M.K. HOWARTH AND N.J. MORRIS 



MINTAQ 



WADI HAJAR 



WADI ARUS 



JEBEL BILLUM 



WADI 

 KILYA 



U.Haut-Aptian 



o° o" o° o°o 



Q 



QISHN 



Berriasian 



1 1 1 



Mi 



Minlaq 



HAJAR 



, 1 , ' , 



Tilhonian 



u 



1 1 1 





A 



Arus 



L 



—_—_—-_—_ 



Ki 



Kilya 



NAIFA 



Kimmeridgian 









1 1 1 



B 



Billum 



1 1 



1 1 1 



Oxfordian 





Ma 



MADBI 



Callovian 



1 1 1 



S 



SHUQRA 



1 1 







1 1 1 



M. Jurassic 

 ?L. Jurassi 







Ko 



KOHLAN 



Pre-Cambrian 



J ^ ^ -f ^ 



PC 



Igneous and 

 metamoqjtiic roclts 



X X X X 



Unconformity between Naifa 

 and Hajar Formations 



Fig. 2 Correlation of (he Jurassic and basal Cretaceous formations in WatJi Hajar. 



fromWadi Kilya, near Naifa Cliff , that the youngest beds extend into 

 the basal zone of the Lower Tithonian. 



Beydoun traced the Naifa Formation about 15 km north-west- 

 wards to the large Jurassic outcrop at Jebel Billum. Here it forms a 

 very striking cliff along the south side of Jebel Billum. Ammonites 

 found by us near the base of the formation near its eastern end, 

 confirm that it is the same age as at Naifa Cliff (though it is truncated 

 at the top by an unconformity, above which are Upper Tithonian 

 marls and limestones of the Hajar Formation). 



In Wadi Arus, 10 km north-west of Jebel Billum, there is a very 

 prominent series of thick limestones and interbedded marls, espec- 

 ially well-exposed in the road gorge leading down into the upper end 

 of Wadi Arus from the south-east, which Beydoun correlated with 

 the Naifa Formation because of their great lithological similarity. He 

 found a few poorly preserved ammonites in them, which were 

 tentatively determined by Arkell as probably of Tithonian age. More 



important, however, was Beydoun's collection of some well-pre- 

 served ammonites from the marls and nodules (the 'Breadloaf 

 Concretions') below the thick limestones, and from a few metres of 

 limestone at the base, which are the lowest beds exposed in Wadi 

 Arus. These ammonites were also determined by Arkell as Lower 

 Kimmeridgian, and belong largely to the same species as found at 

 Naifa Cliff. However, because Beydoun thought that the marls and 

 Breadloaf Concretions were below the Naifa Formation, he identi- 

 fied them as the Madbi Formation and the basal few metres of 

 limestone as the top of the Shuqra Formation. These lithological 

 identifications were made despite the complete absence of 

 brachiopods from these beds in Wadi Arus, in marked contrast to the 

 immense numbers of well-preserved brachiopods that occur in the 

 Madbi and Shuqra Formations in both Jebel Billum and the Naifa 

 Cliff/Al Ma'abir area. This is the origin of Beydoun's (1964: 35, 36) 

 records of ammonites from the Shuqra Formation (Sutneria aff. 



