JURASSIC AND LOWER CRETACEOUS OF WADI HAJAR 



19 



Kilya 

 Member 



"^mm^. 







,ir ., 



Billum V'1^~ i^ - v=-5^ ■ '--^ 7>-sa JlfiJBl ^ 

 Member 1:?^., r ' =^7 - -' ^.'fl^ -^^^-^-^ 





Fig. 15 Detail of the face of the chff on the west side of Wadi Arus. The figure (1.75 m tall) at the base of the cliff gives a rough scale. 



The Billum Member is named after its type locality in the lower 

 half of the long cliff in eastern Jebel Billum (Fig. 7, locality PC; Fig. 

 1 1), where its basal contact with the Madbi Formation is seen at the 

 bottom of the cliff. It is 60 m thick here, and consists of beds of 

 limestone averaging 0.5 m thick, alternating with thinner beds of 

 marly, flaggy limestone. The Billum Member forms the lowest 

 vertical part of the main cliff in central Jebel Billum (Figs 8, 10), and 

 is cut through in the western road entrance to the Jebel Billum inlier. 

 Approximately the top two-thirds of the Billum Member is exposed 

 in Naifa Cliff. The Billum Member is also seen in a long cliff south 

 of the main section of the Kilya Member on the hillside south of 

 Wadi Kilya, and its basal contact is well exposed here. 



The Kilya Member is named after its type section on the Qishn- 



capped hill south of Wadi Kilya. 2 km E by S of Naifa Cliff, which 

 is its most complete development, being 65.4 m thick up to the 

 disconformity at the base of the Qishn Formation (Fig. 5). h contains 

 more marls than the Billum Member, and is subdivided into three 

 parts: marls and thin limestones of the lower and upper parts are 

 separated by a middle part in which thicker limestones are dominant, 

 similar to those of the Billum Member. In Naifa Cliff the lower and 

 middle parts are present but the upper part is missing; ammonite 

 collections were obtained from six horizons, and the lower marly 

 part contains a notable bed of large (0.5 m thick x 1 m diameter) 

 scattered doggers of hard grey limestone (Fig. ?i). \n Jebel Billum 

 exposures are poor or difficult to reach, but there are good exposures 

 in the cliffs on both sides of Wadi Arus. where the lower marly part 



