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

1 2 t r e m ol i t e oc c ur s t hr oughout . the a ge of t he i nt r u s i on i s unkn ow n, but t he l a c k of e vi de nc e f or t e c t oni c de f or m a t i on s ugg e s t s t ha t i t pos t da t e s r e gi ona l m e t a m or phi s m . The ultramafic rock has a high magnetic susceptibility (ca 6000 x 10- 5 si). pe gm atite (pe g) Pe gm a t i t e bodi e s of a r a nge of s c a l e s a r e pr e s e nt i n m os t ar un t a re gi on a r e a s a nd a r e pr oba bl y o f a va r i e t y o f a ge s . mos t f or m r e l a t i ve l y s m a l l dyke s a nd s i l l s , but s om e l a r ge r a r e a s of pe gm a t i t e (hundr e ds of m e t r e s i n s c a l e ) a r e pr e s e nt w i t h i n t he de l ny me t a m or phi c s . mos t pe gm a t i t e s a r e l e uc o c r a t i c , a nd i f pr e s e nt a t a l l , m i c a s a r e us ua l l y r e s t r i c t e d t o m us c ovi t e . Bi ot i t e - be a r i ng pe gm a t i t e s i nt r ude t he cr ooke d H ol e gr a ni t e , ne a r t he s out he r n bound a r y of Woodgreen. Bl a c k t our m a l i ne i s a bunda nt i n s om e pe gm a t i t e s a s s oc i a t e d w i t h s out he r n p a r t s of t he mol l i e gr a ni t e com pl e x, but e l s e w he r e , t our m a l i n e i s a m i nor a c c e s s or y onl y . neoProterozoic to Palaeozoic georgina Basin CRY O GE N I AN Keeperagroup B oko F ormation (LP b o) th e Bo k o Fo r m a t i o n i s a l e n t i c u l a r u n i t o f m a s s i v e g l a c i a l d i a m i c t i t e , w i t h c o b b l e a n d b o u l d e r c l a s t s u p t o 2 m i n s i z e s u p p o r t e d b y a r e d - b r o w n m u d s t o n e m a t r i x (Figure12). cl a s t s c o m p r i s e q u a r t z i t e , s a n d s t o n e , c o n g l o m e r a t e , g r a n i t e , v a r i o u s m e t a m o r p h i c r o c k s a n d r a r e v o l c a n i c r o c k s . th e y c o m m o n l y d i s p l a y f a c e t s a n d s t r i a t i o n s c h a r a c t e r i s t i c o f g l a c i a l a c t i o n (Figure13). go o d e x p o s u r e s o f t h e m a t r i x a r e r e s t r i c t e d t o t w o l o c a l i t i e s n o r t h w e s t o f ne w Bore (428590mE 7554789mN, 427704mE 755976mN). el s e w h e r e e x p o s u r e i s p o o r , w i t h t h e f o r m a t i o n b e i n g r e c o g n i s e d b y t h e p r e s e n c e o f r i s e s a n d l o w h i l l s c o v e r e d b y l o o s e c o b b l e s a n d b o u l d e r s o f q u a r t z i t e , g r a n i t e a n d o t h e r r o c k t y p e s . th e c l a s t a s s e m b l a g e a n d t h e p r e s e n c e o f g l a c i a l f a c e t s a n d s t r i a t i o n s s e r v e s t o d i s t i n g u i s h s u c h o u t c r o p s f r o m c o n g l o m e r a t i c u n i t s w i t h i n t h e oo r a b r a ar k o s e a n d f r o m o l d d i s s e c t e d ce n o z o i c f a n d e p o s i t s . th e Bo k o Fo r m a t i o n u n c o n f o r m a b l y o v e r l i e s r o c k s o f t h e ar u n t a re g i o n a n d i s o v e r l a i n , w i t h p o s s i b l e c o n f o r m i t y , b y t h e oo r a b r a ar k o s e , o r u n c o n f o r m a b l y , b y t h e el y u a h Fo r m a t i o n . a s m a l l o u t c r o p o f t h e u n c o n f o r m i t y s u r f a c e over the Utopia Quartzite at 428621mE 7554960mN (Figure14) h a s a d i s t i n c t l y p o l i s h e d a n d w e a k l y s t r i a t e d (e a s t w e s t t r e n d ) a p p e a r a n c e a n d m a y r e p r e s e n t a s m a l l r e l i c t o f a g l a c i a t e d p a v e m e n t . a s i m i l a r p a v e m e n t i s l o c a l l y p r e s e r v e d b e n e a t h t h e oorabra Arkose. th e Bo k o Fo r m a t i o n i s l e n t i c u l a r a n d o n l y l o c a l l y p r e s e r v e d , p r o b a b l y i n d e p r e s s i o n s o n t h e u n c o n f o r m i t y s u r f a c e . it s t h i c k n e s s r a n g e s u p t o a b o u t 3 0 m . th e t y p e a r e a o f t h e Bo k o Fo r m a t i o n i s i n BarroW creek (H a i n e s et al 1991). In Woodgreen, d i a m i c t i t e s t h a t w e r e p r e v i o u s l y m a p p e d a s p a r t o f t h e f o r m e r ce n t r a l mo u n t Stuart beds (Shaw and Warren 1975), were subsequently r e c o g n i s e d a s a d i s t i n c t , a l t h o u g h u n n a m e d u n i t b y Wa l t e r (1980) and are now recognised as the Boko Formation. Fr o m c o m p a r i s o n s w i t h o t h e r au s t r a l i a n ne o p r o t e r o z o i c s u c c e s s i o n s , t h e Bo k o Fo r m a t i o n i s c o n s i d e r e d t o c o r r e l a t e w i t h t h e y o u n g e r o f t w o w i d e s p r e a d g l a c i a l e p i s o d e s , t h e ca 600 Ma Marinoan glaciation (Haines et al 1991). It is i n t e r p r e t e d a s a n o n - m a r i n e m o r a i n e (t i l l ) d e p o s i t . Oorabr a A rkos e (LP or) The Oorabra Arkose was defined in HUCKITTA and has had a complex history of usage and redefinition (Joklik 1955, Smith 1964, Walter 1980, Freeman 1986). The unit h a s n o t p r e v i o u s l y b e e n r e c o g n i s e d b e y o n d t h a t s h e e t a r e a . Walter (1980) recognised a similar arkose unit at Poomingie Wa t e r h o l e i n utoPia, j u s t e a s t o f Woodgreen, b u t w a s r e l u c t a n t t o e x t e n d t h e g e o g r a p h i c r a n g e o f t h e oo r a b r a ar k o s e , b e c a u s e o f u n c e r t a i n t i e s a b o u t s t r a t i g r a p h i c p o s i t i o n a n d c o r r e l a t i o n . a s i m i l a r u n i t i s h e r e r e c o g n i s e d i n Woodgreen, w h e r e i t c a n b e d e m o n s t r a t e d t o o c c u p y t h e s a m e s t r a t i g r a p h i c p o s i t i o n a s t h e oo r a b r a ar k o s e i n H uckitta, w i t h w h i c h i t a l s o s h a r e s l i t h o l o g i c a l a n d Figure12. Boko For m a t i on. expos ur e ne a r t op of s m a l l hi l l s how n i n Figure14. cl a s t s of qua r t z i t e , gr a ni t e a nd ot he r r oc k t ype s a r e s uppor t e d by da r k r e d- b r ow n mudstone matrix; bouldersize granite c l a s t a bove a nd t o r i ght of ha m m e r . 428590mE 7554789mN, 3 km NNW of ne w Bor e .