The topography and geology of the Fayum province of Egypt

by H. J. L. Beadnell

G.—The Position of the Land-mass from which the Mammal Remains were Derived.

The existence of remains of land animals throughout the larger part of the Qasr el Sagha series and in still greater quantity in the basal beds of the overlying Fluvio-marine series, and occasionally in the highest beds also, points to the presence of continental land within no great distance of the area in which these deposits were laid down. That the animal-remains were carried out from the land by river currents is almost certain, and although in some cases such currents are known to persist to great distances from their points of emergence, it seems probable from the quantity and mode of distribution that the Fayûm bones were deposited within a moderate distance of land. Moreover, the silicified trees, by which the bones are so often accompanied, occur together in very great quantities, and we should imagine that the individual trees would have been far more scattered if they had been floated to considerable distances from land. On the other hand the fact that among the hundreds of trees examined, in no single case were branches found attached to the trunk, points to the conclusion that these trees had travelled great distances; probably the branches were lost during their river journey, from constant jamming together of a great number in a more or less constricted space, and not after they had left the river mouth.

The exact position of this land-mass is a highly interesting and important question. There is no reason to suppose that land of any extent occurred to the north, except possibly an occasional island, such as that of the Cretaceous massif of Abu Roash,[80] west of Cairo, which probably formed an island in the sea at that time; without doubt the great Eocene sea which covered the area stretched northwards, and was continuous with that in which the southern European deposits of this period were laid down. To the west also there was certainly no land-mass within approximate distances. Eastwards, possibly part of the Red Sea Hills igneous range may have formed a restricted land-area, but even this is not probable; in fact, it seems certain that we must look to the south for the nearest land of any extent. In supposing the land lay in this direction we are confronted at the outset with the fact that the Lower Eocene limestones stretch southwards for several hundred kilometres. In Egypt the Lower Eocene consists of a great mass of nummulitic limestones, some 400-500 metres thick, with no intercalated clays or sandstones except at the base, and was evidently formed in water of considerable depth. The thickness of, and superficial area covered by, these limestones show that they were formed in a truly open sea, in contra-distinction to a littoral area; the nummulitic sea in fact covered an enormous part of Europe, North Africa and Asia. To the south of this sea lay the African continent, a land-mass dating possibly from Palæozoic times. Since, and possibly partly during, the deposition of the Lower and Middle Eocene formations, a gradual elevation of the land or lowering of the sea, resulting in a retreat of the latter, took place; this continually brought the shore-line further northwards until, during the deposition of the beds of the Qasr el Sagha series of the Middle Eocene, we may surmise that it was not very far to the south, though the exact distance is extremely doubtful; while in Upper Eocene times it was still further north. We may assume therefore that the Upper Eocene bone-bearing strata of the Fayûm represent sediments transported by rivers and currents from a fairly adjacent continental land-mass to the south and laid down as littoral and delta deposits beyond the margin of the land. That at least one large river emerged from the land in the neighbourhood of the Fayûm is certain; drainage was then, as now, from south to north, although not probably confined to a single channel like the present Nile.

Apart from broader considerations a minute examination of the more typically fluviatile beds favours the conclusion that the currents were from the south or south-west. The general dip of the strata, probably the natural inclination of the sediments at the time of deposit, is from south to north; the most frequent lamination in the current-bedded arenaceous deposits is also from south to north. In our excavations for fossil bones it was noted that of seven tortoise shells exposed at the same time in different parts of the pit, six lay with their long axes similarly orientated and were distinctly tilted to the north-east, or exactly away from the point of the compass from which, as will presently be shown, the main river probably came. As a rule, however, the scattered fossil bones and trees in these beds give no definite clue as to the direction from which they were floated. The existence of separate accumulations of fluviatile sand at different horizons, but lying one above the other in the series and along a north and south line, is of importance as indicating the continued appearance of a river current from the same quarter.

Blanckenhorn has published[81] diagrams showing what he supposes to have been the relative areas occupied by land and sea in Upper Mokattam, Lower Oligocene, Middle Pliocene and Pleistocene times. Various lines of drainage are shown, the main river, which he calls the Ur-Nil, being placed some 70 kilometres to the west of the modern Nile, although closely following the trend of the latter. We have been unable to ascertain on what evidence Blanckenhorn relies for assuming rivers in Upper Mokattam and Lower Oligocene times to have occupied the positions shown on his diagrams; the number and positions of such rivers must remain more or less problematical. In this connection however it is interesting to recall[82] the lacustrine ferruginous grits which were brought to notice by the writer in 1900 as having been deposited in a lake, occupying in post-Middle Eocene times a shallow depression in that part of the Libyan desert now occupied by the oasis-depression of Baharia. Similar deposits were found forming the hills of Gar el Hamra a few kilometres east of the extreme north end of the depression. Finally, during a traverse through the unexplored country south-west of Gar el Gehannem in the winter of 1902-1903, hills capped with dark hard ferruginous silicified grits and puddingstone were met with in the extreme south-west of the Fayûm depression at a point nearly midway, and in the direct line, between the hills of Gar el Hamra and the chief bone-bearing localities in the north of the Fayûm. The deposits in question—at Baharia, at Gar el Hamra and in the hills to the south-west of the Fayûm—are evidently of lacustrine and fluviatile origin; and we may infer, with some degree of probability, that they were laid down along the course of a river which flowed in a north-easterly direction and formed extensive delta deposits in what is now the northern part of the Fayûm. That this river had its origin in the interior of a well-wooded continent hundreds of miles to the south of Baharia is not to be questioned; its size, length and exact position must remain matters of doubt, but of its existence we can be as certain as if in times of flood we had stood on its banks and watched the passage northwards of its turbid swollen waters, laden with matted rafts of forest trees and bearing seawards the carcases of those curious Eocene animals, the remains of which are so abundant in the Fayûm of to-day.

Fig. 6.—Probable Course of chief river of Upper Eocene and Oligocene times.

In the Middle and Upper Eocene beds we first obtain an idea of the animals which inhabited Africa in Tertiary times, and the collecting and working out of this fauna will throw much light, not only on our actual knowledge of the African vertebrata of the Eocene period, which was practically nil until the discovery of the remains here described, but also on other wider biological questions, such as the origin of certain groups of animals, some of which were evolved in this part of the world.

As recently pointed out by a writer in the Field (No. 2605, Nov. 29, 1902) many years ago the late Prof. Huxley, to account for the present distribution of the mammalian fauna of Africa and Magadascar, advanced the theory that in the early part of the Tertiary period Madagascar was connected with Africa, and Africa with Europe or Asia, a connection which allowed of the immigration into Africa and Madagascar of numerous small types of European and Asian mammals. Madagascar later becoming separated from the mainland, its fauna, undisturbed by the larger carnivora, was able to develop to its present remarkable extent. Subsequently to the isolation of Madagascar the ancestors of the modern fauna were presumed to have invaded the African continent from the north.

The extinct fauna of the Fayûm, however, shows that in early Tertiary times Africa already had its own mammalian fauna, which, besides containing some remarkable large types of somewhat doubtful position, such as Arsinoitherium, Barytherium, etc., certainly in Mœritherium and Palæomastodon included the earliest known elephants, the forbears of the Mastodon and the modern elephants. There is little doubt therefore that in Upper Eocene and Oligocene times these early members of the elephant group ranged northward and eastwards into Asia and India, and since in the Upper Tertiary deposits of India and eastern Asia the extinct transitional types between the mastodons and modern elephants appear to have been found, it is not unlikely that during the later phases of the evolution of this group of animals the radiation was back towards Africa, so that the African elephant may be, as it has usually been regarded, an immigrant from the Oriental region. Further research among the later deposits of the Fayûm and the deserts to the north may, however, throw an entirely new light on the subject and it is somewhat premature to theorise at present.