Territory Stories

Woodgreen, Northern Territory : explanatory notes

Details:

Title

Woodgreen, Northern Territory : explanatory notes

Issued by

Northern Territory Geological Survey

Collection

E-Publications; E-Books; PublicationNT; Australia 1:100 000 Geological Map Series

Date

2007

Location

Australia 1:100 000 Geological Map Wood 5458; Australia 1:250 000 Geological MapAlcoota SF5310; Australia 1:250 000 Geological MapAlcoota SF5310

Map scale

1:100 000

Notes

Made available via the Publications (Legal Deposit) Act 2004 (NT); Available from GEMIS - Geoscience Exploration and Mining Information System

Language

English

Subject

Geology; Georgina Basin; Arunta Region

Publisher name

Northern Territory Government; Northern Territory Government

Place of publication

Darwin

Edition

1st ed.

Series

Australia 1:100 000 Geological Map Series

File type

application/pdf

ISBN

9780724571321

ISSN

0811-6296

Use

Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government

License

https://creativecommons.org/licenses/by/4.0/

Related links

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81885 [GEMIS]

Parent handle

https://hdl.handle.net/10070/794795

Citation address

https://hdl.handle.net/10070/794807

Page content

18 s i m i l a r b a s a l m u d s t o n e u n i t r e p o r t e d f r o m s o u t h e r n BarroW creek (H a i n e s et al 1991). The basal mudstone unit may b e w i d e s p r e a d , b u t t h i s i n t e r v a l i s u s u a l l y s c r e e c o v e r e d . in Woodgreen, t h e oc t y Fo r m a t i o n i s u n c o n f o r m a b l y o v e r l a i n by a poorly exposed carbonate unit, tentatively identified as t h e ch a b a l o w e Fo r m a t i o n . re g i o n a l r e l a t i o n s h i p s i n d i c a t e t h a t this contact is significantly angular, such that in central and e a s t e r n Woodgreen, t h e oc t y Fo r m a t i o n h a s b e e n r e m o v e d a n d t h e ch a b a l o w e Fo r m a t i o n (? ) l i e s d i r e c t l y o n t h e ce n t r a l mo u n t st u a r t Fo r m a t i o n . al t h o u g h t h e t h i c k n e s s o f t h e oc t y Fo r m a t i o n c a n n o t b e a c c u r a t e l y d e t e r m i n e d , d u e t o l o w a n g l e s o f d i p a n d f a u l t i n g , i t i s e s t i m a t e d t o r e a c h a m a x i m u m t h i c k n e s s of about 150 m near 421000mE 7556000mN. A moderate Th a n d u r a d i o m e t r i c s i g n a l i s o b s e r v e d o v e r t h e oc t y Fo r m a t i o n w e s t o f t h i s l o c a t i o n , b u t n o t e l s e w h e r e , a n d m a y a r i s e f r o m a r e s i d u e o f p r e v i o u s l y o v e r l y i n g ch a b a l o w e Fo r m a t i o n , w h o s e r a d i o m e t r i c s i g n a t u r e i s v e r y s i m i l a r (s e e chabalowe Formation). th e s e d i m e n t a r y f a c i e s a n d i c h n o f o s s i l s i n d i c a t e a s h a l l o w - m a r i n e d e p o s i t i o n a l e n v i r o n m e n t . th e oc t y Fo r m a t i o n i s c o r r e l a t e d , a t l e a s t i n p a r t , w i t h t h e Mount Baldwin Formation, as mapped in the Jervois Range a r e a o f H uckitta (s e e d i s c u s s i o n u n d e r central Mount Stuart Formation). it c a n a l s o b e c o r r e l a t e d (H a i n e s et al 1991) with upper parts of the Arumbera Sandstone (Amadeus Ba s i n ) a n d yu e n d u m u sa n d s t o n e (ng a l i a Ba s i n ). narpagroup Ch abal ow e Formation (_Cmc) a p o o r l y p r e s e r v e d u n i t , m a r k e d a t t h e s u r f a c e b y c h e r t a n d s a n d s t o n e r u b b l e , a n d c o m m o n l y a s s o c i a t e d w i t h f e r r i c r e t e , u n c o n f o r m a b l y o v e r l i e s t h e oc t y Fo r m a t i o n o r m e m b e r s o f t h e ce n t r a l mo u n t st u a r t Fo r m a t i o n . no o v e r l y i n g u n i t i s p r e s e r v e d a t t h e s u r f a c e i n Woodgreen, b u t o u t c r o p s o f t h e ca m b r o or d o v i c i a n to m a h a w k Fo r m a t i o n , e x p o s e d j u s t e a s t o f n o r t h e r n Woodgreen i n utoPia, a r e p r e s u m a b l y s t r a t i g r a p h i c a l l y y o u n g e r t h a n t h i s u n i t . th e c h e r t h a s r e l i c t t e x t u r e s w h i c h i n d i c a t e t h a t i t is a silicified carbonate rock. This is consistent with the moderate th a n d u r a d i o m e t r i c s i g n a l u s u a l l y o b s e r v e d o v e r o u t c r o p s o f t h i s u n i t . re l i c t s o f d o m a l a n d c o l u m n a r s t r o m a t o l i t e s a r e o f t e n p r e s e r v e d (Figure19), a l t h o u g h n o o t h e r f o s s i l s h a v e b e e n recognised. Cauliflowerlike chert masses are probably after a s u l f a t e e v a p o r i t e , s u c h a s g y p s u m o r a n h y d r i t e . th e t h i c k n e s s o f t h e u n i t i s n o t w e l l c o n s t r a i n e d , b u t m a y r e a c h s e v e r a l h u n d r e d m e t r e s . si m i l a r o u t c r o p s a r e p r e s e n t i n s o u t h - c e n t r a l BarroW creek a n d t h e s e w e r e t e n t a t i v e l y a s s i g n e d t o t h e ch a b a l o w e Fo r m a t i o n (H a i n e s et al 1991), a formation defined from drillcore d a t a f u r t h e r n o r t h (s t r a t o t y p e i n ntgs s t r a t i g r a p h i c d r i l l h o l e BC5 in BARROW CREEK; Stidolph et al 1988). Based on a s i m i l a r s u r f a c e e x p r e s s i o n a n d s t r a t i g r a p h i c r e l a t i o n s h i p s , t h e o u t c r o p s i n Woodgreen a r e t e n t a t i v e l y a s s i g n e d t o t h e same formation, although it is unlikely that a more definitive s t r a t i g r a p h i c a s s i g n m e n t c a n b e p r o v i d e d w i t h o u t s t r a t i g r a p h i c d r i l l i n g . Fr o m d r i l l c o r e i n t e r s e c t i o n s i n BarroW creek a n d elkedra, t h e ch a b a l o w e Fo r m a t i o n c o m p r i s e s i n t e r b e d d e d s a n d s t o n e , d o l o m i t i c s a n d s t o n e , m u d s t o n e , d o l o s t o n e a n d e v a p o r i t e (st i d o l p h et al 1988, Haines et al 1991). Stromatolites are common, but agediagnostic fossils a r e l a c k i n g . th e ch a b a l o w e Fo r m a t i o n i s c o n s i d e r e d t o b e o f e a r l y la t e ca m b r i a n a g e , b a s e d o n i t s l a t e r a l r e l a t i o n s h i p w i t h t h e ar r i n t h r u n g a Fo r m a t i o n (du n s t e r et al 2 0 0 7 ). de p o s i t i o n p r o b a b l y o c c u r r e d i n a r e s t r i c t e d m a r i n e o r m a r g i n a l m a r i n e s a b k h a e n v i r o n m e n t . it i s p o s s i b l e t h a t t h e la t e ca m b r i a n c a r b o n a t e - d o m i n a t e d ar r i n t h r u n g a Fo r m a t i o n , w h i c h c o n f o r m a b l y o v e r l i e s t h e ch a b a l o w e Fo r m a t i o n i n n o r t h e r n a n d e a s t e r n BarroW CREEK, and which was tentatively identified in a small outcrop 6 km northeast of the northeastern corner of Woodgreen i n luraPulla (H a i n e s et al 1991), is also represented in some o u t c r o p s . al t e r n a t i v e l y , t h e ar r i n t h r u n g a Fo r m a t i o n m a y b e p r e s e n t , b u t n o t e x p o s e d a t t h e s u r f a c e , t o t h e e a s t o f o u t c r o p s o f i n f e r r e d ch a b a l o w e Fo r m a t i o n i n t h e f a r n o r t h e a s t o f Woodgreen. cockroachgroup T omah aw k F ormation the ca m br oo r dovi c i a n tom a ha w k For m a t i on (f or m a l i s e d by kr us e et al 2002) doe s not out c r op i n Woodgreen. Figure19. cha ba l ow e For m a t i on( ? ). che r t float with relict stromatolites. 427392mE 7561311mN, 9 km NNW of New Bore.


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