Woodgreen, Northern Territory : explanatory notes
Northern Territory Geological Survey
E-Publications; E-Books; PublicationNT; Australia 1:100 000 Geological Map Series
2007
Australia 1:100 000 Geological Map Wood 5458; Australia 1:250 000 Geological MapAlcoota SF5310; Australia 1:250 000 Geological MapAlcoota SF5310
1:100 000
Made available via the Publications (Legal Deposit) Act 2004 (NT); Available from GEMIS - Geoscience Exploration and Mining Information System
English
Geology; Georgina Basin; Arunta Region
Northern Territory Government; Northern Territory Government
Darwin
1st ed.
Australia 1:100 000 Geological Map Series
application/pdf
9780724571321
0811-6296
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
https://creativecommons.org/licenses/by/4.0/
https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81885 [GEMIS]
https://hdl.handle.net/10070/794795
https://hdl.handle.net/10070/794807
17 T he T ops M e m be r c ont a i ns a body f os s i l a s s e m bl a ge r e f e r r e d t o a s t he M ount S ki nne r f a una ( W a de 196 9) a nd r a r e i c hnof os s i l s ( H a i ne s et al 1991) . T he M ount S ki nne r f a un a i nc l ude s s e ve r a l s of t - bodi e d or ga ni s m s , m os t c ha r a c t e r i s t i c a l l y , t w o s pe c i e s i nt e r pr e t e d a s s c yphoz oa n medusoids ( ellyfish'), H allidaya brueri a nd Sk innera brook si, w hi c h w e r e de s c r i be d by W a de ( 1969) f r om t he M ou nt S ki nne r a r e a . el e m e nt s of t he M ount S ki nne r f a una ha ve a l s o be e n l oc a t e d i n t he l ow e r A r um be r a S a nds t one of t h e A m a de us B a s i n ( W a de 1969) a nd a r e be l i e ve d t o be of edi a c a r a n a ge ( H a i ne s et al 1991) . T he f os s i l s a r e m os t c om m on i n t he M ount S ki nne r a r e a w he r e t he y a r e f oun d ove r a n i nt e r va l br oa dl y c oi nc i de nt w i t h t he gr e e n c upr i f e r ous ba nds ( f os s i l s a r e f ound i n bot h t he r e d a nd gr e e n l i t hof a c i e s ) . M a c r of os s i l s ym bol s on t he m a p r e c or d Wade's (19 9) original collection localities and additional s i t e s l oc a t e d dur i ng t hi s s t udy . Adnera M ember ( LPsa) T he A dne r a M e m be r c om pr i s e s r e d- br ow n, pur pl e a nd w hi t e c r os s be dde d, m e di um s a nds t on e a nd qua r t z i t e . T he r e a r e intervals of tabular, fine to medium sandstone interbedded w i t h r e d- br ow n m uds t one t ha t c l os e l y r e s e m bl e pa r t s of t he T ops M e m be r . T he A dne r a M e m be r c onf or m a bl y ove r l i e s t he T ops M e m be r a nd t he bounda r y i s l i ke l y t o be di a c hr onous . I t i s di s t i ngui s he d by t he f a c t t ha t t he s a nds t one s a r e m os t l y significantly cleaner, better silicified and more resistant than t he u nde r l yi ng T ops M e m be r . T he uni t i s m os t l y de voi d of pos i t i ve r a di om e t r i c e xpr e s s i on, e xc e pt f or e xpos ur e s a t a nd ne a r M ount S ki nne r t ha t e xhi bi t a m ode r a t e T h s i gna l . T he uni t a s a w hol e i s m or e r e s i s t a nt t o e r os i on t ha n t he T ops M e m be r a nd, f or t hi s r e a s on, t he c ont a c t i s of t e n m os t s uc c e s s f ul l y pi c ke d on a e r i a l phot ogr a ph e xpr e s s i on. T he m e m be r ha s not be e n i nt e r s e c t e d i n dr i l l hol e s . I t i s e s t i m a t e d t o r e a c h a bout 200 m t hi c kne s s i n c e nt r a l - nor t he r n W oodgreen. U nc onf or m i t i e s be l ow younge r uni t s i ndi c a t e t ha t t he m e m be r ha s be e n l oc a l l y r e m ove d i n e a s t e r n a r e a s . T he A dne r a M e m be r w a s de pos i t e d unde r s ha l l ow - m a r i ne a nd de l t a i c c ondi t i ons , s i m i l a r t o t hos e i nt e r pr e t e d f or t he uppe r T ops M e m be r . H a i ne s et al ( 1991) r e por t e d i c hnof os s i l s f r om t he A dne r a M e m be r i n B A rroW C reeK , a l t h ough a s ye t , none ha s be e n f ound i n W oodgreen. T he i c hn of os s i l a s s e m bl a ge i nc l ude s f or m s t ha t a r e m or e c ha r a c t e r i s t i c of t he l a t e ne opr ot e r oz oi c t ha n t he C a m br i a n a nd, i m por t a nt l y , t he m os t c ha r a c t e r i s t i c ea r l y C a m br i a n e l e m e nt s , s uc h a s Treptichnus pedum, a r e a bs e nt . W hi l e i t i s pos s i bl e t ha t t he edi a c a r a nC a m br i a n bounda r y l i e s w i t hi n t he A dne r a M e m be r , i t i s c ons i de r e d m or e l i ke l y t ha t t he bounda r y l i e s w i t hi n t he hi a t us m a r ki ng t he di s c onf or m i t y a t t he t op of t he C e nt r a l M ount S t ua r t F or m a t i on. C A M B rI A n Sh adow Grou p Octy Formation (_Clo) dur i ng pr e vi ous m a ppi ng ( S ha w a nd W a r r e n 1975) , s t r a t a now r e c ogni s e d a s oc t y F or m a t i on w e r e i nc l ude d i n the Central Mount Stuart beds'. The type section of the oc t y F or m a t i on i s i n B A rroW C reeK ( H a i ne s et al 1991) . T he f or m a t i on c om pr i s e s pr e dom i na nt l y w hi t e t o br ow n, c r os s be dde d m e di um s a nds t one a nd qua r t z i t e , w i t h s ubor di na t e m uds t one . I n pl a c e s , t he s e di m e nt s a r e gl a uc oni t i c . on l i t hol ogi c a l gr ounds , t h e f or m a t i on i s onl y di f f e r e nt i a t e d f r om t he unde r l yi ng A dn e r a M e m be r w i t h difficulty; however it is awarded formation status on the ba s i s t ha t m a pp i ng i n B A rroW C reeK de m on s t r a t e d a di s c onf or m i t y t o l ow - a ngl e unc onf or m i t y a t i t s ba s e . T he oc t y F or m a t i on i s a l s o di s t i ngui s ha bl e f r om t he A dne r a M e m be r i n L a nds a t 7 i m a ge r y , pa r t i c ul a r l y ba nd 7. T he most distinctive feature is the common presence of definitive ea r l y C a m br i a n i c hn of os s i l s , w hi c h a r e a bs e nt f r om t he unde r l yi ng s uc c e s s i on. I c hnof os s i l s i nc l ude a di ve r s i t y of f or m s , a m ong t he m Treptichnus ( Phycodes' ) pedum, us e d t o define the base of the Cambrian (Landing 1994). The lower f or m a t i on c ont a c t i s not w e l l e xpos e d i n W oodgreen, but does not appear to be significantly angular. At 409500mE 7563600m n, a n e xpl or a t i on c os t e a n e xpos e s a r e c e s s i ve i nt e r va l a t t he ba s e of t he oc t y F or m a t i on. T hi s i nt e r va l c om pr i s e s bi ot ur ba t e d gr e e n, pur pl e a nd r e d m uds t one a nd i nt e r be dde d s a nds t one , a nd i s pr oba bl y e qui va l e nt t o a Figu re 18 . T ops M e m be r of C e nt r a l M oun t S t ua r t F or m a t i on. expl or a t i on c os t e a n e xpos i ng c ha r a c t e r i s t i c r e d - br ow n s a nds t one a nd m uds t one , w i t h gr e e n m uds t one - dom i na t e d i nt e r va l i n f or e gr ound ( be ne a t h h a m m e r a t bot t om r i ght ) . S uc h gr e e n i nt e r va l s t ypi c a l l y di s pl a y m i nor malachite staining at surface. 429223mE 7543511mN, 3 km N of Mount Skinner.