The Palaeozoic The Palaeozoic outcrops of southwestern Sinai

1. The Palaeozoic • The Palaeozoic outcrops of southwestern Sinai • The Palaeozoic outcrops of the north Eastern Desert • The Palaeozoic subsurface rocks in north Western Desert • The Palaeozoic outcrops of southwestern Egypt • Palaeozoogeography • Economic aspects of the Palaeozoic deposits

4. Abu Thora Formation Um Bogma Formation Sarabit El Khadim-Adedia formations Precambrian Basement

11. Um Bogma Formation Adedia Formation Nasib Formation Abu Hamata Formation Sarabit El Khadim Precambrian Basement

38. Um Bogma Formationoverlies unconformably the Adedia Formation. It has a maximumthicknessof41mattheupperpartofWadiKhabobaand Gabal Nukhul. It decreases to about 20 m at Um Bogma mines and to about 10 m at Gabal Sarabit El Khadim and becomes almost absent further southeast. Um Bogma Formation is composed mostly of grey and pink dolostone. Ferromanganese ore lenses associated with shaly beds occur at the base of the formation and were exploited at many localities.

39. The Um Bogma Formation is subdivided by KORA et al. (1994) into three members: Um Shebba Member on top, El-Qor Member in the middle , and Ras Samra Member at base (Fig. 3). The middle member is locally richly fossiliferous (Fig. 4) with corals; Syringopora sp., Michelinia sp., Amplexizaphrentis spp., etc., brachiopods; Spirifer striatus, Dictyoclostus semireticulatus, pelecypods as Saharopteria sinaitica, etc. which confirm an Early Carboniferous "Viséan" age (KORA & JUX 1986).

40. Abu Thora Formation overlies conformably the Um Bogma Formation and is topped by a basaltic sill or flow of probable Triassic or Jurassic age. It varies in thickness from 60-200 m and could be subdivided informally into two members: Glass-sand member on top, and kaolinitic claystone member at base. The lower member is composed of fine-medium grained sandstones interbedded with kaolinitic clays and carbonaceous shale beds. The kaolin of this member is exploited at Wadi Khaboba, Abu Natash and other localities

41. The carbonaceous shale grade laterally into local coal seams which contain many continental plant remains; Lepidodendron, Calamites, Noeggerathia and microfloral elements assigning a Carboniferous "Viséan-Westphalian" age. The upper member is formed mainly of clean, snow white, fine grained friable glass sands that are exploited at Um Rodeiyim, El-Qor and Gabal Abu Qafas. The environment of deposition is mostly of aeolian type.