 1 5 . 2 -4 0 . 3 % ) y a n g t e r m a s u k d a l a m t i p e - I I I y a n g k e m u n g k i n a n s e b a g a i g a s prone potential. P e n g u k u r a n r e f l e k t a n v i t r i n i t p a d a s e r p i h d a r i F o r m a s i

S i s t e m M i g a s di C e k u n g a n T i m o r , N u s a Tenggara T i m u r 251

A i u t u t u r a t a - r a t a a n t a r a 0 , 7 - 1 , 1 % , h a l i n i m e n u n j u k k a n s e r p i h i n i s u d a h t e r m a s u k k e d a l a m k a t e g o r i early mature. D a r i h a s i l a n a l i s i s p e t r o g r a f i m e n u n j u k k a n b a n y a k s e k a l i d i j u m p a i g a n g g a n g l a u t , h a l i n i d a p a t d i s i m p u l k a n b a h w a b a t u a n i n d u k i n i t e r m a s u k k e d a l a m m a r / ' n e carbonate source rock.

D a r i u r a i a n d i a t a s d a p a t d i s i m p u l k a n b a h w a p o t e n s i b a t u a n i n d u k d i C e k u n g a n T i m o r m e l i p u t i s e r p i h F o r m a s i A t a h o c y a n g b e r u m u r P e r e m A w a l , s e r p i h F o r m a s i N i o f y a n g b e r u m u r T r i a s A w a l - T r i a s T e n g a h d a n s e r p i h d a r i F o r m a s i A i t u t u y a n g b e r u m u r T r i a s A k h i r . H a s i l a n a l i s i s p e t r o l o g i o r g a n i k m e n u n j u k k a n h a s i l v i t r i n i t y a n g m e l i m p a h , m e n u n j u k k a n k e r o g e n t i p e - I I I s e b a g a i gas prone. D a r i g a m b a r a n t e r s e b u t d a p a t d i a m b i l k e s i m p u l a n b a h w a r e m b e s a n g a s p a d a l o k a s i p e n e l i t i a n d i p e r k i r a k a n m e m i l i k i m a t e r i a l o r g a n i k d e n g a n s e r p i h d a r i k e t i g a f o r m a s i d i a t a s .

Batuan Waduk

F a k t o r p e n t i n g l a i n d a l a m m e n g i d e n t i f i k a s i s u a t u p o t e n s i s i s t e m p e t r o l e u m a d a l a h a d a a t a u t i d a k n y a b a t u a n w a d u k s e b a g a i t e m p a t h i d r o k a r b o n t e r a k u m u l a s i . H a l i n i d a p a t d i i d e n t i f i k a s i d a r i k e b e r a d a a n p o t e n s i b a t u a n w a d u k d i c e k u n g a n y a n g d i t e l i t i . A n a l i s i s l a b o r a t o r i u m y a n g d i l a k u k a n u n t u k m e n g i d e n t i f i k a s i b a t u a n w a d u k p a d a p e n e l i t i a n i n i a d a l a h i n t e g r a s i d a r i a n a l i s i s p e t r o g r a f i , S E M d a n p o r o s i t a s . D a r i h a s i l k e t i g a a n a l i s i s y a n g t e l a h d i s e b u t k a n d i a t a s d a p a t d i s i m p u l k a n p o t e n s i u n t u k b a t u a n w a d u k d i c e k u n g a n i n i a d a l a h s e b a g a i b e r i k u t :

B a t u p a s i r F o r m a s i C r i b a s , b a t u p a s i r h a l u s - s a m p a i m e d i u m d a r i F o r m a s i C r i b a s b e r u m u r A k h i r P e r m i a n . H a s i l d e k s r i p s i p e n g a m a t a n d i l a p a n g a n m e n u n j u k k a n b e n t u k b u t i r m e m b u n d a r , d e n g a n p e m i l a h a n b a i k , d e n g a n k o m p o s i s i m i n e r a l k u a r s a . D a r i k e n a m p a k a n t e r s e b u t b a t u a n i n i m e m i l i k i p o t e n s i s e b a g a i b a t u a n w a d u k .

B a t u p a s i r F o r m a s i B a b u l u , b a t u p a s i r m e d i u m -s a m p a i k a s a r d a r i F o r m a s i B a b u l u . H a s i l d e k s r i p s i p e n g a m a t a n d i l a p a n g a n m e n u n j u k k a n b e n t u k b u t i r m e m b u n d a r , d e n g a n p e m i l a h a n b a i k , d e n g a n k o m p o s i s i m i n e r a l k u a r s a . D a r i k e n a m p a k a n t e r s e b u t b a t u a n i n i m e m i l i k i p o t e n s i s e b a g a i b a t u a n w a d u k , n a m u n h a l i n i p e r l u d i k a j i l a n j u t d a r i h a s i l a n a l i s i s p e t r o g r a f i d a n S E M y a n g s a m p a i s a a t i n i m a s i h d a l a m p r o s e s p r e p a r a s i . H a s i l a n a l i s i s p o r o s i t a s y a n g d i l a k u k a n o l e h L E M I G A S m e n u n j u k k a n p o r o s i t a s y a n g s a n g a t b a i k d e n g a n n i l a i p o r o s i t a s r a t a - r a t a d i a t a s 5 % . B a t u g a m p i n g F o r m a s i A i t u t u , b a t u g a m p i n g d a r i F o r m a s i A i t u t u b e r u m u r T r i a s

A k h i r . H a s i l d e k s r i p s i p e n g a m a t a n d i l a p a n g a n m e n u n j u k k a n b a t u g a m p i n g wacstone, packstone d a n grainstone. D a r i h a s i l a n a l i s i s p e t r o g r a f i b a t u g a m p i n g i n i d i b a g i m e n j a d i b a t u g a m p i n g b i o k l a s t i k a d e n g a n k o m p o n e n b i o k l a s t i k a b e r u p a c a m p u r a n f o s i l a n t a r a f o r a m i n i f e r a k e c i l p l a n k t o n i k , r a d i o l a r i a , d a n m o l u s k a , d a n b a t u g a m p i n g r a d i o l a r i a d e n g a n k o m p o n e n b i o k l a s u m u m n y a b e r u p a r a d i o l a r i a . D a r i h a s i l a n a l i s i s k e p o r i a n d i b a w a h m i k r o s k o p p e t r o g r a f i m e n u n j u k k a n k e p o r i a n s i s a a n t a r p a r t i k e l , r e t a k a n d a n g e r o w o n g t i d a k t e r a t u r .

D a r i h a s i l a n a l i s i s S E M t e r l i h a t j e n i s p o r o s i t a s y a n g p a d a b a t u g a m p i n g d a r i F o r m a s i A i t u t u u m u m n y a b e r u p a vuggy d a n intergrain porosity. D a r i h a s i l a n a l i s i s k e p o r i a n d e n g a n m e t o d e m e r k u r i m e n u n j u k k a n b a h w a b a t u g a m p i n g grainstone d a r i f o r m a s i i n i m e m i l i k i n i l a i p o r o s i t a s 8 , 6 5 % . D a r i k e n a m p a k a n t e r s e b u t d a p a t d i s i m p u l k a n b a t u a n i n i m e m i l i k i p o t e n s i s e b a g a i b a t u a n w a d u k .

B a t u p a s i r F o r m a s i O e b a a t b e r u k u r a n m e d i u m -s a m p a i k a s a r , m e n g a n d u n g b e l e m n i t b e r u m u r J u r a A k h i r . H a s i l d e k s r i p s i p e n g a m a t a n d i l a p a n g a n m e n u n j u k k a n b e n t u k b u t i r m e m b u n d a r , d e n g a n p e m i l a h a n b a i k , d e n g a n k o m p o s i s i m i n e r a l k u a r s a . D a r i k e n a m p a k a n t e r s e b u t b a t u a n i n i m e m i l i k i p o t e n s i s e b a g a i b a t u a n w a d u k .

Batuan penutup / tudung

F a k t o r l a i n y a n g t i d a k k a l a h p e n t i n g d a l a m m e n g i d e n t i f i k a s i s u a t u p o t e n s i s i s t e m p e t r o l e u m a d a l a h b a t u a n p e n u t u p a t a u t u d u n g {seal I cap rock). H a l i n i d a p a t d i i d e n t i f i k a s i d a r i k e b e r a d a a n p o t e n s i b a t u a n p e n u t u p d i c e k u n g a n y a n g d i t e l i t i . A n a l i s i s l a b o r a t o r i u m y a n g d i l a k u k a n u n t u k m e n g i d e n t i f i k a s i b a t u a n w a d u k p a d a p e n e l i t i a n i n i a d a l a h i n t e g r a s i d a r i a n a l i s i s p e t r o g r a f i d a n S E M .

D a r i h a s i l p e n g a m a t a n d i l a p a n g a n d a p a t d i r a n g k u m b a h w a s e r p i h d a r i F o r m a s i C r i b a s y a n g b e r u m u r P e r e m , s e r p i h d a n b a t u i e m p u n g p a d a s a t u a n b a t u a n b e r u m u r T r i a s d a n s e r p i h a t a u b a t u i e m p u n g p a d a F o r m a s i N a k f u n u m e m i l i k i p o t e n s i y a n g s a n g a t b a i k s e b a g a i b a t u a n p e n u t u p . S e c a r a u m u m k a r a k t e r i s t i k m e g a s k o p i s d i l a p a n g a n m e n u n j u k k a n l a p i s a n y a n g k e d a p a i r {impermeable) d a n s a n g a t tight. H a s i l a n a l i s i s p e t r o g r a f i j u g a m e n u n j u k k a n s e r p i h d a r i u n i t -u n i t b a t u a n t e r s e b u t m e m i l i k i p o s o i s t a s y a n g s a n g a t b u r u k d e n g a n k e p o r i a n y a n g s u d a h t e r i s i o l e h m i n e r a l l e m p u n g a t a u m i n e r a l k a r b o n a t .

252 J . G . S . M . V o l . 1 6 N o . 1 Februari 2 0 1 5 h a l . 2 4 5 - 2 5 4

H a l i n i j u g a d i p e r k u a t o l e h h a s i l a n a l i s i s S E M y a n g m e n u n j u k k a n u n i t - u n i t b a t u a n t e r s e b u t impermeable d i m a n a b e b e r a p a j e n i s p o r o s i t a s b e r u p a pore d a n fracture filling oleh m i n e r a l l e m p u n g . D a r i u r a i a n t e r s e b u t d a p a t d i s i m p u l k a n b a h w a u n i t - u n i t b a t u a n t e r s e b u t s a n g a t b a i k u n t u k m e n j a d i b a t u a n p e n u t u p h i d r o k a r b o n p a d a C e k u n g a n T i m o r .

Perangkap

S e t e l a h m e n g i d e n t i f i k a s i p o t e n s i b a t u a n i n d u k , b a t u a n w a d u k d a n b a t u a n p e n u t u p , t a h a p s e l a n j u t n y a a d a l a h m e n g i d e n t i f i k a s i k e m u n g k i n a n t i p e p e r a n g k a p h i d r o k a r b o n y a n g b e r k e m b a n g , s e h i n g g a d a p a t m e m b e r i k a n a r a h a n t e r h a d a p t a r g e t e k s p l o r a s i h i d r o k a r b o n d i C e k u n g a n T i m o r .

D a r i h a s i l a n a l i s i s g e o l o g i d a n g e o f i s i k a d a p a t d i s i m p u k a n k e m u n g k i n a n p e r a n g k a p h i d r o k a r b o n . S e t i d a k n y a a d a d u a j e n i s p e r a n g k a p h i d r o k a r b o n y a n g d a p a t d i i d e n t i k a s i y a i t u p e r a n g k a p s t r u k t u r d a n p e r a n g k a p s t r a t i g r a f i . P e r a n g k a p s t r u k t u r y a n g b e r k e m b a n g a d a l a h s t r u k t u r b u n g a p o s i t i f , a n t i k l i n l a n d a i , a n t i k l i n t e r s e s a r - n a i k k a n , d a n g r a b e n .

S e d a n g k a n p e r a n g k a p s t r a t i g r a f i d a p a t b e r u p a l e n s a - l e n s a b a t u p a s i r d a n l a p i s a n b a t u g a m p i n g ( G a m b a r 3 ) . D a r i p e r a n g k a p y a n g t e l a h k i t a i d e n t i f i k a s i s e l a n j u t n y a s e b a g a i a r a h a n e k s p l o r a s i h i d r o k a r b o n d i c e k u n g a n p e r l u d i i d e n t i f i k a s i play h i d r o k a r b o n d i C e k u n g a n T i m o r s e b a g a i t a r g e t e k s p l o r a s i ( G a m b a r 4 ) .

S e m e n t a r a d a t a s i s m i k d i l a u t T i m o r m e n u n j u k k a n b a h w a d i L a u t T i m o r b a g i a n b a r a t t e r d a p a t s t r u k t u r a n t i k l i n d a n m o n o k l i n y a n g b e r h u b u n g a n d e n g a n s e s a r , m u n g k i n d a p a t b e r f u n g s i s e b a g a i p e r a n g k a p s t r u k t u r ( G a m b a r 4 a ) . S e m e n t a r a d i L a u t T i m o r s e b e l a h s e l a t a n P u l a u T i m o r b a g i a n t i m u r d i j u m p a i p u l a a n t i k l i n d a n m o n o k l i n y a n g b e r h u b u n g a n d e n g a n s e s a r ( G a m b a r 4 b ) . H a l i n i d i d u g a p u l a m e r u p a k a n p e r a n g k a p p o t e n s i a l d i w i l a y a h T i m o r .

Gambar 3 . T ipe perangkap hidrokarbon di C e k u n g a n T imor. A ) T ipe perangkap struktur pada u n i t batuan Trias - P e r e m di B l o k Kekneno berupa a n t i k l i n tersesar-naikkan, B ) T ipe perangkap stratigrafi dan st ruktur pada u n i t batuan P e r m i a n d i B l o k Kekneno berupa l e n s a batupasir dan b a t u g a m p i n g dan perangkap st ruktur graben, C) T ipe perangkap st ruktur pada uni t batuan Trias, Jura dan Kapur di daerah K o l b a n o berupa struktur bunga posit i f , a n t i k l i n landai , dan a n t i k l i n tersesar n a i k k a n , D ) P e n a m p a n g M a g n e t o l e l l u r i k y a n g m e n u n j u k k a n p e r a n g k a p a n t i k l i n d i daerah K o l b a n o .

S i s t e m M i g a s d i C e k u n g a n T imor, Nusa Tenggara T i m u r 253

Kesimpulan

D i C e k u n g a n T i m o r s a t u a n b a t u a n y a n g b e r p o t e n s i s e b a g a i b a t u a n i n d u k a d a l a h s e r p i h h i t a m d a r i F o r m a s i A t a h o c , F o r m a s i N i o f , F o r m a s i A i t u t u , d a n F o r m a s i W a i l u l i . M a t e r i a l o r g a n i k d a r i k e s e l u r u h b a t u a n i n d u k t e r s e b u t m e r u p a k a n k e r o g e n t i p e I I I y a n g d a p a t m e n j a d i b a t u a n i n d u k g a s b u m i . K e m a t a n g a n k e r o g e n t e r s e b u t b e r k i s a r d a r i early mature s a m p a i early peak mature.

S e m e n t a r a i t u b a t u p a s i r d a r i F o r m a s i - F o r m a s i C r i b a s , B a b u l u d a n O e b a a t b e r p o t e n s i s e b a g a i b a t u a n w a d u k .

A d a p u n t a r g e t - t a r g e t e k s p l o r a s i h i d r o k a r b o n d i c e k u n g a n i n i d a p a t d i r a n g k u m s e b a g a i b e r i k u t : .

1 . B a t u p a s i r ( l e n s a ) F o r m a s i C r i b a s y a n g b e r u m u r P e r e m A k h i r .

2 . B a t u p a s i r F o r m a s i B a b u l u y a n g b e r u m u r T r i a s A k h i r .

3 . B a t u g a m p i n g F o r m a s i A i t u t u y a n g b e r u m u r T r i a s A k h i r

4 . B a t u p a s i r F o r m a s i O e b a a t y a n g b e r u m u r J u r a A k h i r .

Gambar 4 . A) Play h idrokarbon di C e k u n g a n T i m o r yang b e r u m u r Perem - T r i a s ; B) G a m b a r a n p t e y batupasir B a b u l u y a n g b e r u m u r T r i a s A k h i r berupa clean sandstone pada lereng atas (upperslope).

254 J . G . S . M . V o l . 1 6 No. 1 Februari 2 0 1 5 h a l . 2 4 5 - 2 5 4

Acuan

A u d l e y - C h a r l e s , M . G . 1 9 6 8 . T h e G e o l o g y o f P o r t u g e s e T i m o r . Memoirs of theGeological Society of London N o . 4 . U n i v e r s i t y o f L o n d o n .

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B a d a n G e o l o g i , 2 0 0 9 . Peta cekungan sedimen Indonesia berdasarkan data gayaberat dan geologi. P u s a t S u r v e i G e o l o g i , B a d a n G e o l o g i , B a n d u n g .

B a r b e r , A . J . , T j o k r o s a p o e t r o , S . & C h a r l t o n , T . R . , 1 9 8 6 . M u d v o l c a n o e s , s h a l e d i a p e r s , w r e n c h f a u l t s a n d m e l a n g e s i n a c c r e t i o n a r y c o m p l e x e s , e s t e r n I n d o n e s i a . Bull. Am. Petrol. Geol. 7 0 : 1 7 2 9 - 1 7 4 1 .

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B r o w n , M . & E a r l e , M . M . , 1 9 8 3 . C o r d i e r i t e - b e a r i n g s c h i s t a n d g n e i s s e s f r o m T i m o r , e a s t e r n I n d o n e s i a : P - T c o n d i t i o n s o f m r t a m o r p h i s m a n d t e c t o n i c i m p l i c a t i o n s . J. Metamorph. Geol. 1 , 1 8 3 - 2 0 3 .

C a r d w e l l , R . K . & I s a c k s , B . L . , 1 9 7 8 . G e o m e t r y o f s u b d u c t e d l i t h o s p h e r e b e n e a t h t h e B a n d a S e a i n e a s t e r n I n d o n e s i a f r o m s e i s m i c i t y a n d f a u l t p l a n e s o I u t i o n s . J . Geophys. / ? e s . , 8 3 : 2 8 2 5 - 2 8 3 8 .

C h a r l t o n , T . R . 2 0 0 1 . T h e p e t r o l e u m p o t e n t i a l o f W e s t T i m o r . P r o c e e d i n g s o f t h e Indonesian Petroleum Association 2 8 , v o l 1 : 3 0 1 - 3 1 7 .

H a m i l t o n , W , 1 9 7 9 . Tectonics of the Indonesian region. G e o l . S u r v e y P r o f e s s i o n a l P a p e r 1 0 7 8 , 3 4 5 p.

P o w e l , D . E . , 1 9 7 6 . T h e g e o l o g i c a l e v o l u t i o n o f c o n t i n e n t a l m a r g i n o f N o r t h w e s t A u s t r a l i a . J. Aust. Petrol. E x p l . A s s . 1 0 : 1 3 - 2 3 .

S a w y e r , R . K . , S a n i , K. , B r o w n , S . , 1 9 9 3 . S t r a t i g r a p h y a n d S e d i m e n t o l o g y o f W e s t T i m o r , I n d o n e s i a . Proceedings of the Indonesian Association of Geologists, 2 2 : 1 - 2 0 .

R o s i d i H . M . D . , T j o k r o s a p o e t r o S . d a n G a f o e r S . , 1 9 9 6 . Peta GeologiLembar Atambua-Timor, skala 1:250.000. P u s a t P e n e l i t i a n d a n P e n g e m b a n g a n G e o l o g i , B a n d u n g .

S o p a h e l u w a k a n , J . , 1 9 9 1 . H i g h - p r e s s u r e m e t a m o r p h i s m a n d i n t r a - o c e a n i c t h r u s t i n g : T h e r o l e o f u p p e r m a n t l e f l u i d s ( a b s t r a c t ) , I n : P r o c e e d i n g s o f t h e S i l v e r J u b i l e e S y m p o s i u m o n t h e D y n a m i c s o f S u b d u c t i o n a n d i t s P r t s P r o d u c t s , Y o g y a k a r t a , S e p t e m b e r 1 9 9 1 . Indonesian Institute ofSciemces (LIPf).

S u w i t o d i r d j o K. d a n T j o k r o s a p o e t r o S . , 1 9 9 6 . Peta Geologi Lembar Kupang-Atambua, Timor, skala 1:250.000. P u s a t P e n e l i t i a n d a n P e n g e m b a n g a n G e o l o g i , B a n d u n g .

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