The topography and geology of the Fayum province of Egypt

by H. J. L. Beadnell

In the lowest spots the saline frequently consists of soft wet sludge; its area is about half a square kilometre but the depth of the deposit is unknown. In the middle of the scrub-covered area to the north lies Ain Warshat el Melh, a pool of water, fairly fresh and drinkable, although ferruginous, measuring 10 by 5 metres in size and from 2 to 2½ metres deep. The water evidently rises from a spring on the west side, round which are fifty square metres of green rushes, with some larger bushes. The ground around and above is very saliferous; between the spring and the ruins to the north the ground is sandy, with many bushes and much scrub. This ground extends two kilometres to the west, whence it gradually passes up into great masses of drift sand; an occasional small outcrop of the top of the plateau above the sand is all that serves to locate the position of the buried cliff. On the east side the sandy ground with scrub extends about a kilometre, beyond which the plain gradually rises for another kilometre to the base of the cliff beyond, which is fairly steep and well-marked, though with an entire absence of indentations of any kind.

Der el Galamûn.Close to the north end of the valley, and about 33 kilometres from El Gayat, lie the ruins known as Der el Galamûn bil Muêla. At the time of our visit a new square stone building was in course of erection and five or six persons were inhabiting the place. There are several small palms scattered about to the south of the monastery and an excellent running spring of clear water five hundred paces to the south-west. A new well is being sunk within the premises. To the north of the monastery the eastern cliff takes a marked trend to the west for some three kilometres, whence it resumes a northerly direction, always maintaining its character of a steep well-marked escarpment rising some 100 metres above the floor of the wadi. At the corner of the cliffs the lowest bed exposed is a white limestone; this is overlain by gypseous clays passing up into sandy beds, the latter being surmounted by the white limestone capping the escarpment.

Wadi Rayan.We are here on the summit of the divide between Wadi Muêla and Wadi Rayan, the height of the floor being about + 105 metres; to the north stretches a gradually widening bay descending to the lowest ground of the Rayan depression. Immense accumulations of sand almost block the defile and stretch away to the east, and the hitherto well-marked cliff on that side bends back and is lost to view. On the other side however, the bounding wall gradually emerges from the dunes, getting more distinct as it is followed northwards until it becomes quite clear of the sand. The first glimpse of this cliff is seen a couple of kilometres west of the pass in an outcropping headland, the next point visible being some five kilometres further west. Between these portions of the cliff are one or two outliers, surrounded by quantities of blown sand. A depression known as Wadi Korif is reported to lie to the west, and much scrub and some water is said to exist there; such a wadi is marked on Schweinfurth’s map but apparently has not been examined.

Continuing in a N.N.W. direction high rather steep dunes occur on either flank, running N.N.W. and S.S.E. Between the dunes is a fairly hard undulating sand-flat affording an easy route; further on a narrow defile between the dunes leads down to the centre of the depression. The main areas occupied by blown sand are shown in the accompanying maps. The most interesting part of the depression is the bay lying to the south of the narrow well-marked promontory jutting out from the southern plateau, a huge pointer, as it were, in the direction of Gharaq; this is the Cape Rayan of Schweinfurth.

Springs in Wadi Rayan.The bay is on three sides completely enclosed by cliffs and its floor is thickly covered by a luxurious growth of wild scrub—chiefly tamarisk and ghardag; numerous isolated palm trees occur, especially in the neighbourhood of the water which exists at several points. There are three particularly good springs,[25] the positions of which are shown on the accompanying [maps.] According to Colonel Western’s survey the water emerges at about + 20 metres. In 1899 the water of the northern spring was found to have a temperature of 26°C. On our last visit we found an artificially constructed pool of two metres diameter and a depth of 30 centimetres; on the west side of this were two springs, marked by the motion of the grey sand rising and falling in the vents, down which a stick could be easily pushed to a depth of two metres. The output of these springs together amounted to six litres a minute; the water was quite clear and although soft and rather ferruginous not by any means unpalatable (see [analyses] below). The pool lies on an open bare sandy spot and is surrounded by scattered bushes, none of which however are within fifteen metres; a sand dune lies 150 metres to the south-west, with bushes and seven or eight young palms. The southerly spring has an output of 21 litres a minute, and its water does not differ essentially from that of the northern spring. Rising at the foot of a palm tree it forms pools on either side; thence it flows a distance of 20 metres into an artificially constructed shallow basin 2 to 3 metres across, from which it runs away down the slope and disappears after five or six metres. The east spring, which is situated on the east side of the dunes bounding the mouth of the bay, consists of a small hole cut out in soft sand. The water seemed good, although analysis shows the salts content to be high; this spring does not run, but if emptied the hole soon refills. The remains of old buildings occur near the well, in the shape of loose roughly squared limestone blocks, broken pottery, and remains of old walls; the latter are nearly level with the ground and very thickly and solidly built.

To the south of the promontory lies the so-called Little Rayan. Here there is a good deal of scrub, and water can be obtained on the lowest ground at a few metres depth, although there do not appear to be any surface springs.

Geology of Wadi Rayan in broad outline.The geological succession of beds exposed in the cliffs of the promontory is given later. Broadly speaking it consists of two thirty-metre bands of hard limestone separated by 68 metres of softer sandy and clayey beds. The lower of the limestone bands in places forms the floor of the depression but more frequently the latter is composed of the overlying sandy or clayey beds. The depression is bounded on the north side by the same succession, and, as far as could be judged from observations made on the traverse, the bed of limestone capping the ridge, and forming the plain stretching away to the Birket el Qurûn and to Gar el Gehannem, is identical with that capping the cliffs to the south, i.e. is the uppermost of the two thick limestone bands. At the two points more particularly noticed, namely, the spurs projecting southwards into the depression, 23 kilometres west and 18 kilometres W.S.W. of Gharaq basin, the sequence seemed to be the same as in the southern cliffs, although, owing to the northerly dip, the upper bed of limestone lies at a much lower level and the basal beds are not exposed at all. In both these localities, however, some of the underlying clays were exposed, as well as on the lowest spots crossed between the most easterly spur (18 kilom. W.S.W. of Gharaq) and the extensive dunes lying immediately west of Gharaq cultivation. These dunes, though of no height, have remarkably steep sides. In crossing Gharaq to the Fayûm cultivation occasional beds of yellow sandy limestone were noticed, but their horizon was not determined. Numerous bored blocks, probably belonging to the marine Pliocene, were observed scattered about. Apparently the uppermost thirty-metre band of limestone passes continuously northwards under the cultivated lands of Gharaq and the Fayûm; in the ravines of the latter this limestone is not observed, the soft limestones exposed below the alluvial deposits almost certainly belonging to the overlying Ravine beds. The country to the east of Gharaq has not been geologically examined and the exact locality in which the thick bed of limestone dips underground and is overlain by the succeeding beds is doubtful. Further north, in the desert ridge east of Qalamsha, we have observed the Birket el Qurûn beds and a section measured at this point is given later.

Character of Ridge separating Wadi Rayan from Gharaq and the Fayûm.As it appears to have been freely assumed that the ridge separating the Rayan depression from the cultivated lands of Gharaq and the Fayûm is formed throughout of solid limestone, it is important to point out that, on our assumption of the identity of the beds of limestone capping the cliffs to the south and the plain to the north of the Wadi Rayan, the dividing ridge would in part be formed of the underlying arenaceous and argillaceous beds.

Question of leakage through dividing ridge.The absence of Nile deposit and freshwater shells in the Wadi Rayan will, when confirmed after a thorough examination of the area, afford the strongest evidence that the depression was never directly flooded by Nile water. The fact that the dividing ridge is probably everywhere above the highest level attained by Lake Mœris, and by the still more ancient prehistoric lake, is almost sufficient in itself as a proof of this. It does not however follow that there was not leakage through the ridge into the Rayan basin, as such leakage might conceivably have taken place to a considerable extent without the water ever having collected in sufficient quantities to form even moderate sized pools within the depression. The bottom of the depression is for the most part covered with soft porous sandy deposits overlying the Eocene bed-rock below, and at the present time the water of the Rayan springs, though continually running, at once disappears from sight, drains down to the lowest parts of the depression and is then gradually lost by evaporation or underground leakage. In the lowest parts of the depression this water is, as already mentioned, met with on digging to a very moderate depth.

A careful examination of the flanks of the ridge separating the Fayûm and Gharaq cultivated areas from Rayan might prove if such leakage ever took place. If such was the case the seepage was probably along the line of junction of the limestone and underlying clayey or sandy beds. Even if it were proved that there never was leakage from Lake Mœris into Wadi Rayan, it would not be safe to assume that the converse would not happen, as the dip of the beds is from south to north and this fact is one to be reckoned with. Judging from the nature of the Eocene beds forming the Wadi Rayan, my opinion is that leakage on a large scale would not take place, and that owing to the northerly dip any water that escaped from the reservoir would pass indefinitely northwards and would not find its way through the overlying limestone to the surface either in Gharaq or the Fayûm cultivation. A detailed examination of the local geology would, however, be necessary to prove or disprove this. As to the question whether the Wadi Rayan as a whole would hold water, as far as is known there are no faults or other fissures of any magnitude through which the water could escape. No doubt a good deal of water would be lost before the smaller joints and passages, which exist in all rocks, were silted up. Schweinfurth supposes that the freshness of the Birket el Qurûn is due to the existence of subterranean outlets, and such might also be found to exist in the Wadi Rayan. In any case the argillaceous deposits from such a lake would very soon form a bed to all intents and purposes impermeable.