Baharia Oasis

by John Ball; H. J. L. Beadnell

The beds of the series form, as a rule, a well-marked group, individual beds often being traceable for great distances and correlable in different parts of the oasis.

The group as a whole consists of alternations of brown limestone[44] (with grey crystalline varieties) and variegated sandstones and clayey beds. A typical section, as exposed on the west scarp in N. lat. 27° 53′, is as follows:—

Top.	(Buff-coloured limestone and whitechalk of Division 5.)		Metres.
	1.	Soft brown sandstones and sandy beds,much obscured	7·6
	2.	Sandy beds, passing up into a very hardgrey concretionary sandstone, showing ripple-marks	4·6
	3.	Thin-bedded dark sandstones, mostly veryhard	1·5
	4.	Hard compact thick-bedded grey sandstone,very concretionary, false-bedded	2·1
	5.	Shaly sandy beds with ferruginousconcretions	1·5
	6.	Brown impure limestone	0·6
	7.	Soft variegated sandy beds andsandstone	9·0
	8.	Rather friable buff-coloured sandstone,more or less false-bedded, with peculiar iron-staining	6·0
	9.	Gray rather concretionary sandstone, withdark-brown ferruginous bands	3·0
	10.	Brown crystalline limestone with calcite,passing into harder grayish crystalline limestone, flinty attop	6·1
	11.	Gray marls and shaly clays	3·0
	12.	Brown crystalline limestone	0·6
			45·6
Base.	(Sandstones and clays of Division7.)

In Jebel Hefhuf, the long narrow ridge-shaped hill a few kilometres south-east of El Bawitti ([Plate VII]), the beds of this series are implicated in the fold, and are found tilted at angles of 30 and 40 degrees. They here consist of a considerable thickness of crystalline limestone, calcareous grits, shaly clays and sandstones; the softer beds always form a gully between the harder.

The following were noticed at a point about 7 kilometres from the western end of the ridge:—

Top.			Metres.
	Calcareous grit, usually siliceous, withbones (often a true bone-bed).	⎫ ⎪ ⎬ ⎪ ⎭	21
	Sandy clays, etc., with silicifiedwood[45]
	Thick-bedded brown sandstone, siliceousand ferruginous in part.
	Green and gray iron-stained sandyclays
	Thick-bedded brown crystallinelimestone
	Brown crystalline limestone with calcitecavities near base		24
Base.			45

Below come the clays and sandstones of the lowest series, No. 7.

In the section above, the limestones are usually too crystalline to show any traces of organic remains, although numerous casts of shells occur at certain points. The calcareous grit, a very well-marked bed, has been observed at points widely distant within the oasis; in places it is a true bone-bed,[46] often highly siliceous and passing into a hard quartzite. Its occurrence here, at the top of the Cenomanian series and below the White Chalk (to be described later) is of great interest, as its position shows it to be probably homotaxial with the bone-beds of Dakhla Oasis[47] and the Eastern Desert,[48] where they are of Campanian age. The bone-beds on this horizon must thus have been deposited over an enormous area.

If followed round from the south end of the oasis along the east scarp, the beds of this division are found to gradually become more and more calcareous, consisting often almost entirely of limestone,[49] and to dip more and more to the south-east, till in the neighbourhood of the large sandstone-hill near the scarp in latitude 28° 5′, where the tilting reaches its maximum, they dip at 45° and partly disappear under the sandy covering of the ground between the hill and the scarp. Further north the dip grows less and the beds re-appear, forming the top of the main scarp at the oasis-edge.

The organic remains in Division 6 include ammonites, echinids, with Ostrea, Exogyra and masses of Serpulæ; fossil wood and fragments of bone also occur. These fossils are in places abundant, some bands being almost entirely formed of the shells of Exogyra. The ammonites, although apparently specifically identical with those of the lower series, attain a much greater size. The assemblage of forms and the prevalence of bands of limestone point to deeper water conditions than the foregoing underlying series.