black shale its deposition and diagenesis

8/13/2019 Black Shale Its Deposition and Diagenesis

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Clays and Clay Minerals VoL 27 No. 5 pp. 313-321 1979.

B L A C K S H A L E I T S D E P O S I T I O N A N D D I A G E N E S I S 1

HARRY A. TOURTELOTU.S. Geological Survey, Federal Center, Denver, Colorado 80225

Abstract--Black shale is a dark-colored mudrock containing organic matter that may have generated hy-drocarbons in the subsurface or that may yield hydrocarbons by pyrolysis. Many black shale units areenriched in metals severalfold above expected amounts in ordinary shale. Some black shale units haveserved as host rocks for syngenetic metal deposits.Black shales have formed throughout the Earth's history and in all parts of the world. This suggests thatgeologic processes and not geologic settings are the controlling factors in the accumulation of black shale.Geologic processes are those of deposition by which the raw materials of black shale are accumulated andthose of diagenesis in response to increasing depth of burial.Depositional processes involve a range of relationships among such factors as organic productivity, clas-tic sedimentation rate, and the intensity of oxidation by which organic matter is destroyed. If enough or-ganic material is present to exhaust the oxygen in the environment, black shale results.Diagenetic processes involve chemical reactions controlled by the nature of the components and by thepressure and temperature regimens that continuingburial imposes. For a thickness of a few meters beneaththe surface, sulfate is reduced and sulfide minerals may be deposited. Fermentation reactions in the nextseveral hundred meters result in biogenic methane, followed successively at greater depths by decarbox-ylation reactions and thermal maturation that form additional hydrocarbons. Suites of newly formed min-erals are characteristic for each of the zones of diagenesis.Key Words---Black shale, Deposition, Diagenesis, Organic matter, Syngenetic ores.

INTRODUCTIONThe study of black shales has been difficult until a

relative ly few years ago. Outcrop ob serva tions haveyielded relatively few kinds of data for interpre ting theirorigin and the factors governing their formation. Re-cently, however, a growing body of chemical data onthe organic as well as the inorganic constituents ofblack shale has widened the scope of inferences thatcan be drawn on the genesis of such rocks. Current in-vestigations of eastern black shale, particularly theChattanooga Shale and its correlatives of Late Devo-nian and Mississ ippian ages, as a source of gas (Schotte t a l . 1978) are pr oducin g a new ge nerat ion of data;and the time is appropriate to review the processes in-volved in the accumulation of black shale. Recently,data from deep -sea drilling, such as the compos ition ofpore fluids, and new methods applied to the studies oforganic matter and the formation of oil and gas haveclarified many asp ects o f the depos ition and diagenesisof organic-rich sediments.

This paper summarizes the work of many specialistswith emphasis on guides to the study and interpretationof black shale sequences.

DEFINITION OF BLACK SHALEBlack shale is a dark-colored mudrock containing

organic matter an d silt- an d clay-size mineral grainsthat acc umulat ed together (Swan son, 1961, p. 69). Vine

1 Invited paper at 1978 Clay Minerals Conference, Bloom-ington, Indiana.

(1966, p. El -E 2) pointed out the compositional varia-tions incl uded in this definition and the ways that thesevariations can be used to study black shale.

Most shales that immediatel y meet this color crite-rion contain 1% or more organic carbon; 2-10% is acommon range. A few shales contain more than 20%organic carbon. Pyrolysis yields variable amounts ofliquid and gaseous hydrocarb ons, the a mount depend-ing in part on the nature of the original organic materialand in part on subsequent burial history. Minoramounts of authigenic carbonate minerals, either dis-persed in cements or in concretions, are characteristicfeatures of many black shale units. Most black shalesare marine and may have areal extents of thousands ofsquare kilometers.

Black shale units may have beds enriched in metalsby factors greater than 50 for Ag, for example, andgreater than 10 for Mo (Krauskopf, 1955, p. 417). Suchincreased concentrations of Ag, Mo, Zn, Ni, Cu, Cr,V, and less common ly Co, Se, and U are consp icuou sfeatures of only some black shales (Vine and Tourtelot,1970, p. 270).

IMPORTANCE OF BLACK SHALEBlack shales are important to the natural fuel-re-

source economy of the world because black shales,along with their non marine analogue, coal, constitutethe mos t im portant accessible reservoir of organic com-pounds in the Earth's crust. The organic matter mayhave generated liquid and gaseous hydro carbons foundin reservoir rocks in the subsurface into which they

Copyright 9 1979, The Clay MineralsSociety 313


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314 Tourtelot Clays and Clay Minera ls

h a v e m i g r a t e d . R e c e n t l y , h o w e v e r , t h e p o t e n t i a l o fb l a c k s h a l e i t s e lf a s a r e s e r v o i r f o r g a s e o u s h y d r o c a r -b o n s h a s b e e n r e c o g n i z e d , a n d t h i s p o t e n t i a l i s b e i n ge x p l o r e d i n t e n s iv e l y . E s t i m a t e s o f t h e g a s c o n t e n t o ft h e C h a t t a n o o g a S h a l e , f o r i n s t a n c e , r a n g e f r o m t e n st o t h o u s a n d s o f tr il li o n c u b i c f e e t (U . S . D e p t . o f E n e r -gy , 1977 , p . 99 ; Brown, 1976 , p . 94 ) .

H y d r o c a r b o n s a l s o c a n b e o b t a i n e d b y p y r o l y s i sf r o m t h e r m a l l y i m m a t u r e b l a c k s h a l e . I n c r e a s i n g a t t e n -t i o n w i ll b e g i v e n t o t h i s p o s s i b i l it y a s d e m a n d s i n c r e a s ea n d s u p p l i e s f r o m c o n v e n t i o n a l s o u r c e s d w i n d l e .

B l a c k s h a l e u n i t s a l s o a r e i m p o r t a n t a s s y n g e n e t i ch o s t s f o r m e t a l d e p o s it s . T h e K u p f e r s c h i e f e r o f P e r m -i a n a g e i n c e n t r a l E u r o p e i s a s p e c t a c u l a r e x a m p l e o fa m e t a l - e n r i c h e d b l a c k s h a l e , c o n t a i n i n g a f e w p e r c e n tC u a n d P b . R e c e n t l e a d - i s o t o p e d a t a c l e a r l y i n d i c a t et h a t t h e m e t al s i n t h e K u p f e r s c h i e f e r w e r e i n c o r p o r a t e ds y n g e n e t i c a l l y in t h e s h a l e ( W e d e p o h l e t a l . 1978) . T hel e ad - z in c d e p o s i ts a t R a m m e l s b e r g i n W e s t G e r m a n ya r e i n o rg a n i c - r ic h r o c k s o f D e v o n i a n a g e a n d h a v e as i m i la r o ri g in . T h e N o n e s u c h S h a l e o f P r o t e r o z o i c a g eh a s b e e n m i n e d f o r c o p p e r i n M i c h i g a n ( E n s i g n e t a l .1 9 68 , p . 4 6 4 ) , a n d a t l e a s t p a r t o f t h e c o p p e r i s s y n g e -n e t i c . O k l o , t h e n a t u r a l n u c l e a r r e a c t o r a n d u r a n i u md e p o s i t i n A f r i c a , m a y r e p r e s e n t a m a x i m u m c o n c e n -t r a ti o n o f u r a n i u m i n w h i c h t h e b l a c k s h a l e i n v o l v e dm a y h a v e p l a y e d a n i m p o r t a n t r o l e in l o c al i zi n g th e d e -p o s i t a n d i n r e t a in i n g f i s s io n p r o d u c t s ( B r o o k i n s , 1 9 76 ).I n S w e d e n , a l u m s h a l es o f C a m b r i a n a g e co n t a i n i n ga b o u t 1 4 % o r g a n i c c a r b o n h a v e b e e n u s e d a s a s o u r c eo f p y r o l y t i c o il a n d u r a n i u m ( A r m a n d s , 1 97 2) .O n l y a f e w m e t a l d e p o s i t s h a v e b e e n f o u n d i n b l a c ks h a le u n i t s in t h e U n i t e d S t a te s , b u t o t h e r s h a v e n o t y e tb e e n s o u g h t s y s t e m a t i c a l l y . T h e r i c h d e p o s i t s o f R a m -m e l s b e r g o c c u p y l e s s t h a n a s q u a r e k i l o m e t e r ( A n g e re t a l . 1 % 6 ) . I t i s s t il l p o s s i b l e t h a t t h e r o c k s i n a s i m i l a rs m a l l a re a o f t h e C h a t t a n o o g a S h a l e , f o r i n s t a n c e , a r er i c h e n o u g h i n m e t a l s t o c o n s t i t u te a n o r e d e p o s i t . O t h -e r m e t a l - r i c h b l a c k s h a l e s m a y e v e n t u a l l y s e r v e a sm e t a l s o u r c e s w h e n e v e r n o r m a l s o u r c e s a r e d e p l e t e d( D a v i d s o n a n d L a k i n , 1 9 6 1 , 1 9 6 2 ; V i n e a n d T o u r t e l o t ,1970).

M e t a l s c o n c e n t r a t e d s y n g e n e t i c a l l y in a b la c k s h a l eu n i t e i t h e r s u r v i v e m e t a m o r p h i c p r o c e s s e s t o b e r e -t a i n e d i n g r a p h i t i c s c h i s t s ( G a m m o n , 1 9 66 ; P e l t o l a ,1 % 8 ) o r a r e r e l e a s ed b y m e t a m o r p h i c p r o c e s s e s t o b ec o n c e n t r a t e d e l s e w h e r e ( B o y l e , 1 9 6 8, p . 83 8 ). C o n -v e r s e l y , b l a c k s h a l e u n i t s m i g h t b e r e c e p t o r b e d s f o rm e t a l s r e l e a s e d i n h y d r o t h e r m a l o r m e t a m o r p h i c s y s -t e m s . E x p l o r a t i o n s t r a te g i e s i n th e s e a r c h f o r m e t a l d e -p o s i t s a r e b e g i n n in g t o b e b a s e d o n t h e s e c o n c e p t s ( C o xan d Cur t i s , 1977; Gu l son , 1977).

L a s t l y , b l a c k s h a l e u n i t s s e e m t o e x c i t e g r e a t l y t h ei n t e l le c t u a l c u r i o s i t y a n d i m a g i n a t i o n o f t h e p e o p l e i n -v e s t i g at i n g t h e m . T h e r e i s s o m e t h i n g f a s c in a t i n g a b o u tb l a c k s h a l e: a s M a r k T w a i n s ai d a b o u t s c i e n c e , O n e

MI LL I O N I P E R I O D N O R T H S O U T H S I B E R IA & A U S T R A LI AY E A R S A ME R I C A A ME R I C A E U R O P E C E N T R A L A F R I C AA S I A g A S I AQ U A T E R N A R Y O e 9 1 4 9 0 0g TERTIARY

C RE TA CE OU S ~ 0 9 9 ~ I 9 1 4 9- - 1 3 5 -

J U R A S S I C 9 U S el@- - 1 9 a - T R I A S S I C 9 1 4 9

P E R M I A N 9- - 2 8 0 -

' E N N S Y L V A N I A N Q e l O 9 ~ 9- -320- M I S S I S S I P P [ A N- - 3 4 5 - e e o e e o c o o 9 1 4 9 1 4 9 9D B V O N I A N O O- - 3 9 5 -

SILURIAN N ~ 9- - 4 3 5 -

O R D O V I C I A N 9149 9 9 9- - 5oo-

C A M B R I A N @ Q e 9

L? - - _ __ ? . . . . . . .

Figure 1. Distribution of black shale units in t ime and space.Fil led circles indicate occurrences. Compiled from Tourtelot(1970) and Fulto n (1977). Oc curren ces differ greatly in arealextent, thickne ss, an d oth er characteristics.g e t s s u c h w h o l e s a l e re t u r n s o f c o n j e c t u r e o u t o f s u c ha t ri f li n g i n v e s t m e n t o f f a c t ( C l e m e n s , 1 87 4 , p . 1 3 6) .

D I S T R I B U T IO N O F B L A C K S H A L E I NT I M E A N D S P A C E

F i g u r e 1 w a s c o m p i l e d c h i e f ly f r o m t h e b i b l i o g r a p h yo n b l a c k s h a l e p r e p a r e d b y T o u r t e l o t ( 1 9 7 0 ) , b u t t h er e c o r d o f s o m e o c c u r r e n c e s w a s t a k e n f r o m F u l t o n( 19 77 ). T h e s y m b o l s d o n o t h a v e e q u a l s i g n i f i c a n c e : f o ri n s t a n c e , t h e C h a t t a n o o g a S h a l e in t h e A p p a l a c h i a n r e -g i o n a n d t h e H o u y F o r m a t i o n i n T e x a s a r e e a c h c o u n t -e d a s a s i n gl e o c c u r r e n c e a m o n g b l a c k s h a l e s o f L a t eD e v o n i a n a n d M i s s i s s i p p ia n a g e s in N o r t h A m e r i c a d e -s p i t e t h e g r e a t d i s p a r i t y b e t w e e n t h e i r a r e a l e x t e n t a n dt h i c k n e s s . T h e f i g u r e i n d i c a t e s t h a t b l a c k s h a l e u n i t sh a v e f o r m e d c o m m o n l y t h r o u g h o u t m o s t o f th e h i s t o ryo f t h e E a r t h a n d i n m a n y p l a c e s . B l a c k s h a l e u n it s a r eb e i n g f o u n d a l s o in t h e o c e a n b a s i n s n o w b e i n g e x p l o r e db y d r i ll in g ( e . g . , G a r d n e r e t a l . 1 9 77 ; D e a n e t a l . 1977;H a l l a m , 1 9 77 ; K e r r , 1 9 78 ). T h i s w i d e g e o g r a p h i c d i s -t r i b u t i o n o f b l a c k s h a l e o c c u r r e n c e s i n it s e l f s u g g e s t st h a t a r a n g e o f g e o l o g i c s e t t i n g s m u s t b e s u i t a b l e f o r t h ea c c u m u l a t i o n o f b l a c k s h a l e .

T h e o r g a n i c m a t e r i a l t h a t g i v e s b l a c k s h a l e i t s d i s -t i n c t i v e c h a r a c t e r i s t i c s i s d e r i v e d f r o m l i v i n g t h i n g s .S i n c e b l a c k s h a l e h a s a c c u m u l a t e d t h r o u g h o u t t h e e n -t ir e e v o l u t i o n o f li fe o n t h e E a r t h , t h e c o m p o s i t i o n o ft h e o r g a n i c m a t t e r i n a b l a c k s h a l e s h o u l d r e f l e c t e v o -l u t i o n a r y d e v e l o p m e n t o f li v in g th i n g s a t t h e t i m e t h es h a le w a s d e p o s i t e d . T h e i m p o r t a n c e o f b i o c h e m i c a ls t u d i e s o f d i f f e r e n t s t a g e s o f e v o l v i n g li f e, p a r t i c u l a r l yp l a n t m a t e r ia l a s p r e s e r v e d i n b l a c k s h a l e , w a s p o i n t e d


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V ol . 27 , N o. 5 , 1979 Black sha le - - i t s depos i t ion and d iagenes i s 315

o u t b y W o o d r i n g ( 1 9 5 4 ) , b u t s y s t e m a t i c s t u d i e s s t i l lh a v e n o t b e e n m a d e , a n d t h e s i g n i f ic a n c e o f th e e v o -l u t i o n a r y s t a g e o f l if e a v a i la b l e t o p r o v i d e o r g a n i c m a -t e r i a l t o a b l a c k s h a l e h a s b e e n l a r g e l y o v e r l o o k e d . F o re x a m p l e , l a n d p l a n t s d i d n o t e v o l v e u n t il t h e L a t e S i -l u r i a n ( A r n o l d , 1 9 69 , p . 1 2 9). T h e o r g a n i c m a t t e r i nb l a c k s h a l e s o l d e r th a n t h a t m u s t t h e r e f o r e b e d e r i v e df r o m a q u a t i c p l a n t s a n d s i m p l e r l if e f o r m s . T h e p a r a m -e t e r s w i d e l y u s e d t o i n d i c a t e t h e m a r i n e n e s s o r

n o n m a r i n e n e s s o f d e p o s i t i o n a l e n v i r o n m e n t s , s u c ha s t h e h y d r o g e n c o n t e n t o f k e r o g e n ( B r e g e r a n d B r o w n ,1 96 2) o r c a r b o n i s o t o p i c c o m p o s i t i o n , m a y b e m i s l e a d -i n g o r i n v a l i d i f t h e i n t e r p r e t a t i o n i s b a s e d p r i m a r i l y o na n a l o g i e s w i th t h e p r e s e n t . T h e a s s u m p t i o n t h a t g e o -c h e m i c a l e ff e c t s o f m e t a b o l i c p r o c e s s e s h a v e b e e n t h es a m e f r o m t h e b e g i n n i n g a s t h e y a r e n o w p r o b a b l y i sn o t w h o l l y c o r r e c t .

G E O L O G I C S E T T I N G S O F B L A C K S H A L ED E P O S I T I O NT h e g e o l o g i c s e tt i n g s o f t y p i c a l b l a c k s h a l e s w e r e

c l a s s if i e d b y V i n e a n d c o l l e a g u e s i n v e r y b r o a d t e r m s( V i n e a n d T o u r t e l o t , 1 9 7 0 ) t h a t c a n b e f u r t h e r g e n e r -a l i z e d i n t o g e o s y n c l i n e , c r a t o n i c b a s i n , a n d s h e l f , a ss h o w n i n t h e f o l l o w i n g ta b l e ( a s t e r i s k s i n d i c a t e m e t a l -r i c h u n i t s ) :G eosync l ine Per mian

Cr a tonic Bas in

She l f( A l te r na t ingMar ine andN onmar ine )

U pper Pa leozoicL o w e r P a l e o z oi cPennsylvanian

P e n n s y l v a n i a n -Miss i s s ipp ianU pper Miss i s -s ipp ianPennsylvanian

Pr o te r ozoic

Cr e taceousPennsylvanian

D e v o n i a n -Miss i s s ipp ian

( Ent i r e ly M ar ine )

W e s t e r n R o c k yMou nta ins ( Phos -p h o r i a F o r m a -tion*)SW Midcont inentSW Midcont inentC o l o r a d oU t a h ( P a r a d o x F o r -mat ion evapo-r i tes)M o n t a n aW y o m i n gMidcont inent ( Mec-ca Q uar r y Sha leM e m b e r * o fL i n t o n F o r m a -

t ion) (Zanger l andRichardson, 1963)Midcon t inent (o the rs imilar shales)Michigan ( N one-such Shale*)Wes te r n I n te r iorTexasK ansas ( Tacke tFormation) ( Jew-e t t e t a l . , 1965)A p p a l a c h i a nRegion*Midcontinent*Texas*Rocky Mountains*

R E S T R I C T E D C I R C U L A T I O N M O D E L0 2 C O N T E N T O F W A T E R N O T R E N E W E D B Y C f R C U L A T I O N

0 2D EP TH C O N C E N T R A T I O N W A T E R C O L U M N D E PT H C H A R A C T E R I ST I C S(METERS) ,e . . .___ . IN CIREA ES~ N X ~ ~ N N N ~ PHOTIC ZONE/ S O M E ~NPUT ORGANIC MATTER pHOtOSyNTHESIS AND PROOUCTIOFROM LAND ~ LARGELYRECYCLED OF ORGANICMATTER). . . . . . . . . . . . . . . . . . . . . . . . . . . .

8 0 . . . . ~ . ~ - - ~ 0 2 C O M PL ET E LY E U M tN A T ED B Y D I SP H O II C A N D A P H OT I C Z O N ESOX~t~,~ON C~ SEdatiNGORGANIC MATTER

e \ \ \ ~ H2S DFFUSES N T O WATER FROM\ \ . \ \ x \ \ \ \ ~ , Z O N E O F D I A G E N ESiS

~ I N C I R EA S E S H . ~ J = _ _ - ->~00 H 2 SC O N C E N T R A T I O N

PeODUCTION

OXIDATIONAND DEGRADATIONOF ORGANICMATTER)

jZONE OF DtAGEN 1S

A L L O R G A N I C M A T T E R S E T T L IN G P A S T L E V EL O F Z E R O 0 2C O N C E N T R A T I O N A C C U M U L A T E S O N T H E B O T T O M

Figur e 2 . Res t r ic ted c ir cu la t ion mode l f or accumula t ion oforganic- r ich sedim ents . Modif ied f rom Did yk e t a L 1 9 7 8 ) .

I n g e o s y n c l i n a l s et t i n g s , t h e s h a l e s o f P a l e o z o i c a g ef o r m t h i c k d e p o s i t s t h e p a l e o g e o g r a p h y o f w h i c h i s n o te a s y t o r e c o n s t r u c t b e c a u s e o f c o m p l e x l a t e r te c t o n i ch i s t o r y . B l a c k s h a l e in t h e P h o s p h o r i a F o r m a t i o n i s t h eo n l y o n e o f th e g e o s y n c l i n a l s h a l e s t h a t is e n r i c h e d i nm e t a l s ( V in e a n d T o u r t e l o t , 1 97 0). T h e P h o s p h o r i a F o r -m a t i o n i t s e l f i s u n u s u a l a m o n g s e d i m e n t a r y r o c k s b e -c a u s e o f it s e n r i c h m e n t i n P . T h e p a l e o g e o g r a p h y o f t h ec r a t o n i c b a s i n s h a l e s a l s o i s d i ff i c u lt t o r e c o n s t r u c t .N o n e o f th o s e s t u d i e d b y V i n e a n d T o u r t e l o t ( 19 7 0) a r ee n r i c h e d i n m e t a l s . T h e b l a c k , c a r b o n a t e - r i c h s h a l e i nt h e P a r a d o x F o r m a t i o n i s u n u s u a l b e c a u s e o f i t s a s s o -c i a t io n w i t h e v a p o r i t e s .

C l a s s if i c a ti o n o f a s h a l e a s h a v i n g b e e n d e p o s i t e d i na s h e l f s e t ti n g p r o b a b l y w o u l d v a r y f r o m o n e p e r s o n t oa n o t h e r . A l l t h e d e p o s i t s i n c l u d e d h e r e , h o w e v e r , c a nb e v i e w e d b r o a d l y a s b e i n g t r a n s g r e s s i v e . O n e g r o u pi n c l u d e s t h o s e d e p o s i t e d i n s e t t i n g s i n w h i c h m a r i n ea n d n o n m a r i n e d e p o s i t i o n a l t e r n a t e d . T h e o t h e r g r o u pi n c l u d e s s h a l e s t h a t s e e m t o b e e n t i r e ly m a r i n e i n t h e i ra s s o c i a t i o n s .

M o r e e x a m p l e s o f m e t a l - e n r i c h e d s h a l e s a r e f o u n da m o n g t h o s e d e p o s i t e d i n t h e s h e l f s et t i n g th a n i n o t h e rs e t t i n g s , b u t t h e r e s t i l l i s a p u z z l i n g v a r i a b i l i t y b e t w e e ns o m e o f th e s h a l e s i n t h e s h e l f s et t in g . F o r i n s t a n c e , t h eP e n n s y l v a n i a n M e c c a Q u a r r y S h a l e M e m b e r ( Z a n g e rla n d R i c h a r d s o n , 1 % 3 ) o f t h e L i n t o n F o r m a t i o n i s t h eo n l y o n e i n t h e M i d c o n t i n e n t r e g i o n t h a t i s e n r i c h e d i nm e t a l s . O t h e r m a r i n e s h a l e s o f th e s a m e a g e a n d l i t h -o l o g i c a s s o c i a t i o n s i n t h e M i d c o n t i n e n t r e g i o n a r e n o te n r i c h e d i n m e t a l s . O t h e r m e t a l - e n r i c h e d s h e l f s h a l e sa r e t h e N o n e s u c h S h a l e o f P r o t e r o z o i c a g e a n d s h a l e so f D e v o n i a n a n d M i s s i s s ip p i a n a g e s.

T h e i n t e r e s ti n g m e t a l c o n t e n t o f e n r i c h e d s h a l e s i sc l e a r l y r e l a t e d t o t h e a m o u n t o f o r g a n i c m a t t e r i n t h es h a l e s . T r a c e m e t a l a d s o r p t i o n , s u l fa t e r e d u c t i o n , a n ds u lf id e p r e c i p i t a t io n a r e t h e c h i e f p r o c e s s e s i n v o l v e d( S w a n s o n , 1 9 61 ; T o u r t e l o t , 1 96 4; V i n e a n d T o u r t e l o t ,1 97 0). A l a r g e c o n t e n t o f o r g a n i c m a t t e r d o e s n o t n e c -e s s a r i l y i d e n t i f y a m e t a l - r i c h s h a l e . O t h e r f a c t o r s t o b e


4/9

316 Tour telot Clays and Clay MineralsO P E N O C E A N M O D E L

02 CO NT E NT O F W ATER CO NT RO LLED BY C IRCULAT IO N2

D E PT H C O N C E N T R A T I O N W A T E R C O L U M N D E P T H C H A R A C T E R I ST I C S(METERS ~ INCREASES

~ % ~ ~ ~ P H OT I C Z ON Ef SOME INPUT ORGAN IC MATTER ,~,AO~OS,fNT~ESIS ND ~RODUC31- - - - ' ~ . . , ~ , ~ F R OM A N D ~ L A R GE L Y R E CY C LE D OF OR GA N I C M A T T E R )80O 2 MINIMUM CREATED BYOX*DATION

( ) O F S E TT L IN G O R G A N IC M A T T E R D I S P H O T I C N D A P ~ OT I C Z ON E( OX I D AT t ON A N D D E GR A D A T I O~

OF ORGANIC MATTER)

>soo I

~DUC310NER

ND AP~OTIC ZONESAN~ DEGRADATION

ZONE OF DIAGENESIS

A N Y O R G A N I C M A T TE R N O T S U S CE P T IB L ET O F U R TH E R O X I D A T I O NACCUMULAT ES ON BO T T O M

Figur e 3. O pen ocean mod e l f or accumula t ion of o rganic -r ich sediments . Modif ied f rom Didyk et al. (1978).

c o n s i d e r e d i n c l u d e t h e n a t u r e o f th e o r g a n i c m a t e r i a la n d i t s m e t a l c o n t e n t , t h e n a t u r e o f s e d i m e n t s a n d w a t e ri n th e s o u r c e a r e a s , v o l c a n i c a s h , a n d s u b m a r i n e v o l -c a n i c e x h a l a t i o n s .

T h e a b u n d a n c e s o f s o m e e l e m e n t s a r e r e l a t e d tot h o s e o f o t h e r c o n s t i t u e n t s o f b l a c k s h a l e s . T h e c o n -t e n t s o f S i a n d A 1 o b v i o u s l y a r e r e l a t e d t o t h e a b u n -d a n c e o f d e t ri t a l m i n e r a l s , a n d t h e S r c o n t e n t i s r e l a t e dt o t h e a b u n d a n c e o f d i a g e n e t i c c a r b o n a t e m i n e r a l s .V i n e a n d T o u r t e l o t ( 1 9 7 0 ) d i s c u s s e d t h e c o m p l e x i t i e so f t h e s e a n d o t h e r r e la t i o n s b e t w e e n e l e m e n t a l c o m -p o s i t i o n s a n d m i n e r a l o r c o n s t i t u e n t a b u n d a n c e .

T h e f a c t t h a t b l a c k s h a l e h a s a c c u m u l a t e d i n a w i d er a n g e o f g e o l o g i c s e t ti n g s i m p l i e s t h a t g e o l o g i c s e t ti n gs u c h a s g e o s y n c l i n e o r s h e l f i s n o t o f p r i m e i m p o r t a n c ei n th e f o r m a t i o n o f b l a c k s h a l e d e p o s i t s c o m p a r e d t ow h a t g o e s o n i n th e s e s e t ti n g s . F e a t u r e s o f d e p o s i t i o n a le n v i r o n m e n t s w i t h i n g e o l o g i c s e t t in g s , s u c h a s o r g a n i cp r o d u c t i v i t y , s e d i m e n t a t i o n r a t e s , a n d a v a i l a b i li t y o fo x y g e n , a r e t h e i m p o r t a n t f a c t o r s i n c o n t r o l l in g t h e d e -p o s i t i o n o f th e s e d i m e n t s t h a t f o r m b l a c k s h a l e.

D E P O S I T I O N A L E N V I R O N M E N T ST h e r a n g e o f d e p o s i t i o n a l e n v i r o n m e n t s i n w h i c h

b l a c k s h a l e m a y a c c u m u l a t e c a n b e d e s c r i b e d b y t h r e em o d e l s s h o w n i n F i g u r e s 2, 3 , a n d 4 . T h e f o r m u l a t i o no f t h e s e m o d e l s s t e m s d i r e c t l y f r o m s i m i l a r a p p e a r i n gd i a g r am s p r e s e n t e d b y D i d y k et al. ( 1 97 8 ). T h e y p l a c e dg r e a t e m p h a s i s o n t h e c h e m i c a l c h a r a c t e r i s t i c s o f t h ee n v i r o n m e n t per se s u c h a s t h e d i s t r i b u t i o n o f o x y g e na n d h y d r o g e n s u l f id e i n t h e w a t e r c o l u m n a n d s e d i -m e n t s . H e r e , h o w e v e r , t h e r o l e o f t h e a m o u n t o f o r-g a n i c m a t e r i a l in r e l a t i o n to o x y g e n s u p p l y i s e m p h a -s i z ed . A n a b u n d a n c e o f o r g a n i c m a t e r ia l d e p l e t e so x y g e n a n d c r e a t e s t h e c o n d i t i o n s u n d e r w h i c h o r g a n i c -r i c h se d i m e n t s c a n a c c u m u l a t e . S i m i l a r l y , h y d r o g e ns u lf id e i s p r o d u c e d u n d e r t h e c o n d i t i o n s c a u s e d b y t h ea c c u m u l a t i o n o f o rg a n i c m a t e r i a l , w h i c h f a v o r s t h e f u r-t h e r a c c u m u l a t i o n o f o r g a n i c m a t e r i a l. T h e a c c u m u l a -t i o n o f o r g a n i c m a t e r i a l i s a c a u s e o f c o n d i t i o n s , n o t a ne f f e c t .

C O N T I N E N T A L S H E L F M O D E L0 2 C O N T E N T O F W A T ER C O N T R O LL E D B Y A T M O SP H E R IC E X C H A N G E

02 W AT ER CO L UMN DEPT H CHARACT ERIST ICSD E P T H C O N C E N T R A T I O NIMETERS ~ INCREASES

. . . . . DISP H O~ IC ~Z ~N ~ -- - - - - ~

L L O R G A N I C M A T T E R N O T R E C Y CL E D A C C U M U L A T E S O N B O T TO M

Figur e 4. Cont inenta l she l f mode l f or accumula t ion of o r-ganic - rich sed iments . M odi f ied fr om D idyk et al. (1978).

T h e r e s t r i c t e d c i r c u l a ti o n m o d e l i s d i s c u s s e d f i rs t b e -c a u s e i t r e p r e s e n t s t h e c l a s s i c v i e w , a n d u n f o r t u n a t e l yo f t e n t h e o n l y v i e w , o f th e a c c u m u l a t i o n o f o rg a n i cm a t e r i a l i n a n c i e n t r o c k s ( F i g u r e 2 ) .Restricted circulat ion model

T h e s i g n i f ic a n t f e a t u r e o f t h e r e s t r i c t e d c i r c u l a t i o nm o d e l i s t h a t t h e o x y g e n c o n t e n t o f t h e w a t e r c o l u m ni s n o t r e n e w e d b y c i r c u l a t i o n s o t h a t o r g a n i c - r i c h se d -i m e n t s c a n a c c u m u l a t e e v e n i f o r g a n i c p r o d u c t i v i t y i sr e l a t i v e l y s m a l l . O r g a n i c m a t e r i a l i s p r o d u c e d b y p h o -t o s y n t h e s i s i n th e p h o t i c z o n e , m i x e d w i t h s o m e o r g a n -i c m a t e r i a l f r o m l a n d i f t e r r e s t r i a l p l a n t l i f e e x i s t s , a n di s l a r g e l y r e c y c l e d i n t h e p h o t i c z o n e b y c h e m i c a l a n db i o l o g i c a l p r o c e s s e s s u c h a s b i g g e r th i n g s e a ti n g l i t tl e rt h i n g s . T h e o x y g e n c o n t e n t o f t h e w a t e r m a y i n c r e a s et o w a r d s t h e b o t t o m o f t h e p h o t i c z o n e b e c a u s e o f p h o -t o s y n t h e s i s , b u t a t s o m e p o i n t i t i s c o m p l e t e l y c o n -s u m e d b y t h e o x i d a t i o n o f t h e s e t t li n g o r g a n ic m a t e r i a l .T h e o x y g e n d e p l e t i o n d i d n o t e x i s t a priori b u t w a sc a u s e d b y t h e l a r g e o x y g e n d e m a n d o f t h e d e c o m p o s i n go r g a n i c m a t e r i a l i t s e lf . A l l t h e o r g a n i c m a t t e r t h a t s e t -t l es b e l o w t h e l e v e l o f z e r o o x y g e n c o n t e n t a c c u m u l a t e so n t h e b o t t o m w h e r e i t c a n b e r e m o v e d o n l y b y a n a e r -o b i c d e c o m p o s i t i o n . H y d r o g e n s u l f id e g e n e r a t e d i n t h eb o t t o m s e d i m e n t s m a y d i f fu s e i nt o t h e o v e r l y i n g w a t e rm a s s . B o t h t h e s e d i m e n t a t i o n a l e n v i r o n m e n t a n d t h es e d i m e n t s a r e a n o x i c .

T h i s s i t u a t i o n p r e v a i l s b e c a u s e t h e r e i s to o l i t t l e c i r -c u l a t i o n in t h e w a t e r m a s s t o s u p p l y o x y g e n a t a r a t ef a s t e n o u g h t o e q u a l o r e x c e e d t h e o x y g e n d e m a n d o ft h e a v a i l a b l e o r g a n i c m a t e r i a l, f f e n o u g h o r g a n i c m a -t e r ia l is p r o d u c e d i n t h e p h o t i c z o n e , c o n s i d e r a b l ea m o u n t s o f o x y g e n c o u l d b e s u p p l i e d a n d o r g a n i c m a t -t e r s ti ll w o u l d a c c u m u l a t e i n t h e b o t t o m s e d i m e n t s .

T h e r e s t r i c t e d c i r c u l a ti o n m o d e l i s r e p r e s e n t e d i np a r t b y t h e B l a c k S e a ( t h e t y p e e u x i n i c s e t t i n g : s e eG o l d h a b e r , 1 97 8) o r N o r w e g i a n a n d o t h e r l ]o r d s , w h i c hp r o v i d e g o o d m o d e r n e x a m p l e s o f th e c h e m i c a l a n ds e d i m e n t a t i o n a l p r o c e s s e s o u t l i n e d a b o v e . O r g a n i c -r i ch d e p o s i t s w i l l a c c u m u l a t e i n s u c h r e s t r i c t e d b a s i n s ,i n c l u d in g b a s i n s f o r m e d t e c t o n i c a l l y s u c h a s t h e C a r -i o c o t r e n c h o r t h o s e o f f t h e C a l i fo r n i a c o a s t , u n l e s s t h er a t e o f o rg a n i c p r o d u c t i v i t y i n t h e p h o t i c z o n e a b o v et h e m i s l o w . H o w e v e r , c o n c e p t s o f t ] o rd s a n d t e c t o n i cb a s i n s c a n n o t b e a p p l i e d t o t h e o r i g i n o f w i d e s p r e a d


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Vol. 27, No. 5, 1979 Black sha le- - i ts depo si t ion and diagen esis 317

b l a c k s h a l e u n i t s b e c a u s e o f t h e c o n t r a s t i n a r e a a n d t h ed e f i n it e m o r p h o l o g i c c h a r a c t e r i s t i c s o f s u c h b a s i n s .Open ocean model

I n th e o p e n o c e a n F i g u r e 3 ), t h e o x y g e n c o n t e n t o ft h e w a t e r m a y b e c o n t r o l l e d p r im a r i l y b y c i r c u l a t i o n ,b u t i t is a l s o s t r o n g l y i n f l u e n c e d b y t h e a m o u n t o f o r-g a n i c m a t e r i a l t h a t e s c a p e s f r o m t h e p h o t i c z o n e a n ds e t t l e s t h r o u g h t h e w a t e r c o l u m n . T h e o x y g e n m i n i -m u m , ju s t b e l o w t h e p h o t i c z o n e , i s c r e a t e d b y t h e o x -i d a t i o n o f o rg a n i c m a t e r i a l . S o m e o f th e m o r e r e s i s t a n to r g a n i c m a t e r i a l s e t tl i n g p a s t t h e o x y g e n m i n i m u m m a yu n d e r g o n o f u r t h e r d e g r a d a t i o n e n r o u t e t o i t s a c c u -m u l a t i o n o n t h e b o t t o m . S e t t li n g ra t e s t o o r a p i d f o r o x -i d a t i o n o f o r g a n i c p a r t i c le s t o b e c o m p l e t e c a n b ec a u s e d b y i n c o r p o r a t i o n o f o r g a n i c m a t e r i a l i n fe c a lp e l l e t s o r b y a g g r e g a t i o n w i t h m i n e r a l p a r t i c l e s , e v e ni f t h e o r g a n i c c o m p o u n d s a r e s u s c e p t i b l e t o o x i d a t i o n .O r g a n i c - ri c h s e d i m e n t s t h u s c a n a c c u m u l a t e e v e nt h o u g h t h e s e d i m e n t a t i o n a l e n v i r o n m e n t i s c o m p l e t e l yo x i c . I n a n y e v e n t , t h e s e d i m e n t s t h e m s e l v e s w i l l b e -c o m e a n o x i c a f e w m i l l i m e t e r s b e l o w t h e s e d i m e n t s u r-f a c e b e c a u s e o f b a c t e r ia l p r o c e s s e s a n d t h e s l o w r e -p l e n i s h m e n t o f d i s s o l v e d o x y g e n b y d i f f u s io n b e l o wa n y z o n e o f b u r r o w i n g t h a t i s p r e s e n t .

T h e b a l a n c e b e t w e e n o r g a n i c p r o d u c t i v i t y an d a v a i l -a b l e o x y g e n c a n s h if t b e c a u s e o f c h a n g e s i n p a t t e r n s o fs u r f a c e c u r r e n t s i n re s p o n s e t o t e c t o n i c e v e n t s d i s t a n tf r o m t h e d e p o s i t i o n a l s it e . O r , t h e d e p o s i t i o n a l s i t em i g h t b e c a r r ie d b y s e a f l o o r s p r e a d i n g i n t h e c a s e o fy o u n g e r r o c k s ) fr o m a n a r e a o f l o w o r g a n i c p r o d u c t i v i t ytO c n e o f h ig h p r o d u c t i v i t y a n d t h e n t o a n a r e a o f l o wp r o d u c t i v i t y a g a i n e . g . , W h i t e , 1 97 9). T h e s e d i m e n t sd e p o s i t e d b e n e a t h t h e a r e a o f h i g h p r o d u c t i v i t y c o u l db e r i c h i n o r g a n ic m a t t e r a n d f o r m b l a c k s h a l e s w i t h o u tt h e r e n e c e s s a r i l y b e i n g an a n o x i c e v e n t i n t h e s e n s e o ft h e f o r m a t i o n o f a b a r r e d b a s i n o r t h e c e s s a t i o n o f ci r -c u l a t i o n .Continental s helf model

T h e c o n t i n e n t a l s h e l f m o d e l F i g u r e 4 ) c o n t a i n s t h es a m e i n p u t f a c t o r s a s t h e o t h e r m o d e l s , b u t t h e r e i s l i t t leo r n o w a t e r b e t w e e n t h e p h o t i c z o n e a n d t h e b o t t o m .O r g a n i c m a t e r i a l i s r e c y c l e d i n t h e p h o t i c z o n e t o a l e s s -e r e x t e n t b e c a u s e o f m o r e r a p i d s e t tl i n g t o t h e b o t t o m .T h e c o n c e n t r a t i o n o f o x y g e n i n t h e w a t e r m a y r e m a i nl a rg e d o w n t o t h e t o p o f th e a c c u m u l a t i n g s e d i m e n t b e -c a u s e o f c ir c u l a t i o n a n d t h e p r o d u c t i o n o f o x y g e n i n t h ep h o t i c z o n e . I n t h is s e t ti n g a l so , t h e s e d i m e n t s b e c o m ea n o x i c a v e r y s h o r t d i s t a n c e b e n e a t h t h e s u r f a c e b e -c a u s e o f b a c t e r i a l p r o c e s s e s .

T h i s k i n d o f s e d i m e n t a t i o n a l e n v i r o n m e n t h a s b e e nd e d u c e d f o r s e v e r a l t r a n s g r e s s i v e b l a c k s h a l es i n N o r t hA m e r i c a , s u c h a s t h o s e in c y c l o t h e m s o f P e n n s y l v a n i a na g e Z a n g e r l a n d R i c h a r d s o n , 1 96 3) a n d th e b l a c k s h a l e so f D e v o n i a n a n d M i s s i s s ip p i a n a g e s C o n a n t an d S w a n -

s o n , 1 96 1). T h i s m o d e l , l i k e t h e o p e n o c e a n m o d e l , d o e sn o t r e q u i r e a n y a priori c o n d i t i o n s s u c h a s a r e s t r i c t e db a s i n , d e n s i t y s t r a t i f i c a t i o n , h y d r o g e n s u l f i d e i n t h ew a t e r , o r o t h e r c h a r a c t e r i s t i c s b a s e d o n a n a l o g i e s w i t ht h e B l a c k S e a .

R E L A T I V I T Y O F F A C T O R S I ND E P O S I T I O N

D i f f e re n t r e l a t i o n s b e t w e e n r a t e s o f c l a sf i c s e d i m e n -t a t io n , o r g a n i c p r o d u c t i v i t y , a n d t h e i n t e n s i t y o f o x i -d a t i o n r e s u l t i n s i m i l a r k i n d s a n d , p e r h a p s , s i m i l a ra m o u n t s o f b l a c k s h a l e b e in g d e p o s i t e d . O r g a n i c p r o -d u c t i v i t y i s c o n t r o l l e d c h i e f l y b y t h e a v a i l a b i l i t y o f n u -t r i en t s , a l t h o u g h o t h e r f a c t o r s s u c h a s t e m p e r a t u r e , s a -l i n it y , a n d w a t e r c l a r i t y a l so a r e i n v o l v e d . I n t r y i n g t ou n d e r s t a n d t h e r e a s o n s f o r t h e d i s t ri b u t i o n o f b l a c ks h a l e s in t im e a n d s p a c e , t h e f u n d a m e n t a l c o n c e p t t ob e k e p t i n m i n d i s t h a t o r g a n i c - ri c h r o c k s r e s u l t w h e na n d w h e r e o r g a n i c m a t e r i a l a c c u m u l a t e s b e c a u s e i t i sp r o d u c e d f a s t e r t h a n i t c a n b e d e s t r o y e d .

Z O N E S O F D I A G E N E S I ST h e c h a r a c t e r i s t i c s o f t h e e n v i r o n m e n t i n w h i c h

b l a c k s h a l e s w e r e d e p o s i t e d a r e m o r e o r le s s im a g i n a r yi n th e s e n s e t h a t t h e c h a r a c t e r i s t i c s h a v e t o b e d e d u c e df r o m v e r y f e w d a t a o f u n c e r t a i n s i g n i f ic a n c e . I n c o n -t r a s t , t h e z o n e s o f d i a g e n e s i s c a n b e f a i r l y w e l l d e f i n e do n t h e b a s i s o f d a t a o n p o r e f l u id s a n d s e d i m e n t s f r o md e e p - s e a d r il l in g , l a b o r a t o r y e x p e r i m e n t , a n d t h e o r e t -i c a l c o n s i d e r a t i o n s . I n a d d i t i o n , m o s t o f t h e p r o d u c t so f d ia g e n e t i c p r o c e s s e s r e m a i n i n t h e r o c k s a n d p r o v i d ea r e c o r d t h a t c a n b e d e c i p h e r e d . I t is im p o r t a n t t o r e c -o g n i z e t h e p r o d u c t s o f d i a g e n e s i s s o t h a t d a t a o n t h e ma r e n o t u s e d m i s l e a d i n g l y in t h e i n t e r p r e t a t i o n o f c o n -d i t i o n s o f d e p o s i t i o n .

K r u m b e i n a n d G a r r e l s 1 95 2) m a d e c l e a r t h e r o l e o fp H a n d o x i d a t i o n - r e d u c t i o n p o t e n t i a l s i n i n f l u e n c i n gr o c k c o m p o s i t i o n s d u r i n g d i a g e n e s i s . P o s t d e p o s i t io n a td i a g e n e t ic ) c h a n g e s d u r i n g t h e a c c u m u l a t i o n o f s e di -

m e n t a r y r o c k s h a d , o f c o u r s e , b e e n r e c o g n i z e d e a r li e rK r u m b e i n , 1 94 2). L a t e r , B e r n e r 1 96 4) e x p l o r e d i r o n

a n d s u l f u r r e a c t i o n s i n e a r l y d i a g e n e s i s . S i n c e t h e n ,d i a g e n e t i c p r o c e s s e s h a v e b e e n w i d e l y s t u d i e d . T h e f o l-l o w i n g d i s c u s s i o n i s b a s e d o n f o u r p r i n c i p a l p a p e r sC l a y p o o l a n d K a p l a n , 1 9 7 4; C u r t i s , 1 97 7; G o l d h a b e r

a n d K a p l a n , 1 9 7 4 ; a n d I r w i n et al. 1 9 7 7 ) t h a t r e v i e w ,w i t h s o m e d i f f e r e n c e s i n e m p h a s i s , t h e p r o c e s s e s o fd i a g e n e s i s o f s e d i m e n t a r y r o c k s c o n t a i n i n g o r g a n i cm a t t e r .

F i g u r e 5 r e p r e s e n t s a s e q u e n c e o f d i a g e n e t i c z o n e sw i t h d e p t h a t a p a r t i c u l a r p o i n t in t i m e . T h e r o c k s i n t h ez o n e o f h y d r o c a r b o n f o r m a t io n a l r e a d y h a v e p a s s e dt h r o u g h a l l o f t h e o v e r l y i n g z o n e s . I f s e d i m e n t a t i o nc o n t i n u e s , t h e s e d i m e n t s i n t h e p r e s e n t z o n e o f s u lf a ter e d u c t i o n c a n b e e x p e c t e d t o p a s s s e q u e n t i a l ly i n o r d e rt h r o u g h t h e u n d e r l y i n g z o n e s . T h e u l t i m a t e n a t u r e o f


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V ol . 27 , N o. 5 , 1979 Black sha le - - i t s depos i t ion and d iagenes i s 319

r e g i o n a l l y w i th i n a b l a c k s h a l e o f g r e a t a r e a l e x t e n t . T h ee a s t e r n e x t e n t o f a b l a c k s h a l e u n i t , a s a g e n e r a l e x -a m p l e , m a y r e a c h a m o r e a d v a n c e d z o n e o f d i a g e n e si st h a n t h e w e s t e r n e x t e n t b e c a u s e o f g r e a t e r b u ri a l f r o mt h i c k e r o v e r l y i n g r o c k s , t e c t o n i s m , o r i g n e o u s i n t r u -s i o n s . V a r i a t i o n o f t h i s k i n d i s i n d i c a t e d b y t h e d i s t r i -b u t i o n o f c o n o d o n t c o l o r a l te r a ti o n i n d i c e s s h o w n b yH a r r i s e t a l . ( 1 97 8 ). T h e r e l a t i o n s o f d i a g e n e t i c f a c t o r sc a n v a r y b e t w e e n s h a l e s , a ls o . A s h a l e o f T e r t i a r y ag ea t a d e p t h o f 3 - 5 k m i n a re g i o n o f l a rg e t h e r m a l g r a d i e n tm a y h a v e h a d m o s t o f i t s o r i g in a l m o n t m o r i l l o n i t et r a n s f o r m e d t o i l li te . A n o t h e r s h a l e o f C r e t a c e o u s a g ei n a r e g i o n o f s m a l l g e o t h e r m a l g r a d i e n t m a y s t il l r e t a ini t s o r i g i n a l m o n t m o r i l l o n i t i c c o m p o s i t i o n e v e n t h o u g ha t s o m e t i m e d u r i n g i t s h i s t o r y it h a s b e e n b u r i e d t o ad e p t h o f 1 0 k m . G i v e n e q u a l b u r i a l d e p t h s a n d t h e r m a lg r a d i e n t s , m i n e r a l t r a n s f o r m a t i o n s m a y h a v e g o n e f u r -t h e r i n a s h a l e o f P a l e o z o i c a g e t h a n i n o n e o f M e s o z o i ca g e , s i m p l y b e c a u s e o f m o r e t i m e h a v i n g p a s s e d . I t t h u ss e e m s l i k e l y t h a t a m o d e r a t e r a n g e o f r e l a t io n s b e t w e e np r e s s u r e , t e m p e r a t u r e , a n d t i m e c a n y i e l d t h e c h a r a c -t e r i s ti c s o f a g i v e n d i a g e n e t i c z o n e . T h i s r e l a t iv i t y o f

B L A C K D E P O S I T I O N A LS H A L E E N V I R O N M E N T

p a r a m e t e r s m u s t b e t a k e n i n t o a c c o u n t i n i n t e r p r e t i n gd a t a o n t h e c h e m i c a l a n d m i n e r a l o g i c c o m p o s i t i o n o fb l a c k s h a l e s .

C O N C L U S I O N SI n a n y d e p o s i t i o n a l s e t ti n g , r a t e s o f c l a s t i c s e d i m e n -

t a t i o n a n d o r g a n i c p r o d u c t i v i t y a n d t h e i n t e n s i t y o f o x -i d a t i o n a r e t h e p r i m a r y c o n t r o l s f o r t h e a c c u m u l a t i o no f o r g a n i c m a t e r i a l .

I n z o n e s o f p r o g e s s i v e d i a g e n e s i s , t h e m i x t u r e o f o r -g a n i c m a t t e r a n d c l a s t i c s e d i m e n t i s o p e r a t e d o n i n ra t h -e r p r e d i c t a b l e w a y s b y b i o l o g i c an d c h e m i c a l p r o c e s s e sc o n t r o l l e d c h i ef l y b y t e m p e r a t u r e , p r e s s u r e , a n d t i m e .

T h e s e p a r a t e p r o d u c t s o f t h e p r o c e s s e s o p e r a t in g i nt h e d e p o s i t i o n a l e n v i r o n m e n t a n d i n t h e z o n e s o f d i a -g e n e s i s s h o u l d b e c l e a r l y d i s ti n g u i s h e d t o a v o i d m i s -l e a d i n g i n t e r p r e t a t i o n s o f e i t h e r s e t ti n g .

T h e f a c t o r s i n fl u e n c in g b o t h t h e a m o u n t a n d c o m -p o s i t i o n o f o r g a n ic m a t t e r i n a b l a c k s h a l e c a n b e e x -p r e s s e d i n a n e q u a t i o n o f t h e f o r m s o m e t i m e s d e r i s i v e l ys t a t e d a s s o m e o f i t p l u s t h e r e s t o f i t e q u a l s a l l o f i t ,a s f o l l o w s :

Z O N E O F D I A G E N E S I S[ O x i d a t i o n )

O r g a n i c ~ O r g a n i c ~ ] S u l f a t e r e d u c t i o nm a t t er = [ p r o d u c ti v i ty - O x i d a t i o n ) - ] F e r m e n t a t i o n| D e c a r b o x y l a t i o n[ P y r o c a t a l y t i c r e a c ti o n s

~ M i g r a t i o n ]+ o f- l p r o d u c t s l

R E F E R E N C E SA nger , G . , N ie l sen , H . , Puche l t , H . , and Ricke , W . ( 1966)Sul f ur iso topes in the R amm elsber g or e depos i t ( G er many) :E c o n . G e o l . 61, 511-536.A r mands , G r s ta ( 1972) G eochemica l s tud ies of u r an ium,molybd enum and vanad ium in a Sw edish a lum sha le : S t o c k -h o l m C o n t r i b . G e o l . 27, 148 pp.A r nold , C . A . ( 1%9) The f os s i l -p lan t r ecor d : in A s p e c t s o fp a l y n o l o g y R. H . Tschudy and R. A . Scot t , eds . , Wi ley-Interscience, New York, 127-143.Ber ner , R . A . ( 1964) S tab i l i ty f i e lds of i ron m iner a l s in an-ae r obic mar ine sed iments : J . G e o l . 72, 826-834.Bo yle, R. W. (1%8) Fahlb ands , sulf ide schis ts , and ore de-posi t ion: E c o n . G e o l . 63, 835-840.Br eger , I . A . and Br ow n, A n dr ew ( 1962) K er oge n in the Cha t -tanooga Sha le : S c i e n c e 137 , 221-224.Br ookins , D . G . ( 1976) Sha le as a r epos i to r y f or r ad ioac t ivew as te : the ev iden ce f r om O klo : E n v i r o n . G e o l . 1, 255-259.Br ow n, J . P . ( 1976) Ener gy fr om sh a le - - a li t t le used na tur a lr esour ce : in N a t u r a l G a s f r o m U n c o n v e n t i o n a l S o u rc e s :N at l . A cad . Sc i . , Boar d on Miner a l Resour ces , Comm . onNatu ral Reso urces , m tg. , Jan. 15, 1976, 86-89.Clay poo l , G. E. and K aplan , I . R. (1974) The or igin and dis-t r ibu t ion of methane in mar ine sed iments : in N a t u r a l G a s e si n M a r i n e S e d i m e n t s I . R . K aplan , ed . , P lenum, N ew Y or k ,99-139.Clem ens, S . L. [Mark Twain] (1874) [1896] L i f e o n t h e M i s -

s i s s i p p i : H ar per and Br os . , N ew Y or k , 465 pp .Conan t , L . C . and Sw anson , V . E . ( 1961) Cha t tanooga Sha le

and r e la ted r ocks of cen t r a l Tennessee and near by a r eas :U . S . G e o l . S u r v . P r o f . P a p . 357, 91 pp.Cox, R . and Cur t i s , R . ( 1977) D iscover y of the Lad y Lor e t tazinc- lead-s i lver deposi t , nor thwest Queensland, Au stral ia- -a geochem ica l case h i s tor y : J . G e o c h e m . E x p l o r . 8, 189-202.Cur t i s , C . D . ( 1977) Sedimenta r y geochem is t r y : envi r on-m e n t s a n d p r o c e s s e s d o m i n a t e d b y i n v o l v e m e n t o f a naqueous phase : P h i l o s . T r a n s . R o y . S o c . L o n d o n A 286,353-372.D avidson , D . F . and L akin , H . W. ( 1961) Meta l conten t o fsome b lack sh a les of the w es te r n U ni ted S ta tes : in G eolog-ica l Sur vey Resear ch 1961, Shor t paper s in the geologic andhydr o logic sc iences : U . S . G e o l . S u r v . P r o f . P a p . 424-C,C329-C331.D avidson , D . F . and Lakin , H . W . ( 1962) Meta l conten t o fsome b lack sh a les - - P t . 2 : in G eologica l Sur vey R esear ch1962, Shor t paper s in the g eologic and hydr o logic sc iences :U . S . G e o l . S u r v . P r o f . P a p . 450-C, C740.D ean , W . E . , G ar dner , J . V . , J ansa , L . F . , Cepek , PaveL andSe ibold , Eugen ( 1977) Cyc l ic s ed imenta t ion a long the con-t inen ta l mar g in of nor thw es t A f r ica: in I n i ti a l R e p o r t s o fD e e p S e a D r i l li n g P r o j e c t 41, Y ves Lance lo t and EugenSeibo ld, eds . , U.S . Go v. Pr int ing Off ice, W ashingto n, 965-989.Didyk, B. M. , Simoneit , B. R. T. , Brassel l , S . C. , and Eglin-ton , G eof f r ey ( 1978) O r ganic geochemica l ind ica tor s of pa -leoenvi r onmenta l condi t ions of s ed imenta t ion : N a t u r e 272,216-222.


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3 2 0 T o u r t e l o t C l a y s a n d C l a y M i n e r a l s

E n s i g n , C . O . , J r . , W h i t e , W . S . , W r i g h t , J . C . , P a t r i c k , J . L . ,L e o n e , R . J . , H a t h a w a y , D . J . , T r a m e l l , J . W . , F r i t t s , J. J . ,a n d W r i g h t , T . L . 1 96 8) C o p p e r d e p o s i t s i n t h e N o n e s u c hS h a l e , W h i t e P i n e , M i c h i g a n : i n O r e D e p o s i t s o f t h e U n i t e dS t a t e s , 1 9 3 3 - 1 9 6 7 , G r a t o n - S a l e s V o l u m e I , A m e r . I n s t .M i n . M e t a l l . P e t . E n g . , N e w Y o r k , 4 6 0 - 4 8 8 .F u l t o n , L . J . P . 1 97 7) S t r a t i g r a p h y a n d s e d i m e n t o l o g y o f r a -d i o a c t i v e D e v o n i a n - M i s s i s s i p p i a n s h a l e s o f t h e c e n t r a l A p -p a l a c h i a n B a s i n : P h . D . t h e s i s , U n i v e r s i t y o f C i n c i n n a t i , 1 2 8p p .G a m m o n , J . B . 1 96 6) F a h l b a n d s in t h e P r o t e r o z o i c o f s o u t h -e r n N o r w a y : E c o n . G e o l . 61 , 174-188 .G a r d n e r , J . V . , D e a n , W . E . , a n d J a n s a , L . F . 1 97 7) S e d i -m e n t s r e c o v e r e d f r o m t h e n o r t h w e s t A f r i c a n c o n t i n e n ta lm a r g i n , L e g 4 1 , D e e p s e a d r i l li n g p r o j e c t : i n l n i t ia l R e p o r t so f D e e p S e a D r i l li n g P r o j e c t 4 1 , Y v e s L a n c e l o t a n d E u g e nS e i b o l d , e d s . , U . S . G o v . P r i n t i n g O f f ic e , W a s h i n g t o n , 1 1 2 1 -1134.G o l d h a b e r , M . B . 1 9 78 ) E u x i n i c f a c i e s : i n T h e E n c y c l o p e d i ao f S e d i m e n t o l o g y: R h o d e s F a i r b r i d g e a n d J o a n n e B u r g e o i s ,e d s . , D o w d e n , H u t c h i n s o n , a n d R o s s , I n c . , S t r o u d s b u r g ,P e n n s y l v a n i a , 2 9 6 - 3 0 0 .G o l d h a b e r , M . B . a n d K a p l a n , I. R . 1 9 74 ) T h e s u l f u r c y c l e :in T h e S e a 5 M a r i n e C h e m i s t r y , th e S e d i m e n t a r y C y c l e ,E . D . G o l d b e r g , e d . , J o h n W i l e y , N e w Y o r k , 5 6 9 - 6 5 5 .G u l s o n , B . L . 1 97 7) A p p l i c a t i o n o f l e a d is o t o p e s a n d t r a c ee l e m e n t s t o m a p p i n g b l a c k s h a l e s a r o u n d a b a s e m e t a l s u l -f i d e d e p o s i t : J . G e o c h e m . E x p l o r . 8 , 8 5 - 1 0 3 .H a l l a m , A n t h o n y 1 97 7) A n o x i c e v e n t s in t h e C r e t a c e o u so c e a n : N a t u r e 268 , 15-16 .H a r r i s , A . G . , H a r r i s , L . G . , a n d E p s t e i n , J . B . 1 9 78 ) O i l a n dg a s d a t a f r o m P a l e o z o i c r o c k s i n t h e A p p a l a c h i a n B a s i n :m a p s f o r a s s e s s i n g h y d r o c a r b o n p o t e n ti a l a n d t h e r m a l m a -t u r i t y c o n o d o n t c o l o r a l t e r a t i o n i s o g r a d s a n d o v e r b u r d e ni s o p a c h s ) : U . S . G e o l . S u r v . M a p 1-917-E.I r w i n , H i la r y , C u r t is , C . D . , a n d C o l e m a n , M a x 1 97 7) I s o -t o p i c e v i d e n c e f o r s o u r c e s o f d ia g e n e t i c c a r b o n a t e s f o r m e dd u r i n g b u r i a l o f o r g a n i c - r i c h s e d i m e n t s : N a t u r e 2 6 9 , 2 0 9 -213 .J e w e t t , J . M . , E m e r y , P . A . , a n d H a t c h e r , D . A . 1 96 5) T h eP l e a s a n t o n G r o u p U p p e r P e n n s y l v a n ia n ) i n K a n s a s : K a n -s a s G e o l . S u r v . B u l l . 175 , p t . 4 , 1 -11 .K e r r , R . A . 1 9 7 8 ) G l o m a r E x p l o r e r : N e w e r a . in d e e p - s e adr i l l ing : S c i e n c e 200 , 1254-1255 .K r a u s k o p f , K . B . 1 95 5) S e d i m e n t a r y d e p o s i t s o f r a r e m e t a l s :in E c o n o m i c G e o l o g y 5 0 t h A n n i v e r s a r y V o l u m e , 1 9 0 5 -1955), A . M . B a t e m a n , e d . E c o n . G e o l . 4 1 1 - 4 6 3 .K r u m b e i n , W . C . 1 94 2) P h y s i c a l a n d c h e m i c a l c h a n g e s i ns e d i m e n t s a f t e r d e p o s i t i o n : J . S e d i m e n t . P e t r o l o g y 1 2 , 1 1 1 -117.

K r u m b e i n , W . C . a n d G a r r e l s , R . M . 1 95 2) O r i g i n a n d c l as -s i fi c a ti o n o f c h e m i c a l s e d i m e n t s i n t e r m s o f p H a n d o x i d a -t i o n - r e d u c t i o n p o t e n t i a ls : J . G e o l . 60 , 1 -33 .P e l t o la , E s k o 1 96 8) O n s o m e g e o c h e m i c a l fe a t u r e s i n t h eb l a c k s c h i s t s o f t h e O u t o k u m p u a r e a , F i n l a n d : G e o l . S o c .F i n l a n d B u l l . 4 0 , 3 9 - 5 0 .R i c e , D . D . 1 9 75 ) O r i g i n o f a n d c o n d i t i o n s f o r s h a l l o w a c -c u m u l a t i o n s o f n a t u r a l g a s : W y o m i n g G e o l . A s s o c . , 2 7 t hA n n . F i e l d C o n f . 1 9 75 , G u i d e b o o k , 2 6 7 - 2 7 1 .S c h o t t , G . L . , O v e r b e y , W . K . , J r . , H u n t , A . E . , a n d K o m a r ,C . A . , e d s. 1 97 8) F i r s t e a s t e r n g a s s h a l e s s y m p o s i u m , O c -t o b e r 1 7 - 1 9 , 19 7 7, M o r g a n t o w n , W e s t V i r g i n i a : U . S . D e p .E n e r g y , M o r g a n t o w n E n e r g y R e s . C e n t er , M E R C / S P - 7 7/ 5 ,783 pp .S w a n s o n , V . E . 1 96 1) G e o l o g y a n d g e o c h e m i s t r y o f u r a n i u mi n m a r i n e b l a c k s h a l e s - - -a r e v ie w : U . S . G e o l . S u r v . P r o f .P a p . 3 5 6 - C , 6 7 - 1 1 2 .T o u r t e l o t , E . B . 1 9 70 ) S e l e c t e d a n n o t a t e d b ib l i o g r a p h y o fm i n o r - e l e m e n t c o n t e n t o f m a r i n e b l a c k s h a l e s a n d r e l a t e ds e d i m e n t a r y r o c k s , 1 9 3 0 -6 5 : U .S . G e o l . S u r v . B u l l . 1293,1 1 8 p p .T o u r t e l o t , E . B . a n d V i n e , J . D . 1 97 6) C o p p e r d e p o s i t s i ns e d i m e n t a r y a n d v o l c a n o g e n i c r o c k s : U .S . G e o l . S u r v .P r o f . P a p . 9 0 7 - C , 3 4 p p .T o u r t e l o t , H . A . 1 96 4) M i n o r - e l e m e n t c o m p o s i t i o n a n d o r -g a n i c c a r b o n c o n t e n t o f m a r i n e a n d n o n m a r i n e s h a l e s o fL a t e C r e t a c e o u s a g e i n t h e w e s t e r n i n t e r i o r o f t h e U n i t e dS t a t e s : G e o c h i m . C o s m o c h i m . A c t a 28 , 1579-1604 .U . S . D e p t . E n e r g y 1 97 7) N a t i o n a l g a s s u r v e y : S u p p l y - t e c h -n i c a l A d v i s o r y T a s k F o r c e o n N o n - c o n v e n t i o n a l N a t u r a lG a s R e s o u r c e s , J . W . H a r b a u g h , C h a i r m a n , F e d e r a l E n e r g yR e g u l a t o r y C o m m i s s i o n D O E / F E R C - 0 0 1 0 , U C - 1 3 ) , 10 8p p .V i n e , J . D . 1 96 6) E l e m e n t d i s t r ib u t i o n in s o m e s h e l f a n d g e o -s y n c l i n a l b l a c k s h a l e s : U .S . G e o l . S u r v . B u l l . 1214E, 31 pp .V i n e , J. D . a n d T o u r t e l o t , E . B . 1 97 0) G e o c h e m i s t r y o f b l a c ks h a l e d e p o s i t s - - - a s u m m a r y r e p o r t : E c o n . G e o l . 6 5 , 2 5 3 -272.W e d e p o h l , K . H . , D e l e v a u x , M . H . , a n d D o e , B . R . 1 97 8)T h e p o t e n t i a l s o u r c e o f l e a d i n t h e P e r m i a n K u p f e r s c h i e f e rb e d o f E u r o p e a n d s o m e s e l e c t e d P a l e o z o i c m i n e r a l d e p o s i t si n t h e F e d e r a l R e p u b l i c o f G e r m a n y : C o n t r i b . M i n e r a l . P e -t ro l . 6 5 , 2 7 3 - 2 8 1 .W h i t e , S . M . 1 9 79 ) D e e p - s e a d r i l li n g : G e o t i m e s 2 4 , 2 1 - 2 3 .W o o d r i n g , W . P. 1 95 4) C o n f e r e n c e o n b i o c h e m i s t r y , p a l e o -e c o l o g y , a n d e v o l u t i o n : N a t l . A c a d . S c i . 4 0 , 2 1 9 - 2 2 4 .Z a n g e r l , R a i n e r a n d R i c h a r d s o n , E . S . 1 96 3) T h e p a l e o e c o -l o g ic a l h i s t o r y o f t w o P e n n s y l v a n i a n b l a c k s h a le s : F i e l d i a n a ,G e o l . M e m . 4 , 352 pp .R e c e i v e d 2 1 D e c e m b e r 1 97 8; a c c e p t e d 7 J u n e 1 97 9)


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Vol. 27, No. 5, 1979 Black shal e--i ts deposition and diagenesis 321

Pe31oble---LlepHbIe C~aHetK ~IB2LqeTC~I TeMHO oKpameuuofi rJItlHMCTOfi nopo~ofi , co~iep>ga~efi opraHn-qecKHfi MaTepHa2l, KOTOpbl~ MOt ~IBHTbC~ HCTOqHHKOM yrs~eno~Iopo~oa a He,pax u~n u3 KOTOpOFOMO:>KHO nO.rlyqI4Tb yrJIeBO~1OpO~Ibl IU4pO2IH3OM. BO MHOFMXBn~Iax q~puoro caautta co~ep>KaHHe MeTaJI2IOBB HeCKO2IbKO pan npeBbImaeT ax co~lep>Kaane B O6blKHOBeHHblX caaHttax. HeKoTOpble BIl~bl q~pHorocaautta Cay>KaT BMe~aIOmnMn nopo~IaMn ~ cnnreueTnqecKnx OT~omennfi MeTamaoB.q~pnble cJlant~bi qbOpMHpOBaJIHCb B TeqeHne aeefi ~lCTOpHrl 3eM~n Vl BO Bcex HaCT~IX MHpa. 9TO yKaabt-BaeT Ha TO, qTO reoJ~orllqeCKlle llpotleccbl I4 Be reoJtor~lqecK~ie ycJ~oB~t~ ItB.rlNIOTC~I onpe~eJ~:a~oul~iM~iqbaKTOpa3tH upH qbopMttpoBannlt qiSpnbix CJ~antleB. FeoJ~orrlqecKne npoueccbl BlCdlIO'LlalOT OTSto>reune,B pe3yJ~hTaTe KOTOpOrO HaKanJntaa~oTcfl nepariqubie ocaJIKH qiSpnoro cJ~antla, lI )lnarene3, np nc xo~ tt ta fin pe3yJIbTaTe yaeJ~ri'~nBaroiJiefic~rny6nm,t 3axoporIeunn oca4Ixoa.IlpolIeCCbl OTJ~O~Keltlltl BlCdIIOqaloT lle.rlbl~ /lnana3oH OTHOmeUltl~ Me~4Iy TaKI, MIt ~aKTopaMlt KaKopraaa,~ecKan npoJIyKTitBnOeTb, CKOpOCTb Ce/IltMenTallltll, I, HTeHCltBHOCTb oxncJieurm, paapyma~otReroopranplqecKoe BeIIIeCT80. Ec.r ln IlpnCyTCTByeT /IOCTaTOqItoe KOJIMqeCTBO opraul tqecKoro BelReCTBa,qTO6bl UCTOnlIITb Kncnopo~I B cpe~le, o6paayeTcn qepHblfI cnaneil .~ltarHeTltqecKile llpollecchi BK.rnotlalOT XHMnnecKne peaxttnn , orIpe~leJL~eMb~e npripo/lofi COCTaaus~xqacTefl R pe~

black shale its deposition and diagenesis

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