Upper cretaceous ammonites of Duwi Formation in Gabal Abu Had and Wadi Hamama, Eastern Desert, Egypt

Journal of Afrtcan Earth Sctences, Vol 10, No 3, pp 453-464, 1990

0899-5362/90 $3 00 + 0 00 Pergamon Press pie

Pnnted m Great Britain

Upper Cretaceous ammonites of Duwi Formation in Gabal Abu Had and Wadi Hamama, Eastern Desert, Egypt H. H HAMAMA*and A S KASSAB** *Geology Dept., Faculty of Science, E1 Mansoura Umverslty, El Mansoura, Egypt **Geology Dept., Faculty of Selanee, Assmt Umverslty, Assmt, Egypt

Abstract- This paper Is an attempt to clarify the paleontologle, ehronosttatagrapluc, paleoecologlc mad bmgeograpluc relations of the heteromorph and sphanodL%ad ammomtes The spectmens were collected from sharply def'med stratagraptnc honzons of the Duwl Formauon m two sectaons exposed at G Abu Had and Wa& Hamama to the northeast of Qena Two ammomte zones are recorded m the Duwl Formauon Ltbycoceras lsmaeh (Zlttel) Zone and Bostrychoceras polyplocum Zone The ammomtes of the first zone are restricted to the first lower phosphate bed and are only represented by a frequent assoclatmn of the species L~bycoceras tsmaeh This zone defines the base of the Duwl Formation m the area of study. The second zone m the topmost part of the formataon ~s rich m the mdex species and the other heteromorph amraomtes It Is represented by a bed of very hard hmestone of thickness about 20 cm at top of the Duwl Formataon The maxmaurnbulk tluckness of the formataonis 105 m The stratagraplucrange of the fosstls o f both zones assigns a Campaman age for the sedmaents of the Duwl Formataon m the area of study Furthermore, the Campanlan-Maastnchuan boundary ls fixed above the bed wlth Bostrychoceras polyplocum The L~bycoceras lsmaeh (Zl ttel ) ls found m a stratagrapbacposltaon

lower than that pubhshed before The paleontological study of the antmomtes led to therecogmuono f 11 species belonging to 6 genera (Ltbycoceras Hyatt, Nostoceras Hyatt Solenoceras Conrad, Bostrychoceras Hyatt, Bacuhtes Lamarck, Exaeloceras Hyatt), and representing 3 fanuhes (Sphenodiscldae. Hyatt, Nostoceratadae. Hyatt and Baculmdae Meek) TwonewsubspeclesaredescnbedS~len~cerahumelaequ*c~stataandExael~cerasunc~f~rmeLewy qenaense~ besides many species which are recorded for the first tame m the Egypuan ammomtes, they include the followings Solenoceras cf reestdel, S humet denstcostata, Nostoceras (Planstoceras) rehavamt, Nostoceras cf dracone and Bacuhtes scout Paleoecologlcally, the Llbycoceratlds from the base of Duwl Forrnataonhved m Late Carnpanlan partly isolated rnarme basra of abnormal bottom conchtaons On the other hand. the mode of hfe of the heteromorph ammomtes collected from the topmost part of the formation was diverse

INTRODUCTION G h o r a b (1956) i n t r o d u c e d t h e t e r m " D u w i Formation" to describe the Upper Cretaceous phosphate-bearlng sediments in the Qusier area, t h e t y p e l o c a l i t y of t h e D u w i F o r m a t i o n , s e e Y o u s s e f , 1 9 4 9 , 1959. S o m e authors gave new n a m e s f o r s i m i l a r a n d e q u i v a l e n t s u c c e s s i o n s in different parts in Egypt, the Sibaiy Formation (EI-Naggar, 1966), E1 H l n d a w M e m b e r ( B a r t h El Herman-Degen, 1981), and the Rakhiyat F o r m a t i o n ( H e n d r i k s a n d L u g e r , 1987). T h e a g e o f t h e D u w i F o r m a t i o n is still a m a t t e r of controversy. In this connection, a Campanian, and Campanian-Maastrichtian age are assigned to the f o r m a t i o n . S u c h c o n t r o v e r s y a s t o t h e age o f t h e Duwi Formation may be due to the lack of a precise collecting of the biostratigraphically significant fauna, and consequently the subjective determination of the stratigraphic range.

T h e a i m o f t h i s w o r k is t o s t u d y t h e a m m o n i t e f a u n a of t h e D u w i F o r m a t i o n t o r e f i n e t h e c h r o n o s t r a t i g r a p h i c p o s i t a o n o f t h i s r o c k u n i t . A t t e n t i o n is d i r e c t e d to s t u d y t h e h e t e r o m o r p h a m m o n i t e s . Therefore ammonite fauna was carefully collected for b i o s t r a t l g r a p h i c p u r p o s e f r o m two s e c t i o n s of G a b a l A b u H a d a n d W a d i H a m a m a (Fig 1).

LITHOSTRATIGRAPHY The measured thickness of the Duwi Formation is a b o u t 7 5 m a t W a d i H a m a m a a n d 105 m a t G A b u H a d (Fig 2). S h a l e is t h e d o m i n a n t f a c i e s o f t h e formation with thin intercalations of sandstone, f e r r u g e n o u s b a n d s a n d l e n t i c l e s a n d r a r e b e d s of m a r l a n d l i m e s t o n e T h e f o r m a t i o n is m a r k e d l y characterized by the presence of phosphate and phosphatic beds particularly in the lower and u p p e r p a r t s of t h e s e c t i o n s . T h e D u w i F o r m a t i o n in b o t h localities c a n be subdivided into three u n i t s namely; lower phosphate unit, middle shale unit

453

454

H H HAMAMAand A S KASSAB o

Abu Hod ~¢tlon

,

*

z~3d

~Shale [---~ Sandstone F,g 1-GeoLog,caL map of the ,nveshgated area,northeast Qena(after the Egyptian 9eotog,ca[ Survey,19?8)

l--~] Nubia Group ~

Duwt Fm ~Dakhta Fm

~m[JJ Pa~eocene j 3 " ~ L E o c e n e ~ Phocene [____~ Quaternary

[ ~ Marl ~ i ] Phosphorct'e

~ Phosphatic ~L

=mestone 0 6

12m

and upper p h o s p h a t e u m t It is conformably underlain by the variegated shale The topmost part of the latter unit is composed ofvaricoloured, Fig 2 Stratagraphy of the Duwi Formatlon, east of laminated, fissile shale with g y p s u m interQena, Egypt calatlons The lower p h o s p h a t e unit is composed of phosphatic s a n d s t o n e Two p h o s p h a t e b e d s were variegated shale Furthermore, we beheve that recorded The lower one is rich in ammonites, there is no reason to introduce a new n a m e for the s h a r k teeth and bone fragments, friable, con- Duwi Formation on basis of only lithological glomeratac p h o s p h a t e at base, hard p h o s p h a t e at variation top Its thickness reaches 5-17 cm The middle BIOSTRATIGRAPHY unit is c o m p o s e d of shale, cross-bedded siltstone below and papery shale above, the shales have The Duwi F o r m a h o n is herein defined as the different colours being darker u p w a r d s Iron b a n d s often intercalate the shale The shale thickness formation which is b o u n d e d b y two strictly ammovaries from 56 m at Wadi H a m a m a to about 90 m nite zones, the fn-st zone, is the L. ~smaeli zone at G Abu Had No ammonites are recorded from found at the basal part of the formation and is thin unit except for badly preserved fragments restricted to the lower p h o s p h a t e unit The ammopossibly Canadoceras sp? The u p p e r phosphate nites herein are represented only by L. tsmaeh m e m b e r is composed of marly phosphatic beds, (Zittel) besides m a n y bone fragments and s h a r k sandstone, marl, and limestone The formation is teeth The first appearance of this index species is topped with 10-20 cm cap rock of highly fossil- u s e d to determine the lower b o u n d a r y of the Duwi iferous hmestone very rich in heteromorph ammo- Formation On the other hand, the second zone at rotes The Duwi Formation is overlain by the the topmost part is the Bostrychoceras polyplocum Dakhla Shale Formation having the characteristic zone which is confined to a bed of hard limestone 20 cm thick Ammonites of the heteromoph type Maastrichtian Pycnodonta vesicularis (Lamarck) Further investigations will be required to dec,de are c o m m o n in this zone The stratigraphic range whether the two lower units described by Hendriks of a m m o m t e s of both zones assigns Late and Luger (1978) in thelr Rakhiyat Formation are Campanian age for the Duwi Formation Moreover, to be included m the Duw~ Formation or to be the u p p e r b o u n d a r y of the formation is marked by grouped with the u p p e r part of the Qusier t h e d i s a p p e a r a n c e of t h e h e t e r o m o r p h

Upper Cretaceous ammomtes of Duwt Formatmn m Gabal Abu Had and Wadl Hamama a m m o n i t e s a n d t h e first a p p e a r a n c e of Pycnodonta ves/cu/ar/s (Lamarck) Certainly t h e rapid evolution of t h e a m m o n i t e s t h r o u g h o u t t h e time of deposition of the Duwi F o r m a t i o n led to r a t h e r distinct groups, w h e r e a s m o n o m o r p h type d o m i n a t e d the lower part of the formation, h e t e r o m o p h assemblage is diversified in the u p p e r part. Therefore, the a m m o n i t e s are considered as a good tool for t h e correlation of the Duwi F o r m a t i o n in t h e region. The

Libycoceras ismaeli Z o n e

455

Palestine (Lewy, 1977). The

Bostrychoceras polyplocum Z o n e .

The index species Bostrychoceras polyplocum (Roemer) of this zone is f o u n d with frequent association with other h e t e r o m o r p h a m m o n i t e s b e l o n g i n g to g e n e r a Bostrychoceras Hyatt, Nostoceras Hyatt, So/enoceras Conrad a n d Bacu//tes Larnarck. In t h e field, this zone is r e p r e s e n t e d by one h a r d silicified fossiliferous limestone bed, 20 c m thick a n d with white fine calcareous chalky materials at the surface This bed is widely distrib u t e d in Egypt. In the D a k h l a Oasis, it is rep r e s e n t e d by 110 c m dolostone at t h e top of the Duwi F o r m a t i o n (Hassan et aL, 1982), by 150 c m c h a l k y p h o s p h a t i c facies with Pycnodonta ves/cu/ar/s Lamarck in El-Galala El Qibliya (Mazhar et al., 1979 The t h i n n i n g of this b e d is probably d u e to s y n s e d i m e n t a r y t e c t o n i s m which give rise to uplift of this bed by t h e e n d of C a m p a n i a n forming h i a t u s The zone is also equivalent to the bed with h e t e r o m o r p h a m m o n i t e s recorded in the Western Desert by Barthel a n d H e r m a n n (1981). It is correlated with t h e u p p e r horizon of u n i t 3 of G. Qreiya However, it is difficult to correlate this zone with t h a t of G h a n e m et al., 1970. Outside Egypt, this zone is equivalent to t h e t o p m o s t part of the Mishash Formation (Lewy, 1977) a n d to the polyplocum Zone of the T e t h y a n province (Van Hinte, 1976) This zone yields all the h e t e r o m o r p h a m m o n i t e s described herein.

The index species of this zone is the Libycoceras ismaell (Zittel) w h i c h s h o w s a wide range of interaspecific variations t h a t will be d i s c u s s e d later While, t h e first lower p h o s p h a t e bed is very rich in a m m o n i t e s , n o n e of t h e m were recorded from the s e c o n d u p p e r p h o s p h a t e bed. However, m a n y foraminiferal species are identified from the basal part of t h e middle shale unit, they include Trochammina wickendeni, Tr. undulosa, Tr. borealts, Haplophragmolds galbra, H. rota and L~tuola taybrensls. These species are kindly identified by Prof. A. Kenawy This zone is equivalent to t h e Baculites anceps Zone suggested by Faris (1974) at G Abu Had including beds 21, 22 a n d 23 reaching 6 m in total t h i c k n e s s . Moreover the middle shale m e m b e r herein could be c o m p a r e d with the lower part of t h e Dakhla Shale of t h e s a m e a u t h o r Because t h e p h o s p h a t e b e d s were recorded in the Variegated Shale Formation, their occurrence a n d the first a p p e a r a n c e of Libycoceras ismaeli (Zittel) SYSTEMATIC PALAEONTOLOGY help to d e t e r m i n e t h e lower contact of the Duw~ Formation. This zone is also equivalent to the lower horizon The palaeontological s t u d y of the a m m o n i t e with Libycoceras Ismaeli (Zittel) recorded by f a u n a led to identify eleven species a n d s u b s p e c i e s Hendriks a n d Luger (1987) in u n i t 3 of G. Qreiya belonging to six genera a n d three families The area. However the a m m o n i t e s of this horizon appear taxonomic list, including a detailed description of in a stratigraphic level higher t h a n t h a t of the t h e taxa, is as follows. Libycoceras ismaeli Zone. The Baculites found at A) Sphenodiscid ammonites: t h e base of t h e Duwi Formation by t h e s a m e Family Sphenodiscidae, Hyatt a u t h o r s are t h o u g h t to be t r a n s p o r t e d from above G e n u s Ltbycoceras, Hyatt a n d t h e zone yielding Baculites is therefore not Libycoceras ismaeIL (Zittel) easily defined in the field. (pl 1, Figs 1-6) According to Awad, Naim a n d Abdu (1964) L. Detailed s t u d y of a large p o p u l a t i o n of this ismaell (Zittel), L. ber/sens/sAwad a n d Naim a n d L. species enabled the a u t h o r s (in preparation) to give Khargense B l a n k e n h o r n are M a a s t r i c h t i a n a full description of t h e ontogenetic developments, species They a d d e d t h a t L. phosphaticus Awad, variation, a n d d i m o r p h i s m in t h e Libycoceras Naim a n d A b d u w a s n o t reported from W. Qena. As ismaell (Zittel), to revise its systematic, a n d to will be d i s c u s s e d , L. phosphaticus is t h e d i s c u s s the various opinions concerning the ontocompressed, s u b d u d e d o m a m e n t e d form of L. geny ofL. ismaehdealt by m a n y a u t h o r s (Awad a n d ismaeIL in addition to t h e u n k n o w n precise strati- Naim, 1964, Reyment, 1980 a n d Zaborski, 1982, graphic position of L. fsmaeli reported by t h e m Kassab a n d H a m a m a , 1988) (1964). B) N o s t o c e r a t i d a n d B a c u l i t i d a m m o n i t e s This zone is also equivalent to t h e t o p m o s t part (Heteromorph ammonites): of the Mishash Formation, of Late C a m p a n i a n of

456

H H HAMAMAand A S KASSAB

3

4 i

Plate 1 (All figures XI) Figs I-6 Libycoceras usmaeh (Zittel), internal molds ol adult s p e c l m e n s

Upper Cretaceous ammonites of Duwl Formauon in Gabal Abu Had and Wach Hamama Family Nostoceratidae Hyatt a) G e n u s So/enoccras Conrad 1- Solenoceras humel humei (Douvflle) (pl 2, Figs. 2, 3 a n d 4, pl. 3,Figs. 9 and I0).

Ptychoceras humei: DouviUe, 1928, p 37, PI VI, Figs 9a a n d b) So/enoceras humei hume/, Lewy, 1967, p. 170, PI III, Figs. 1 and 3. Material: A large n u m b e r of specimens of well p r e s e r v e d shafts, from the Bostrychoceras polyplocum Zone, U p p e r C a m p a n i a n , Duwi Formation Measurements: First shaft Last shaft D 33 m m 32 m m H 6.8mm 9 mm w 6 2 mm 8.6mm ribs No. 25 18 D = diameter or length Description: The two shafts are subparallel, nearly close with a n almond-like space in the dorsal bending portion. The young shaft is straight a n d the last m a t u r e one is slightly convex outwards Just after the bent, after t h a t the latter a r m r u n s parallel to the first one The ventral is r o u n d e d Ribs are irregular, prorsiradiate and dense o n t h e y o u n g arm, rectiradiate to sinuousoidal at the bent, frequently bifurcated and became rursiradiate to rectiradiate at the last shaft. The ribs bear two rows of tubercles. Remarks: Although the described specimens herein are very similar to t h a t figured by Lewy (1967), both have a n almond-like-space and more or less dense thin sharp ribs, however the specimens given in Figs 9 and 10 in plate 3 differ by its distinct outward shifting of the long a r m and the irregular ribbing style. The incomplete materials we have are not suited for establishing a new subspecies or even a species 2 Solenoceras humei aequicostata subsp nov (PI 3, Fig 8, pl. 4, Figs 3 and 4, 6-10) Holotype AsK2 Pl. 4, Fig. 6, deposited at Assiut University Type locality: Gabal Abu Had, east of Qena Etymology" referring to the ribbing style on both shafts M a t e r i a l Several specimens from both Wadi H a m a m a and G. Abu Had sections, within the B o s t r y c h o c e r a s polyplocum Z o n e , U p p e r Campanian, Duwi Formation Measurements (holotype)- in m m First shaft U-part Last shaft D 30 12 24 h 5 5-6 5 5 5-6 0 8 4-8 6 W 5 5-7 0 7.4-7 6 8 0-8 2

457

Description" The young shaft of the holotype is curved a n d inclined forming a n angle of 15 ° with plane of the adult one. Whorl section is orbicular at early stages becoming trapezoidal to ellipsoidal with growth. The venter is r o u n d e d early, slightly tabulated t h r o u g h o u t the y o u n g shall a n d bent part, a n d broadly r o u n d e d afterwards. Ribs are simple and of equal n u m b e r and interspaces (8 ribs per c m on ventrum) on both shafts at comparable size, becoming slightly narrower and denser on the bent part. They are prorsiradiate on the young shaft, rectiradiate to sinuosoidal at the bent part, and rursiradiate on the last shaft. The angle between the two ribbing s y s t e m s is 152 ° . Each rib bears a pair of ventrolateral tubercles which weaken or disappear with growth after the bent part 3 Solenoceras cf reestdei (Stephenson) (PI 3, Fig, 11 and Pl 4, Figs. 12 and 13) Solenoceras cf S. reesidet, Lewy, 1969, p. 126, pl Ill, Fig. 7a and b Material" Four specimens representing the long shaft and the bents from Wadi H a m a m a and Gabal Abu Had, from the Bostrychoceras polyplocum Zone, Upper Campanian, Duwi Formation Measurements: Bent part Last shaft V h w

4 mm 8 mm 7 5 mm

4 5-4 2 m m 90-10 mm 9 3-9 0 m m

Description: The shaft (last one) and a part of the bent part are only preserved The shaft attains a size of 43 m m length with m a x i m u m thickness at the mid-lateral. The venter is broadly r o u n d e d to slightly fiat and generally narrower t h a n the concaved dorsum. The trapezoidal whorl section is compressed at the bent part, depressed at the beginning of the shaft, and became compressed again with growth Primary ribs are rectiradiate to slightly convex forwards bearing a pair of ventrolateral tubercles on the bent part, rursiradiate with faint ventrolateral tubercles at the beginning of the shaft and rectiradiate at last stage of growth. The ventrolateral tubercles disappear on the m a i n part of the last shaft, w h e r e a s the secondary ribs appeared. Bifurcation arose at the dorso-lateral shoulder or very close to it. The bifurcated ribs take sinuosoidal appearance Remarks: This species shows intermediate characters between S. multicostatum (Stephenson) in the Treatise, 1957 a n d S cf S. reesidei described by Lewy (1969, p 126, PI III, Figs. 7a and b) It differs from the former by having less dense ribs and from the latter by its bigger size.

458

H H I'IAMAMAand A S KASSAB

2 5

I

6

Plate 2 (All figures XI) I Nostoceras hyatt~ Stephenson, Lateral vlew 2-4 Solenceras humel (Douville) humei Lewy, 2 and 4, lateral views, 3, dorso Lateral view 5-9 Baculites scotti Cobban 10 Nostoceras cf draconeStephenson s u b s p nov splral slde 11 Nostoceras cf hyatti Stephenson, ventral view 12-15 Bostnjchoceras polyplocum (Roemer)

Upper Cretaceous ammomtes of Duw~ Formation in Gabal Abu Had and Wach Hamama

ID

,'u

2b

4

I Z

k

Plate 3 I-5 E~eloceras unc~orme qenuense subsp nov, 2a and b holotyl~ All XI. Duwl Baculltes scottl Cobban. XI, Duwi Fm 6-7 Solenocesas, humei, aequlcostata subsp nov, XI. 8 9-10 So/enoceras humei (Douville) humei Lewy I l a and b Solenoceras cf reesu=lei Stephenson X. 65, 12-13 Exlteloceras sp 12 large specimen, XI and 13 part of the early stage

459

H H HAMAMAand A S KASSAB

460

4- Solenoceras humei denstcostata Lewy (PI 4, Fig 11) Solenoceras humei dens/costata, Lewy, 1967, p 170, pl. Ill, Fig. 4 b) G e n u s Nostoceras Hyatt

I- Nostoceras (planstoceras) rehavaml, Lewy, (PI 4, Fig. 5)

Nostoceras (planstoceras) rehavamz, Lewy, 1967, p 168) PI. IV, Fig. 3a and b

Material" Two specimens from the Bostrychoceras polyplocum Zone, Upper Campanian Measurements Last part of the tortlcone First shaft U-part

LastshaR

h

11

14:19

19

20

w

20

14 18

18

19

Description" The two specimens revealed a part of the torticone phragmocone followed by a slightly curved short and a hooked body c h a m b e r of broad U-Form Whorl section is clrcular at early stages becoming oval to trapezoidal with growth The venter is narrower t h a n the slightly convex d o r s u m at any stage of growth On the last part of the torticonic spire, ribs are closely spaced (9 ribs per cm on the ventrum), rursiradiate on the lateral-side, and convex forward on the d o r s u m Each second rib bears a pair of strong ventrolateral tubercles of rounded base On the first shaft, ribs are rectiradiate early, becoming prorsiradiate and widely spaced (5 ribs per cm) onwards, they are convex backward on the dorso-lateral shoulder On the bent part, ribs are more distant (3 n b s per cm), rectiradiate and bearing a pair of slender ventrolateral tubercles No bifurcated ribs are recognized on the venter at a n y stage of growth. No suture has been observed

2 Nostoceras cf. dracone Stephenson (Pl 2, Fig 10)

Nostoceras cf. N. draconts, Lewy, 1969, p 119, Pl II, Fig 2

Material: One specimen was collected from the Bostrychcceras polyplocum Z o n e , D u w i Formation. Upper Campanian Gabal Abu Had Measurements Maximum diameter = 45 mm Length of the last whorl = 90 nIn Height of the phragmocone = 4 4 m m

Description" Sinstrally coiled pharagmocone and J - s h a p e d body c h a m b e r The phragrnocone of the specimen included here is incomplete, wlth 3 / 2

whorls, faintly touchlng, forming a shallow helix 33 m m in diameter The body c h a m b e r occupies the last third whorl a n d also touches the phragmocone The cross r o u n d e d whorl section of the phragmocone became trapezoid with growth The venter of the body c h a m b e r is nearly fiat and is narrower t h a n the d o r s u m The ribs are dense rectiradiate on the phragmocone, prorsiradiate on the latero-spiral and the ventral side of the body chamber, being rursiradiate to rectiradiate on the latero-umbilical slde Each rib bears a pair of strong ventro-lateral tubercles

Remarks It m believed that the holotype, Nostoceras (N.)gracile of Lewy, 1967 (Pl. II, Fig. l a and b) Is a typical N cf N. dracone Stephenson described by Lewy, 1969 (PI. If, Fig. 2 a and b)

3 Nostoceras hyattt Stephenson (PI 2, Fig i Pl4, Figs I and 2)

Nostoceras hyattt, Lewy, 1969, p 117, Pl I, Fig 5, Material: Flve fragments of the body chambers, from Bostrychoceras polyplocum Zones, G abal Abu Had and Wadi Hamama, Upper C a m p a m a n

4 Nostocera cf hyatti Stephenson (PI 2, Fig 11) c) Genus Extteloceras Hyatt

1-Extteloceras unczforme Lewy qenaense subsp nov (PI 3. Fig s 1-5) Holotype MHQI. PI Ill, Fig 2, deposited at Mansoura Umverslty Type locality Gabal Abu Had, east ol Qena Etymology from the n a m e of the type area

Material: Several fragments of body chambers, from Bostrychoceras polyplocum Zone, Upper Campanian, Duwi Formation of Wadi H a m a m a and Gabal Abu Had sections Description" Rabs are strong, widely spaced and simple Each rib bears a pair of ventrolateral tubercles They are sinuousoidal and prosiradiate at the begmmng of the body c h a m b e r (4 ribs per c m on ventrum), and rectiradiate and widely spaced (2 ribs per cm on ventrum) on the bent part and afterwards R~bs on the venter are also strong and with no interruption The dorsal ribs are convex forward No bifurcated ribs are recognized No suture has been o observed Remarks" The strong ribbing style which is widely spaced and u n d u l a t e d on the dorsum, the whorl section, and the absence of bifurcation or intercalations distinguish this subspecies from the Nostoceras unctforme Lewy

Upper Cretaceous ammomtes of Duw~ Formation in Gabal Abu Had and Wad~ Hamama

la 2

It)

4.

6 5 St}

|

Plate 4 Nostoceras hyattl Stephenson, XI, 3,4. ~olenoceras humei aequlcostata subsp nov, 3 XI, 4xl 5 5 Nostoceras (Planstoceras} rehavaml, Lewy, XI 6-10 Solenoceras humel aequ~c)stata sub sp nov, XI.5 11 Solenoceras hume( dgns~costata Lewy XI 12,13 So/enoceras clr. reesldei Stephenson, XI All specimens from the Duwi Formation, U, Carnpanlan.

I-2

461

462

H H HAMAMAand A S KASSAB 2) Exiteloceras sp (PI 3 , Figs. 12 a n d 13)

Two fragments possess some of the mare characters of Exiteloceras. The smaller one (PI 3, Fig 13) represents a part of very young stage, and shows asymmetrical whorl section and ornament A row of fine tubercles confined to the midventral Another row is displaced towards one side; ribs are closely spaced (14 ribs per cm) The larger specimen (PI. 3, Fig 12) indicates a later stage of growth with widely spaced rlbs (6 ribs per cm) Each rib bears a pair of ventrolateral tubercles. The venter is narrower t h a n the convex d o r s u m The specimen shows no signs for deflection or irregularity in whorl section and o r n a m e n t It seems t h a t the two fragments m a y belong to a single individual of the same species. d) Genus Bostychoceras Hyatt 1) BosRjchoceras polyplocum (Roemer) ( Pl 2, Figs 12 - 15) C) Family Bacultidae Meek Genus Baculites Lamarck Baculites scotti Cobban (PI. 2, Figs 5-9) Baculites scotti Cobban, 1958, p 660, PI 90, Figs. 1-9

e

c

J Fig 3 Suture lines of Baculites scottl Cobban a} S No 164 b-e) S No 176

w 16 6 i0 0

H 23 12 4

W/H 72 80

L 135 mm 41 mm

The palaeoecologlcal interpretation of aminorotes of the Duwi Formatlon is based essentially on the morphotypes of the ammonites and on the types of sediments housing t h e m Regarding the monomorph ammonite, the knowledge of conThe Baculites anceps Orbigny is quitely different ditions of the phosphorites deposition is very from the present material by its wedge-shaped n e c e s s a r y The s y n s e d i m e n t a r y - t e c t o n i s m is cross-section, and its sharp keel at the siphonal reported by m a n y authors end Suture of this material (Fig 3) closely Hendriks a n d Luger (1987) reported the resembles the s u t u r e of Baculites bailyi of Ward phosphate-bearing sediments in the area of study (1978, Fig 5a-c) B. palestinensis Picard (1929, are depomted u n d e r tectonically controlled seatext-fig. 3), and S. vertebra//s Lamarck of Picard level oscillation (1929, text-figs, 3-5). The two end m e m b e r s of the Soliman et al.. (1986) suggested deposition in variation series of B. scotti Cobban, 1958 are deltaic and of coastal bays for the Duwi Formataon represented in the present material m Gabal Abu Had and Wadi Hamama. Moreover, they mentioned that the fossfliferous beds PAI.AFA~O~GY (including our two a m m o m t e horizons) might be deposited in mterd~stributary bay with phases of Because the ammonites became extinct at the oxic and anoxic conditions close of the Cretaceous. m u c h controversies exist The sphenodiscid arvanonites of the lower as to their palaeoecology. Ammonites are recorded horizon are preserved as phosphatized shells with from sediments of coastal or strand line (Reyment, infillings of phosphate materials. 1958, in Reyment a n d Tait, 1972), neritic Lewy (I 977) mentioned that the L. tsmaeh (Zittel) (Kennedy and Cobban, 1976; Mancini, 1977), and hved in a n isolated abnormal marine condition in deep-water (Scott, 1940; Ziegler, 1967) Late Campanian time in a water of high salinity, In the studied sections, ammonites occur at only wRh r a t h e r a b u n d a n t phosphate and iron The two horizons coinciding with the most-lower and drop of salinity is evidenced by the richness in most-upper parts of the formation Restriction of n u m b e r of individuals and deficiency in species the a m m o n i t e s with great n u m b e r s to two narrow diversity The deepening and stagnation cause horizons can be t a k e n as indicator of episodes of anoxaty of the sea bottom The oxygen deficiency is m a s s mortality brought on by shifts in salinity indicated by the presence of the dark, bxtuminous (Offodile and Reyment, 1977) The ammonite- claystone Such deficiency, in addition to the episodes relationship is outside the scope of this reducing environment led to a m a s s death of living work and further studies are needed ammonites and fish Oscillataon of the sea and

Upper Cretaceous ammomtes of Duw~Formation m Gabal Abu Had and Wad~ Hamama other abnormal conditions, especially fluctuating upweUing marine c u r r e n t s affect the reworklng a n d t r a n s p o r t a t i o n of the phosphatic shales and the concentration of the phosphorites (Phflobbs, 1969 as well as the a m m o n i t e s preservation The absence of the b o d y c h a m b e r points to their winnowing. Post deposition phosphatization and s e c o n d a r y replacement possibly took place in the internal s t r u c t u r e of the ammonite shell. The Upper part of the Duwi Formation yields a great n u m b e r of p h o s p h a t i c molds o f h e t e r o m o r p h a m m o n i t e s associated with a b u n d a n t buliminids a n d few planktonic foraminifera From the topm o s t part, m a n y planktonic foraminifera are recorded, among t h e m Globotruncan aegyptiaca, G, arca, Rugoglobigenlnamacrocepb~!ota, etc. Such f a u n a s u g g e s t s deposition in shallow marginal marine environment (Hendriks and Luger, 1987) The early phragmocone and the adult b o d y c h a m b e r are generally not found together, t h u s suggesting t h a t age segregation took place. This m u s t be related to the animal itself, i.e since environmental factors do not come into consideration. This probably m e a n s t h a t the mode ofllfe in the early phragmoconic stage m u s t have b e e n different from that of the adult stage (Wiedmann, 1969) The great n u m b e r of the b o d y c h a m b e r relative to the few n u m b e r of the Phragmocone m a y point out to vertical m o v e m e n t across the substrate. On the other h a n d the orthocone baculitids are adapted to rapid swimming or even rapid movement (Klinger, 1980). Moreover, vertically e m b e d d e d a m m o n i t e s are not recorded, b u t all specimes are found preserved coinciding with the bedding planes. DISCUSSION AND CONCLUSION To designate the Upper Cretaceous phosphatebearing s u c c e s s i o n overlying the Qusier Shale and underlying the Dakhla Shale, the a u t h o r s r e c o m m e n d the term "Duwi" on the basis of its priority, and advocate its retention as a formation The palaeontological s t u d y led to identify eleven species a n d s u b s p e c i c s including 2 new taxa of h e t e r o m o r p h a m m o n i t e s . Solenoceras humet aequicostata s u b s p , nov., a n d Exiteloceras unc/formeqenaensesubsp nov., So/enoceras humei densicostata, S. cf. reesidel, Nostoceras cf. dracone, Exiteloceras unc~orme, and Baculites scotti are recorded for the first time from Egypt The Libycoceras ismaell, previously regarded as a Maastrichtian index fossil h a s proved to be an Upper C a m p a n i a n index fossil on the basis of its occurrence in stratigraphic level lower t h a n that bearing the Bostrychoceras polyplocum assemblage which is considered a s a s t a n d a r d ammonite zone of C a m p a n i a n age (Kennedy, 1984). The

463

presence of Upper C a m p a n i a n foraminifera from a b e d directly overlying this a m m o n i t e zone s u p p o r t s this conclusion. The Libycoceras ismaeli seems to be endemic a n d links Egypt with Sudan, J o r d a n , Libya, Israel, West Africa and Mali etc., suggesting a direct marine connection between these countries at the Upper C a m p a n i a n time. Many a u t h o r s exaggerated the co-existence of the Ltbycoceras ismaeli and Bostrychoceras polyplocum assemblage in different localities from Egypt, however s u c h co-existence is not recorded in the studied localities The a u t h o r s do not s u p p o r t the opinion of Awad et al., 1964 that the Campanian-Maastrichtian b o u n d a r y coincides with the b a s e of Libycoceras tsmaeli (Zittel), and advocate the suggestion of El Naggar (1966) to place the b o u n d a r y above the Bostrychoceras polyplocum Zone. Palaeobiogeographically, the ammonite fauna shows a strong affinity to the Mediterranean province of the Tethyan realm of M a t s u m o t o (in Hallam, 1973), a n d to the Atlantic realm of Henderson (1970), and proved b e y o n d d o u b t the Upper C a m p a n i a n age of the Duwi Formation in Egypt

Acknowledgements- The authors wish to express their gratitude to Prof. Dr Z. Zaghloul and Prof. Dr. M Abed of EI-Mansoura University for crltically reading the manuscript, and to Prof Dr A. Kenawy of Assiut University for his kind identification of the microfossfls REFERENCES Awad, G. H., Naim, I M,. and Abdou, H. F 1964. The Campanian-Maastrichtian boundary and the phosphate series Bull Fac ScL, Alexandria, 8, 257270 Barthel, K W. and Herman-Degen, W 1981. Late Cretaceous and Early Tertiary stratigraphy in the Great Sand Sea and its SE Margins (Farafra and Dakhla Oases) SW Desert, Egypt Mitt Bayer Staatssammlg Palaont hzst. Geol. 21, 141-184 Cobban, W ~ 1958 Two new species of Baculites from Western Interior Region J Paleont, 32 (4), 660-665. Douville, H 1928 Les Ammonites de la Craie Superieure en Egypte etau Sinai Mem Acad Sci. Inst., France, Paris, 60 El Naggar, Z R 1966. Stratigraphy and planktonic foraminifera of the Upper Cretaceous-Lower Tertiary succession in the Esna-ldfu Region (NileValley, Egypt). BulL Brlt Mus (Nat H~st.)Geol. London, 2, 291 pp Farrm, 1975 Late Cretaceous - Early Tertmry Biostratigraphy of Wadi Qena and Nile Valley M Sc thesis, Assiut University, Egypt. Ghanem, M, Mlkhalov, I A, Zalata, A A., Razvaliaev, A V, Abdel Razik, T, Mirtov, Y V. and Abdel Ghani, M S 1970. Stratigraphy of the phosphate bearing Cretaceous and Paleogene sediments of the Nile Valley between Idfu and (lena In Moharrem, 0 et al., (eds.). Studies on some mineral deposites of Egypt Geo/. Surv. Egypt, art. 7, 109-134

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