Journal of African Earth Sciences, Vol. 9, No. 1, pp. 87-95, 1989 0899-5362/89 $3.00 + 0.00 Printed in Great Britain. Pergamon Press plc

Elemental Chemical Composition of the Bivalvian Shells from Gebel Mokattam, Cairo, Egypt, and their Significance

in Classification and Paleoecology

A.A. ABDEL AAL* AND KH.M. FAWZI**

*Geology Department, Faculty of Science, Alexandria University, Alexandria, EgypL

**General Petroleum Company, Egypt.

Abstract - The M S, A1, Si, Mn, Fe and Sr contents of 124 bivalvian shcUs from Gebel Mokattam, Cairo, Egypt, were determined by means of quantitative spectral analysis. The concentrations of Sr, Mn, Fe and Si increase from Middle to Upper Eocene, and vice versa with respect to Mg content. The concentration of AI is nearly stable in both the Middle and Upper Eocene bivalvian shells. This study showed that the Upper Eocene basin in Gebel Mokattam was warmer, shallower and more saline than that of the Middle Eocene. The postdepositional changes of the studied faunas were interpreted. Finally, an attempt was made to classify four of the studied families according to their chemical composition.

I N T R O D U C T I O N

The b iogeochemica l inves t iga t ions are very im- p o r t an t in paleoecological s tud ies , s t ra t igraphica l corre la t ion a n d a 1so for the sys t ema t i c classif ica- t ion of the organism.

The b iogeochemis t ry w a s originally ini t ia ted as an i ndependen t ly b r a n c h of paleontology at the s econd ha l f of the twen t i e th cen tury . Historically, we classif ied t he b iogeochemis t ry into th ree s t ages as follows :

1 - Theoret ical s tage (1920-1950) : W h e n V e r n a d s k y (1922, 1923 and 1925),

Samoflov ( 1925) and Vinogradov ( 1931, 1932, 1935 and 1944) de t e rmined the chemica l compos i t ion of the different t y p e s of m a r i n e shel ls and the b lood of mar ine o rgan i sms , t hey c o n c l u d e d t ha t the chemica l compos i t ion of mar ine o rgan i sms de- p e n d s u p o n the i r morpho logy and classif ication.

2 - Analyt ical s tage (1950-1970) : In th is s tage, the inves t iga tors compared bet-

w e e n the chemica l compos i t ion of the Recen t orga- n i s m s and the t e m p e r a t u r e and sal ini ty of thei r env i ronments . The impor t an t w o r k s in th is s tage were done b y L o w e n s t a m (I 954), Tu rek i an (1955), O d u m (1957), T u r e k i a n and Arms t rong (1960), R u c h e r and Valent ine (1961), Dodd (1961 and 1963), Pi lkey and Hower ( 1961), Pilkey and Goodel (1963), Leutwein (1963), Su l tanov and Isayev (1966) and Su l t anov and Efendiev (1969). 3 - Applied s tage (1970 up to date) :

The inves t iga tors d e d u c e d the pa l eo t empe ra t u r e

and paleosal in i ty f rom the chemica l compos i t ion of the fossil shells. Among the w o r k e r s who ha d carr ied ou t t he se s t ud i e s are L a b s h i n s k a i a (1970 and 1973), Smis lova (1974}, Kats a n d Kokonko (1975), Zolotarev (1976), Su l t anov et al. (1978), Regland et al. (1978) Kats and Abdel Aal (1979), Abdel Aal (1983), Ismafl and Abdel Aa i (1986) and Abdel Aal et al. (1987).

S T R A T I G R A P H Y

The s t ra t igraphy ofGebel Mokat tam, Cairo, Egypt (Fig. I) s t ud i ed b y several a u t h o r s : Zittel (1883), Four t au ( 1897), H u m e (1911), B lanckenhorn ( 1921 ), Cuvillier (1930), A b b a s s (1953), B i shay (1953), H a s s a n (1966), S t rougo (1977) and Fawzy (1986). The following sec t ion w a s m e a s u r e d and s u m m a - rized a s follows f rom top to b a s e :

Upper Eocene (Maadi Formation} : The lower pa r t cons i s t s of whi te and yel lowish whi te l imestones , where the u p p e r pa r t is fo rmed of mar ly lime- s tones , sha les , s a n d y l imes tones and s i l iceous l imestones , fossflfferous wi th : Turritella boghosi C o s s m . , S p o n d y l u s a e g y p t i a c u s N e w t . , M i m a c h l a m y s h e l u a n e n s i s (Opp.) , Carolla p/acuno/des Cantr. , Vulsella c r i spa ta Fisch., Pecten (PseudoamusiurrO s a d e k i A b b a s s , Ost rea (Turkostrea) elegans (Desh.), 0. (T.) multicostata (Desh.), O. I T . ) p u n c t a t a (Desh.), Pycnodonta pharaonica (Opp.), Schizaster sp. and others .

Middle Eocene (Mokat tam Format ion) : White, yel lowish whi te and b r o w n i s h whi te l imestones , fossi l i ferous wi th : Numrnulites gizehensis Forsk,

87

88 A.A. ABDEL AAL and Kn. M. FAWn

3 0 32 3~ | , I J

MEDITERRANEAN SEA - / / ~

1o- -.~o,ro ~ ,,~ L3(

/ )\ // / \ ~ ; f l / \ x ,

!

3 0 32 3~

Fig. I Location map of the studied area

Genus Pecten Muller, 1776 Pecten (PseudoamusiurrO sadekl, Abbass Pecten sp.

Family SPONDILIDAE Gray, 1826 Genus Spondylus Linn6, 1758 Spondylus aegyntiacus Newton Spondylus sp.

Superfamily ANOMIACEA Rafinesque, 1815 Family ANOMIIDAE Rafinesque, 1815

Genus Carolia Cantraine, 1838 Carolia placunoides Cantra ine Carolia sp.

Superfamly LIMACEA Rafinesque, 1815 Family LIMIDAE Rafinesque, 1815

Genus L/ma Brugui6re, 1797 L/ma sp.

Turritella boghosl Cossm., Spondylus aegyptiacus Newt., Vulsella crispata Fisch., Chlamys (Hilberia) cailliaudi (Opp.), Ostrea {Turkostrea) callifera (Desh.), 0. (T . )punc ta ta (Desh.), 0. fT.) elegans (Desh.), 0. (T.) mutabilis (Desh.), Pycnodontapha- raonica (Opp.), Echinolampas africanus De Lor. and others.

MATERIAL AND METHOD

One h u n d r e d and twenty four well preserved bivalvian shells were selected from the fossil as- semblage collected from the different horizons of the s tudied Eocene Format ions and prepared for analysis by m e a n s of a Carl Zeiss spect rograph u s i n g t h e m e t h o d described byAbdeIAal and Frihy (1984). The s tud ied shells represent twenty six species belonging to four teen genera of the class Bivalvia.

Suborder OSTREINA ferussac, 1822 Family OSTREIDAE L a m a r c k , 1809

Ostrea (Turkostrea) multicostata (Desh.) Ostrea (Turkostrea) elegans (Desh.) Ostrea (Turkostrea] punctata (Desh.) Ostrea (Turkostrea] call~fera (Desh.) Ostrea (Turkostrea) mutabilis (Desh.) Pycnodonta pharaonica (Opp.). Pycnodonta sp. Gryphaea sp, Liostrea sp. Lopha sp.

Subclass HETERODONTA Neumayer, 1884 Order VENEROIDA H. Adams and A. Adams Superfamily LUCINICEA Fleming . 1828 Family LUCINIDAE Fleming, 1828

Genus Lucina Bruguiere, 1797 Lucina sp.

Phy lum MOLLUSCA Class BIVALVIA Linn6, 1758 (Buonannl, 1681) Subclass PTERIOMORPHIA Beurlen, 1944 Order PTEIOIDA Newell, 1965 Suborder PTEIOIDA Newell, 1965 Superfamily PTERIACEA Gray, 1847 Family MALLEIDAE Lamarck, 1819

Genus Vulsella RSding, 1798 Vulsella crispata Fischer Vulsella sp.

Superfamfly PECTINACEA Raflnesque, 1815 Family PECTINIDAE Rafinesque, 1815

Genus Chlamys Roding , 1798 Chlan~s cailliaudi (Opp.) Genus Mimachlamys I redale , 1929 Miachlamys solarium (Mayer-Eymar) Mimachlamys heluanensis (Opp.) Mimachlamys sp.

Superfamily VENERACEA Rafinesque, 1815 Family VENERIDAE Raflnesque, 1815 Subfamily MERETRICINAE Gray, 1847

Genus Meretrix Lamarck, 1799 Meretrix (Meretrir) nitidula (Lamarck)

Resul t s The resul ts of the chemical analysis of the stu-

died bivalvian shells are summar ized in (Table 1). The dis tr ibut ion of the chemical e lements in the

s tudied shells (Figs. 2-7} revealed the following :

1 - The a m o u n t s of Sr , Mn , fe and Si increase from Middle to Upper Eocene.

2 - The a m o u n t of Mg decreases from Middle to Upper Eocene.

3 - The con ten t s of Al is nearly stable in both the Middle and Upper Eocene.

Elemental Chemical Composition oft.he Bivalvian Shells from C-ebel Mokattam, Cairo, Egypt 89

S I G N I F I C A N C E OF C H E M I C A L A N A L Y S E S IN S Y S T E M A T I C C L A S S I F I C A T I O N

OF M S T U D I E D BIVALVIAN S H E L L S

The chemical composit ion is very important in the recent classifications of organisms. The first a t tempt for such classification was done by Vinogradov (1931 and 1935), who concluded that the chemical composit ion of marine organisms d e p e n d s u p o n t h e i r m o r p h o l o g y a n d classif icat ion. Lowens tam (1954} classif ied organisms secreting calcareous shells into: orders composed ofaragonite, orders composed of calcite, and mixture of bo th calcite and aragonite. Turekian ( 19 55) concluded that the Sr and Ca con- tents in marine carbonate shells depends on the

taxonomy. Smislova (1974) classified the Upper Ju ra s s i c art iculated brachiopods according to their chemical composition. Kokonko (1976) c l a s s i f i e d t h e D a n i a n s h e l l s of f ami ly Terebratul idae according to their chemical composition.

The present s tudy is a trial to classify four of the s tudied families accordinig to their chemical com- position (Fig. 8) and (Table 2). Based o n t h e results arrived at by the spectral analyses the following conclusion was done :

I- Family Malleidae is characterized by a hlgh concentrat ion of Mg, Al and Si, b u t low amoun t s of Mn, Fe And St. 2- Family Ostreidae is characterized by a high

Table 1 : Ranges (R), arithmetic mean (A) and mode (M) of chemical element concentrat ion of the studied bivalvian shells.

Element%

Mg

AI

Si

Mn

Fe

Sr

Middle Eocene shells

R= 0.24% - 1.00% A= 0.59% M= 0.55%

R= 0.042% A= 0.086% M= 0.050%

- 0.2600/0

R= 0.04% - 1.00% A= 0.21% M= 0.10°/o

R= 0.014% A= 0.018% M= 0.015%

- 0.028%

R= 0.24% - 0.58% A= 0.300/o M= 0.25%

R= 0.005% - 0.074% A= 0.019% M= 0.015%

Upper Eocene shells

R= 0.18% - 0.64% A= 0.390/0 M= 0.25%

R= 0.042% A= 0.098% M= 0.150%

R= 0.04% - 3.10% A= 0.46% M= 0.20%

0.380%

R= 0.014% - 0.064% A= 0.023% M= 0.025%

R= 0.25% - 1.10% A= 0.45% M= 0.35%

R= 0.012% - 0.096% A= 0.046% M= 0.035%

concentrat ion ofAl, b u t low amoun t s ofMg, Si, Mn, Fe and Sr. 3- Family Pectinidae is characterized by a high concentrat ion ofMg, Si, Fe and Sr, bu t low amount of AI and Mn. 4- Family Anomiidae is characterized by a high concentrat ion ofMn, Fe and Sr, b u t low amount of Mg, AI and Si.

C O N C L U S I O N

The concentra t ions of Sr, Mn, Fe, and Si in the s tudied shells increase from Middle to Upper

Eocene, vice versa with respect to Mg content. The concentrat ion of Al is nearly stable in bo th the Middle and Upper Eocene bivalvian shens.

According to the Mn concentration, the Middle Eocene basin was deeper than that of the Upper Eocene. This agrees with the resul ts of Ronov and Ermishkina (1959) who reported that the Mn content increases along the shores of the ancient shallow seas and decreases far from the shores.

The contents of Sr in the s tudied bivalvian shells indicate tha t the climate during the Upper Eocene time was warmer than that of the Middle Eocene. This agrees with the resul ts of

90 A.A. ABDEL AhL and I ~ . M. F^w~

Mg %

1.0-

0 . 8 "

O ° 6 "

0 . 4 "

0 . 2 -

o • o o

o x l

o

; . ~ i x . , , ° o . ~ o ~ X ~ -

× X e o

o

o o o o o

X o

X ~ o o o

o o

Q

• X

• •

~ o

' I ' l ' I I t I , I i I i I ! I '

MIDDLE EOCENE I UPPER EO C E N E i

Fig. 2 - D i s t r i b u t i o n of Mg wi th in the studied shells a long the Eocene strata, ee=Ma l l e i dae ,

o o = O s t r e i d a e g x x = P e c i i n i d a e , a a = A n o m i i d a e , o o = S p o n d y l i d a e ~ , ~ = L i m i d a e •

aa=Lucin idae and ~ = V e n e r i d a e

A L •/o

0.5-

0.4-

0 , 3 "

0.2-

0.1"

X • o

0 ° O IOD ~C~ 0 0

Q '~ X ~

x j \ X r', o

X ,,, %" • ( ~ 8 8 = - o " g

O

I I ' I I I I t ' ' ' I E ' I '

M I D D L E EOCENE U PPE R EOC E N i

Fig. 3 - D i s t r i b u t i o n of AI w i th in the studied shel ls along the Eocene strata, oe=Mal le idae•

o o = O s t r e i d a e • xx=Pect in idae• a • = A n • m i l d • e , o o = S p o n d y l i d a e , ~ ' = L i m i d a e ,

• •=Lucin idae and ~'~=Venerida

Elemental Chemical Composition of the Bivalvian Shells from Oebel Mokattam, Cairo, Egypt 91

Si %

3.2"

2 . 8 -

2.4

2.0

1.6"

1.2-

0 . 8 -

0.4-

%

• x

x

0

o o

. .~ I ° x

"~x*_,, o o . ~ ' J ~ a m •

~= ~ ' ~ . = L # ' o ~ o o x x . ~ o ~ . - - ~ • ~x ° x,, I u I ' I I ' I

MIDDLE E O C E N E J U P P ER

x

: o/

I I

E O C E N E I Fig. 4 - D i s t r i b u t i o n of Si w i t h i n the s t u d i e d shel ls a long the Eocene s t ra ta , ee=Ma l l e i dae~

o o = O s t r e i d a e ~ xx=Pec t i n i dae ~ A A = A n o m i i d a e ~ o a = S p o n d y l i d a e • # # = L im idae •

A a = L u c i n i d a e and F # = V e n e r i d a e

Mn°/,

0 .05 -

O. 04-

0.03

0 . 0 2

0.01-

o A

• OO

• •X X X X

& A =o

A~ / • x

• X

o clo •

' ' E ' O ' E' II ' ' ' ' ' ' M I D D L E C E N U P P E R E O C E N E I Fig. 5 - D i s t r i b u t i o n of Mn w i t h i n t h e s tud ied she l l s a long the Eocene s t r a t a , e e = M a l l e i d a e

o o = O s t r e i d a e x x = P e c t i n i d a e ~ & & = A n o m i i d a e ~ D a = S p o n d y l i d a e • ~ c m ' = L i m i d a e

A A = L u c i n i d a e and ~ = V e n e r i d a e

92 A.A. w~BDEL ~ and Ka. M. FAwza

Fe%

1.2-

1.0-

0 ° 8 -

0.6-

0.4-

0 , 2 "

x

X o

o o,~ x ° • / o ~ °

° x o

A e

X " X

o o /\ /o\=,

• O OOe ~WO o o o

I 1 i l ! I I I I I

MIDDLE EOCENE UPPER E O C E N E

Fig 6 - D i s t r i b u t i o n of Fe wi th in the studied shells a long the Eocene strata, ee=Ma l l e i dae~

o o = O s t r e i d a e , xx=Pect in idaeg&&=Anomi idae ,aa=Spondy l idae , ~ = = L i m i d a e

• • =Lucinidae and .e'e=Veneridae

Sr %

0 , I0 -

0.08-

0.06-

0.04-

0.02-

X

AX

A

• o

• J~" o

x

x x

o ~ X • * - - %

x ~ . ~ oo-.° / \ . .o

x ~ ~ o ~

• •

o o • • e X

MIDDLE EOCENE I U PPE R EOCENE

F ig 7 - D i s t r i b u t i o n of Sr w i th in the studied shells along the Eocene. e e = M a l l e i d a e 9

o o = O s t r e i d a e ~ xx=Pec t i n i dae , a a = A n o m i i d a e , a o = S p o n d y l i d a e , ~ ' = L i m i d a e ,

&A=Lucin idae and # f =Veneridae

Elemental Chemical Composition of the Bivalvi~ Shells f rom Gcbel Mokattam, Cairo, Egypt 93

Table 2 : Ranges (R), a r i thmet ic m e a n (M) a n d mode |M) of chemica l e l ement concen t ra t ion of the s tud ied bivalvian families.

Element%

Mg

Al

Si

Mn

Fe

Sr

MaIleidae

Rffi0.24%-0.90% Affi0.54% Mffi0.55%

R=0.04% -0.38% A=0.12% M=0.05%

R=0.08%-3.10 Affi0.65% M=0.20%

R=0.016%-0.038 Affi0.020% M=0,015%

R=0.25%- 1.00% A=0.35% M=0.25%

R=0.007%-0.050% Affi0.022%

Ostreidae

R=0.18%-I.00% A=0.35 M=0.25%

R=0.04%-0.35% Affi0.08% M=0.05%

R=0.04%-0.80% A=0.22% M=0.20%

R=0.014%-0.035% A=0.020 M=0.015%

R=0.25%- 1.10% A=0.37% M=0.25%

R=0.005%-0.0609/o A=0.031%

Pectinidae

R=0.28% - 1.00% A=0.47% M=0.45%

R=0.07% -0.26% A=0.13% M=0.15%

R=0.04%- 1.82% A=0.34% M=0.20%

R=0.016%-0.030% A=0.021% M=0.025%

R=0.24%-0.8% A=0.40% M--0.35%

R=0.010%-0.096% A=0.048%

Anomiidae

R=0.24% - 0.52% A=0.41% M=0.45%

R=0.07% -0.18% A=0.13% M=0.15%

R=0.07%-0.82% A=0.18% M=0.20%

R-0.024%-0.046% A=0.033% M=0.025%

R=0.24%-0.70% A=0.38% M=0.35%

R=0.014%-0.090% A=0.05 I%

Si %

3.0

2.0

1.0

\

%

i/~'\'xl \ .'" . ¢

"~V' "~'

M 0 P A

Fe % 1.2

0.8

0.4

q¢~.- , "'~.

2

3 o.- ~ ~ -o

M 0 P A

Mn*l° 0.05

0.03

Q.OI

.o I / "

• -4~ /

-,.,4" 2

AI% 1.5

0.3

0.1

~"-o 2

I / I I I I I I M 0 P A M 0 P A

Mg % S r %

1"01 "~" 0"10 f I p...1 \ / "\ / "

0.6 2 ' \ 0.06 . J r . ~ 2 .__..o

0.2 ~ ~ 0.02 .~- 3 -4

i , ~ - - - - ' r " - , , M 0 P A M 0 P A

Fig. 8 Graphs illustrating the maximum (1) arithmetic (2) and minimum means of Mg, Sr, Mn, AI, Si and Fe percenta-

ges in Malleldae ffi M, Ostreidae ffi O, Pectinldae = P and Anomlldae = A

Pilkey a n d Goodel (1963) who conc luded t h a t the Sr con ten t in m o l l u s c a n shel ls exhibi ts a positive correlat ion wi th t e m p e r a t u r e a n d a negative corre- la t ion with salinity.

The concen t r a t ion of Mg in the s tud ied Middle Eocene shells is h igher t h a n t h a t in the Upper Eocene shells, The increase in Mg concen t ra t ion in shells is accompan ied by an increase in sal ini ty and dep th of the mar ine deposi t ional bas in , This agrees wi th the conc lus ions achieved by Chave (1954), Ismail a n d A b d e l Aal (1986) a n d AbdeIAal etal. (1987) who conc luded t h a t the total a m o u n t of Mg in ske le tons increases wi th a n increase of sal ini ty and dep th of water .

The Upper Eocene f o r m a t i o n s in Gebel M o k a t t a m are of s i l iceous and fe r rug inous charac- ters. This h a d been formed due to the effect of si l iceous and iron oxide so lu t ions on the Upper Eocene rocks, The bivalvian shel ls conta ined in these rocks h a d been affected by s u c h so lu t ions evident from the i r relatively h igher Si and Fe con t en t s wi th respect to Middle Eocene shells.

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