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Mars: New evidence for origin of some Valles Marineris layered deposits
| Content Provider | Semantic Scholar |
|---|---|
| Author | Scott, David H. |
| Copyright Year | 1993 |
| Abstract | The d i scovery o f l ayered d e p o s i t s i n t h e w a l l s of a deep trough in Lunae Planum [ l ] has i m p l i c a t i o n s f o r t h e o r i g i n of s imi la r -appear ing d e p o s i t s in some canyons o f Va l les Mariner is . A1 though l a y e r i n g i s v i s i b l e in t h e competent, c l i f f fo rming upper w a l l s of t h e canyons, t h e d i s s i m i l a r i t y in appearance between canyon wall s and s o f t rounded h i l l s of 1 ayered d e p o s i t s on canyon f l o o r s , a s well a s t h e i r c o n t r a s t i n g p a t t e r n s of e r o s i o n , has been considered s t r o n g evidence t h a t t h e i r modes of o r i g i n were d i f f e r e n t . Most workers agree t h a t t h e wall rocks a r e vo lcan ic f lows der ived from f i s s u r e ven t s and o t h e r vo lcan ic sources in t h e region [2-51. However, several hypotheses have been advanced t o account f o r t h e s o f t e r a p p e a r i n g s t r a t i f i e d f l o o r d e p o s i t s . Chief among them i s t h e proposal t h a t t h e f l o o r d e p o s i t s a r e w a t e r l a i d sediments t h a t accumulated in l a r g e l a k e s wi th in t h e canyons and include m a t e r i a l s eroded from canyon w a l l s , e o l i a n d e p o s i t s , and subaqueous vo lcan ic e r u p t i v e s [ 2 , 6 , 7 , a ] . The trough on t h e Lunae Planum p la teau i s about 1000 m deep and exposes e i g h t l i g h t and dark l a y e r s (Fig . 1 ) . No s t r a t i g r a p h i c break i s v i s i b l e in t h e w a l l s o f t h e t rough , which probably c o n s i s t of a sequence of l a v a flows and i nterbedded pyrocl a s t i c materi a1 s t h a t form t h e r idged p l a i n s geologic u n i t . These l a v a flows cover t h e s u r f a c e of Lunae Planum and a r e Hesperian in age [ 1 , 4 ] ; an a l t e r n a t e i n t e r p r e t a t i o n [9] p laces t h e lower p a r t of t h e layered mate r ia l in t h e Noachian Per iod. The in terbedded vo lcan ic m a t e r i a l s c l o s e l y resemble l ayered d e p o s i t s t h a t form a h i l l i n Juventae Chasma (F ig . 2) more than 1500 km t o t h e sou th ; in both p l a c e s t h e a t t i t u d e , t h i c k n e s s , and albedo c o n t r a s t s of l a y e r s appear t o be s i m i l a r , al though more individual beds a r e exposed in t h e 2000-m-deep Juventae Chasma [ l o ] . Although many i n v e s t i g a t o r s have favored l a c u s t r i n e depos i t ion f o r t h e l ayered d e p o s i t s in t h e canyons of Va l les Mar iner i s , o t h e r s have considered t h a t deep f i l l i n g of t h e canyons was improbable [ l l ] , o r t h a t r es idence t imes o f water were i n s u f f i c i e n t t o account f o r t h i c k accumulations of sedimentary m a t e r i a l [12]; they i n t e r p r e t e d t h e layered d e p o s i t s t o be remnants o f t h e a d j a c e n t p la teau mate r ia l (which a t Juventae Chasma c o n s i s t s of r idged p l a i n s l a v a flows and poss ib ly o l d e r vo lcan ics o f Late Noachian age [ 4 , 1 3 ] ) . Th i s i n t e r p r e t a t i o n i s now supported by t h e l a y e r i n g found i n t h e l a v a flows of Lunae Planum. I t i s e s p e c i a l l y a p p l i c a b l e t o Juventae Chasma, where stream1 ined blocks wi th in c h a o t i c t e r r a i n on t h e re1 a t i v e l y shal low chasma f l o o r a t t e s t t o a s h o r t dura t ion of ponded water . |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.lpi.usra.edu/meetings/lpsc1993/pdf/1634.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
