M.K. HOWARTH AND N.J. MORRIS 



lowest Cretaceous in Wadi Hajar is given in Fig. 2, and a scheme of 

 zones for the Callovian to Berriasian stages showing the positions of 

 the dateable ammonite faunas in the Wadi Hajar succession, is given 

 in Table 2. 



Naifa Cliff 



The splendid cliff section in the right bank of the river below the 

 village of Naifa (=Neifa, Nayfa and Nayfah). approximately 2 km 

 upstream from the road/river crossing at Al Ma'abir, is the type 

 section of the Naifa Formation (see Fig. 9). The base of the Billum 

 Member is not exposed in this cliff, but it is clear in the nearby 

 locality south of Wadi Kilya (see below, and Fig. 5) and is also 

 exposed immediately west of the road/river crossing at Al Ma'abir. 

 In Naifa Cliff 33 m of alternating limestones and marly limestones 

 of the Billum Member, in which no ammonites were found, are 

 followed by the Kilya Member, which consists of 21.6 m of marls 

 with subsidiary limestones in its lower part, then 21 m of thicker 

 limestones in the upper part (Fig. 3). The upper marly part of the 

 Kilya Member is missing at Naifa Cliff, where the highest horizon is 

 near the top of the middle limestone part (as compared with the 

 thicker development of the Kilya Member in Wadi Kilya), and the 

 eroded top is overlain by Quaternary river gravels. The 'oil shales" of 

 Little (1925: pi. 24) are probably at the base of the Kilya Member on 

 Fig. 3. Considerable numbers of ammonites (mainly large 

 perisphinctids) were found loose at the foot of the cliff, and they 

 were traced to a mid-brown-weathering limestone near the bottom 

 of the middle limestone part of the Kilya Member, as shown on Fig. 

 3. Some of the perisphinctids attain sizes larger than 250 mm 

 diameter, and two exceptionally large (400-500 mm diameter) 

 specimens of Idoceras cf. hararinum Venzo were seen, one of which 

 was collected. Below this horizon of prolific ammonites, ammonites 

 were collected from three other horizons. The upper one has body- 

 chambers of Orthaspidoceras gortani (Venzo), the middle one has 

 large examples of two species of Simaspidoceras preserved in grey 

 limestone, while the lowest horizon has a new species of 

 Torqiiatisphinctes (Fig. 3). The highest ammonites in Naifa Cliff are 



crushed specimens from a shell bed high in the middle limestones of 

 the Kilya Member. All these ammonites belong to the Beckeri Zone 

 of the (Tethyan) Upper Kimmeridgian. The single example of the 

 Lower Kimmeridgian, Divisum Zone, ammonite Crussoliceras cf. 

 wegelei Enay shown on Fig. 3 was collected from the upper part of 

 the Billum Member in a nearby new road cutting, 0.5 km east of the 

 road/river crossing at Al Ma'abir. 



Wadi Kilya 



This section through the Naifa Formation lies on the south side of the 

 hill that is capped by the Qishn Formation on the south side of Wadi 

 Kilya, 2.5 km E by S of Naifa Cliff (Fig. 4). The Kilya Member is 

 thick and well-exposed here, being subdivided into three horizons. 

 The lower marly horizon and the middle limestone horizon are both 

 thicker than at Naifa Cliff, and are followed by a return to marls and 

 thin limestones in an upper horizon (Fig. 5). The middle limestones 

 contain many of the same perisphinctids and aspidoceratid ammo- 

 nites as found in Naifa Cliff, while the lower marly horizon contains 

 an horizon rich in crushed Lithacoceras and Orthaspidoceras. The 

 section also extends to an upper marly horizon in the Kilya Member, 

 which is at a higher horizon than the truncated top of Naifa Cliff. 

 These upper marls are 15 m thick, and contain a bed with the best 

 preserved ammonites in Wadi Hajar, especially Katroliceras, and 

 species of Hyhonoticeras that are distinctive of the LowerTithonian, 

 Hybonotum Zone. They are overlain unconformably by the Qishn 

 Formation of Upper Hauterivian to Barremian age. To the south of 

 the main section there is a long cliff exposure of the Billum Member, 

 with a good basal contact with the shales of the Madbi Formation. 

 The Billum Member limestones are 48 m thick here, and crushed 

 Orthosphinctes polygyratus (Reinecke) and other ammonites dis- 

 tinctive of the Upper Oxfordian. Bimammatum Zone, were collected 

 from the basal few metres. 



The Kohlan, Shuqra and Madbi Formations were also examined 

 in the area about 1 km south of Wadi Kilya and 1-1.5 km SE of the 

 road/river crossing at Al Ma'abir. Detailed logs were made here of 

 the Kohlan and lower and middle parts of the Shuqra Formations, 





— 



W/a 





o o cy 



O O O O 



Q 



1 1 1 





1 1 



1 1 1 















::::: 































Quaternary 



Cretaceous, post-Qishn Formation 



Qishn Formation, U. Haut.-Aptian 



Naifa Formation, U. Oxf.-Kimm. 



Madbi Formation, Oxfordian 



Shuqra Formation, Callovian 



Kohlan Formation, ?M. Jurassic 



Pre-Cambrian 



Un metalled roads 



River in Wadi Hajar 



Fig. 4 Geological map of the area around Al Ma'abir, Naifa Cliff and Wadi Kilya. The Wadi Kilya section of Fig. 5 is on the southern side of the Qishn 

 Formation capped hill on the south side of Wadi Kilya. The section through the top Kohlan, Shuqra and Madbi Formations is at A south of Wadi Kilya. 



