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

2 1 m y l o n i t i s e d Wo o d g r e e n gr a n i t e co m p l e x (Figure20). th e m e t a m o r p h i c g r a d e o f t h e s e s h e a r z o n e s i s g r e e n s c h i s t f a c i e s , w i t h g r a d e d e c r e a s i n g t o t h e n o r t h . Fu r t h e r n o r t h w i t h i n Woodgreen, s t e e p l y s o u t h - s o u t h w e s t - d i p p i n g r e v e r s e f a u l t s a l s o t r u n c a t e t h e ge o r g i n a Ba s i n a n d j u x t a p o s e b a s e m e n t a g a i n s t i t . th e s e f a u l t s a r e p a r t o f a m o r e e x t e n s i v e b e l t e x t e n d i n g e a s t w a r d i n t o H uckitta, w h e r e t h e y h a v e b e e n i n t e r p r e t e d b y Greene (2003) as reflecting reactivation and inversion of a n o r m a l f a u l t s y s t e m , d u e t o t h e p r e f e r e n t i a l p r e s e r v a t i o n o f ne o p r o t e r o z o i c r i f t s e d i m e n t s i n t h e h a n g i n g w a l l . th e f a u l t s a r e t y p i c a l l y a s s o c i a t e d w i t h m o n o c l i n a l f o l d s , a n d h a v e s t e e p t o o v e r t u r n e d b e d d i n g i n t h e f o o t w a l l , i m m e d i a t e l y a d j a c e n t t o t h e f a u l t . in Woodgreen, t h i s s t y l e o f t e c t o n i c s i s b e s t s e e n b y t h e d e v e l o p m e n t o f a n e l o n g a t e a s y m m e t r i c s y n c l i n e s i t u a t e d i n t h e f o o t w a l l o f a n i n f e r r e d n o r t h w e s t - t r e n d i n g t h r u s t f a u l t t h a t j u x t a p o s e s ar u n t a re g i o n g r a n i t e (mo l l i e gr a n i t e co m p l e x ) w i t h ge o r g i n a Ba s i n r o c k s i n t h e v i c i n i t y o f mo l l i e Bl u f f . th e l i m b a d j a c e n t t o t h e f a u l t d i s p l a y s l o c a l l y s t e e p t o o v e r t u r n e d s t r a t a . gEophySIcS Airborne Woodgreen i s e nt i r e l y c ove r e d by a i r bor ne ge ophys i c a l (m a gne t i c , r a di om e t r i c , e l e va t i on) da t a , a c qui r e d by ntgs a s part of the AlcootaAlice Springs survey in 1997. These data were acquired on northsouthoriented, 400 mspaced flight lines, with a nominal terrain clearance of 60 m. Nominal s a m pl i ng i nt e r va l s f or t he m a gne t om e t e r a nd s pe c t r om e t e r (33 L NaI crystal detector) were 7 m and 80 m, respectively. Further specification details are available through the NTGS w e bs i t e w w w .m i ne r a l s .nt .gov .a u/ nt gs a nd Wor l d ge os c i e nc e Corporation (1997). The magnetic field over Woodgreen r a nge s i n i nt e ns i t y up to 900 nT and +700 nT either side of the nominal base l e ve l f ol l ow i ng igrF r e m ova l . me a n a nd m e di a n tmi va l ue s f or Woodgreen a r e a l s o 1 00 nt or m or e be l ow t he nom i na l ba s e l e ve l . thi s ne ga t i ve s ke w i s due , a t l e a s t i n pa r t , t o a c ont i n e nt - s c a l e w e s t - nor t hw e s t e r l y z one of l ow m a gne t i c i nt e ns i t y pa s s i ng t hr ough t he s he e t a r e a , pa r a l l e l t o t h e al i c e spr i ngs or oge ny- a ge s he a r z one s i ndi c a t e d on t he m a pf a c e (mount ida a nd de l ny s he a r z one s ). the m os t e xt r e m e ne ga t i ve tmi va l ue s , i n t he vi c i ni t y of t he mount ida she a r zone i n s out he a s t e r n Woodgreen, m a y ha ve a c om pone nt s our c e d f r om ne a r - s ur f a c e m e t a m or p hi c uni t s (Delny Metamorphics). However, a significant proportion of t hi s f e a t ur e i s c ons i de r e d t o a r i s e f r om t he ge om e t r i c e f f e c t s of c r us t a l - s c a l e a nom a l i e s . sour c e s of t he a nom a l i e s of gr e a t e s t i nt e ns i t y (nor t h a nd s out he a s t of mount ski nne r ) a r e concealed beneath significant thicknesses of Georgina Basin cover and thus are of uncertain affinity, but are presumably m e t a m or phi c r oc ks of t he ai l e r on Pr ovi n c e , pos s i bl y s ubuni t lPgw 3 of t he Woodgr e e n gr a ni t e com pl e x. ma gne t i c f e a t ur e s of t he va r i ous m a ppe d a nd i nt e r pr e t e d uni t s a r e di s c us s e d unde r t he i r r e s pe c t i ve he a di ngs (s e e Stratigraphy). de t a i l s of obs e r ve d r a di o m e t r i c s i gna t ur e s a r e s i m i l a r l y i nc or por a t e d in the descriptions of mapped units; also noteworthy is the e xpr e s s i on of m a ny f e a t ur e s of c ur r e nt a nd f or m e r dr a i na ge s ys t e m s i n t he r a di om e t r i c da t a . gravity the onl y gr a vi t y da t a on Woodgreen, a ddi t i ona l t o t he na t i ona l nom i na l 1 1 km - s pa c e d c ove r a ge of ge os c i e nc e aus t r a l i a (25 s t a t i ons ), a r e a s e r i e s of gPs- l e ve l l e d 500 m a nd 1 km s t a t i on- s pa c e d r oa d a nd t r a c k t r a ve r s e s c onduc t e d f or ntgs (H a i ne s sur ve ys 2002 ). the s e l a t t e r da t a hi ghl i ght s e ve r a l ne w f e a t ur e s , i nc l udi ng a hi gh t ha t i s c oi nc i de nt w i t h de e pl y s our c e d, nor t hw e s t - t r e ndi ng l i ne a r f e a t ur e s a t mount di xon, a nd a l ow t ha t i s a ppa r e nt l y a s s oc i a t e d w i t h a gr a ni t e i nt r us i on s out h of mount ski nne r hom e s t e a d. The data also demonstrate the lack of significant density contrast between Neoproterozoic basin fill and adjacent gr a ni t i c ba s e m e nt a t mount ski nne r . thi s i s a s c r i be d t o w e l l compacted fine siliciclastic and calcareous sediment in the former. Thus, significant thicknesses of preserved Centralian supe r ba s i n s uc c e s s i ons w i l l not ne c e s s a r i l y ha ve a ny gr a vi t y e xpr e s s i on. re gi ona l gr a vi t y c ha r a c t e r i s t i c s i nc l ude a r a nge f r om - 544 t o - 237 m / s 2 , w i t h va l ue s br oa dl y i nc r e a s i ng f r om nor t h t o s out h. a l ow , e nc om pa s s i ng t he nor t he a s t a nd c e nt r a l e a s t of Figure20. Woodg r e e n gr a ni t e com pl e x. We l l de v e l ope d s- c f a br i c i n m yl oni t i s e d granite. 429200mE 7523264mN, 6 km NW of no 3 B or e .