Analysis of Fluvial Depositional Systems...ANALYSIS OF FLUVIAL DEPOSITIONAL SYSTEMS 1. Sediment...

Analysis of Fluvial Depositional Systems

Andrew D. Miall University of Toronto

Originally presented at the American Association of Petroleum Geologists

Fall Education Conference, Calgary, 1981.

ANALYSIS OF FLUVIAL DEPOSITIONAL SYSTEMS 1. Sediment types and transport modes __________________________ 2

1.1 Debris flows ______________________________________ 2 1.2 Bedload _________________________________________ 3 1.3 Suspended load __________________________________ 3

2. Channel morphology ______________________________________ 4 2.1 Definition of channel types __________________________ 4 2.2 Controls of channel morphology ______________________ 5

3. Methods of facies analysis __________________________________ 10 3.1 Lithofacies types __________________________________ 10 3.2 Lithofacies associations and vertical profiles ____________ 12 3.3 Paleocurrent analysis ______________________________ 17

4. Bars ___________________________________________________ 20 4.1 Planar or massive bedded bars ______________________ 21 4.2 Simple foreset bars _________________________________ 23 4.3 Compound bars __________________________________ 23

5. Facies models for alluvial fans and braided rivers _________________ 23 5.1 Trollheim type ____________________________________ 25 5.2 Scott type _______________________________________ 28 5.3 Donjek type ______________________________________ 28 5.4 South Saskatchewan type __________________________ 30 5.5 Platte type _______________________________________ 31 5.6 Bijou Creek type __________________________________ 32

6. Facies models for meandering rivers __________________________ 32 6.1 The basic model ___________________________________ 33 6.2 Muddy fine-grained rivers ____________________________ 37 6.3 Sandy rivers with thin fine member ____________________ 37 6.4 Sandy rivers without mud or gravel ____________________ 37 6.5 Gravelly sand-bed rivers ____________________________ 37 6.6 Gravel-dominated rivers ____________________________ 38

7. Facies model for anastomosing rivers _________________________ 38 8. Recognition of large rivers __________________________________ 40 9. Large scale fluvial cycles ___________________________________ 40

9.1 Cycles of vertical aggradation ________________________ 43 9.2 Cycles related to variations in basin margin relief _________ 44

10. Other complications ______________________________________ 46 10.1 Importance of geological age ________________________ 46 10.2 Syndepositional tectonics ___________________________ 49 10.3 Climatic controls __________________________________ 52

11. Basin architecture and tectonic setting ________________________ 52 12. Fuels and minerals in fluvial deposits _________________________ 56

12.1 Placer deposits ___________________________________ 60 12.2 Coal ___________________________________________ 62 12.3 Secondary deposits _______________________________ 62

ANALYSIS OF FLUVIAL DEPOSITIONAL SYSTEMS

1. Sediment t y p e s and t r a n s p o r t modes

F l u v i a l d e p o s i t s a r e predominant ly c l a s t i c , and range i n g r a i n s i z e

from g i a n t b o u l d e r s t o t h e f i n e s t c l a y . Coal i s commonly a s s o c i a t e d w i t h

f l u v i a l s ed imen t s , and some sequences c o n t a i n ca rbona te c o n c r e t i o n s r e p r e s e n t i n g

f o s s i l s o i l h o r i z o n s .

Sediment is t r a n s p o r t e d i n t h r e e ways:

1.1 Debr i s f lows: These c o n s i s t o f poo r ly s o r t e d masses o f sed iment , which

f low a s a cohes ive body when s a t u r a t e d w i t h w a t e r . They r e q u i r e a s t e e p

s l o p e , an abundance of c l a s t i c d e b r i s and a h igh d i s c h a r g e f o r t h e i r i n i t i a t i o n .

These c o n d i t i o n s a r e commonly met i n a r i d o r semi-arid environments o r where

v e g e t a t i o n cover h a s been removed by logg ing o p e r a t i o n s o r f i r e . I n such

s e t t i n g s c l a s t i c d e b r i s i s gene ra t ed by mechanica l wea the r ing p r o c e s s e s , and

i s removed a s d e b r i s f l ows du r ing i n f r e q u e n t f l a s h f l o o d s . Vege ta t i on and

t h e p re sence of s o i l cover w i t h i t s r o o t network i n h i b i t r a p i d r u n o f f , and

s o d e b r i s f lows a r e r a r e i n humid c l i m a t e s . They u s u a l l y ex tend o n l y a few

k i l o m e t r e s from a mountainous sou rce a r e a i n t o t h e a l l u v i a l p l a i n , and a r e

most t y p i c a l of a l l u v i a l f a n s ( B u l l , 1977; Rus t , 1979; s e e S e c t i o n 5 ) .

Debr i s f low d e p o s i t s a r e l o b a t e i n o u t l i n e . They can u s u a l l y be

recognized i n a n c i e n t d e p o s i t s by t h e i r poor s o r t i n g , l a r g e g r a i n s i z e r ange ,

mat r ix-suppor ted framework, and l a c k of i n t e r n a l s t r u c t u r e o r c l a s t o r i e n t a t i o n .

F l a t c l a s t s r a r e l y a r e s u b h o r i z o n t a l o r v e r t i c a l , b u t t h e o r i e n t a t i o n

normal ly i s n o t c o n s i s t e n t .

Billy

Highlight

Billy

Highlight

1 . 2 Bedload: In most r i v e r s t h e c o a r s e s t sediment i s t r a n s p o r t e d a s

i n d i v i d u a l g r a i n s r o l l i n g , s l i d i n g o r bouncing a l o n g t h e bed . The bedload

may c o n s i s t of sand o r g r a v e l o r bo th . Gra in s i z e d i s t r i b u t i o n is governed

by t h e competence (power) of t h e f low, and v a r i e s mainly i n r e sponse t o f low

v e l o c i t y . The bedload i s noncohes ive , and i s moulded i n t o a v a r i e t y of

b a r s and bedforms by t h e f low. The l a t t e r i n c l u d e such forms a s r i p p l e s ,

megar ipples o r dunes , and sand waves, e a c h o f which i s s t a b l e under c e r t a i n

f low c o n d i t i o n s governed by f low dep th , v e l o c i t y and bedload g r a i n s i z e

(Harms e t a l . , 1975) . A v a r i e t y of sedimentary s t r u c t u r e s r e s u l t s .

The h i g h e s t f low energy and t h e c o a r s e s t bedload normally a r e conf ined

t o channe l s , but f low may ove r top channel banks d u r i n g p e r i o d s of h i g h

d i s c h a r g e , i n which c a s e some bedload w i l l b e d e p o s i t e d on f loodp la ins .

On many a l l u v i a l f a n s and i n a r i d t o semi-ar id a r e a s channels may be sha l low

and poor ly d e f i n e d , i n which c a s e much of t h e runoff and bedload i s sp read

ou t over wide a r e a s a s s h e e t f l o o d s .

1.3 Suspended l oad : Mud and d i l t a r e c a r r i e d i n suspens ion . I n a c t i v e

channels w i t h abundant sand o r g r a v e l bedload energy l e v e l s normally a r e

t oo h i g h f o r s ed imen ta t ion of t h e suspended load t o occu r . Mud and s i l t

l a y e r s t h e r e f o r e a r e most t y p i c a l of overbank ( f l o o d p l a i n ) a r e a s where t h e

f i n e sediment s e t t l e s o u t of suspens ion from s lowly moving o r s t a t i c f l o o d

wa te r s . Vege ta t ion may provide a sediment t r a p . I n areas of ephemeral

f low mud and s i l t may be d e p o s i t e d from p o o l s of s t a n d i n g wa te r a f t e r t h e

passage of a f l a s h f l o o d .

The b u l k of t h e suspended load i n most r i v e r s i s c a r r i e d o u t t o s e a ,

where c l a y p a r t i c l e s a r e f l o c c u l a t e d i n t o l a r g e r g r a i n s . The s i l t and

mud a r e depos i t ed on d e l t a f r o n t o r p r o d e l t a a r e a s , t i d a l f l a t s o r submarine f a n s .

Billy

Highlight

Billy

Highlight

2. Channel morphology

2 . 1 D e f i n i t i o n of channel t ypes : The most impor tant c o n t r o l on t h e

geometry of f l u v i a l d e p o s i t s i s channel morphology. Th i s i s de f ined us ing

two pa rame te r s , s i n u o s i t y and a b r a i d i n g parameter (Rus t , 1978a) .

S i n u o s i t y i s d e f i n e d as t h e r a t i o of thalweg l e n g t h t o v a l l e y l e n g t h .

The thalweg i s t h e l i n e of deepes t channel . Va l l ey l e n g t h is t h e s t r a i g h t

l i n e d i s t a n c e down t h a t p a r t of t h e v a l l e y over which t h e thalweg l e n g t h

is measured. R ive r s a r e d iv ided a r b i t r a r i l y i n t o those of h i g h s i n u o s i t y

(>1.5) and low s i n u o s i t y ( (1 .5 ) .

The b r a i d i n g parameter (B.P.) measures t h e number of b a r s o r i s l a n d s

i n t h e channe l , and t h u s a l s o d e f i n e s t h e channel m u l t i p l i c i t y . Rust (1978a)

sugges ted t h a t each b r a i d o r i s l a n d b e de f ined by us ing t h e mid-l ine of t h e

channels sur rounding i t . T h e o r e t i c a l l y t h i s avo ids t h e problem t h a t t h e

number of b a r s o r i s l a n d s i n c r e a s e s a s water Level d r o p s , a l t hough i n p r a c t i c e

it i s d i f f i c u l t t o d e f i n e channels o r submerged i s l a n d s i f a r i v e r i s i n

f u l l f l o o d . The b r a i d i n g parameter i s de f ined as t h e number of b a r s o r

i s l a n d s p e r meander wavelength. S i n g l e channel r i v e r s are t h o s e w i t h a

b r a i d i n g parameter l e s s than 1, and m u l t i p l e channel r i v e r s a r e t hose w i t h

a b r a i d i n g parameter g r e a t e r t han 1.

These two i n d i c e s d e f i n e f o u r b a s i c channel t ypes (Table l ) , a s

i l l u s t r a t e d i n F i g u r e 1.

Table 1: channel c l a s s i f i c a t i o n

s ingle-channel mu1 t ip l e -channe l s i n u o s i t y (B.P. <1) (B.P. ; 1)

low(< 1 .5) s t r a i g h t h i g h f' 1 .5 ) meandering

b r a i d e d anastomosing

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Braided r i v e r s a r e c h a r a c t e r i z e d by h i g h wid th /dep th r a t i o s , normally g r e a t e r

than 40 and commonly exceeding 300. Leopold and Wolman (1957) found t h a t

t hey have s t e e p e r s l o p e s t h a n o t h e r t y p e s of r i v e n , i n t h e equat ion:

S = 0.0134 - 0 . 4 4

where S i s s l o p e and Q is b a n k f u l l d i s c h a r g e i n m3/sec , f o r a g iven d i s c h a r g e

b ra ided r i v e r s have a s l o p e s t e e p e r t han t h a t g iven by t h e e q u a t i o n , whereas

meandering r i v e r s have g e n t l e r s l o p e s .

Meandering r i v e r s have wid th ldep th r a t i o s l e s s t han 40, and f o r anastornosing

r i v e r s t h e r a t i o may be l e s s t han 10.

Schurnrn (1960, 1963) a t tempted t o c l a s s i f y r i v e r s i n t o bedload , mixed-load

and suspended-load r i v e r s . Meandering and anastornosed r i v e r s were thought t o

be of mixed- o r suspended-load t y p e , whereas b ra ided r i v e r s were s t a t e d t o be

of bedload type . However, a s po in t ed o u t by M i a l l (1977) and Jackson (1978)

t h e r e a r e many e x c e p t i o n s t o t h i s c l a s s i f i c a t i o n . Braided r i v e r s a r e

i n v a r i a b l y of bedload type bu t h igh s i n u o s i t y (meandering) r i v e r s can a l s o

t r a n s p o r t abundant c o a r s e bedload .

2 . 2 C o n t r o l s of channel morphology: Th i s i s an ext remely complex s u b j e c t .

A t l e a s t t e n v a r i a b l e s i n t e r a c t t o govern channel behaviour . These a r e

d i scha rge (amount and v a r i a b i l i t y ) , sediment l o a d (amount and g r a i n s i z e ) ,

w id th , d e p t h , v e l o c i t y , s l o p e , bed roughness and bank v e g e t a t i o n d e n s i t y

(Leopold and Wolman, 1957; Schumm, 1960, 1963, 1968) . Each of t h e s e is

a f f e c t e d by c l i m a t i c and g e o l o g i c a l v a r i a b l e s , such a s r a i n f a l l , s e a s o n a l

tempera ture v a r i a t i o n , and r e g i o n a l s l o p e . It is no t y e t p o s s i b l e t o d e f i n e

t h e ranges of v a l u e s t h a t w i l l i n v a r i a b l y produce a r i v e r of a g iven t y p e ,

a l t hough some g e n e r a l i z a t i o n s can be made.

Bra id ing i s favoured by s t e e p s l o p e s , an abundance of c o a r s e bedload ,

h i g h l y v a r i a b l e d i scha rge and e a s i l y eroded banks. Leopold and Wolman (1957)

s t a t e d : "b ra id ing i s developed by s o r t i n g a s t h e s t r eam l e a v e s behind those

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

s i z e s of t h e l o a d which i t i s incompetent t o handle ... i f t h e s t r eam i s

competent t o move a l l s i z e s comprising t h e load b u t i s unable t o move t h e

t o t a l q u a n t i t y provided t o i t , than aggrada t ion may t a k e p l a c e wi thou t

bra id ing" . Depos i t ion of bedload r e s u l t s i n t h e development of v a r i o u s

b a r s and bedforms. These impede and d i v e r t t h e f low, a p rocess which i s

f a c i l i t a t e d i f t h e banks a r e e a s i l y e roded, a l t hough bank e r o s i o n i t s e l f

s e r v e s t o i n c r e a s e t h e bedload . I n r i v e r s of h i g h l y v a r i a b l e d i s c h a r g e

competency i s s i m i l a r l y v a r i a b l e , and t h e r e w i l l be extended p e r i o d s of

t ime du r ing which t h e r i v e r w i l l be unable t o move a l l i t s bedload . The

inc idence of b a r i n i t i a t i o n , f low d i v e r s i o n , and t h e c r e a t i o n of new

channels ( b r a i d i n g ) w i l l t h u s by h i g h ( M i a l l , 1977).

The causes of v a r i a b l e disc-harge and abundant bedload a r e d i v e r s e .

Alpine and A r c t i c r e g i o n s a r e c h a r a c t e r i z e d by s t r o n g l y s e a s o n a l r u n o f f ;

i n a r i d r eg ions runoff may on ly occu r a t i n t e r v a l s of months o r y e a r s .

I n both c a s e s v e g e t a t i o n is s p a r s e , s o t h a t r a p i d runoff is f a c i l i t a t e d ,

and abundant c o a r s e d e b r i s i s provided by mechanical weather ing p rocesses .

G l a c i a l outwash s t r eams a l s o c o n t a i n abundant bedload and a r e almost

i n v a r i a b l y b ra ided .

Meandering is favoured by a predominance of suspended l o a d , cohes ive

banks and g e n t l e s l o p e s . Banks composed of c l a y a r e f a r l e s s e a s i l y eroded

than t h o s e c o n s i s t i n g of unconso l ida t ed sand and g r a v e l . Where t h e banks

a r e p e n e t r a t e d by a dense r o o t network t h e i r s t a b i l i t y i s i n c r e a s e d cons ide rab ly

a s proved expe r imen ta l ly by Smith (1976) . Bank s t a b i l i t y r e s u l t s i n a low

width / d e p t h r a t i o , and meandering p a t t e r n s tend t o develop , even i f t h e

r i v e r i s c a r r y i n g a c o a r s e bedload.

straight

meander~ng

anastomoslng

bar surfaces covered during fbod stages

bra~ded

Fig. 1 The f o u r p r i n c i p a l r i v e r t y p e s (from M i a l l , 1977).

b / RANK 3.

_----

RANK 6. RANK 4.

F i g . 3 The bedform h ie ra rchy . The s m a l l square i n each diagram r e p r e s e n t s t h e a r e a enlarged i n t h e diagram f o r t h e nex t rank. Rose diagrams i n d i c a t e t h e d i r e c t i o n a l v a r i a b i l i t y t o be expected a t each rank; 1. o r i e n t a t i o n of r i v e r systems, 2 . channels w i t h i n a system, 3 . meanders, 4 . b a r s w i t h i n a meander reach , 5. Crossbedding f l a n k i n g a l i n g u o i d b a r , 6 . r i p p l e f o r e s e t s ( b i f u r c a t i n g l i n e s r e p r e s e n t r i p p l e c r e s t s ) (from M i a l l , 1974) .

Anastomosing r i v e r s a r e c h a r a c t e r i z e d by two o r more s t a b l e channels

e x h i b i t i n g low t o high s i n u o s i t y . They seem t o occur i n a r e a s where there is

rap id subsidence but where s l o p e s grade t o a s t a b l e base l e v e l and remain

l o w (Smith and Smith, 1980; Smith and Putnam, 1980). Channel s t a b i l i t y

i s favoured by abundant bank v e g e t a t i o n .

S t r a i g h t r i v e r s a r e n o t common, and few have been recognized from

a n c i e n t d e p o s i t s . A t t h e p r e s e n t day they occur mainly a s d e l t a d i s t r i b u t a r i e s

where t h e s l o p e is extremely low (e .g . M i s s i s s i p p i d e l t a ) .

Many of our c u r r e n t i d e a s about f l u v i a l morphology and i t s c o n t r o l s

r e f l e c t t h e f a c t t h a t most geomorphic work has been c a r r i e d ou t i n a few

c l i m a t i c regimes, p a r t i c u l a r l y ho t -a r id , temperate-humid f l u v i o g l a c i a I

regimes. L i t t l e i s known about tropical-humid c l imates .

Baker (1978) desc r ibed an example of a complex morphological p a t t e r n

i n a t r o p i c a l c l i m a t e , t h e Amazon Basin , and t h i s s e r v e s a s an example of

some of t h e d i f f i c u l t i e s t h a t f l u v i a l sed imento log i s t s a r e l i k e l y t o encounter

i n ana lys ing a n c i e n t rocks formed i n a s i m i l a r environment. Adjacent

t r i b u t a r i e s i n t h e upper Amazon Basin a r e of widely va ry ing morphology

(Figure 2 ) . I n p lan view they range from t y p i c a l meandering systems

t o n e a r l y s t r a i g h t r i v e r s wi th few i s l a n d s . None of t h e s e r i v e r s c a r r y

l a r g e q u a n t i t i e s of bedload, a l though some t r a n s p o r t an enormous suspended

load. The d i f f e r e n c e s r e l a t e , i n p a r t , t o t h e l o c a t i o n of t h e headwaters.

Mixed load s t reams , such a s t h e Solimoes and Japura , r i s e i n a r e a s of r e l i c t

c o a r s e a l luvium formed dur ing e a r l i e r , d r i e r , g l a c i a l phases , whereas

suspended load r i v e r s such a s t h e Ju rua a r e de r ived from s h i e l d a r e a s

which l a c k t h i s r e a d i l y eroded sediment source . The s t r a i g h t e r r i v e r s a r e

those wi th headwaters i n t h e Andes; they have a l a r g e seasona l d i scharge

v a r i a b i l i t y . Vegeta t ion is extremely dense. It s t a b i l i z e s banks and i s l a n d s ,

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

and i n h i b i t s meandering and t h e development o f t r u e b r a i d i n g .

River morphology can change downstream i n response t o changes i n t h e

c o n t r o l l i n g v a r i a b l e s . Adjacent t r i b u t a r i e s may show d i f f e r e n t c h a r a c t e r i s t i c s ,

a s i n t h e example j u s t d i scussed . Morphology may a l s o change w i t h t ime a s

a r e s u l t of c l i m a t e change, change i n s l o p e e t c . A l l t h e s e p o i n t s should

be borne i n mind when ana lyz ing a n c i e n t f l u v i a l d e p o s i t s .

3 . Methods of f a c i e s a n a l y s i s

Sys t ema t i c s t u d y of f l u v i a l d e p o s i t s r e q u i r e s a t l e a s t t h r e e main

s t e p s . F i r s t t h e major and minor l i t h o f a c i e s components must be i d e n t i f i e d

and desc r ibed . Secondly, t h e s e should be s t u d i e d t o de termine impor tant

l i t h o f a c i e s a s s o c i a t i o n s and i n t e r n a l r e l a t i o n s h i p s ; and t h i r d l y t h e

geometry and o r i e n t a t i o n of t h e d e p o s i t i o n a l u n i t s should be s t u d i e d . A

s e r i e s of f a c i e s models i s a v a i l a b l e w i t h which t h e r e s u l t s of t h e s e

a n a l y s e s can be compared i n o r d e r t o a r r i v e a t a s a t i s f a c t o r y i n t e r p r e t a t i o n .

These s t e p s a r e taken one a t a t ime i n t h e fo l lowing d i s c u s s i o n :

3 . 1 L i t h o f a c i e s t ypes : It has been found t h a t most f l u v i a l d e p o s i t s

can be s a t i s f a c t o r i l y desc r ibed us ing a s e t of approximate ly twenty s t a n d a r d

l i t h o f a c i e s t ypes ( M i a l l , 1977, 1978a) . These have been a s s igned c o ~ l e

l e t t e r s f o r convenience i n logging , n o t e t a k i n g and i l l u s t r a t i o n . The codes

a r e i n two p a r t s . The f i r s t p a r t c o n s i s t s of t h e c a p i t a l l e t t e r G , S o r F ,

which s t and f o r g r a v e l , sand o r f i n e s ( s i l t a n d / o r mud). The second p a r t

of t h e code c o n s i s t s of one o r two l e t t e r s des igned a s mnemonics f o r t h e

most c h a r a c t e r i s t i c f e a t u r e of t h e l i t h o f a c i e s , e . g . G m s f o r mat r ix-suppor ted

g r a v e l , Sp f o r p l a n a r cross-bedded s a n d , e t c .

The p r i n c i p a l l i t h o f a c i e s a r e l i s t e d i n Tab le 2 , w i t h b r i e f n o t e s on

t h e i r composi t ion , s t r u c t u r e and i n t e r p r e t a t i o n . Greek l e t t e r s f o r sedimentary

s t r u c t u r e s r e f e r t o t h e c l a s s i f i c a t i o n of A l l en (1963a). F u l l e r d e s c r i p t i o n s

a r e t o be found i n M i a l l (1977, 1978a) .

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

T a b l e 2 L i t h o f a c i e s a n d s e d i m e n t a r y s t r u c t u r e s o f f l u v i a l d e p o s i t s ( f r o m Miall, 1978a).

Fscler Cock Lithofacies Sdimontary structures Interpmtatlon

none debris flow deposits

Gms massive, matrix supported gravel

Gm massive or crudely bedded gravel

horizontal bedding, imbrication

longitudinal bars, lag deposits, sieve deposits

trough crossbeds

planar crossbeds

minor channel fills Gt gravel, stratified

linguoid bars or deltaic growths from older bar remnants

Gp gravel, stratified

St sand, medium to v. coarse, may be pebbly

solitary (theta) or grouped (pi) trough crossbeds

dunes (lower flow regime)

Sp sand, medium to v. coarse, may be pebbly

solitary (alpha) or grouped (omikron) planar crossbeds

linguoid, transverse bars, sand waves (lower flow regime)

Sr sand, very fine to coarse

Sh sand, very fine to very coarse, may be peubly

SI sand, fine

ripple marks of all types horizontal lamination, parting or streaming lineation low angle (< lo0) crossbeds

ripples (lower flow regime) planar bed flow (I. and u. flow regime)

scour fills, crevasse splays, antidunes

Se erosional scours with intraclasts

crude crossbedding scour fills

Ss sand, fine to coarse, may be pebbly

broad, shallow scours including eta cross- stratification

scour fills

Sse, She, Spe sand analogous to Ss, Sh, Sp eolian deposits

Fl sand, silt, mud fine lamination, very small ripples

overbank or waning flood deposits

backswamp deposits

backswamp pond deposits

Fsc silt, mud

Fcf mud

laminated to massive

massive, with freshwater molluscs

Fm mud, silt massive, desiccation cracks

overbank or drape deposits

Fr silt, mud

C coal, carbonaceous mud

rootlets seatearth

plants, mud films swamp deposits

P carbonate pedogenic features soil

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Care must be taken i n using t h e s e l i t h o f a c i e s codes f o r d e s c r i p t i v e

and i n t e r p r e t i v e purposes, beczuse they a r e not a u n i v e r s a l panacea f o r

s o r t i n g o u t t h e complexity of f l u v i a l d e p o s i t s . It i s p o s s i b l e f o r s e v e r a l

of them t o be found i n more than one environment w i t h i n a r i v e r ; f o r example

l i t h o f a c i e s Sp could r e p r e s e n t mid-channel l inguo id o r t r a n s v e r s e b a r s

o r sand waves migrat ing a c r o s s a sand f l a t . Fac ies S1 could represen t

crevasse sp lay d e p o s i t s , t h e f i l l of low r e l i e f scours , o r ant idunes . Each

example of each l i t h o f a c i e s must be examined wi th ca re . Evidence of s c a l e ,

g r a i n s i z e , i n t e r n a l s t r u c t u r e s , o r i e n t a t i o n and f a c i e s a s s o c i a t i o n s should

be used t o ensure t h a t u n i t s of d i s s i m i l a r o r i g i n a r e n o t grouped toge the r

under one d e s c r i p t i v e code.

3.2 L i t h o f a c i e s a s s o c i a t i o n s and v e r t i c a l p r o f i l e s : It i s now widely

recognized t h a t most d p o s i t i o n a l environments can be charac te r i zed by

d i s t i n c t i v e a s s o c i a t i o n s of l i t h o f a c i e s . The v e r t i c a l l i t h o f a c i e s a s s o c i a t i o n

( v e r t i c a l p r o f i l e ) i s p a r t i c u l a r l y d i a g n o s t i c , a s was expla ined i n t h e

c l a s s i c paper by Visher (1965).

F l u v i a l sediments a r e s t r o n g l y c y c l i c . Many types of c y c l i c mechanism

opera te , and they can b e c l a s s i f i e d i n t o those of a u t o c y c l i c o r a l l o c y c l i c

o r i g i n (Beerbower, 1964). Autocyclic processes a r e those which occur a s an

i n t e g r a l p a r t of t h e d e p o s i t i o n a l environment, such a s l a t e r a l meander

migrat ion o r seasonal f loods . A l l o c y c l i c processes a r e those e x t e r n a l t o t h e

system, such a s t e c t o n i c even t s o r c l ima te change. The e f f e c t s of s e v e r a l

of these c y c l i c processes may be superimposed, wi th complex r e s u l t s and, a s

a r e s u l t , t h e production of a v e r t i c a l sequence i s n e i t h e r completely random

nor completely d e t e r m i n i s t i c . S t a t i s t i c a l methods of a n a l y s i s a r e t h e most

s a t i s f a c t o r y , and the b e s t a v a i l a b l e technique i s Markov chain a n a l y s i s .

Billy

Highlight

A Markov p rocess i s one " i n which t h e p r o b a b i l i t y of t h e p rocess be ing

i n a g iven s t a t e a t a p a r t i c u l a r t i m e may b e deduced from knowledge o f t h e

immediately p reced ing state" (Harbaugh and Bonham-Carter, 1970, p. 98).

A s a p p l i e d t o sedimentary r o c k s , t h e t echn ique t e s t s f o r a "memory" e f f e c t

c o n t r o l l i n g t h e v e r t i c a l t r a n s i t i o n s from one l i t h o f a c i e s s t a t e t o ano the r .

a n a l y t i c a l methods and some examples of t h e i r a p p l i c a t i o n t o f l u v i a l d e p o s i t s

were f u l l y d e s c r i b e d by Miall (1973), Cant and Walker (1976) and M i a l l and

Gib l ing (1978). There are a v a r i e t y o f Plarkovian methods a v a i l a b l e . The one

desc r ibed h e r e i s a "single-dependency, embedded chain" method (Krumbein and

Dacey, 1969) . The s t a r t i n g p o i n t of t h e a n a l y s i s i s a coded s t r a t i g r a p h i c sequence,

measured e i t h e r i n ou tc rop o r c o r e . An example i s i l l u s t r a t e d i n Table 3 .

The a c q u i s i t i o n o f such d a t a r e q u i r e s p a i n s t a k i n g o b s e r v a t i o n on a n a lmost

cen t ime t re by c e n t i m e t r e s c a l e o v e r cont inuous c o r e o r outcrop f o r t e n s o r

hundreds of me t re s of s e c t i o n . However, t h e e f f o r t i s e s s e n t i a l i f t h e

maximum amount of i n fo rma t ion is t o be g leaned from t h e rocks (Core i s

expens ive and wor th us ing p r o p e r l y ! ) . With p r a c t i c e t h e r a p i d logging

technique d e s c r i b e d below may pe rmi t 200-300 m of c o r e t o be logged p e r day.

Outcrop logg ing normally t a k e s longe r because o f t h e t ime r e q u i r e d t o g a i n

a c c e s s t o every p a r t of a cont inuous exposure .

Outcrop and c o r e should p r e f e r a b l y be logged from t h e base up, a s t h i s

p e r m i t s t h e obse rve r t o s t u d y t h e rocks i n t h e o r d e r t h a t t hey were depos i t ed .

U n i t s a r e a s s igned t o one o r o t h e r of t h e l i t h o f a c i e s l i s t e d i n Tab le 2 , and

t h e a p p r o p r i a t e code noted . It i s a l s o n e c e s s a r y t o observe t h e c o n t a c t s

between u n i t s , as t h i s has impor tant s ed imen to log ica l i m p l i c a t i o n s . An .

e r o s i o n a l base i s i n d i c a t e d by a s l a s h p reced ing t h e l i t h o f a c i e s code; a

g r a d a t i o n a l base o r t op i s i n d i c a t e d by an ar row fo l lowing t h e l i t h o f a c i e s

code. A d d i t i o n a l o b s e r v a t i o n s , such as g r a i n s i z e , minor s t r u c t u r e s e t c . ,

should a l s o be recorded.

Table 3 . Example of p a r t of a coded s t r a t i g r a p h i c sequence

u n i t no. d r i l l i n g l i t h o f a c l e s a d d i t i o n a l o b s e r v a t i o n s dep th t o t o top (m)

b a s a l c o n t a c t obscured

mainly medium ss pebbly a t base+ coa r se 1 0 cm e r o s i o n a l r e l i e f

The sequence is then conver ted t o a t r a n s i t i o n count m a t r i x , which i s

a two-dimensional a r r a y t a b u l a t i n g t h e number of times t h a t a l l p o s s i b l e

v e r t i c a l l i t h o l o g i c t r a n s i t i o n s occu r i n t h e s t r a t i g r a p h i c success ion .

The lower bed of each t r a n s i t i o n c o u p l e t is g iven by t h e row number of

t h e m a t r i x ( s u b s c r i p t i ) and t h e upper bed by t h e column number ( s u b s c r i p t j).

Elements i n t h e a r r a y a r e a s s igned t h e symbol f . T r a n s i t i o n s a r e counted i j

r e g a r d l e s s of l i t h o f a c i e s u n i t t h i c k n e s s . T r a n s i t i o n s between i n d i v i d u a l

beds of t h e same l i t h o f a c i e s are n o t r eco rded , and s o t h e p r i n c i p a l d i agona l

of t h e m a t r i x ( c e l l s where i = j ) c o n s i s t s of a row of ze ros . An example

of a t r a n s i t i o n count m a t r i x de r ived from a s tudy of some Devonian f l u v i a l

rocks i s g iven i n Table 4 (from Miall and G i b l i n g , 1978) .

From t h e t r a n s i t i o n count m a t r i x t h r e e p r o b a b i l i t y m a t r i c e s may be de r ived ,

as fo l lows :

r is a n independant t r i a l s m a t r i x , which r e p r e s e n t s t h e p r o b a b i l i t y of a i j

g iven t r a n s i t i o n o c c u r r i n g randomly. S . i s t h e column t o t a l and t t h e t o t a l 3

number of t r a n s i t i o n s recorded. Values of r depend o n l y on t h e r e l a t i v e i j

abundance of t h e f a c i e s states.

P i s t h e t r a n s i t i o n p r o b a b i l i t y m a t r i x , r eco rd ing t h e a c t u a l p r o b a b i l i t y i j

of occurrence of each t r a n s i t i o n

dij is t h e d i f f e x e n c e ma t r ix . P o s i t i v e e n t r i e s i n d i c a t e which t r a n s i t i o n s

have occurred w i t h g r e a t e r t han random f requency. An example of a d i f f e r e n c e

m a t r i c e s i s given i n Tab le 5 , us ing d a t a from Table 4 .

E i t h e r t h e t r a n s i t i o n p r o b a b i l i t y m a t r i x o r t h e d i f f e r e n c e m a t r i x

may t h e n be used t o c o n s t r u c t one o r more p a t h diagrams showing t h e p r i n c i p a l

c y c l i c r e l a t i o n s h i p s . Tab le 6 shows t h e seven c y c l e t ypes t h a t can be

deduced from t h e d i f f e r e n c e m a t r i x i n Table 5 . Values under "frequency" show

t h e number of t imes t h e s e c y c l e s a c t u a l l y occu r . Commas i n t h e p a t h diagram

i n d i c a t e a l t e r n a t e l i t h o f a c i e s s t a t e s .

Data from s e v e r a l s e c t i o n s may be pooled f o r t h e purpose of a n a l y s i s ,

but o n l y i f t h e d a t a s e t s show s i m i l a r l i t h o f a c i e s sequences. A s t a t i o n a r i t y

t e s t can b e used t o compare two segments of a s t r a t i g r a p h i c success ion o r

two complete s e c t i o n s a g a i n s t one a n o t h e r i n o r d e r t o de termine whether t h e

n a t u r e of t h e c y c l i c i t y v a r i e s between them (Harbaugh and Bonham-Carter , 1970,

p. 124; Miall, 1973, p . 352). Chi-squared t e s t s may be used t o test f o r

s i g n i f i c a n c e , u s ing e i t h e r t h e e n t i r e m a t r i x ( M i a l l , 1973) o r i n d i v i d u a l l i n e s

o r c e l l s of t h e m a t r i x (Hobday, e t a l . , 1975) .

It i s impor tant f o r t h e purpose o f s ed imen to log ica l i n t e r p r e t a t i o n t o

de termine whether c o n t a c t s b e t w e e r , l i t h o f a c f & states a r e e r o s i o n a l o r

g r a d a t i o n a l . G r a d a t i o n a l c o n t a c t s i n d i c a t e g r a d u a l change i n d e p o s i t i o n a l

environment, whereas e r o s i o n a l c o n t a c t s i n d i c a t e r a p i d change and, commonly,

t h e i n i t i a t i o n of a new c y c l i c sequence. To q u a n t i f y o b s e r v a t i o n s of

l i t h o f a c i e s c o n t a c t s a "con tac t mat r ix" i s e r e c t e d (Mia l l and Gib l ing , 1978).

This i s d e r i v e d from two p r e l i m i n a r y m a t r i c e s , a G m a t r i x which t a b u l a t e s i j

Table 4 T r a n s i t i o n count m a t r i x , P e e l Sound Formation, lower member, Somerset I s l a n d (from M i a l l and Gibl ing , 1978) .

Table 5 Di f fe rence mat r ix , d a t a from t a b l e 4 (from Miall and Gib l ing , 1978).

Table 6 Cycle t y p e s and t h e i r occurrence, P e e l Sound Formation, lower member (from M i a l l and G i b l i n g , 1978).

- Type Sequence Frequency Mean thickness

1 / S t + F1 24 2 /St + Sr -* F1, Fm 14 3 /Sp + F1 3 4 /Sp + Sh 1 5 ISp + Sr + Fm, FI 2 6 /Sh + Fm, F1 15 7 /Sr + Fm, F1 10

Table 7 Contact mat r ix , P e e l Sound Formation, lower member (from Miall and Gib l ing , 1978).

t h e number of g r a d a t i o n a l con tac t s occur r ing a t each f a c i e s t r a n s i t i o n ,

and an E ma t r ix , t a b u l a t i n g e r o s i o n a l con tac t s . The contact ma t r ix i j

c o n s i s t s of elements C and is c a l c u l a t e d a s fo l lows: i i

Values i n the con tac t ma t r ix range from +1 t o -1. Negative scores i n d i c a t e

a preponderance of scour ing o r sediment b reaks , p o s i t i v e s c o r e s i n d i c a t e

a dominance of g r a d a t i o n a l c o n t a c t s . Zero s c o r e s i n d i c a t e t h a t t h e two

con tac t types a r e equa l ly common (o r a l a c k of d a t a ) . The con tac t matr ix

f o r t h e Devonian s e c t i o n s i l l u s t r a t e d i n Tables 4 , 5 and 6 i s given i n

Table 7. The l i t h o f a c i e s i n t h i s t a b l e a r e arranged i n o rde r of i n c r e a s i n g

g r a i n s i z e and s t r u c t u r e s c a l e from l e f t t o r i g h t and top t o bottom. C e l l s

below and t o the l e f t of the p r i n c i p a l d iagonal t h e r e f o r e record upward-

f i n i n g t r a n s i t i o n s and, i n Table 7 these a l l have p o s i t i v e scores .

Coarsening-upward t r a n s i t i o n s above and t o t h e r i g h t of t h e p r i n c i p a l

d iagonal , a l l show nega t ive scores . This c l e a r l y confirms t h a t g r a d a t i o n a l

c y c l i c sequences i n t h i s example a r e v i r t u a l l y a l l of upward-fining

charac te r and t b a t each has an e r o s i v e base .

3.3 Paleocurrent a n a l y s i s : Most hydrodynamic sedimentary s t r u c t u r e s

con ta in i n t e r n a l evidence of t h e d i r e c t i o n of t h e cur ren t which formed them.

Regional s t u d i e s of o r i e n t a t i o n w i l l t h e r e f o r e y i e l d u s e f u l information on

paleoslope, t o supplement d a t a obta ined from f a c i e s and isopach maps.

The most u s e f u l s t r u c t u r e s f o r pa leocur ren t purposes a r e :

1. Large s c a l e f o r e s e t s t r u c t u r e s ( t rough and p lanar crossbedding) 2. Ripples ( c r e s t o r f o r e s e t o r i e n t a t i o n ) 3. Channels and scours 4. P a r t i n g l i n e a t i o n 5 . Gravel c l a s t imbricat ion

O r i e n t a t i o n s t u d i e s can r a r e l y be c a r r i e d o u t i n c o r e , u n l e s s t h e r e

i s a r ecogn izab le s t r u c t u r a l d i p t h a t i s known from o t h e r ev idence , which

e n a b l e s t h e c o r e t o be r e -o r i en ted .

Regional p a l e o c u r r e n t p a t t e r n s can be produced by p l o t t i n g l o c a t i o n

d a t a i n a s e r i e s of c u r r e n t r o s e d iagrams, o r by c o n s t r u c t i n g moving

average o r t r e n d maps. Useful i n fo rma t ion on t echn iques and i n t e r p r e t a t i o n

a r e g iven by Al l en (1966), P o t t e r and P e t t i j o h n (1977) and M i a l l (1974).

D e t a i l e d p a l e o c u r r e n t work can y i e l d c o n s i d e r a b l e amount of i n fo rma t ion

about t h e i n t e r n a l geometry of a f l u v i a l d e p o s i t , T h i s may be of p a r t i c u l a r

importance i n p rospec t ing a coa l - o r minera l -bear ing u n i t . For example

both p l a c e r and e p i g e n e t i c o r e s tend t o f o l l o w channel t r e n d s , which c o n t a i n

t h e c o a r s e s t and most porous u n i t s .

Bedforms and sedimentary s t r u c t u r e s i n f l u v i a l - d e l t a i c d e p o s i t s can

be c l a s s i f i e d i n a h i e r a r c h y of s i x r a n k s , r e f l e c t i n g t h e va ry ing s c a l e s of

t h e f low f i e l d s t h a t depos i t ed them (Al l en , 1966; M i a l l , 1974) . The concept

i s i l l u s t r a t e d i n F i g u r e 3 . The r anks a r e a s fo l lows :

1. r i v e r system 2 . meander b e l t 3. channel r each 4. minor channel ; l a t e r a l o r p o i n t b a r 5. dune, sand wave, l i n g u o i d o r t r a n s v e r s e b a r 6. r i p p l e s

F igu re 3 i l l u s t r a t e s t h e range of d i r e c t i o n a l v a r i a b i l i t y t o be expected

from t h e s t r u c t u r e s of each r ank . With in l a r g e ou tc rops i t i s c l e a r t h a t a

g iven assemblage of s t r u c t u r e s might c o n t a i n s e v e r a l s o u r c e s of v a r i a n c e , and

so i t i s e s s e n t i a l t o r e l a t e each observed s t r u c t u r e t o i t s p o s i t i o n i n t h e

sediment body. Its p o s i t i o n w i t h i n a measured s e c t i o n should be r eco rded ,

and i t s r e l a t i o n s h i p t o any r e c o g n i z a b l e c y c l i c p rocess observed . The sampling

p l a n should be chosen t o s u i t p a r t i c u l a r o b j e c t i v e s , and i t may be a d v i s a b l e

i n t h e c a s e o f p a r t i c u l a r l y d e t a i l e d work t o r e c o r d every measurable s t r u c t u r e

t h a t can be seen .

CAPE VESEY HAMILTON MOV. AV. AZIMUTH MOV. AV. SET n THICKNESS

METRES

I LIGNITE 25{=1+ PEBBLE BEDS I

0 SANDS WITH LARGE SCALE CROSSBEDDING

0 OTHER SANDS

AZIMUTH MOV. AV. VARIANCE FORESET DIP GSC

F i g . 5 P a l e o c u r r e n t d a t a from a P l a t t e type b ra ided r i v e r d e p o s i t ( f rom.Mial1, 1976) .

For each s t r u c t u r e i t i s n e c e s s a r y t o r eco rd s t r u c t u r e type (us ing

a c l a s s i f i c a t i o n such as t h a t of A l l e n , 1963a) , i n d i c a t e d c u r r e n t d i r e c t i o n ,

and s t r u c t u r e s i z e ( t h i c k n e s s of c ros sbed , depth of channel , c l a s t s i z e

i n i m b r i c a t e g r a v e l ) . I n d i v i d u a l r e a d i n g s may be p l o t t e d on a s t r a t i g r a p h i c

s e c t i o n , o r s m a l l sets of r e a d i n g s may be grouped t o produce a c u r r e n t

r o s e diagram. F igu re 4 (from Cant , 1978) i l l u s t r a t e s t h e f i r s t method,

and demonst ra tes t h a t i n t h i s s e c t i o n p l a n a r c rossbedding h a s a much h i g h e r

d i r e c t i o n a l v a r i a n c e than t rough crossbedding . T h i s i s a common o b s e r v a t i o n

i n f l u v i a l d e p o s i t s ( M i a l l , 1974); t h e r easons w i l l be d i s c u s s e d i n S e c t i o n 5.

F i g u r e 5 (from M i a l l , 1976) i l l u s t r a t e s p l a n a r c rossbed d a t a measured over a

32 m t h i c k s e c t i o n . A moving ave rage azimuth p l o t and c u r r e n t r o s e diagrams

demonst ra te a 60° swing i n mean az imuth , a change accompanied by a marked

i n c r e a s e i n c rossbed s e t t h i c k n e s s . T h i s s e c t i o n l i e s c l o s e t o t h e edge of a

faul t-bounded b a s i n , and t h e change i n s t r u c t u r e s i z e and o r i e n t a t i o n was

i n t e r p r e t e d as t h e r e s u l t of l o c a l f au l t - i nduced p a l e o s l o p e changes. Many

o t h e r examples of t h e use of d e t a i l e d p a l e o c u r r e n t d a t a could be g iven . The

use of such d a t a i n i n t e r p r e t i n g channel geometry and e r e c t i n g o r t e s t i n g

f a c i e s models w i l l be d i scussed i n S e c t i o n s 5 and 6 .

4. Bars

F l u v i a l channel systems c o n s i s t o f a c t i v e and i n a c t i v e channe l s , b a r s

and s t a b l e (commonly vege ta t ed ) i s l a n d s . Bars r e p r e s e n t a r e a s of n e t sediment

accumulat ion and a r e t h e r e f o r e of c o n s i d e r a b l e i n t e r e s t t o s e d i m e n t o l o g i s t s .

There is a g r e a t d e a l of con fus ion i n t h e f l u v i a l l i t e r a t u r e about what

c o n s t i t u t e s a b a r , and over t h i r t y terms have been used t o name b a r s w i t h

s p e c i f i c shapes , o r i e n t a t i o n s and p o s i t i o n s w i t h i n a channel (Smith, 1978) . A

convenient d e f i n i t i o n of a b a r i s t h a t i t i s a bedform of a s i z e comparable

i n magnitude t o t h a t o f t h e channel i n which i t occur s . Smith (1978) s u g g e s t s

t h a t b a r s should a l s o be define.d a s t h o s e bedEorms which have a non-per iodic

( i . e . i r r e g u l a r ) occurrence w i t h i n a channel , t o d i s t i n g u i s h them from

l a r g e p e r i o d i c bedforms such a s sand waves. Bars may be t h e product of

both d e p o s i t i o n a l and e r o s i o n a l even t s , and preserved b a r s i n t h e anc ien t

record commonly c o n s i s t only of e r o s i o n a l remnants which have had a

complex h i s t o r y be fo re f i n a l b u r i a l .

Bars may be c l a s s i f i e d i n t o t h r e e broad groups (Table 8). Such a

c l ' a s s i f i c a t i o n i s l i a b l e t o offend t h e f l u v i a l geomorphologist, who can

recognize many v a r i a t i o n s i n f low p a t t e r n and sediment response , but t o

the g e o l o g i s t dea l ing mainly wi th l i m i t e d v e r t i c a l exposure and l i t t l e

l a t e r a l c o n t r o l a s i m p l i f i e d c l a s s i f i c a t i o n i s t h e most u s e f u l . Some

of the main b a r types a r e i l l u s t r a t e d i n Figure 6 .

Small b a r s have been termed "mesoforms" by Jackson (1975). Their

development depends mainly on i n d i v i d u a l dynamic even t s such a s seasona l

f loods . Larger b a r s a r e "macroforms", which develop over pe r iods of

many y e a r s , commonly from t h e coalescence of many mesoforms dur ing numerous

dynamic even t s . 4 . 1 P lanar o r massive bedded bars : These a r e t y p i c a l l y composed of

l i t h o f a c i e s Gm. They a r e diamond- o r lozenge-shaped i n p l a n , a r e e longa te

p a r a l l e l t o flow d i r e c t i o n , and commonly a r e bounded by a c t i v e channels

and have eroded margins. They develop by v e r t i c a l c l a s t a c c r e t i o n and,

a s they b u i l d v e r t i c a l l y t h e water shallows over them and the reduced

competency r e s u l t s i n a decreased c l a s t s i z e . Longi tudinal b a r s may a l s o

be a s t a b l e bedform (a kind of g r a v e l wave) under very high energy f lood

cond i t ions .

The i n t e r n a l s t r u c t u r e of t h e b a r s i s massive o r crude h o r i z o n t a l

bedding. C l a s t imbricat ion may be common bu t crossbedding i s absent .

Superimposed (mul t i s to rey) b a r d e p o s i t s a r e common i n t h e anc ien t record.

Table 8: A simple c lass i f ica t ion of bar types

r' bar t Y Pe

b

Planar o r massive bedded bars

Simple foreset bars

Compound bars

1 i thology

gravel

usually sand, rarely gravel

sand o r gravel

internal s t ructure

planar bedded o r massive

planar crossbedding

complex, with several crossbeddi ng types and internal erosion surfaces

height

lm o r l e s s

typical ly .5 - lm

equal t o channel bankfull depth

length

several hundred metres

several hundred metres

hundreds t o thousands of metres

bedform rank

mesoform

mesoform

macroform

common name

longitudinal-

1 i nguoid- transverse- lobate- chute-

point- side- 1 ateral-

occurrence

dominant bar form i n gravel r ivers , eg. proximal braided streams

dominant bar form i n sandy i braided r ivers , rarely present in gravel r ivers

occur i n a l l types of r ivers , but best developed i n sandy meandering systems

4.2 Simple f o r e s e t b a r s : The m a j o r i t y of t h e s e b a r s are composed

of sand, a l t hough some g r a v e l d e p o s i t s w i t h f o r e s e t s have been recorded.

Typ ica l l i t h o f a c i e s are Sp and Gp.

The commonest t y p e s a r e l i n g u o i d and t r a n s v e r s e b a r s . Both have

g e n t l y d ipp ing s t o s s (upcur ren t ) s u r f a c e s and s t e e p avalanche-slope

( f o r e s e t ) t e r m i n a t i o n s downstream. Linguoid b a r s have a l o b a t e shape

and may advance downstream i n t r a i n s a t rates i n t h e o r d e r of 100 mlday.

The s i d e s of t h e s e b a r s may b e o r i e n t e d a t h igh a n g l e s t o t h e channel

d i r e c t i o n , p a r t i c u l a r l y i f one end i s a t t a c h e d t o a mid channel i s l a n d

(Cant and Walker, 1978). T h i s accoun t s f o r t h e l a r g e d i r e c t i o n a l

v a r i a n c e of many f l u v i a l planar-crossbedded sands tones . T ransve r se b a r s

have s t r a i g h t e r c r e s t s t han l i n g u o i d b a r s . They may r e p r e s e n t coa le sced

l i n g u o i d b a r s o r s o l i t a r y b a r s t h a t ex t end comple te ly a c r o s s t h e channel

o r t h e space between i s l a n d s .

4.3 Compound b a r s : These a r e much more complex than t h e o t h e r

two b a r t ypes . They develop i n p a r t from t h e coalescence of mesoform

type b a r s over p e r i o d s of many y e a r s .

I n h i g h s i n u o s i t y r i v e r s p o i n t b a r s t y p i c a l l y form on t h e i n s i d e s of

meanders, a s t h e bend m i g r a t e s l a t e r a l l y a c r o s s t h e f l o o d p l a i n . An upward

f i n i n g sediment p r o f i l e is developed, a s d i s c u s s e d i n Sec t ion 6.

I n low s i n u o s i t y , m u l t i p l e channel (b ra ided ) r i v e r s l a t e r a l b a r s , s i d e

b a r s and sand f l a t s may develop ( C o l l i n s o n , 1970; Cant and Walkdr, 1978).

These may be s e v e r a l k i l o m e t r e s i n l e n g t h and may e v e n t u a l l y be co lon ized

by v e g e t a t i o n and s t a b i l i z e d . They a r e d i s c u s s e d f u r t h e r i n S e c t i o n 5.

5 . F a c i e s models f o r a l l u v i a l f a n s and b r a i d e d r i v e r s

Because of t h e i r r e l a t i v e l y s t e e p s l o p e and abundant c o a r s e bedload

t h e proximal r eaches o f r i v e r s tend t o be o f low-s inuos i ty , mul t ip le-channel

type . These a r e u s u a l l y c a l l e d b ra ided r i v e r s , a l t hough t h i s term h a s a l s o

bar types - LO longitudinal o longitudinal with

diagonal flow R eroded bar remnant LI linguoid M modified linguoid P point s side

Fig. 6 Plan view of some common bar types (from Mia l l , 1977).

Fig. 7 Diagrammatic c ross s e c t i o n of an a l l u v i a l fan . Dashed l i n e suggests sea l e v e l f o r c o a s t a l a l l u v i a l fans; t o be ignored i n t h e case of in land fans . Facies codes a s i n Table 2 (from Rust, 1979).

been used f o r c e r t a i n t y p e s of h igh-s inuos i ty , mult iple-channel , bedload

r i v e r s . Rust (1978a) at tempted t o c l a r i f y t h e d e f i n i t i o n s of channel p a t t e r n s .

I n a l j u v i a l b a s i n s t h e r i v e r network may be e i t h e r of d i s t r i b u t a r y

type, i n which c a s e t h e i n d i v i d u a l d i s t r i b u t a r y systems a r e commonly

r e f e r r e d t o as a l l u v i a l f a n s , o r they may be c o n t r i b u t a r y , i n which

case t h e term a l l u v i a l p l a i n may be used (Rust , 1979). The d i s t i n c t i o n

i s a morphological one which may be d i f f i c u l t t o make i n t h e a n c i e n t

record . A l l u v i a l f a n s tend t o occur where r i v e r s i n confined mountain

v a l l e y s emerge onto an a l l u v i a l bas in o r t runk r i v e r . The f low expands

l a t e r a l l y and may become sha l lower ; i t s e p a r a t e s i n t o mere than one

chsnnel , and t h e r e is a l o s s i n competency which r e s u l t s i n d e p o s i t i o n

of t h e c o a r s e r bedload. Therefore a l l u v i a l f a n s may be recognized

commonly by t h e presence of coarse f a c i e s banked a g a i n s t t h e b a s i n

margin (Figure 7 ) . However, such an a s s o c i a t i o n does n o t prove t h e

p r i o r e x i s t e n c e of a f a n d i s t r i b u t a r y network because similar d e p o s i t s

can occur i n any proximal r i v e r s e t t i n g . The term a l l u v i a l f a n is

t h e r e f o r e a d i f f i c u l t one t o use w i t h p r e c i s i o n when working w i t h a n c i e n t

rocks .

M i a l l (1977, 1978a) de f ined s i x t y p e s of d e p o s i t i o n a l environment

and r e s u l t a n t f a c i e s assemblages f o r low s i n u o s i t y , m u l t i p l e channel

r i v e r s , as l i s t e d i n Tab le 9 and i l l u s t r a t e d i n F igu re 8. Rust (1978b) e r e c t e d

a s i m i l a r c l a s s i f i c a t i o n , us ing codes G I , G11 e t c . ( s ee Table 9 ) .

5 . 1 Trol lhe im type: Under t h e r i g h t c o n d i t i o n s of s t e e p s l o p e , abundant

sediment supply and in f r equen t f l a s h f l o o d s sedimenta t ion may be dominated

by d e b r i s f lows. Such cond i t ions a r e most t y p i c a l of a l l u v i a l f a n s i n a r i d

o r semi-arid r e g i o n s , and t h e Trol lhe im f a n i n C a l i f o r n i a may be taken a s

a t ype example (Figure 9 , a f t e r Hooke, 1967). A t y p i c a l v e r t i c a l p r o f i l e is

i l l u s t r a t e d i n F igure 8 , and would correspond t o t h e proximal reaches of t h e

diagrammatic f a n wedge shown i n F igu re 7 .

Table 9 The six principal lithofacies assemblage models for gravel- and sand-dominated braided river deposits (from Miall, 1978a).

Name Environmental Maln Minor setting facie8 fades

Trollheirn type proximal rivers Gms, Gm St, Sp, FI, Fm (GI) (predominantly alluvial

fans) subject to debris flows

Scott type proximal rivers (including Gm GP, Gt, SP, (GII) alluvial fans) with stream St, Sr, FI,

flows Fm

Donjek type distal gravelly rivers Gm, Gt, GP, Sh, Sr, (GIII) (cyclic deposits) St Sp, FI, Fm

South Saskatchewan sandy braided rivers St SP, Se, Sr, type (SII) (cyclic deposits) Sh, Ss, SI,

Gm, FI, Fm

Platte type sandy braided rivers St, SP Sh, Sr, Ss. ( S I ~ (virtually non cyclic) Gm, FI, Fm Bijou Creek type Ephemeral or perennial Sh, SI SP, Sr (st? rivers subject to flash

floods

Modified from Miall (1977) and Rust (!97%b).

TROLLHEIM TYPE SCOTT TYPE DONJEK TYPE

minor 1 channel

bar-edge sand wedge

I debris flow deposit

t

1 superimposed bars

S. SASKATCHEWAN TYPE PLATTE TYPE BlJOU CREEK TYPE

major channel

f

superimposed linguoid bars

longitudinal bar

SP I

S h

Sr I superimposed Sh flood

cycles

1

i f 1

5 -

i rn

0-

Fig. 8 Generalized vertical profiles for the six braided river depositional models (from Miall, 1978a).

C h a r a c t e r i s t i c s of t h e Trol lhe im type f a c i e s assemblage inc lude t h e

fo l lowing (based on Hooke, 1967; Rust 1978b; 1979; Wasson, 1977; M i a l l , 1978a):

1. The Succession is dominated by superimposed d e b r i s flow d e p o s i t s

( l i t h o f a c i e s Gms) , i n d i v i d u a l f lows r each ing 3m i n t h i c k n e s s ; 2 . Debr is

f low u n i t s commonly have f l a t (not channe l l ed ) , g e n e r a l l y abrupt bases and

a l o b a t e geometry, except where they i n f i l l s t r eam flow channels ; 3 . Interbedded

u n i t s of Gm g e n e r a l l y a r e f i n e r g ra ined and may occupy prominent- s cour s

r e f l e c t i n g t h e f a c t t h a t s t ream f lows r e q u i r e a lower s l o p e than d e b r i s

f lows and t h e r e l o r e comnoniy cause fa:i- i i ~ c i s i o n . Stream flow snee t floo:s

may a l s o be p r e s e n t i n crude fining-upward cyc le s ; 4. Minor u n i t s of S t ,

Sp, F1 and Fm may be p r e s e n t , a s i n t h e S c o t t model ( s e e S e c t i o n 5 .2) .

Var i a t ions i n t h e p ropor t ion of d e b r i s f low d e p o s i t s on ad jacen t f a n s

probably r e f l e c t v a r i a t i o n s i n sediment supply.

5.2 S c o t t type: On a l l u v l a l f a n s beyond the l i m i t of d e b r i s f lows

(mid-portion of F igu re 7 ) , on f a n s l a c k i n g d e b r i s f lows, and on o t h e r

proximal g r a v e l l y r i v e r s sedimenta t ion i s dominated by l i t h o f a c i e s Gm,

forming superimposed l o n g i t u d i n a l ba r d e p o s i t s (F igure 8 ) . These r e p r e s e n t

f l ood processes . Minor f a c i e s i n l c u d e Gp, G t , Sp, S t and S r , and a r e

depos i ted du r ing low water ep i sodes a s i n t h e waning s t a g e s of a f l ood

event . They may form smal l -sca le f i n i n g upward c y c l e s up t o about l m i n t h i ckness .

The sand u n i t s a r e depos i t ed i n abandoned channels o r as micro-del ta wedges

prograding from g r a v e l b a r s a s t h e l a t t e r emerge du r ing a drop i n water

l e v e l . Ancient examples have been desc r ibed by Mia l l (1370b), M i a l l and

Gibl ing (1978), McGowen and Groat (1971), and Rust(1978b). The assemblage i s

named a f t e r t h e S c o t t outwash r i v e r , Alaska (Boothroyd and Ashley , (1975).

5.3 Donj ek type: This l i t h o f a c i e s assemblage develops under t h e

fo l lowing cond i t ions : 1. bra ided r i v e r s w i t h w e l l de f ined , a c t i v e channels

and e l e v a t e d , p a r t i a l l y t o e n t i r e l y i n a c t i v e channel reaches . Topographic

US-CRESTED DUNES

Fig . 10 Block diagram showing t h e morphological elements of a South Saskatchewan type r i v e r . S t i p p l e d a r e a s a r e emergent. S ing le s h a f t e d arrows i n d i c a t e d i r e c t i o n s of bed fa rn movement, double s h a f t e d arrows i n d i c a t e f low d i r e c t i o n s (from Cant and Walker, 1978) .

r e l i e f a c r o s s t h e system may be i n t h e o r d e r of 3-7 m; 2 . A bedload c o n s i s t i n g

of abundant sand and g r a v e l .

Fining-upward c y c l e s occur i n r i v e r s o f t h i s t y p e , a s f i r s t c l e a r l y

documented by W i l l i a m s and Rust (1969) i n t h e Donjek R ive r , Yukon, a f t e r

which t h e assemblage i s named. Examples a r e i l l u s t r a t e d i n F igu re 8 . The

c o a r s e s t sediments occu r i n t h e deeper channe l s , and may i n c l u d e l i t h o f a c i e s

Gm ( l o n g i t u d i n a l b a r s ) , Gp ( t r a n s v e r s e b a r s ) , and G t ( l o b a t e b a r s ) . P a r t i a l l y

i n a c t i v e t r a c t s above t h e deep channe l s r e c e i v e sand and g r a v e l du r ing f l o o d

s t a g e s , and t h e h i g h e s t p a r t s of t h e system may be covered by dense v e g e t a t i o n

which t r a p s f i n e sediment from i n f i l t r a t e d f l o o d wa te r s .

Ancient examples have been d e s c r i b e d by M i a l l (1970a), S t e e l (1974),

Minter (1978) and Rust (1978b).

The S c o t t , Donjek and South Saskatchewan assemblages may occur i n a

g r a d a t i o n a l p rox ima l -d i s t a l r e l a t i o n s h i p on t h e same a l l u v i a l system.

It is sugges ted t h a t t h e fo l lowing numer i ca l l i m i t s of g r a v e l con ten t

(pe rcen t of cumula t ive t h i c k n e s s i n a s e c t i o n ) be used t o d i s t i n g u i s h t h e

t h r e e types : S c o t t >go%, Donjek 10-90%, South Saskatchewan < lo% (See s e c t i o n

9 f o r a d e s c r i p t i o n of some o t h e r t y p e s o f g r a v e l l y o r sandy fining-upward

c y c l e s ) .

5.4 South S a s k a t c h ~ w a n type: I n sand-dominated b ra ided r i v e r s f i n i n g -

upward c y c l e s may develop by a combinat ion of channel and b a r e v o l u t i o n ,

as d e s c r i b e d by Cant and Walker (1976, 1978) , Cant (1378) and Walker and

Cant (1979). A model of t h e sedimentary p r o c e s s e s i s i l l u s t r a t e d i n F i g u r e

1Q and i s based on o b s e r v a t i o n s i n t h e South Saskatchewan River a f t e r

which t h e assemblage i s named.

Channels commonly a r e f l o o r e d by l a g g r a v e l s ( l i t h o f a c i e s Gm),

above which sand i s t r a n s p o r t e d as a c o a r s e bedload. Bedforms i n t h e

deeper channe l s (3m o r deeper) t end t o be s inuous c r e s t e d dunes t h a t

g i v e r i s e t o l i t h o f a c i e s S t . Sandwaves ( l i t h o f a c i e s Sp) a r e common i n

sha l low channel r eaches . Sandy f o r e s e t b a r s of a v a r i e t y of t y p e s m i g r a t e

downstream. I n t h e South Saskatchewan River ( b u t not n e c e s s a r i l y i n a l l

sandy b r a i d e d r i v e r s ) l a r g e sand f l a t s may develop by t h e coalescence of

small b a r s around a nuc leus . These aggrade upstream and may a l s o grow

downstream by t h e development of s t r a i g h t - c r e s t e d b a r s a t h i g h a n g l e s

t o t h e channel t r e n d (cross-channel b a r s ) . On the b a r t o p s l i t h o f a c i e s

S r and Sh w i l l form d u r i n g f l o o d submergence, and t h e r e may a l s o be f i n e

g ra ined overbank d e p o s i t s i n i n a c t i v e a r e a s .

Typ ica l c y c l e s a r e i l l u s t r a t e d i n F i g u r e 8. These are s i m i l a r t o

some p o i n t b a r c y c l e s of meandering r i v e r s ( s e e S e c t i o n 6 ) . In v e r t i c a l

p r o f i l e t hey may be d i s t i n g u i s h e d by c a r e f u l p a l e o c u r r e n t work; f o r example

F i g u r e 4 i l l u s t r a t e s t h e d i v e r g e n t c u r r e n t d i r e c t i o n s of b a r and sand f l a t

d e p o s i t s , a q u i t e d i f f e r e n t p a t t e r n t o t h a t expected on a f l u v i a l p o i n t b a r .

Ancient examples of t h i s assemblage have been d e s c r i b e d by Cant and

Walker (1976), Miall and Gib l ing (1978), Minter (1978), and Rust (1978b).

5.5 P l a t t e type: Th i s i s a v a r i a n t o f t h e South Saskatchewan type ,

which probably occu r s i n e x c e p t i o n a l l y broad, sha l low r i v e r s l a c k i n g w e l l

de f ined topographic d i f f e r e n t i o n between a c t i v e and i n a c t i v e areas. The

P l a t t e River (Smith, 1970, 1971, 1972) is a t y p i c a l example.

The sediments a r e dominated by i n g u o i d o r t r a n s v e r s e sandy f o r e s e t

b a r s , o r by sand waves, g i v i n g r i s e t o superimposed s e t s of l i t h o f a c i e s

Sp. L i t h o f a c i e s S t i s s p a r s e , r e f l e c t i n g t h e r a r i t y of deep channels . Bar

top sands and s i l t s ( l i t h o f a c i z s S r , Sh, F1, Fm) may occur , a s i n t h e South

Saskatchewan type . Few c y c l e s a r e developed. A t y p i c a l p r o f i l e i s i l l u s t r a t e d

i n F i g u r e 8 .

Ancient examples have been desc r ibed by M i a l l (1976, 1979) and

Asquith and Cramer (1975).

5 .6 Bi jou Creek type: Under upper flow regime cond i t ions sand is

moulded i n t o a p lane bed, and may develop p a r t i n g o r s t reaming l i n e a t i o n

on bedding p lane s u r f a c e s ( l i t h o f a c i e s Sh). This e x c e p t i o n a l l y h igh

flow energy is r a r e i n p e r e n n i a l r i v e r s bu t i s common i n ephemeral r i v e r s

c h a r a c t e r i z e d by i n f r e q u e n t , v i o l e n t f l a s h f l o o d s . Flow may e i t h e r be

channelized o r occur a s s h e e t f l o o d s . Examples inc lude B i jou Creek,

Colorado (ElcKee e t a l . , (19.67) a f t e r which t h e assemblage type i l l u s t r a t e d

i n F igure 8 i s named, and p a r t s of t h e Lake Eyre Basin (Will iams, 1971).

General d e s c r i p t i o n s a r e a l s o g iven by P ica rd and High (1973).

F a c i e s models f o r ephemeral r i v e r s have been d i scussed by Mia l l (1977,

1979), Rust (1978b), and Tunbridge (1981). They a l l emphasize t h e importance

of l i t h o f a c i e s Sh i n t h e sedimentary assemblage. L i t h o f a c i e s Sp, S r , F1 and

Fm may be produced - i n t h e waning f l o o d s t a g e s , gene ra t ing t h i n f i n i n g upward

c y c l e s . Thicknesses of sediment i n excess of 1.5m may be depos i t ed i n

a s i n g l e f lood . E ros iona l s u r f a c e s w i t h i n t r a c l a s t s ( l i t h o f a c i e s Se)

and low a n g l e c rossbeds f i l l i n g scour s ( l i t h o f a c i e s S1) may a l s o be

impor t an t , a s i n t h e "Malbaie type" assemblage descr ibed by Rust (1978b).

Des i cca t ion f e a t u r e s may a l s o be impor tant .

6. F a c i e s models f o r meandering r i v e r s

The fining-upward p o i n t b a r model was one of t h e f i r s t f a c i e s models

eve r t o be e r e c t e d . It was developed more o r l e s s s imul taneous ly by Al len

(1963b) and by Bernard e t a l . (1962) and Bernard and Major (1963). I n

l a t e r papers A l l en (1964, 1965, 1970) documented t h e model i n d e t a i l and i t

became s o widely used t h a t o t h e r s t y l e s of f l u v i a l sedimenta t ion were f o r a

time almost ignored ( e .g . s e e review by Vi she r , 1972). Large ly a s a r e s u l t

of c r i t i c a l work by Jackson (1978) i t i s now r e a l i z e d t h a t t h e c l a s s i c

Al len model i s on ly one of s e v e r a l a p p l i c a b l e t o meandering r i v e r d e p o s i t s .

Jackson (1978) proposed f i v e models based mainly on o b s e r v a t i o n s i n modern

r i v e r s . Not a l l of t h e s e a r e e q u a l l y w e l l documented. V a r i a t i o n s between

t h e models r e l a t e mainly t o d i f f e r e n c e s i n sediment c a l i b r e .

6 . 1 The b a s i c model: A g e n e r a l i z e d model of t h e meandering r i v e r

environment i s shown i n F igu re 11. Meanders m i g r a t e by u n d e r c u t t i n g t h e

bank on t h e o u t s i d e of t h e bend, and by d e p o s i t i n g sediment on a p o i n t b a r

on t h e i n s i d e o f t h e bend. The c l a s s i c f i n i n g upward p r o f i l e i s produced

by l a t e r a l a c c r e t i o n of t h e p o i n t b a r . A s f low e n t e r s t h e bend a h e l i c a l

o v e r t u r n deve lops , s u r f a c e f low be ing d i r e c t e d a g a i n s t t h e cu tbank, where

i t t u r n s down and a long t h e p o i n t b a r s u r f a c e . Flow a c r o s s t h e p o i n t b a r

t e n d s t o s o r t t h e sediment ; i t becomes f i n e r on t h e sha l lower p a r t s of t h e

b a r away from t h e r e g i o n of h i g h e s t f low energy. Th i s i s t h e b a s i c cause

of t h e upward f i n i n g (F igu re 1 2 ) , a l t hough i t can be complicated by t h e

presence of benches o r s u b s i d i a r y b a r s , as d i s c u s s e d below.

The l a t e r a l a c c r e t i o n s u r f a c e s a r e p re se rved w i t h i n t h e d e p o s i t as a

form of l a r g e s c a l e , low ang le c rossbedding , termed e p s i l o n c r o s s - s t t a t i -

f i c a t i o n by A l l e n (1963a). The d i p o f t h e crossbedding ranges from lo

( f o r v e r y l a r g e r i v e r s ) up t o about 25' ( f o r s m a l l r i v e r s ) , and t h e t h i c k n e s s

of t h e crossbcd set may under c e r t a i n c i rcumstances be approximate ly equa l

t o channel depth, which can p rov ide a u s e f u l indicaXor of t h e s a a l e of t h e

o r i g i n a l r i v e r (Leeder , 1973). Minor bedforms on t h e p o i n t b a r s u r f a c e are

o r i e n t e d downstream, approximate ly p a r a l l e l t o t h e s t r i k e of t h e e p s i l o n

crossbedding , which i s a u s e f u l c l u e i n t h e a n c i e n t r eco rd t o d i s t i n g u i s h

e p s i l ~ u sets from o t h e r forms of l a r g e s c a l e c rossbedding .

Jackson (19 76) showed t h a t t h e c l a s s i c " f u l l y developed" f i n i n g upward

p r o f i l e (F igure 13 , l e f t column) occu r s on ly i n t h e downstream p a r t of a

EARLIER I CREVASSE- SPLAY 1 CHANNEL-FILL 1 DEPOSIT I DEPOSIT

DEPOSIT DEPOSIT DEPOSIT

Fig. 11 P r i n c i p a l environments and d e p o s i t i o n a l f a c i e s of a meandering r i v e r (from Al l en , 1964) .

- surface current ---* bottom current I

E 0 (V

I (\I

1

Fig. 12 Flow d i r e c t i o n s and bedform development on a p o i n t b a r (D: dunes, T: t r a n s v e r s e b a r s o r sand waves R: r i p p l e s ) , showing development o f la teral a c c r e t i o n s u r f a c e s o r e p s i l o n crossbedding (Miall, unpublished, a f t e r A l l en , 1963b; Jackson, 1976).

FULLY DEVELOPED DEPOSITIONAL FACIES

- - - - 'HIGW FLOV . + ..lOwg FLOW

9-

0-

7- - a -

8 6- E s-

i 4-

F 1 3- W

W

2-

I -

c- - 3 0 3 6 0 SO loow0

MEAN SIZE (PHI) MEAN VEL I M E C ) - 'HIGH' FLOW

* 'LOW' FLOW

TRANSITIONAL DEPOSITIONAL FACIES A

R k! HIGH' FLOW z:z:\W F m - - - %IGW Fl.W

CWRENT + + + W F L O W

8 0 b d MEAN SIZE (PHI) MEAN VEL ( C M M C I - 'HIGK F L W

W'W ROW

Fig. 13 Point ba r sequences i n g rave l ly sand-bed r i v e r s , based on the WabashRiver. Numbers i n c i r c l e s a t r i g h t a r e s u b f a c i e s : 1. channel l a g , 2 . lower po in t ba r , 3 . upper point ba r , 4 . levee, 5 . overbank (from Jackson, 1976) .

Channel Migration Shear zone

Fig . 1 4 The formation of a flow separa t ion zone and s i l t banks on a point bar (from Nanson, 1980).

r i v e r bend, because t h e h e l i c a l o v e r t u r n of t h e f low i s i t s e l f no t f u l l y

developed u n t i l p a r t way round t h e bend. I n upstream p a r t s of t h e bend a

" t r a n s i t i o n a l " p r o f i l e occu r s , w i t h t h i c k e r upper po in t b a r f a c i e s and

th inne r l e v e e and overbank d e p o s i t s (F igure 13, r i g h t column). Meander

cu rva tu re a l s o a f f e c t s t h e f low p a t t e r n .

Meander bends may be modified by chute o r neck c u t o f f s . A chute

is shown i n Figure 12. These s u b s i d i a r y channels a r e occupied during

f lood s t a g e s and may d i v e r t much of t h e flow. Neck c u t o f f s occur when

t h e two l imbs of a meander mig ra t e i n t o each o t h e r . The f low i s s h o r t

c i r c u i t e d , and t h e abandoned meander bend may become i s o l a t e d by l e v e e s

f l a n k i n g t h e new channel . For a t i m e t h e abandoned meander p e r s i s t s

a s a n "oxbow l ake" ( see examples i n F igu re 1 ) , b u t e v e n t u a l l y i t becomes

f i l l e d w i t h f i n e sediment .

Crevasse sp l ay d e p o s i t s develop when f l o o d d i scha rge breaks through

t h e l e v e e and sp reads o u t on t o t h e f l o o d p l a i n (Figure 11) . The d e p o s i t s

t y p i c a l l y c o n s i s t of sand b l a n k e t s which may l o c a l l y show a coarsening

upward t e x t u r e .

Floodplain d e p o s i t s a r e dominantly f i n e g ra ined . Coal may occur i n

humid environments. Pedogenic carbonate conc re t ions develop by l each ing

p rocesses i n semi-arid environments ( t h e s e may a l s o be p re sen t i n bra ided

and anastomosing f l u v i a l environments but a r e u s u a l l y l e s s widely developed).

Channe l - f i l l sands tones and/or conglomerates may form i s o l a t e d porous

u n i t s w i t h i n f i n e f l o o d p l a i n sequences, o r they may be s t acked v e r t i c a l l y

(mul t i s to rey u n i t s ) o r i n t e rconnec t l a t e r a l l y , i n d i c a t i n g vary ing p a t t e r n s

of channel s h i f t i n g and subs idence rates i n the d e p o s i t i o n a l bas in .

Jackson ' s (1978) f i v e models, which show v a r i a t i o n s on t h e b a s i c

d e s c r i p t i o n g iven h e r e , a r e d i scussed b r i e f l y below.

6 .2 Muddy f ine -g ra ined r i v e r s : These r i v e r s show a low wid th ldep th

r a t i o , s t e e p p o i n t b a r s l o p e s , o f t e n exceeding 20°, and prominent l e v e e s .

Channel d e p o s i t s a r e medium sand o r f i n e r , and muddy c h a n n e l - f i l l and

overbank d e p o s i t s are abundant . Jackson s t a t e d t h a t c h u t e s and s c r o l l

b a r s a r e a b s e n t , b u t s c r o l l b a r s and benches have been observed i n two

f l u v i a l u n i t s t h a t c o n t a i n t h i s t y p e o f f l u v i a l d e p o s i t ( M i a l l , 1979;

Nanson, 1980) . T h e i r format ion i s i l l u s t r a t e d i n F igu re 14 . Nanson (1980)

e x p l a i n s t h e i r development i n terms o f s e p a r a t i o n e d d i e s which occur du r ing

f l o o d even t s .

6 . 3 Sandy r i v e r s w i t h t h i n f i n e member: S c r o l l b a r s , c h u t e s , and

l e v e e s a r e common. Chute and neck c u t o f f s may occur . P o i n t b a r d i p may

be s t e e p . The c o a r s e member of t h e f i n i n g upward c y c l e i s composed e n t i r e l y

of s and , excep t f o r a p o s s i b l e b a s a l l a g g r a v e l . The modern lower M i s s i s s i p p i

(F i sk , 1944) i s a good example of t h i s c a t e g o r y , and i t i s perhaps t h e

c l o s e s t t o t h e o r i g i n a l A l l e n (1963b) model. Ancient examples a r e

d e s c r i b e d by Nami and Leeder (1978), Puigdefabregas and Van V l i e t (1978) and

Al l en (1964).

6.4 Sandy r i v e r s w i thou t mud o r g r a v e l : The occurrence of t h i s c l a s s

may depend on a supply of sediment w i t h a r e s t r i c t e d g r a i n s i z e range . The

channels have a h ighe r w id th /dep th r a t i o t han t h e muddy type , and l a c k l e v e e s .

S c r o l l b a r s may be common. Development o f b r a i d i n g i n t h i s t ype of r i v e r

may b e prevented by t h e p re sence of channe l banks t h a t are s t a b i l i z e d by

v e g e t a t i o n .

6.5 S r a v e l l y sand-bed r i v e r s : Gravel i s common i n t h e deeper p a r t s - of t h e channel and i n t h e lower p a r t of t h e p o i n t ba r d e p o s i t . Chutes and

s c r o l l b a r s may be common so t h a t s imp le e p s i l o n crossbedding t e n d s t o be

r a r e . P o i n t b a r s u r f a c e s may be covered by abundant sandy bedforms such a s

dunes (on t h e lower p o i n t ba r ) and t r a n s v e r s e b a r s (middle p o i n t b a r ) . Muddy

overbank o r channel f i l l d e p o s i t s a r e v o l u m e t r i c a l l y of minor importance.

Seve ra l good sedimentologica l d e s c r i p t i o n s of modern r i v e r s of t h i s type

have been publ i shed (McGowen, and Garner , 1970; Jackson, 1976, Levey, 1978);

a w e l l exposed a n c i e n t example is desc r ibed by Nijman and Puigdefabregas

(1978). The i r p o i n t b a r model i s i l l u s t r a t e d i n F igure 15 , and t y p i c a l

v e r t i c a l p r o f i l e s through modern Wabash River p o i n t b a r s a r e shown i n Figure 13.

6 .6 Gravel-dominated r i v e r s : I r r e g u l a r bed topography w i t h l o n g i t u d i n a l

b a r s , and a complex po in t ba r development l ack ing i n e p s i l o n crossbedding a r e

t h e most c h a r a c t e r i s t i c f e a t u r e s of t h i s model. The River Endrick inc ludes

some of t h e s e f e a t u r e s and has been w e l l de sc r ibed by Bluck (1971). A l l

known examples of t h i s t ype occur on s t e e p s l o p e s i n o r n e a r mountainous

r eg ions (Leopold and Wolman, 1957; Jackson, 1978) . No a n c i e n t examples

have y e t been i d e n t i f i e d and t h e g e o l o g i c a l importance of t h e model i s

unc lea r . Ancient g r a v e l l y f l u v i a l d e p o s i t s tend t o be i n t e r p r e t e d a s t h e

product of bra ided r i v e r s r a t h e r than meandering r i v e r s and c a r e f u l f a c i e s

and pa l eocur ren t work is reqmired t o i d e n t i f y channel morphology c o r r e c t l y .

7. Fac i e s model f o r anastomosing r i v e r s

Not a l l h igh s i n u o s i t y r i v e r s can be ca t egor i zed i n terms of t he

meandering models desc r ibed above. Smith and Smith (1980) and Smith and

Putnam (1980) de f ined a new f a c i e s model f o r r i v e r s c o n s i s t i n g of a low

energy complex of s e v e r a l i n t e rconnec ted channels of v a r i a b l e s i n u o s i t y ,

t y p i c a l l y >1.5. I n humid environments wet lands , p e a t bogs and f l o o d p l a i n

ponds a r e common, b u t t h i s f l u v i a l s t y l e a l s o occurs i n a r i d environments,

e .g . Lake Eyre Bas in , A u s t r a l i a . Channel g r a d i e n t s a r e low and overbank

f loods a r e f r equen t . Channel banks are s t a b i l i z e d by vege ta t ion . This

type of r i v e r p a t t e r n seems t o develop where t h e r i v e r bas in is subs id ing

r e l a t i v e t o downstream base l e v e l o r where t h e base l e v e l i t s e l f i s r i s i n g .

An example of an anastomosing b e l t of t h e Saskatchewan River is shown i n

Figure 16.

L a t e r a l channel mig ra t ion and p o i n t bar a c c r e t i o n is no t c h a r a c t e r i s t i c

of anastomosed r i v e r s . I n s t e a d they a c c r e t e v e r t i c a l l y , a s shown i n t h e

f a c i e s model diagram (Figure 17) . The most d i s t i n c t i v e f e a t u r e of t he

r e s u l t i n g d e p o s i t s i s t h e n e a r - v e r t i c a l f a c i e s c o n t a c t s . Bore h o l e s

p e n e t r a t i n g such a success ion would encounter anomalously t h i c k channel

and overbank u n i t s and c o r r e l a t i o n between boreholes would be impossible.

Smith and Smith (1980) and Smith and Putnam (1980) desc r ibed modern and

in terpre ted a n c i e n t examples of anastomosed r i v e r s . Recogni t ion of

subsu r face examples i s d i f f i c u l t because of t h e requirement f o r very

t i g h t w e l l c o n t r o l .

8. Recognit ion of l a r g e r i v e r s

Most o f t h e f a c i e s models desc r ibed above have been developed f o r

r i v e r s of moderate dimensions, w i t h channels t y p i c a l l y only a few metres

deep. Recognit ion of t h e d e p o s i t s of major r i v e r s comparable t o t h e g i a n t s

of today (e.g. M i s s i s s i p p i , Amazon, Ganges, Brahmaputra) r e q u i r e s ve ry

l a r g e outcrop o r good w e l l c o n t r o l .

Mossop (1980) desc r ibed fining-upward f l u v i a l sequences i n t h e o r d e r

of 50m t h i c k con ta in ing e p s i l o n c r o s s s t r a t i f i e d u n i t s up t o 2 5 m t h i c k

(Figure 18 ) . Deep channels might be expected t o c o n t a i n g i a n t bedforms,

and t h e s e have been recorded i n a few cases . Coleman (1969) desc r ibed

sand waves i n t h e Brahmaputra 8 t o 15m h i g h which migra ted as much a s

600m i n 24 hours du r ing f lood ep i sodes (Figure 1 9 ) . I n t e r n a l l y they comprise

extremely l a r g e s c a l e sets of t rough and p l ana r crossbedding. A p o s s i b l e

a n c i e n t analogue was descr ibed by Conaghan and Jones (1975). Jones and

McCabe (1980) desc r ibed crossbed s e t s 40m t h i c k con ta in ing a complex

p a t t e r n of i n t e r n a l e r o s i o n s u r f a c e s . They i n t e r p r e t e d them as t h e d e p o s i t s

of a l t e r n a t e b a r s i n a low s i n u o s i t y d e l t a d i s t r i b u t a r y channel .

9. Large s c a l e f l u v i a l c y c l e s

The f a c i e s models we have been cons ide r ing up t o t h i s po in t a r e b a s e d l a r g e l y

Billy

Highlight

.b.+4$L . GRAVEL SANDY SILT I ORGANIC

CONTENTS

FJ F. - C. SAND MUD. SILTY MUD ) VARIABLE

PEAT BEDROCK

Fig. 1 7 Facies model block diagram f o r anastornosed r i v e r (from Smith and Smith, 1980).

CLEARWATER SHALE

- -.

Fig. 18 Schematic c ross s e c t i o n through t h e main f a c i e s of the McMurray Formation (from Mossop, 1980).

Fig . 19 Fathometer p r o f i l e s , Brahmaputra R ive r , showing mig ra t ion of g i a n t bedforms (from Coleman, 1969) .

- BOUNOING UNCONFORMITY - PRINCIPAL CORRELATION HORIZON -- BASE WESTWATER CANYON MBR. SCOURED 8ASESOF SMALLERCHANNELS

VERT EXAG - 52

PALEOCURRENT MEASUREMENTS

AVERAGE BEARING -6 NUMBER OF TROUGH AXES

BLUEWATER S I N MATE0 FAULT FAULT SE

Fig . 20 S t r a t i g r a p h i c s e c t i o n through a channel complex, t r a n s v e r s e t o p a l e o c u r r e n t d i r e c t i o n , J u r a s s i c , New Mexico (from Campbell, 1976) .

on t h e concept of c y c l i c i t y . Processes such a s channel migra t ion, and

flood even t s , genera te c e r t a i n l i t h o f a c i e s i n a p r e d i c t a b l e sequence causing

a s t r a t i g r a p h i c r e p e t i t i o n throughout a f l u v i a l success ion. However,

we have d e a l t wi th only one type of c y c l i c i t y , t h a t which Beerbower (1964)

termed a u t o c y c l i c , a r i s i n g from e n e r g y d i s t r i b u t i o n wi th in the d e p o s i t i o n a l

bas in . A l l o c y c l i c processes a r e those which o r i g i n a t e o u t s i d e t h e

d e p o s i t i o n a l b a s i n through t e c t o n i c o r c l i m a t i c causes . They can a l s o

genera te c y c l i c sequences, and t h e r e i s p o t e n t i a l f o r confusion between

the v a r i o u s cyc le types . A t p resen t we do no t have all-encompassing

models t o incorpora te t h i s complexity and, i n f a c t , t o a t tempt t h i s would

r e q u i r e a considerable broadening of t h e f a c i e s model concept. This problem

was discussed i n d e t a i l by Mia l l (1980), and a summary of p a r t of t h a t

paper fo l lows . 9 .1 Cycles of v e r t i c a l aggradat ion: A p a r t i c u l a r l y important type

of c y c l i c i t y is t h a t caused by v e r t i c a l aggradat ion i n a channel system

and t h e p rogress ive o r sudden abandonmat of t h e channel i n favour of a

complet-ly new course . Th i s process i s common on s u b a e r i a l and submarine

fans and on d e l t a s . Sedimentation w i t h i n a channel may have the e f f e c t

of reducing t h e s lope . This r e s u l t s i n a p rogress ive l o s s of competency

and t h e sediments become f i n e r gra ined a s t h e channel f i l l b u i l d s v e r t i c a l l y .

Eventual ly , t y p i c a l l y dur ing a f lood even t when t h e r i v e r over tops i t s

banks, t h e f low may f i n d a s t e e p e r rou te down t h e d e p o s i t i o n a l s u r f a c e ,

and t h e channel i s d i v e r t e d . I n t h e now abandoned channel a fining-upward

sequence has been genera ted. It i s n o t c l e a r what s c a l e of c y c l i c sequence

can be formed by t h i s p rocess , and i t i s a l s o unclear whether t h e mechanism

r e q u i r e s a t e c t o n i c t r i g g e r o r whether i t i s e n t i r e l y au tocyc l i c .

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Billy

Highlight

Some examples of t h i c k c y c l e s t h a t may have been gene ra t ed i n t h i s

way have been desc r ibed by Miall (1970a) , Cant and Walker (1976), Campbell

(1976), and K e l l i n g (1968). They range up t o 60m i n t h i c k n e s s and may

c o n t a i n s m a l l e r s c a l e a u t o c y c l i c c y c l e s n e s t e d w i t h i n them. F igu re 20

i l l u s t r a t e s a s e r i e s of channel f i l l sequences i n a J u r a s s i c u n i t i n New

Mexico, (from Campbell, 1976) . Each o f t h e s e f i n e s upwards and c o n t a i n s

nes t ed c y c l e s , as i l l u s t r a t e d i n column B i n F i g u r e 21. Column C shows

a s i m i l a r l a r g e s c a l e c y c l e from K e l l i n g (1968), and column A i s a p r o f i l e

through Mossop's (1980) g i a n t p o i n t b a r d e p o s i t s , as a comparison. The

p a t t e r n of i n t e r s e c t i n g sand bod ie s i n t h e upper p a r t of F i g u r e 20 appears

t o sugges t t h a t a major channel on t h e a l l u v i a l p l a i n s h i f t e d toward t h e

nor thwest ( l e f t ) i n a s e r i e s of s t e p s . A p o s s i b l e modern analogue f o r

t h i s p r o c e s s i s t h e Kosi f a n i n I n d i a , where t h e p r i n c i p a l d i s t r i b u t a r y

h a s moved westwards a d i s t a n c e of 112 km i n 228 y e a r s , g r a d u a l l y b u i l d i n g

up a cone o f a l luv ium (Fig . 22) .

9.2 Cycles r e l a t e d t o v a r i a t i o n s i n b a s i n margin r e l i e f : Changes i n

b a s i n margin r e l i e f cause changes i n r i v e r s l o p e , competency and sediment

c a l i b r e . Under t e c t o n i c a l l y s t a b l e c o n d i t i o n s s l o p e s a r e p r o g r e s s i v e l y

reduced by e r o s i o n and t h e sediments i n t h e a l l u v i a l b a s i n become g r a d u a l l y

f i n e r upwards.

Conversely, a c t i v e u p l i f t i n t h e sou rce a r e a may cause a wave of

i n c r e a s i n g l y c o a r s e d e b r i s t o p rog rade o u t i n t o t h e b a s i n , c r e a t i n g a g r o s s

coa r sen ing upward c y c l e . Many examples of t h i s p r o c e s s have been d e s c r i b e d

i n t h e l i t e r a t u r e . It i s p a r t i c u l a r l y common i n a l l u v i a l f a n d e p o s i t s

(Mia l l , 1978b; S t e e l e t a l . , 1977; S t e e l and Aasheim, 1978) . Some c y c l e s

hundreds t o thousands of metres t h i c k may be c o r r e l a t e d e i t h major o rogen ic

p u l s e s ( s e e examples i n Miall, 1978b, 1981a; s e e a l s o Sec t ion 1 1 ) .

v burrows il0 m 4 ripples d trough c.b. ?ZZ planar c.b.

s m g c f c - scour surface UlLU - cool

. . . . . . . SlltStone . . . . . . , laminated ss *- lntrafrnnl cong -*.* extrofmnl cong

COMPARISON OF THICK FINING -UPWARD CYCLES ( 3 0 - 5 0 m )

C

Fig . 21 A. Typica l c y c l i c sequence through t h e McMurray Formation (Fig . 18 ) ; B. Typica l c y c l i c sequence through t h e Morrison Formation New Mexico (Fig. 20) ; C. Typ ica l Carboni ferous c y c l e , South Wales (Ke l l ing , 1968) (from M i a l l , 1980).

F i g . 22 The channel system of t h e Kosi a l l u v i a l f a n , I n d i a , showing westward mig ra t ion of t h e p r i n c i p a l d i s t r i b u t a r y (from Holmes, 1965).

F i g u r e 23 i l l u s t r a t e s t h e g e n e r a t i o n o f s u c c e s s i v e c o a r s e a l l u v i a l

f a n wedges banked a g a i n s t s tepped normal f a u l t s . F i g u r e s 24 and 25

compare f i n i n g and coarsening upward c y c l e s o f t e c t o n i c o r i g i n w i t h s i m i l a r

c y c l e s t h a t have been depos i t ed by q u i t e d i f f e r e n t p rocesses . Columns A ,

B and C i n F igu re 24 i l l u s t r a t e a u t o c y c l i c c y c l e s from t y p i c a l b ra ided

and meandering r i v e r s , whereas column D i s caused by p r o g r e s s i v e abandonment

o r decay o f a n a l l u v i a l f a n lobe . I n F i g u r e 25 columns A and B r e p r e s e n t

p rog rada t ion of a l l u v i a l f a n s , whereas column C w a s caused by v e r t i c a l

agg rada t ion on an outwash p l a i n i n f r o n t of an advancing g l a c i e r . Column

D i s a s m a l l s c a l e outwash cyc le . C l e a r l y t h e s tudy of v e r t i c a l p r o f i l e s

alone, i s inadqquate t o d i s t i n g u i s h t h e s e v a r i o u s c y c l e t y p e s . Knowledge

of l a t e r a l f a c i e s v a r i a b i l i t y , t e c t o n i c and c l i m a t i c s e t t i n g i s a l s o necegsary .

10. Other compl i ca t ions

Under t h i s heading a r e cons ide red some a d d i t i o n a l sedimentary e f f e c t s

of a g e , t e c t o n i c s and c l i m a t e which compl i ca t e t h e accumulat ion of f l u v i a l

d e p o s i t s b u t which, i f i n t e r p r e t e d c o r r e c t l y , may add cons ide rab ly t o t h e

o v e r a l l g e o l o g i c a l s y n t h e s i s .

1 0 . 1 Importance of g e o l o g i c a l age : Schumm (1968) sugges ted t h a t t h e

e v o l u t i o n of l and v e g e t a t i o n i n t h e mid-Paleozoic had a n impor tant i n f l u e n c e

on f l u v i a l s t y l e , i n t h a t i t i n c r e a s e d bank cohes ion and the reby caused a

g e n e r a l l y i n c r e a s e d c h a n n e l i z a t i o n of flow. The sugges t ion w a s t h a t f l u v i a l

environments would be dominated by bedload "braided" r i v e r s b e f o r e land

v e g e t a t i o n evolved , and by a g r e a t e r v a r i a t i o n i n f l u v i a l s t y l e t h e r e a f t e r .

C o t t e r (1978) has s i n c e confirmed t h i s sugges t ion f o r p a r t s of t h e Appalachian

r eg ion by a l i t e r a t u r e survey of p u b l i c a t i o n s d e a l i n g w i t h Phanerozoic

f l u v i a l d e p o s i t s . The i n c r e a s e d d i v e r s i t y of f l u v i a l s t y l e s a p p a r e n t l y

d a t e s from S i l u r i a n t ime. Long (1978) showed t h a t e p s i l o n crossbedding is

rare i n P r o t e r o z o i c d e p o s i t s . A p a r t i c u l a r l y common f l u v i a l s t y l e i n Devonian

Fig. 23 S t r a t i g r a p h i c response t o pu l sed t e c t o n i c movement. Pe r iods of a c t i v e f a u l t movemeht a r e accompanied by development of an a l l u v i a l f a n apron , w i t h t h e development of l a r g e s c a l e c y c l i c sequences. Based on t h e Miocene-Pliocene geology o f Tuscany (from M i a l l , 1978b).

COMPARISON OF MEDIUM SCALE FINING UPWARD CYCLES (7-13m)

s m g c f c LLLLU

Fig . 24 A-C a r e c h a n n e l - f i l l sequences; A . a t y p i c a l South Saskatchewan- type bra ided p r o f i l e (from Cant and Walker, 1976) ; B. an Eocene p o i n t b a r (Nijman and Puigdefabregas , 1978; s e e Fig . 15 o f t h e s e n o t e s ) , C . A modem p o i n t b a r , Amite River (McGowen and Garner , 1970); D. Sequence formed by v e r t i c a l agg rada t ion and p rogres s ive abandonment of a n a l l u v i b l f a n lobe (Heward, 1978) (from Miall, 1980) .

s m g c f c ULLU

.. . .. . . . .. .. -

., .. L i

COMPARISON OF MEDIUM SCALE COARSENING UP CYCLES (3- l lm)

Fig. 25 A, B. progradation of alluvial fan lobes, A from Heward (1978) B. from Steel and Aasheim (1978); C. vertical aggradation on a glacial outwash plain in front of an advancing glacier; D. cycle formed by bar progradation or fill of a channel progressively deepened by melting ice (Costello and Walker) (from Miall, 1980).

Fig. 26 Watershed formed over an active anticline, Lesser Balkan Range, Asia (from Trifonov, 1978) .

and o l d e r u n i t s i s what C o t t e r (1978) termed "shee t b ra id ing" . C y c l i c

sequences rest on v i r t u a l l y p l a n a r e r o s i o n s u r f a c e s o r show a much

a t t e n u a t e d wedging-out a t t h e i r base a g a i n s t ex t remely broad , sha l low

channe l s , r e p r e s e n t i n g v i r t u a l l y unconfined f low.

10.2 Syndepos i t i ona l t e c t o n i c s : I n s e c t i o n 9.2 I d i s c u s s e d t h e

e f f e c t s of t e c t o n i c p u l s e s i n g e n e r a t i n g l a r g e s c a l e coa r sen ing and f i n i n g

upward c y c l e s . S~-ndepositionalmovement may a l s o cause t h e p re sence of

i n t r a f o r m a t i o n a l f o l d s , f a u l t s and un ton fo r rn i t i e s . I n a d d i t i o n t o c r e a t i n g

d i s c o n t i n u i t i e s i n t h e sediments t h e i r growth du r ing sed imen ta t ion may

a l t e r l o c a l p a l e o s l o p e , and s o t h e r e may be d i v e r s i o n of r i v e r channels

and a r e s u l t i n g m o d i f i c a t i o n of sediment t h i c k n e s s e s and f a c i e s d i s t r i b u t i o n .

Th i s s u b j e c t was d i s c u s s e d i n d e t a i l by M i a l l (1978b).

The marg ina l zone of many a l l u v i a l b a s i n s , p a r t i c u l a r l y i n compress ional

t e c t o n i c environments, may be u n d e r l a i n o r bounded by a s e r i e s of f o l d s and/or

t h r u s t f a u l t s . Growth of such s t r u c t u r e s h a s r e s u l t e d i n 20' d i p s i n modern

a l luv ium on t h e Himalayan margin of t h e Indo-Gangetic p l a i n , t i l t i n g and

i n c i s i o n of a 1700 yea r o l d d ra inage c a n a l i n t h e Mesopotamian b a s i n ,

and d i v e r s i o n of r i v e r channels i n p a r t s of c e n t r a l Asia (F igu re 26, from

Tr i fonov , 1978) .

T i l t i n g of a l l uv ium i s t h e f i r s t s t a g e i n t h e development of i n t r a f o r m a t i o n a l

unconformi t ies . These may l o c a l l y be s t r o n g l y angu la r b u t p e r s i s t l a t e r a l l y

a long s t r i k e f o r only a few k i l o m e t r e s , and a l s o d i e o u t i n t o t h e d e p o s i t i o n a l

b a s i n . Exce l l en t examples i n some T e r t i a r y rocks i n Spain were d e s c r i b e d by

Riba (1976); some examples a r e i l l u s t r a t e d .in F i g u r e 27. A l t e r n a t i v e l y i f

s ed imen ta t ion keeps pace w i t h subs idence t h e b a s i n margin may be deformed

i n t o a syndepos i tona l f o l d , a s i l l u s t r a t e d i n F i g u r e 28. Many l o c a l wedge-

o u t s and i n t e r n a l unconfo rmi t i e s a r e t o be expected i n t h e proximal limb

of t h e f o l d .

Fig . 27 Superimposed i n t r a f o r m a t i o n a l unconformi t ies ; A. T e r t i a r y , Pyrenees; B. Cretaceous-Paleocene, Utah. s o u r c e s t o l e f t (from M i a l l , 1978b) .

n Fig . 28 Genera t ion of s y e e p o s i t i o n a l f o l d s by p r o g r e s s i v e upwarp. A.

Uinta Bas in , B. A Devonian Bas in i n Norway. Sources t o l e f t (from M i a l l , 19 78b ) .

Fig. 29 Neogenic a n t i c l i n e s , p a r t l y f a u l t bounded,Po Basin, I t a l y . M i : Miocene, P I : Pl iocene Q: Quaternary(from Mia l l , 1978b).

Utah Coiorado

lOOkrn

Fig. 30 Development of o f f l app ing c l a s t i c wedges i n Cretaceous molasse of the Western I n t e r i o r . A-C mark l o c i of depocentres formed progress ively f u r t h e r from source ( t o l e f t ) (from Mia l l , 1978b, a f t e r Weimer , 19 70) .

Growth of f o l d s w i t h i n a sedimentary b a s i n may cause i n t r a f o r m a t i o n a l

unconformi t ies and "neogenic a n t i c l i n e s " . Examples from t h e Po Bas in ,

I t a l y a r e i l l u s t r a t e d i n F i g u r e 29. D ive r s ion of channels around such

s t r u c t u r e s i s i l l u s t r a t e d i n F i g u r e 26, and has been mapped i n p a r t s of

t h e Witwatersrand go ld f i e l d (South A f r i c a ) . P l a c e r gold i n t h e s e Archean

rocks is conf ined mainly t o a c t i v e channe l s , and p r o s p e c t i n g i n some

a r e a s h a s used a sedimentological - tec tonic model which focussed e x p l o r a t i o n

i n t h e s y n c l i n e s (A. But ton , p e r s . com. 1981).

Weimer (1970) showed i n t h e Cre taceous molasse of t h e wes t e rn

United S t a t e s , how s y n d e p o s i t i o n a l s y n c l i n e s w i t h t h i c k molasse accumula t ions

formed p r o g r e s s i v e l y f u r t h e r away from t h e mountains (F igu re 30). Both

sedimentary l o a d i n g and t h e growth o f low ampl i tude a r c h e s deep i n t h e

b a s i n caused t h i s p a t t e r n . Weimer (1970) a l s o desc r ibed what he termed

a l o c a l " r e s i d u a l a n t i c l i n a l a rch" a s t r u c t u r a l h i g h l e f t behind by subs idence

t a k i n g p l a c e w i t h i n d e l t a i c depocen t r e s on e i t h e r s i d e of t h e a r c h .

1 0 . 3 C l i m a t i c c o n t r o l s : Some of t h e e f f e c t s of va ry ing c l i m a t e on

r i v e r morphology were d i scussed i n s e c t i o n 2.2. Climate c o n t r o l s humidity

and t h e presence and d e n s i t y of v e g e t a t i o n , bo th of which have impor tant

e f f e c t s on channel and sediment t ype . F a c i e s models are not y e t a v a i l a b l e

f o r t r o p i c a l humid c l i m a t e s . A s mentioned i n s e c t i o n 9.2 advancing i c e

s h e e t s may g e n e r a t e a l a r g e s c a l e coa r sen ing upward c y c l e (F igu re 2 5 C ) .

R e t r e a t i n g i c e s h e e t s may be accompanied by f i n i n g upward f l u v i a l c y c l e s ,

a l t hough none have y e t been recorded i n t h e l i t e r a t u r e .

11, Basin a r c h i t e c t u r e and t e c t o n i c s e t t i n g

The a r c h i t e c t u r e of a b a s i n can b e d e s c r i b e d a s t h e geometry and

r e l a t i v e arrangement of t h e major f a c i e s assemblages i n t h e b a s i n f i l l .

It r e f l e c t s b a s i n shape , subs idence r a t e s and t h e p o s i t i o n of major sediment

sources . Most of t h e s e parameters a r e governed by t e c t o n i c s .

Miall (1981b) showed t h a t i n most a l l u v i a l b a s i n s t h e d r a i n a g e

network has an o r thogona l r e l a t i o n s h i p t o l o c a l t e c t o n i c g r a i n . The

main d ra inage from surrounding s o u r c e a r e a s descends a p a l e o s l o p e o r i e n t e d

pe rpend icu la r t o t h e main c o n t r o l l i n g t e c t o n i c e lements .

These t r a n s v e r s e r i v e r s maydrain i n t o a l a k e a t t h e b a s i n c e n t r e o r i n t o

t h e s e a . A l t e r n a t i v e l y t h e c e n t r e of t h e b a s i n may b e occupied by a t r u n k

r i v e r f lowing a long t h e b a s i n a x i s a s a l o n g i t u d i n a l r i v e r .

T ransve r se r i v e r s may i n c l u d e a b e l t of a l l u v i a l f a n s (ba j ada )

a t t h e b a s i n margin. They form a l l u v i a l p l a i n s o rp i edmont s t e n s t o a

few hundreds of k i l o m e t r e s i n w id th . L o n g i t u d i n a l ~ i v e r s may b e hundreds

t o thousands o f k i l o m e t r e s long. A l l t h e wor ld ' s major r i v e r s (Amazon,

N i l e , M i s s i s s i p p i , Ganges, Brahmaputra e t c . ) a r e l o n g i t u d i n a l .

R ive r s end a s e s t u a r i e s , o r a s d e l t a s , o r as ephemeral channels dying

o u t on Lake margins o r t i d a l f l a t s . D e l t a s may conven ien t ly by c l a s s i f i e d

i n t o t h r e e t y p e s , r e f l e c t i n g t h e predominance of e i t h e r f l u v i a l , wave o r

t i d a l energy a s t h e main sediment d i s p e r s a l mechanism on t h e d e l t a f r o n t

(Galloway, 1975) . River dominated d e l t a s b u i l d ou t a b i r d s f o o t o r l o b a t e

p a t t e r n unimpeded by marine d i s p e r s a l p r o c e s s e s . I n a r e a s of h i g h wave

energy t h e r ive r -bo rne sediment i s c a r r i e d back onshore where i t i s

d e p o s i t e d a s a s e r i e s of l i n e a r o r a r c u a t e beach r i d g e s s u b p a r a l l e l t o

sho re . I n t i d a l d e l t a s t h e s t r o n g r e v e r s i n g c u r r e n t s b u i l d l i n e a r sand

s h o a l s s e p a r a t e d by scour channels o r i e n t e d sub-perpendicular t o s h o r e .

These v a r i o u s d e l t a geometr ies i n t u r n c o n t r o l t h e arrangement of f l u v i a l

sediments on the d e l t a p l a i n .

Using t h e t r a n s v e r s e / l o n g i t u d i n a l c r i t e r i o n and t h e v a r i o u s r i v e r

t e r m i n a t i o n P a t t e r n s d e s c r i b e d above n i n e common b a s i n f i l l models can be

de f ined f o r a l l u v i a l d e p o s i t i o n a l systems. These a r e l i s t e d i n Table 1 0 and

TABLEIO: a l l u v i a l b a s i n - f i l l p a t t e r n s

Model proximal medial d i s t a l c h a r a c t e r i s t i c t e c t o n i c s e t t i n g s (Table I t )

T fan

T fan-delta

T f a n l r i v e r

T f a n l r i v e r

T b r a id p la in

-

T r i v e r

T r i v e r

T r i v e r

L r i v e r

L r i v e r

L r i v e r

L r i v e r

l ake marginlnon d e l t a i c coas t

l ake marginlsea coas t

river-dominated d e l t a

river-dom. d e l t a wi th barrier-lagoon

wave-dominated d e l t a

lake marginlestuary

r i v e r dominated d e l t a

tide-dominated d e l t a

wave dominated d e l t a

T = . t r a n s v e r s e , L = longi tudinal

i l l u s t r a t e d i n F i g u r e 31. Modern and a n c i e n t examples of each were

d i scussed by Miall (1981b) b u t t h i s must be omi t t ed h e r e because of space

l i m i t a t i o n s .

Models 1 and 2 are c h a r a c t e r i s t i c of small b a s i n s such a s in termontane

grabens o r wrench f a u l t b a s i n s . Model 6 may a l s o occur he re . Models 3 ,

4 and 5 a r e t y p i c a l of c o a s t a l p l a i n s , i n c l u d i n g f o r e a r c and r e t r o a r c

b a s i n s and d i v e r g e n t c o n t i n e n t a l margins. (These and o t h e r p l a t e t e c t o n i c

terms a r e i l l u s t r a t e d i n F i g u r e 3 2 ) . Models 6 , 7 and 8 occur a long o r

p a r a l l e l t o s u t u r e b e l t s , o r where p l a t e boundar ies c r o s s from oceanic t o

c o n t i n e n t a l c r u s t . Models 6 , 7 and 9 can occur where graben systems s t r i k e

a t h i g h a n g l e s t o t h e c o a s t , such as aulacogens .

A l l u v i a l b a s i n s can occur i n twelve p r i n c i p l e t e c t o n i c s e t t i n g s . These

are l i s t e d i n Table 11, w i t h modern and a n c i e n t examples, and a l i s t i n g

of t y p i c a l b a s i n f i l l models. The t h i c k e s t a l l u v i a l sequences (up t o 1 0 km)

a r e t h o s e which occu r i n r e t r o a r c and foredeep b a s i n s . These commonly a r e

termed molasse. Miall (1981b) d i s c u s s e s t h e s u b j e c t o f t e c t o n i c s e t t i n g

a t g r e a t e r l e n g t h .

12 . F u e l s and m i n e r a l s i n f l u v i a l d e p o s i t s

Three t y p e s ofeconomic d e p o s i t a r e a s s o c i a t e d w i t h f l u v i a l sediments:

1. Primary d e p o s i t s accumulated by h y d r a u l i c s o r t i n g and concen t r a t ion

of d e t r i t a l g r a i n s i n f l u v i a l channe l s . These are p l a c e r d e p o s i t s , i n c l u d i n g

gold , p la t inum, uranium, diamonds, t i t a n i u m ( r u t i l e , i l m e n i t e ) , z irconium

(z i r con) cesium (monazite) and t i n ( c a s s i t e r i t e ) .

2. Primary d e p o s i t s formed as a n i n t e g r a l p a r t of t h e d e p o s i t i o n a l

system. Coal i s t h e most impor tant o f t h e s e . S i d e r i t i c i r o n o r e s were

a l s o impor tant a t one t ime b u t a r e no longe r mined.

Table 11 Tectonic c l a s s i f i c a t i o n of a l l u v i a l bas ins

Divergent p l a t e margins

1 111 p r e - d r i f t r i f t grabens E. Afr ican r i f t s T r i a s s i c . N.E. North Hubert e_t &., 1976 1 . 6 America

Cretaceous , sou the rn I .C . Rust, 1979 S. A f r i c a

Cretaceous-Ter t iary . P u r c e l l et ~ l . , 1980; Mia l l e_t a l . . west Ba f f in Bay margins 1980

B r a z i l Coast Ponte ~t a l . . 1980

f a i l e d arms, aulacogens Benue Trough Athapuscow Basin Hoffman. 1969; Hoffman e_t a l . , 1974

T e r t i a r y . margins of Z i e g l e r . 1980 Viking-Central Graben

Table M t . Ss. of S.E. Hobday and von Brunn. 1979 South A f r i c a

pas s ive ocean ic margins U.S. A t l a n t i c P ro t e rozo ic , W. North S tewar t , 1972; Winston, 1978 coas t America

Gulf Coast T r i a s s i c , A lbe r t a H i a l l , 1976 B r a z i l Coast

f l a n k i n g t r a n s v e r s e e lements

P r e - c o l l i s i o n convergent p l a t e margins

5 31 1 f o r e a r c b a s i n s

Gilwood Ss . (Peace- Ro t t en fusse r and Ol ive r , 1977 River Arch)

Vendom F io rd Fm (Bache T r e t t i n . 1978 Pen insu la Arch)

P e e l Sound Formation Mia l l and Gib l ing , 1978 (Boothia U p l i f t )

P a c i f i c coas t . Eocene. Oregon Dot t , 1964. 1966 Guatemala

P n c i f i c C p a s t . Devonian. Midland Mitchell and McKerrow, 1976; Ch i l e Va l l ey , Scot land Bluck, 1978

North c o a s t . New Bowser Lake G p . , B.C. EiSbacher. i nma l l . l 9 8 l a Guinea

Cook I n l e t , Alaska Western Trough, Burma

Model Ba l ly and type Snelson

c l a s s i f i c a t i o n

modern examples anc ien t examples r e f e r e n c e s f o r a n c i e n t exallples

most t y p i c a l b a s i n - f i l l

models (Table 10)

6 312 backarc b a s i n s and W. Japan Skeena Gp. . B r i t i s h Eisbacher , in id, 19alcc 1.2.3.4.5 marginal s e a s Northern Nev Columbia (? )

Guinea

7 22 r e t r o a r c o r f o r e l a n d N. Sumatra k v o n i a n . Anglo-Welsh bas ins Cuve t te

Amazon Basin Ebro Basin. Spain Eocene. Peru-Maracaibo

Trough Argent ina Beaufor t Gp., Karoo

Basin. S. A f r i c a Alaska North Slope Jurass ic-Cretaceous ,

A lbe r t a Ordovician t o Carboni-

f e r o u s Appalachian c l a s t i c vedges

Al l en , 1979

Van Houten. 1974 1.3.4,5.7,8 Van Houten and Trav i s . 1968;

Browning, 1980

Hobday. 1978 Cran tz g.. 1979 Eisbacher . etg.. 1974

Meckel, 1970; Donaldson and Shumaker, in Miall, 1981a

312. 321. in termontane. succe- Va l l e l ong i tud i - Devonian of Svalbard F r i end and Moody S t u a r t , 1972 1.2.6 331 s s o r b a s i n s n a l , Chi le

Magdalena Val ley, Devonian of Lake Orcadie, Columbia Scot land Donovan, i n F r i end and Williams.

1978 T e r t i a r y . N.E., E l l e s -

lnere Is. Miall, in Miall, 1981a

pseudo-foredeep S. Timor bas ins (subduct ion Ni l e Cone and s u t u r i n g o f ( i n c i p i e n t pas s ive margin) eubduction)

P o s t - c o l l i s i o n and s u t u r i n g convergent margins

S t r i k e - S l i p p l a t e margins

p e r i p h e r a l o r foredeep M"so~'otamla basins (on su,,ducting I"do-(;""kFtic

p l a t e ) Trougll

Po hasill

I I 3 3 pu l l - apa r t and f a u l t - Sa l ton Trough f l ank dep res s ion San Francisco Bay bas ins

Dead Sea

C r a t o n i c b a s i n s

12 121 broad downwarps o r Lake Eyre sags

Lake Chad

Indo-(:ange t l c Trough Da t t a and S a s t r i , 1977 Mesopotamia Basin Kukal and Al-Jassim, 1971

A111 lncs mol;lssc Van, Houten. 1974

Ridge Basin C r o v e l l , 197-b Hornelen Basin S t e e l . 1976; S t e e l and

Aasheim. 1978 Carboniferous

Cantabr ian M t s . Reading. 1975

La te Paleozoic . Wanless, 3 &. , 1970 American i n t e r i o r

Ecca Gp, Karoo Basin Hobday, 1978

North Sea B r a z i l Soa res &. . 1978 Eyre Fm, A u s t r a l i a Wopfner g. , 1974

8-subductton mr, volcanic arc - rnwgiml sea A - ~ u c t i o n zone dtvsrgent morpin

intermontane baain posscve oceanic margin

CONTINENTAL CRUST

Fig . 32 P l a t e t e c t o n i c s e t t i n g o f a l l u v i a l b a s i n s (heavy d o t p a t t e r n ) and o t h e r sedimentary f a c i e s ( l i g h t d o t p a t t e r n ) (from Miall, 1981b).

F ig . 33 A Witwatersrand p l a c e r channelway, showing m u l t i p l e s cour s u r f a c e s and t rough crossbedding. Gold and uranium c o n t e n t s a r e h i g h e s t i n t h e c h a n n e l - f i l l conglomerates (from Minter , 1978) .

3 . Secondary d e p o s i t s i n which t h e porous ~ ~ n d b o d y a c t s as a

condu i t f o r low-temperature f l u i d m i g r a t i o n and as a h o s t f o r t h e

u l t i m a t e depos i t . O i l , g a s ; heavy o i l - s , copper and uranium a r e t h e

p r i n c i p l e examples.

The fo l lowing n o t e s d i s c u s s t h e a p p l i c a t i o n of f l u v i a l sedimentology

t o e x p l o r a t i o n o r i n t e r p r e t a t i o n of t h e s e d e p o s i t s .

1 2 . 1 P l a c e r d e p o s i t s : Some of t h e wor ld ' s l a r g e s t gold and uranium

d e p o s i t s a r e of t h i s t ype , i n c l u d i n g t h e Witwatersrand f i e l d s i n South

A f r i c a (go ld , uranium) and t h e b a s a l Huronian d e p o s i t s (uranium) of

E l l i o t Lake, On ta r io . A c o n s i d e r a b l e amount of s ed imen to log ia l work h a s

been done on t h e Witwatersrand d e p o s i t s of P r o t e r o z o i c age. Minter

(1978) provided a r e g i o n a l summary, and Smith and Minter (1980) r e p o r t e d

a d e t a i l e d s tudy of pay v a l u e s i n r e l a t i o n t o channel and b a r t r e n d s .

Minter (1978) showed t h a t t h e p l a c e r d e p o s i t s occu r i n a t e x t u r a l l y

andminera log ica l lymatu re conglomerate-quartz s ands tone success ion depos i t ed

i n b ra ided r i v e r and c o a s t a l environments. The f l u v i a l d e p o s i t s show a

Scott-Donjek-South Saskatchewan-Plat te g r a d a t i o n from proximal t o d i s t a l

s e t t i n g s w i t h most of t h e b e s t p l a c e r s occu r ing i n t h e Donjek t y p e seqences .

An example i s shown i n F i g u r e 33. Gold and uranium a r e concen t r a t ed i n

t rough c r o s s bedded c h a n n e l - f i l l conglomera tes , and maps of t h e i r d i s t r i b u t i o n

r e v e a l an i n t r i c a t e b r a i d e d channel network (F igu re 34). P a l e o c u r r e n t

d a t a have been used t o conf i rm t h e sed imen to log ica l t r e n d s . S i m i l a r i n t e r -

p r e t a t i o n s of o t h e r p l a c e r d e p o s i t s have been pub l i shed by McGowen and Groat

(1971) and S e s t i n i ( i n Amstutz and Bernard , 1973) . The E l l i o t Lake uranium-

bea r ing conglomerates have a l s o been i n t e r p r e t e d as p l a c e r s (e .g . Roscoe, 1969),

b u t d e t a i l e d sedimentolgocal work on them h a s n o t been c a r r i e d ou t ( i t i s

i n p r o g r e s s a t t h e U n i v e r s i t y o f Toron to ) .

fix 4'\ Sample locotlonr pK 4 \ Sample locotions

O4>\ LOW uroniurn O+>\ I.. LOW rotio High uranium n10h rot10

Fig . 34 A. Pa leocur ren t s and pebble s i z e s i n a Witwatersrand p l a c e r . B , C , D show go ld , uranium and uranium/gold r a t i o va lues i n r e l a t i o n t o channel network (from Minter , 1978). Only t h e major channels a r e shown i n t h e s e diagrams.

12.2 Coal: Coal i s formed i n t h e f l o o d p l a i n s of r i v e r systems and

c o a s t a l marshes. The Carboniferous coa l s of B r i t a i n , t h e United S t a t e s

and Maritime Canada, and t h e Jurass ic-Cretaceous c o a l s of western Canada

were formed l a r g e l y i n marginal marine f l u v i a l - d e l t a i c environments. Some

were formed i n landlocked f l u v i a l b a s i n s , such a s the Carboniferous Saar

C o a l f i e l d , Germany,Permian c o a l f i e l d s of c e n t r a l France (Williamson,

1967), and t h e P ic tou c o a l f i e l d , Nova S c o t i a (Hacquebard and Donalason,

i n Dapples and Hopkins, 1969).

An understanding of c o a l d i s t r i b u t i o n r e q u i r e s knowledge regarding

f l u v i a l nnd d e l t a i c c y c l i c d e p o s i t i o n a l p rocesses , p a r t i c u l a r l y t h e i n t e r p l a y

between subsidence r a t e s and the r a t e of v e r t i c a l aggradat ion and l a t e r a l

channel s h i f t i n g . Horne e t a l . (1978) app l i ed a meandering channel model

t o f l u v i a l ( d e l t a p l a i n ) c o a l s i n p a r t s of the Appalachian Basin (Figure 35),

showing c o a l seams i n t e r f i n g e r i n g w i t h l evee d e p o s i t s and t runca ted a t

channel margins. Channel and c o a l seam geometry have been i n t e r p r e t e d i n

terms of an anastornosing f l u v i a l model i n the case of some Permian c o a l s

i n South Af r i ca (Leblanc Smith and Er iksson, 1979) and some of t h e Cretaceous

c o a l s of Alber ta (Smith and Putnam, 1980). Padget t and Ehr l i ch (1978)

showed how coa l d i s t r i b u t i o n i n p a r t s of West Vi rg in ia is governed by a

d e n d r i t i c dra inage system. I n F igure 36 shaded a r e a s show t h e mined-out

c o a l seam, unshaded a r e a s a r e p laces where t h e c o a l is t h i n o r absent due t o

scour ing by an over ly ing sands tone- f i l l ed channel. The mining process has

picked o u t a l a r g e channel wi th s e v e r a l t r i b u t a r i e s .

12 .3 Secondary depos i t s : I n petroleum exp lo ra t ion f l u v i a l d e p o s i t s

commonly a r e recognized i n t h e subsurface by a "blocky" o r "bell-shaped"

gamma ray o r spontaneous p o t e n t i a l l o g curve. The shape r e f l e c t s the

SWAMP POINT BAR

SCALES

SANDSTONE

SILTSTONE AND SHALE

o.o-. PEBBLE LAG - COAL 7 7 1 ~ ROOTING

METE:kET ':I - - ,

TROUGH CROSS-BEDS 0 300 0 500 1000 -/ 4 BEDDING PLANES METERS FEET

Fig. 35 A block diagram illustrating depositional environments of coal in a meandering fluvial setting, based on the Carboniferous of Kentucky (from Horne et al., 1978).

Fig. 36 A composite mine map,Pocahontas#4 coal, (Carboniferous), West Virginia. Unshaded areas show where coa,l is thin or absent due to channel scouring (from Padgett and Ehrich 1978).

t y p i c a l fining-upward c y c l e s t h a t occur i n most f l u v i a l d e p o s i t s . An

example i s i l l u s t r a t e d i n F igure 37 (from MacKenzie, i n King, 1972). Care

must be taken i n i n t e r p r e t i n g t h e s e c y c l e s . There i s a tendency t o equate

them w i t h c h a n n e l - f i l l models, such a s t h e p o i n t b a r c y c l e , but many a r e

much too t h i c k f o r such an i n t e r p r e t a t i o n t o be c o r r e c t . The t h i c k sands tone

i n t h e t h i r d h o l d from t h e l e f t i n F igu re 37 is an example. It probably

r e p r e s e n t s a composite c h a n n e l - f i l l sequence produced by v e r t i c a l aggradat ion

and p r o g r e s s i v e abandonment, such a s t h e type o f c y c l e i l l u s t r a t e d i n F igu res

20, 21B, C .

F i g u r e s 38 and39 i l l u s t r a t e net-sand i sopach maps from two .o i1 pools

i n f l u v i a l channel sands tone bod ie s . F igu re 38 shows a Miocene d e l t a - p l a i n

channel from t h e M i s s i s s i p p i b a s i n s o u t h e a s t of New Orleans (Hartman, 1972).

The t r a p mechanism is a combination of s t r a t i g r a p h y and s t r u c t u r e , t h e o i l

pool be ing l o c a t e d a t t h e c r e s t of a r o l l - o v e r a n t i c l i n e ad jacen t t o a

contemporaneous growth f a u l t . F igu re 39 shows a Pennsylvanian s h o e s t r i n g

channel sandstonefoikowing a p a l e o v a l l e y . The beds d i p westward and most

o i l i s i n the wes tern c h a m e l reach , much of t h e updip p o r t i o n of t h e

channel u n i t be ing occupied by gas (Lyons and Dobrin, i n King, 1972).

Mossop (1980) i n t e r p r e t e d t h e d i s t r i b u t i o n of heavy o i l i n t h e Athabasca

d e p o s i t s a s be ing c o n t r o l l e d by t h e t r e n d of deep channels i n c i s e d i n t o

p re -ex i s t i ng f i n e r g ra ined sediments (F igure 40) .

Most secondary mine ra l d e p o s i t s i n f l u v i a l sands tones have t h e i r o r i g i n

i n t h e l each ing and e r o s i o n of igneous o r metamorphic rocks i n upland r eg ions .

The most important such d e p o s i t s a r e t h o s e of uranium, which occur i n va r ious

P ro te rozo ic sands tones i n t h e Canadian Sh ie ld (e.g. Miller, 19801, Mesozoic

rocks of t h e wes tern United S t a t e s ( B u t l e r , 1372) , T e r t i a r y sediments of t h e

Gulf Coast (Galloway, 1978) and Permian (Beaufort Group) sediments of t h e

Karoo Bas in , South A f r i c a (Turner , 1978) . The o r i g i n of t h e uranium i n many

Fig . 37 Typ ica l e l e c t r i c l o g s thraugh a f l u v i a l sequence; a Cretaceous u n i t i n Colorado (from Mackenzie, i n King, 1972).

F i g . 38 Oil f i e l d i n a Miocene channel sand, Lou i s i ana (from Hartman, 1972).

BLOCK 31

4

0 * 0 0 0 0 0 0 0

O 0 0 0 0 0 0 0 0 8

0 O Ou, 0

8 0 0 0

0

i NET CHANNEL SANDSTONE

0 0 - 4 0 FEET

a 40 -00 FEET

L EGENO > 8 0 FEET . WELLS PRODUCINGFROM C W N U # AOANDONED CHANNEL PRODUCERS 0 WELLS PROWCING FROM OTHER SANOSTONES + D R Y HOLES

BLOCK 32

0

Fig. 39 O i l and gas f i e l d i n a Pennsylvanian channel sand, Oklahoma Tfrom Lyons and Dobrin, i n King, 1972).

. . . .g :. . .,. + ea.. . . . . . + . . . . . . . . . ... SOUTH CERES POOL AREA

. . . + + . . Nablo Co,, Oklahomo

. . . I ' 0 4 ..

+

++ ' I . . Red Fork S'ndsione

PRE-EXISTING EPSILON CHANNEL MEANDER BELT SEQUENCE

. . . . . . . . . . .

Fig. 40 Hypo the t i ca l c r o s s s e c t i o n i l l u s t r a t i n g t h e conf ines of a probable e p s i l o n channel meander b e l t and i t s l a t e r a l e r o s i o n a l r e l a t i o n s h i p wi th p re -ex i s t i ng sediments; Athabasca O i l Sands, A lbe r t a (from Mossop , 1980) .

I . - - -- . -

/SOPACH P . . . . .

4 %, . +* 4 , ~ C.L -20' U

P.4.1plu 7f

1 . . 4

of t h e s e d e p o s i t s i s u n c l e a r ; C!ic) inay have been de r ived from .the under ly ing

basement, from c r o s s c u t t i n g dykes o r from i n t e r c a l a t e d v o l c a n i c t u f f s .

However, t h e i r d i s t r u b t i o n depends on t h e p o r o s i t y of t h e sands tones and

on t h e presence of reducing a g e n t s t o p r e c i p i t a t e t h e uranium from ox id i zed

groundwaters. Carbonaceous p l a n t d e b r i s i n channel sands tones commonly

f u l f i l l s t h e la t ter cond i t ion . Uranium d e p o s i t s commonly occu r i n a c l a s s i c

" r o l l f r o n t " c o n f i g u r a t i o n (F igu re 41) . L i t t l e s ed imen to log ica l work has

beenpublished on such d e p o s i t s b u t undoubtedly i n d e t a i l t h e i r d i s t r i b u t i o n

is c o n t r o l l e d by channel t r e n d s , which a r e w h e r e t h e h i g h e s t p o r o s i t i e s and

p e r m e a b i l i t e s a r e t o be found (e.g. See land, 1978; E l l i s , 1980). There is

scope f o r much u s e f u l r e s e a r c h i n t h i s a r e a .

Silty davabne

. . . . . . . . . .

0 I0 20 FEET I 1 I I . I I

Fig . 4 1 A t y p i c a l r o l l - f r o n t uranium d e p o s i t (from Ridge, 1968).

REFERENCES

ALLEN, J.R.L., 1963a: The c l a s s i f i c a t i o n of c r o s s - s t r a t i f i e d u n i t s w i t h n o t e s on t h e i r o r i g i n ; Sedimentology, v. 2 , p . 93-114.

ALLEN, J .R.L. , 1963b: Henry C l i f t o n Sorby and t h e sedimentary s t r u c t u r e s o f s ands and sands tones i n r e l a t i o n t o f low c o n d i t i o n s ; Geol. en Mijnbouw, v . 42, p. 223-228.

ALLEN, J.R.L., 1964: S t u d i e s i n f l u v i a t i l e sedimenta t ion: S i x cyclothems from t h e Lower Old Red Sandstone. Anglo-Welsh Bas in . Sedimentology, v. 3, p. 163-198.

ALLEN, J.R.L., 1965: The sed imen ta t ion and palaeogeography of t h e Old Red Sands tone of Anglesey, North Wales; Yorks. Geol. Soc. P roc . , v . 35, p. 139-185.

ALLEN, J .R.L. , 1966: On bed forms and p a l e o c u r r e n t s . Sedimentology, v . 6 , p. 153-190.

ALLEN, J.R.L., 1970: A q u a n t i t a t i v e model of g r a i n s i z e and sedimentary s t r u c t u r e s i n l a t e r a l d e p o s i t s , Geol. J o u r , Vol. 7 , p. 129-146.

AMSTUTZ, G.C. and BERNARD, A.J . , 1973: Ores i n sediments ; Sp r inge r Ver lag , B e r l i n , 350p.

BAKER, V . R . , 1978: Adjustment of f l u v i a l sys tems t o c l i m a t e and source t e r r a i n i n t r o p i c a l and s u b t r o p i c a l environments; A . D . M i a l l , ed. , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol. Mem. 5 , p . 211-230. -

ASQUITH, G . B . , and CRAMER, S.L., 1975: T ransve r se b r a i d b a r s i n t h e Upper T r i a s s i c T r u j i l l o Sandstone o f t h e Texas panhandle, J o u r . Geol., Vol. 83 , p. 657-661.

BEERBOWER, J .R, 1964: Cyclothems and c y c l i c d e p o s i t i o n a l mechanisms i n a l l u v i a l p l a i n sed imen ta t ion , - i n D.F. Merriam, &., C y c l i c Sedimenta t ion , Geol. Surv. Kansas Bu l l . 169, p. 31-42.

BERNARD, H.A. , LEBLANC, R.J . , and MAJOR, C . J . , 1962: Recent and P l e i s t o c e n e geology o f s o u t h e a s t Texas; & E.H. Rainwater and R.P. Z ingula , - e d s . , Geology o f t h e Gulf Coast and c e n t r a l Texas; Geol . Soc. Am. Guidebook f o r 1962 Ann, M t g . , p. 175-224.

BERNARD, H . A . , and MAJOR, C . J . , 1963: Recent meander b e l t d e p o s i t s o f t h e Brazos River : a n a l l u v i a l "sand" model ( a b s . ) : Am. Assoc. P e t r o l . Geol. B u l l . , v . 47, p. 350.

BLUCK, B . J . , 1971: Sedimenta t ion i n t h e meandering R ive r Endr ick , Sco t . J o u r . Geol . , v . 7 , p. 93-138.

BOOTHROYD, J . C . , and ASHLEY, G.M. , 1975: P r o c e s s , b a r morphology, and sedimentary s t r u c t u r e s on b r a i d e d outwash f a n s , n o r t h e a s t e r n Gulf of Alaska; i n A.V. J o p l i n g and B . C . McDonald, eds . , G l a c i o f l u v i a l and g l a c i o l & u s t r i n e sed imen ta t ion ; Soc. ~ c o n . P a l e o n t . Mine ra l . Spec. Pub. 23, p . 193-222.

BULL, W.B., 1977: The a l l u v i a l f a n environment, Progr . Phys. Geogr. V! 1, p. 222-270.

BUTLER, A.P., j r . , 1972: Uranium, in Geologic A t l a s of t h e Rocky Mountain r e g i o n , Rocky M t . Assoc. Geol . , p . 315-317.

CAMPBELL, C . V . , 1976: R e s e r v o i r geometry o f a f l u v i a l s h e e t s ands tone , Am. Assoc. P e t r o l . Geol . , v . 60, p. 1009-1020.

CANT, D . J . , 1978: Development o f a f a c i e s model f o r sandy b ra ided r i v e r sedimenta t ion: Comparison o f t h e South Saskatchewan River and t h e B a t t e r y P o i n t Formation: in A.D. Miall, e d . , F l u v i a l Sedimentology; Can. Soc. P e t r o l . Geol. Mem. 5 , p . 627-640,

CANT, D . J . , and WALKER, R.G., 1976: Development of a b r a i d e d - f l u v i a l f a c i e s model f o r t h e Devonian B a t t e r y P o i n t s ands tone , Quebec; Can. J. E a r t h S c i . , v . 1 3 , p . 102-119.

CANT, D . J . , and WALKER, R.G., 1978: F l u v i a l p r o c e s s e s and f a c i e s sequences i n t h e sandy b r a i d e d South Saskatchewan R ive r , Canada; Sedimentology, V. 25, p. 625-648.

COLEMAN, J . M . , 1969: Brahmaputra River : channel p r o c e s s e s and sed imen ta t ion ; Sediment. Geol . , v . 3 , p. 129-239.

COLLINSON, J . D . , 1970: Bedforms of t h e Tana R ive r , Norway: Geog. Annaler , Vol. 52A, p . 31-55.

CONAGHAN, P . J . , and JONES, J . G . , 1975: The Hawkesbury Sandstone and t h e Brahmaputra: a d e p o s i t i o n a l model f o r c o n t i n e n t a l s h e e t s ands tones , Jou r . Geol. Soc. A u s t r a l i a , v . 22, p . 275-283.

COTTER, E . , 1978: The e v o l u t i o n of f l u v i a l s t y l e , w i t h s p e c i a l r e f e r e n c e t o t h e c e n t r a l Appalachian P a l e o z o i c , i n A.D. Miall, e d . , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol . , Mem. 5 , p . 361-384.

DAPPLES, E.C., and HOPKINS, M.E., eds . 1969: Environments of c o a l d e p o s i t i o n , Geol. Soc. Am. Spec. Paper 114.

ELLIS, G.K., 1980: D i s t r i b u t i o n and g e n e s i s of sedimentary uranium n e a r Curnamona, Lake Frome r e g i o n . South A u s t r a l i a , AAPG B u l l . , v . 64, p . 1643-1657.

FISK, H . N . , 1944: Geo log ica l i n v e s t i g a t i o n o f t h e a l l u v i a l v a l l e y of t h e Lower M i s s i s s i p p i R i v e r ; M i s s i s s i p p i River Commission, 78p.

GALLOWAY, W . E . , 1975: P rocess framework f o r d e s c r i b i n g t h e morphologic and s t r a t i g r a p h i c e v o l u t i o n of d e l t a i c d e p o s i t i o n a l sys tems, M.L. Broussard , e d . , D e l t a s , models f o r e x p l o r a t i o n , Houston Geol. Soc., p . 87-98.

GALLOWAY, W . E . , 1978: Uranium m i n e r a l i z a t i o n i n a c o a s t a l - p l a i n f l u v i a l a q u i f e r system: Catahoula Formation, Texas; Econ. Geol . , v . 73, p. 1655-1676.

HARBAUGH, J . , and BONHAM-CARTER, G . , 1970: Computer s i m u l a t i o n i n geology, Wiley, New York, 575p.

HARMS, J . C . , SOUTHARD, J . B . , SPEARING, D.R. and WALKER, R.G., 1975: Depos i t i ona l environments as i n t e r p r e t e d from primary sedimentary s t r u c t u r e s and s t r a t i f i c a t i o n sequences ; Soc. Econ. P a l e o n t . Mineral Shor t Course 2, D a l l a s , 161p.

HARTMAN, J . A , 1972: "G2" channel s ands tone , Main Pass Block 35 f i e l d , Of f shore Lou i s i ana ; AAPG B u l l , Vol . 56 , p . 554-558.

HEWARD, A.P., 1978: A l l u v i a l f a n sequence and megasequence models: w i t h examples from Westphalian D - Stephanian B c o a l f i e l d s , no r the rn Spain ; & A.D. Miall, e d . , F l u v i a l Sedimentology; Can. Soc. P e t r o l . Geol. Mem. 5 , p . 669-702.

HOBDAY, D . K . , TAVENER-SMITH, R. , and MATTHEW, D . , 1975: Markov a n a l y s i s and t h e r e c o g n i t i o n of pa laeoenvi ronments i n t h e Ecca Group n e a r Vryheid, Na ta l . Trans. Geol. Soc. South A f r i c a , v. 78, p. 75-82.

HOLMES, A., 1965: P r i n c i p l e s of P h y s i c a l Geology, 2nd e d . , Nelson, London, 1288p.

HOOKE, R.L.e.B., 1967: P rocesses on a r i d - r e g i o n a l l u v i a l f a n s : J . Geol. v . 75, p . 438-460.

HORNE, J . C . , FEW, J . C . , CARUCCIO, F . T . , and BAGANZ, B.P., 1978: Depos i t i ona l models i n c o a l e x p l o r a t i o n and mine p lanning i n Appalachian r eg ion ; Am. Assoc. P e t r o l . Geol. B u l l . , v . 62, p . 2379-2411.

JACKSON, R . G . , I I . , 1975: H i e r a r c h i a l a t t r i b u t e s and a u n i f y i n g model of bed forms composed of c o h e s i o n l e s s m a t e r i a l and produced by s h e a r i n g f low, Geol. Soc. Am. B u l l . , v . 86 , p . 1523-1533.

JACKSON, R.G., 11, 1976: D e p o s i t i o n a l model of p o i n t b a r s i n t h e lower Wabash R i v e r , J . Sediment. P e t r o l . v. 46, p . 579-594.

JACKSON, R . G . , 11, 1978: P r e l i n a r y e v a l u a t i o n of l i t h o f a c i e s models f o r meandering a l l u v i a l s t r eams ; &I A . D . M i a l l , - ed . , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol . , Mem. 5 , p . 543-576.

JONES, C . M . , and McCABE, P . J . , 1980: Eros ion s u r f a c e s w i t h i n g i a n t f l u v i a l cross-beds of t h e Carboni ferous i n n o r t h e r n England, JSP, v . 50, p . 613-620.

KELLING, G., 1968: Patterns of sedimentation in Rhondda Beds of South Wales, Am. Assoc. Petrol. Geol. Bull., v. 52, p. 2369-2386.

KING, R.E., &., 1972: Stratigraphic oil and gas fields - classification, exploration methods, and case histories, Am. Assoc. Petrol. Geol. Mem. 16

KRUMBEIN, W.C., and DACEY, M.F., 1969: Markov chains and embedded Markov chains in geology: Jour. Internat. Assoc. for Mathematical Geology, v. 1, p. 79-96.

LEBLANC SMITH, G., and ERIKSSON, K.A., 1979: A fluvioglacial and glacio- lacustrine deltaic depositional model for Permo-Carboniferous coals of the northeastern Karoo Basin, Vouth Africa, Palaeogeog., Palaeoclim., Palaeoec., v. 27, p. 67-84.

LEEDER, M.R., 1973b: Fluviatile fining-upward cycles and the magaitude of paleochannels, Geol. Mag., V. 110, p. 265-276.

LEOPOLD, L.B., and WOLMAN,II.G., 1957: River channel patterns, braided, meandering and straight. U.S. Geol. Surv. Prof. Paper. 282-B.

LEVEY, R.A., 1978: Bed-form distrfbution and internal stratification of coarse-grained point bars, Upper Congaree River, S.C.; A.D. Miall, ed., Fluvial Sedimentology; Can. Soc. Petrol. Geol. Mem. 5, p. 1E-127.

LONG, D.G.F., 1978: Proterozoic stream deposits: some problems of recognition and interpretation of ancient sandy fluvial systems; in A.D. Miall, ed., Fluvial sedimentology, Can. Soc. Petrol. Geol. Mem. 5, p. 313-342.

McGOWEN, J.H., and GARNER, L.E., 1970: Physiographic features and stratification types of coarse-grained point bars; modern and ancient examples; Sedimentology, v. 14, p. 77-112.

McGOWEN, J.H., and GROAT, C.G., 1971: Van Horn Sandstone, west Texas: an alluvial fan model for mineral exploration, Bur. Econ. Geol, Texas, Rept. Invest. 72.

McKEE, E.D., CROSBY, E.J., and BERRYHILL, H.L., 1967: Flood deposits, Bijou Creek, Colorado; J. Sediment Petrol. v. 37, p. 829-851.

MIALL, A.D., 1970a: Continental-marine transition in the Devonian of Prince of WalesIsland , Northwest Territories. Can. Jour. Earth Sci., v. 7, p. 125-144.

MIALL, A.D., 1970b: Devonian Alluvial Fans, Prince of Wales IBLand, Arctic Canada. JSP, Vol 40, p. 556-571.

MIALL, A.D., 1973: Markov chain analysis applied to an ancient alluvial plain succession, Sedimentology, v. 20, p. 347-364.

MIALL, A.D., 1974: P a l e o c u r r e n t a n a l y s i s of a l l u v i a l sediments - a d i s c u s s i o n of d i r e c t i o n a l v a r i a n c e and v e c t o r magnitude; J . Sediment P e t r o l . , v . 4 4 , p . 1174-1185.

MIALL, A.D. , 1976: P a l e o c u r r e n t and paLeohydrologic a n a l y s i s of some v e r t i c a l p r o f i l e s through a Cre taceous b r a i d e d s t r e a m d e p o s i t ; Sedimentology, v. 23, p. 459-484.

MIALL, A.D. , 1977: A review of t h e b r a i d e d r i v e r d e p o s i t i o n a l environment, E a r t h Sc ience Reviews, v . 1 3 , p. 1-62.

MIALL, A.D., 1978a: L i t h o f a c i e s t y p e s and v e r t i c a l p r o f i l e models i n b ra ided r i v e r s : a summary; in A.D. Miall, ed . , F l u v i a l Sedimentology; Can. Soc. P e t r o l . Geol . Mem. 5 , p. 597-604.

MULL, A . D . , 1978b: Tec ton ic s e t t i n g and s y n d e p o s i t i o n a l s e t t i n g o f molasse and o t h e r nonmarine-paral ic sedimentary b a s i n s ; Can. J . Ea r th . S c i . , v . 15 , p. 1613-1632.

MIALL, A.D., 1979: T e r t i a r y f l u v i a l sediments i n t h e Lake Hazen i n t e r - montane b a s i n , El lesmere I s l a n d , A r c t i c Canada; Geol. Surv. Can. Paper 79-9.

MULL, A.D., 1980: c y c l i c i t y and t h e f a c i e s model concept i n f l u v i a l d e p o s i t s ; Bu l l . Can. P e t r o l . Geol . , v . 28, p . 59-80.

MIALL, A.D., e d . , 1981a: Sedimenta t ion and t e c t o n i c s i n a l l u v i a l b a s i n s , w i t h examples from North America, Geol.. Assoc. Can. Spec. Paper 23.

MIALL, A.D., 1981b: A l l u v i a l sedimentary b a s i n s : t e c t o n i c s e t t i n g and b a s i n a r c h i t e c t u r e , i n A.D. M i a l l , ed . , Sedimenta t ion and t e c t o n i c s i n a l l u v i a l b a s i n s , w i t h examples from North America; Geol. Assoc. Can. Spec. Paper 2/3.

MIALL, A.D., and GIBLING, M.R., 1978: The Siluro-Devonian c l a s t i c wedge of Somerset I s l a n d , A r c t i c Canada, and some r e g i o n a l pa leogeographic i m p l i c a t i o n s ; Sedimentary Geology, v . 21, p . 85-127.

MILLER, A . R . , 1980: Uranium geology of t h e E a s t e r n Baker Lake Basin D i s t r i c t of Keewatin, Northwest T e r r i t o r i e s , Geol. Surv. Can. Bu l l . 33s.

MINTZR, W.E.Z., 1972: A sed imen to log ica l s y n t h e s i s of f o s s i l go ld , uranium and p y r i t e c o n c e n t r a t i o n s i n P r o t e r o z o i c Witwatersrand p l a c e r s . South A f r i c a ; i n A.D. M i a l l , ed . , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol. Zrn. 5 , p. 801-m9.

MOSSOP, G . D . , 1980: F a c i e s c o n t r o l on bitumen s a t u r a t i o n i n t h e Athabasca O i l Sands, i n A.D. M i a l l , ed . , F a c t s and P r i n c i p l e s of World petroleum occur rence , Can. Soc. P e t r o l . Geol . Mem. 6 , p . 609-632.

NAMI, M . , and LEEDER, M.R . , 1978: Changing channel morphology and magnitude i n t h e Scalby Formation (M. J u r a s s i c ) o f Yorksh i r e , England: i n A.D. Miall, - ed . , F l u v i a l Sedimentology; Can. Soc. P e t r o l . ~ e o l x Mem. 5 , p! 431-440.

NANSON, G.C. , 1980: P o i n t b a r and f l o o d p l a i n fo rma t ion of t h e meandering Beat ton R ive r , n o r t h e a s t e r n B r i t i s h Columbia, Canada; Sedimentology, V. 27, p. 3-30.

N I J M A N , W. , and PUIGDEFABREGAS, C . , 1978: Coarse-grained p o i n t b a r s t r u c t u r e i n a molasse-type f l u v i a l system, Eocene C a s t i s e n t Sandstone Formation, South Pyrenean Basin: i n A.D. M i a l l , - e d . , F l u v i a l Sedirnentology; Can. Soc. P e t r o l . ~zl. Mem. 5 , p. 487-510.

PADGETT, G . , and EHRLICH, R., 1978: An a n a l y s i s of two t e c t o n i c a l l y c o n t r o l l e d i n t e g r a t e d d ra inage n e t s of Mid-Carboniferous age i n s o u t h e r n West V i r g i n i a , i n A.D. M i a l l , e d . , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol. Mem. 5 , p . 789-800.

PICARD, M.D., and HIGH. L.R., j r . , 1973: Sedimentary s t r u c t u r e s of ephemeral s t reams. Dev. i n Sed. No. 1 7 , E l s e v i e r , Amsterdam, 223 p.

POTTER, P.E., and PETTIJOHN, F .J . , 1977: P a l e o c u r r e n t s and b a s i n a n a l y s i s ; Second c o r r e c t e d and updated e d i t i o n , Sp r inge r -ve r l ag , New York, 425 p .

PUIGDEFABREGAS, C . , and VAN VLIET, A . , 1978: Meandering s t r eam d e p o s i t s from t h e T e r t i a r y of t h e sou the rnpyrenees , . i n A.D. M i a l l , e d . , F l u v i a l sedimentology, Can. Soc. P e t r o l Geol . Mem. 5 , p . 46K486.

RIBA, O., 1976: S y n t e c t o n i c unconformi tes o f t h e A l t o Cardener, Spanish Pyreness : a g e n e t i c i n t e r p r e t a t i o n , Sediment, Geol . , v . 1 5 , p. 213-233.

RIDGE, J . D . , ed . , 1968: Ore d e p s o s i t s i n t h e United S t a t e s , 1933-1967, Gra ton S a l e s Volumes, Am. I n s t . Min. Metall. Eng.

ROSCOE, S.M., 1969: Huronian rocks and u r a n i f e r o u s conglomerates i n t h e Canadian S h i e l d ; Geol. Surv. Canada Paper 68-40.

RUST, B.R., 1978a: A c l a s s i f i c a t i o n of a l l u v i a l channel sys tems, & A.D. Miall, e d . , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol. Mem. 5, p. 1G-198.

RUST, B.R. , 1978b: Depos i t i ona l models f o r b ra ided a l luvium; in A.D. M i a l l , - e d . , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol. Mem. 5 , p . 605-625.

RUST, B.R., 1979: F a c i e s models 2 . Coarse a l l u v i a l d e p o s i t s , in R.G. Walker, ed. , F a c i e s models, Geoscience Canada Repr in t S e r i e s 1, p. 9-21. -

SCHUMM, S.A., 1960: The e f f e c t of sediment t ype i n t h e shape and s t r a t i f i c a t i o n of some modern f l u v i a l d e p o s i t s , Am. Jou rn . S c i . , Vol 258, p . 177-184.

SCHUMM, S.A., 1963: A t e n t a t i v e c l a s s i f i c a t i o n o f a l l u v i a l r i v e r channe l s , U.S. Geol. Surv. Circ- 477.

SCHUMM, S . A . , 1968: S p e c u l a t i o n s concerning pa l eohydro log ic c o n t r o l s of t e r r e s t r i a l s ed imen ta t ion , Geol. Soc. Am., B u l l . , V . 79, p. 1573-1588.

SEELAND, D.A. , 1978: Eocene d ra inage p a t t e r n s and t h e i r i m p l i c a t i o n s f o r uranium and hydrocarbon e x p l o r a t i o n i n t h e Wind River Basin, Wyoming; U.S. Geol. Surv. Bu l l . 1446.

SMITH, D . G . , 1976: E f f e c t of v e g e t a t i o n on l a t e r a l mig ra t ion of anastomosed channels of a g l a c i a l meltwater r i v e r . Geol. Soc. Am. B u l l . , v . 87, p. 857-860.

SMITH, D.G. , and PUTNAM, P.E., 1980: Anastomosed r i v e r d e p o s i t s : modem and a n c i e n t examples i n A l b e r t a , Canada, Can. J . Ea r th S c i . , v. 17 , p. 1396-1406.

SMITH D.G. , and SMITH, N.D., 1980: Sedimentat ion i n anastomosed r i v e r systems: examples from a l l u v i a l v a l l e y s nea r Banff , A l b e r t a , J. Sediment. P e t r o l . , v. 50, p . 157-164.

SMITH N.D., 1970: The bra ided s t r eam d e p o s i t i o n a l environment: comparison of t h e P l a t t e River w i t h some S i l u r i a n c l a s t i c rocks , nor th- c e n t r a l Appalachians: GSA B u l l . , Vol. 81, p. 2993-3014.

SMITH, N.D. , 1971a: Transverse b a r s and b r a i d i n g i n t h e lower P l a t t e R ive r , Nebraska, GSA Bul l , Vol. 82, p. 3407-3420.

SMITH, N . D . , 1972: Some sed imen to log ica l a s p e c t s of p l a n a r c ros s - s t r a t i f i c a t i o n i n a sandy b ra ided r i v e r . JSP, Vol. 42, p. 624-634.

SMITH, N.D., 1978: Some comments on terminology f o r b a r s i n sha l low r i v e r s ; in'A.D. M i a l l , ed . , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol. Mem. 5 , p. 85-88.

SMITH, N.D. , and MINTER, W.E.L., 1980: Sedimentologica l con t , ro l s of gold and uranium i n two Witwatersrand p a l e o p l a c e r s , Econ. Geol., V. 75,. p . 1-14.

STEEL, R.J., 1974: New Red Sandstone f l o o d p l a i n and piedmont sedimenta t ion i n t h e Hebridean Province , Sco t l and , JSP, Vol. 44, p. 336-357.

STEEL, R . J . , and AASHEIM., 1978: A l l u v i a l sand d e p o s i t i o n i n a r a p i d l y subs id ing b a s i n (Devonian, Norway), i n A.D. Miall, &. , F l u v i a l Sedimentology, Can. Soc. P e t r o l . Geol. Mem. 5 , p . 385-412.

STEEL, R.J., MAEHLE, S., NILSEN, H., ROE., S.L., and SPINNANGR, A . , 1977: Coarsening-upward c y c l e s i n t h e a l luvium of Hornelen Basin (Devonian), Norway. Sedimentary response t o t e c t o n i c e v e n t s ; Geol. Soc. Am. B u l l . , V. 88, p. 1124-1134.

TRIFONOV, V . G . , 1978: Late Qua te rna ry t e c t o n i c movements of wes tern and c e n t r a l Asia ; Geol. Soc. Am. B u l l . , v . 89, p. 1059-1072.

TUNBRIDGE, I .P . , 1981: Sandy high-energy f l o o d sedimenta t ion - some c r i t e r i a f o r r e c o g n i t i o n , w i t h an example from t h e Devonian of S.W. England, Sediment. Geol . , v . 28, p. 79-96.

TURNER, B.R., 1978: Sedimentary patterns of uranium mineralization in the Beaufort Group of the sourthern Karoo (Gondwana) Basin South Africa, in A.D. Miall, ed., Fluvial Sedimentology, Can. Soc. Petrol. Geol. Mem. 5, p. 831-848.

VISHER, G.S., 1972: after Visher 1965, Physical characteristics of fluvial deposits, in J.K. Rigby and W.K. Hambling eds., Recognition of ancient sedimentary environments, Soc. Econ. Raleont . . Mineral. Spec. Pub. 16, p. 84-97.

VISHER, G.S., 1965: Use of vertical profile in environmental reconstruction, -Am, Assoc. Petrol. Geol. Bull., v. 49, p. 41-61.

WALKER, R.G., and CANT, D.J., 1979: Facies models 3: Sandy fluvial systems, in R.G. Walker, ed., Facies models, Geol. Assoc. Can. Reprint Series 1, p. 23-32.

WASSON,.R.J., 1977: Last-glacial alluvial fan sedimentation in the Lower Dervent Valley, Tasmania, Sedimentology , v. 24, p . 781-799.

WEIMER, R.J., 1970: Rates of deltaic sedimentation and intrabasin deformation, Upper Cretaceous of Rocky Mountain region, in J .P . Morgan, ed., Deltaic sedimentation modem and ancient, Soc. Econ. Paleont. - i45neral. Spec. Pub. 15, p. 270-292.

WILLIAMS, G.E., 1971: Flood deposits of the sand-bed ephemeral streams of central Australia, Sedimentology, v. 17, p. 1-40.

WILLIAMS, P.F., and RUST, B.R., 1969: The sedimentology of a braided river, J. Sediment Petrol., v. 39, p. 649-679.

WILLIAMSON, I.A., 1967: Coal Mining geology, Oxford Univ. Press, 266 p.

Date post:	31-Dec-2020
Category:	Documents
Upload:	others
View:	33 times
Download:	1 times

Analysis of Fluvial Depositional Systems...ANALYSIS OF FLUVIAL DEPOSITIONAL SYSTEMS 1. Sediment...

Documents