PART III.—GEOLOGY.

SECTION IX.—GENERAL AND CLASSIFICATION OF STRATA—

Depression cut out in sedimentary rocks. Local lava flows. Dip. Oldest beds the Nummulites gizehensis limestones of Middle Eocene. Fluviomarine series of Upper Eocene and Oligocene age. Absence of Miocene strata. Pliocene, Pleistocene and Recent. Table showing succession and classification of strata 33

SECTION X.—MIDDLE EOCENE—

A.—_Wadi Rayan Series._—Work of Schweinfurth and Mayer-Eymar. Section at entrance to Wadi Muêla on Nile Valley side. Strata of cliffs near Der el Galamûn. Detailed section measured at Jebel Rayan. Mayer Eymar’s section in Wadi Muêla 35

B.—_Ravine Beds._—In ravines of El Bats and El Wadi. Relation to underlying series seen at Gar el Gehannem. Section at Gar el Gehannem. Fauna of strata. In ravines unconformably overlain by Pleistocene, etc. Form plain bordering cultivation on east side. Extension into Nile Valley. Occurrence at Sersena and Tamia. Forming base of Geziret el Qorn and lower part of northern escarpment of Birket el Qurûn. West end of lake. Hard siliceous bands give rise to horns or promontories of lake. Ravine Beds in the Medinet el Fayûm boring. Thickness 37

C.—_Birket el Qurun Series._—Homotaxial with quarried limestones of Cairo. Foraminiferal beds. Extension of series. Section at Ezba Qalamsha. Section north of Lahûn pyramid. East of Sersena and north-east of Rubiyat. Section 17 kilometres 28° N. of E. of Tamia. Series characterized by large globular concretions. Development and fauna in Geziret el Qorn. Zeuglodon remains. Profile at Geziret el Qorn. Rich molluscan fauna. Section on mainland opposite Geziret el Qorn. Section at west end of Birket el Qurûn. Formation of earth-pillars. Extension west of the lake. Development of the series in the Zeuglodon Valley. Abundance of skeletons of whales. Molluscan fauna. Pseudomorphs in celestine. Hill mass south of the Zeuglodon Valley. Junction of Birket el Qurûn series with overlying stage 41

D.—_Qasr el Sagha Series._—Equivalent of the Upper Mokattam of Cairo. Greater development in Fayûm. Vertebrate fauna of series. Schweinfurth’s original discovery of cetacean remains. Recent discovery of land and marine mammals. Extension of series generally. N.N.E. of Tamia. At Garat el Faras. In the cliffs north of the Birket el Qurûn. Detailed section near ruin of Qasr el Sagha. At Gar el Gehannem and westwards. Land animals floated out from land by river currents. The series a littoral deposit. Lignitic beds and thin seams of coal 49

SECTION XI.—UPPER EOCENE — LOWER OLIGOCENE—

E.—_Fluvio-marine Series._—Nature of sediments, Interbedded basalts in upper part. Character of its invertebrate fauna. Conditions of deposition of series. Continuance of similar conditions to Miocene and even Pliocene times. Bone-beds at base of series. Association of skeletons of animals and forest trees. Preservation of remains. Analysis of fossil bones. Relation of Fluvio-marine series to underlying stage. Characteristics of the group. Its development in the field. Its slight development at Elwat Hialla. Section near Elwat Hialla. Constant northerly dip. Organic (molluscan) remains 9 and 14 kilometres north of Qasr el Sagha. Detailed section from near Qasr el Sagha to Widan el Faras. Determinations of mollusca from the series. Tripartite character of the series west of Widan el Faras and Qasr el Sagha. Occurrence of calcite, gypsum and chalcedony. Tabular chert and flint. Ancient workings. Extent of basalt. Silicified trees 53

F.—_Age of the Fluvio-Marine Series._—Difficulty in the determination of age owing to paucity of fossils. Zittel’s tabulation of “Schichten von Birket el Qurûn” as Oligocene. Mayer-Eymar’s age determinations. Schweinfurth’s comparison of the series with the Scutella beds of Der el Beda near Cairo. Blanckenhorn’s determinations. The stratigraphical position of the series and relationship to Qasr el Sagha series. Stratigraphically lower than the Lower Miocene of Mogara. Whole complex in all probability of Upper Eocene and Oligocene age, the transition being at or near the basalt sheets 63

G.—_The Position of the Land Mass from which the Mammals were derived._—Proximity of continental land. Absence of branches on fossil trees. Massif of Abu Roash perhaps an island to the north. Extension of Eocene sea. Continual retreat of the sea northwards. Rivers emerging from the land. Number and positions of such rivers doubtful. Evidence for river passing from the modern oasis of Baharia through Gar el Hamra to the Fayûm. Lacustrine and fluviatile deposits along the course. Huxley’s theory of immigration and invasion of animals into Africa. Fayûm animals belong to an extinct African fauna of Tertiary times. Contains the earliest and most primitive forms of elephants and other groups. Emigration and immigration. Prof. Osborn’s theory of the African continent as a centre of radiation. Confirmation by the Fayûm mammal discoveries. List of new species obtained from the Fayûm 65

H.—_The Absence of Miocene deposits in the Fayûm._—The Fayûm a land area in Miocene times. Miocene deposits of Mogara. Lithological similarity. Probable persistence of geographical conditions 71

SECTION XII.—PLIOCENE—

J.—_Marine deposits: Middle Pliocene._—Marine deposits of Sidmant with typical Middle Pliocene mollusca. Relation of these deposits to the gravel terraces as yet unknown though important 71

K.—_Borings on Rock Surfaces; of doubtful age._—Apparently due to marine boring mollusca. No exact evidence as to age. (α) Low level borings from zero to 20 metres above sea-level. (β) High level borings at 112 metres above sea-level. Limited occurrences of borings 71

L.—_Gravel Terraces:? Upper Pliocene._—Well marked terraces of gravel up to 170-180 metres above sea-level. East of Sêla. Character of deposit. East of Sersena and Roda. N.N.E. of Tamia, N.N.E. of Garat el Faras, east and north-east of Garat el Gindi. Relation to different series. Character of gravels at Elwat Hialla. West of Elwat Hialla gravel terraces almost completely removed by denudation. Traces near Widan el Faras and near Garat el Esh. Height of terraces in latter locality determined as 170 metres above sea-level. Terrace marks shore line of great sheet of water, whether freshwater or marine. The great plains of the Fayûm possibly in part plains of marine denudation 73

M.—_Gypseous Deposits: probably dating from the close of the Pliocene._—Extension in Nile Valley and Fayûm. Section at Medum. On the east side of the Fayûm. Gypsum cemented conglomerate. Close connection with upper part of gravel terraces 77

N.—_Summary of Pliocene Period_ 78

SECTION XIII.—PLEISTOCENE—

Earliest existence of a freshwater lake. Probably not a remnant of the Pliocene sea or lake in which gravel terraces were formed. Intermediate denudation of area. Date of earliest entry of Nile waters doubtful. Freshwater lake of Nile Valley. Drainage down the Nile Valley and establishment of river. Breaking down of gravel ridge separating the valley and the Fayûm. Entrance of flood waters. Formation of lake and deposition of sediment. Subsequent disconnection of Nile Valley and Fayûm owing to erosion of river bed. Rise of Nile in prehistoric and historic times. Reconnection. Geological evidence for the existence of great freshwater Pleistocene lake. Position and dimensions. Fossil fauna of the lake, and its difference from all other Egyptian faunas. Blanckenhorn’s conclusions 79

SECTION XIV.—RECENT 81

O.—_Prehistoric._—Abundance of worked flints. Shores of lake inhabited by Neolithic and probably prehistoric man. Tamarisk remains. Probable age of flints anterior to Egyptian historic period 82

P.—_Historic._—Relations of the Nile Valley river system and the Fayûm. Lake Moeris a regulator of the Nile floods. Brought under control in XIIth dynasty. Early references to Lake Moeris. Its position disputed in modern times. Linant de Bellefonds’ assertion disproved by Sir Hanbury Brown. Archæological evidence for the site. Present day fauna of the Birket el Qurûn. Modern deposits. Blown sand. Erosion 82

APPENDICES 87

1. Previous literature relating to the Fayûm 87

2. Fayûm lamellibranchs mentioned in Oppenheim’s “Zur Kenntnis alttertiärer Faunen in Ægypten.” 89

INDEX 91

LIST OF ILLUSTRATIONS.

* * * * *

PHOTOGRAPHS.

PLATES. PAGE.

I. — North side of the Birket el Qurûn, looking west _Frontispiece._

II. — Bahr Yusef at Lahûn before entering the Fayûm _to face_ 11

III. — El Wadi, Ravine near Qasr Gebali „ 19

IV. — Western extremity of the Birket el Qurûn „ 29

V. — Alluvial deposits overlying marly limestones (Ravine Beds) in El Wadi, Ravine near Qasr Gebali „ 37

VI. — Escarpment of the Birket el Qurûn series near the western end of the lake „ 41

VII. — Weathered concretionary sandstone (Birket el Qurûn series) on north shore, near Geziret el Qorn „ 45

VIII. — Middle Eocene escarpment (Qasr el Sagha series) 12 kilometres west of Qasr el Sagha „ 49

IX. — Upper beds of Fluvio-marine series with basalt cap, looking west from the eastern extremity of Jebel el Qatrani „ 53

X. — El Qatrani range from the south-east „ 57

XI. — Silicified trees of Fluvio-marine series, 4½ kilometres north of Qasr el Sagha „ 63

XII. — Raised Beach unconformably overlying Middle Eocene limestones (Birket el Qurûn series) in the desert east of Sersena „ 69

XIII. — Borings in false-bedded sandstone, 2 kilometres south of Dimê „ 73

XIV. — Pleistocene lacustrine clays with tamarisk stumps _in situ_ at 50 metres above the present surface of the Birket el Qurûn „ 77

XV. — Isolated sand-dune near Gar el Gehannem „ 81

XVI. — The Birket el Qurûn near the western end „ 85

PLANS.

XVII. — General Map of the Fayûm depression, with Wadi Rayan and Wadi Muêla, 1/250000 end

XVIII. — Map of the area north-west of Qasr el Sagha, showing principal bone-bearing localities, 1/50000 „

SECTIONS.

XIX. — From the Birket el Qurûn through Dimê and Qasr el Sagha to the summit of Jebel el Qatrani end

XX. — From Wadi Rayan to the summit of the escarpment north of Gar el Gehannem „

XXI. — The Desert Ridge separating the Nile Valley and the Fayûm „

XXII. — From Sidmant el Jebel in the Nile Valley through Medinet el Fayûm to the summit of Jebel el Qatrani, near Widan el Faras „

XXIII. — Middle Eocene escarpment near Qasr el Sagha „

XXIV. — From Garat el Esh to summit of Jebel el Qatrani „

FIGURES (IN THE TEXT.)

1. — Fault near Qasr el Sagha 32

2. — Section at Gar el Gehannem, showing the relation of the Wadi Rayan series to the Ravine Beds 38

3. — Sketch-section across El Bats, one kilometre west of Sêla 40

4. — Profile of beds of Geziret el Qorn 44

5. — Section of cliffs, western end of the Birket el-Qurûn 47

6. — Probable course of chief river of Upper Eocene and Oligocene times 67

7. — Block of sandstone pierced by numerous borings 72

8. — Sketch showing relations of the Eocene to Pliocene gravel terraces on the east side of the Fayûm 74

9. — Sketch-section through the summit of the Fayûm escarpment at Elwat Hialla 76

10. — Sketch-map showing approximately the site of Lake Mœris 83

INTRODUCTION.

* * * * *

The geological survey of the desert surrounding the Fayûm was commenced in October 1898. At that time the area, although so near to Cairo, was little known; the Rohlfs Expedition maps marked the region as “unexplored,” and in fact with the exception of a publication by Schweinfurth, who had traversed the region from north to south, _via_ Qasr el Sagha and Gar el Gehannem to Rayan, there was little information obtainable. The area being of considerable size (12,000 sq. kilom.) and almost unexplored, both geologically and topographically, the primary object was to construct as rapidly as possible a general map of the depression, at the same time laying down in broad outline the chief geological formations and trusting to future opportunity to examine in more detail places of special interest.

Commencing work at Sêla, on the eastern side of the depression, the survey was carried northwards along the east side of the cultivated lands and thence through the northern desert, up to the summit of the depression. After mapping westwards as far as the isolated hill-mass of Gar el Gehannem the work was temporarily suspended until, in the spring, the narrow defile of Wadi Muêla, and the Wadi Rayan, forming the southern part of the Fayûm depression, were provisionally examined.

In January 1901, samples of soil and water from the cultivated lands were collected as an experimental soil-survey, and the results have been published.[1]

During the winter’s work of 1902-03 a traverse was carried from Gar el Gehannem in a south-west direction through a hitherto unexplored part of the depression. On reaching a point midway between Cairo and the oasis of Baharia a connection was made eastwards to Wadi Rayan. In the winter of 1903-04 further exploration was carried out in the neighbourhood of Gar el Gehannem.

It will be convenient here to briefly relate the history of the discovery of the remarkable series of new and extinct animal forms, the recovery of which from the Fayûm deposits has created such widespread interest in the zoological world. When Schweinfurth crossed the region in 1879 he obtained fossil bones, which were examined and determined by Dames to be the remains of cetacea of the genus _Zeuglodon_, from certain beds of the escarpment west of Qasr el Sagha; these, it is believed, were the earliest vertebrate remains obtained from the Fayûm. During the early part of the survey of the district, remains of fish and crocodiles were frequently found in one of the beds of the Middle Eocene, probably on the same horizon as that from which Schweinfurth had collected. Fragments of bone were also commonly met with on a much higher horizon (_i.e._, near the base of the Fluvio-marine series) but nothing of particular interest was obtained, as no detailed search could be made at that time. In April 1901, during the survey of the western end of the Birket el Qurûn, some of the localities found to be bone-bearing in 1898 were re-visited in company with Dr. C. W. Andrews, who was in Egypt at the time and had accompanied the survey in order to obtain specimens of jackals, hares, etc., for the British Museum, in connection with the forthcoming work on Egyptian mammals. In one of these Dr. Andrews picked up several vertebrae which turned out to belong to a new species of _Pterosphenus_.

Further north, when descending the Middle Eocene escarpments at a place not previously examined, we crossed the outcrop of the bone-beds at a point where a considerable number of mammalian and reptilian bones lay exposed on the surface, many in an excellent state of preservation. The importance of the find was evident, and a short examination of the material on the spot enabled Dr. Andrews to pronounce the discovery to be of the highest importance from a palaeontological point of view.

Some three weeks’ work in the immediate neighbourhood resulted in a very good collection of vertebrates from the Middle Eocene beds, including several new genera afterwards described[2] under the names of _Eosiren_, _Barytherium_, _Mœritherium_, _Gigantophis_, etc. Moreover, a fossil tooth brought in by one of the camelmen from a point several kilometres to the north led to a careful examination of the lower beds of the overlying Upper Eocene formation, which resulted in obtaining well-preserved remains belonging to a new genus, since described as _Palaeomastodon_. All the material so far obtained was taken home to be worked up and determined at the British Museum and a preliminary description was published by Dr. Andrews in the Geological Magazine.

In the winter of 1901-02 the survey of the Fayûm was resumed with the special intention of following up the highest beds, those in which _Palaeomastodon_ had been found. Continued search westwards eventually led to the discovery of the remains of a large and remarkable horned ungulate (_Arsinoitherium_), a preliminary notice[3] of which was published in the spring of 1902. Shortly after, the remains of several new smaller mammals and reptiles (_Phiomia_, _Saghatherium_), including the shell of a large land tortoise (_Testudo Ammon_), were obtained[4]. Further work in the winters of 1902-03-04 led to a great deal more material being obtained[5], mostly of course belonging to the same species, but including some new genera _Geniohyus_, _Megalohyrax_, _Pterodon_.

The amount of palaeontological material is now so large that the Egyptian Government has arranged with the Trustees of the British Museum for the publication of the whole in a monograph to be issued by the Trustees. The present report, therefore, deals only with the geology and topography of the district.

[Footnote 1: A. LUCAS, _A preliminary investigation of the Soil and Water of the Fayum Province_; Survey Dep., P.W.M. Cairo, 1902.]

[Footnote 2: ANDREWS, _Extinct Vertebrates from Egypt_. Parts I and II. Geol. Mag. N. 8. Dec. IV, Vol. VIII, Sept. and Oct. 1901, pp. 400-409 and 436-444.]

[Footnote 3: BEADNELL, _A Preliminary Note on Arsinoitherium Zitteli, Beadn._ Survey Dept. P.W.M., Cairo, 1902. See also _A New Egyptian Mammal (Arsinoitherium) from the Fayûm_. Geol. Mag. N.S. Dec. IV, Vol. X. Dec. 1903, pp. 529-532.]

[Footnote 4: ANDREWS and BEADNELL, _A Preliminary Note on Some New Mammals from the Upper Eocene of Egypt_. Survey Dept. P.W.M., Cairo, 1902.]

[Footnote 5: ANDREWS, _Notes on an Expedition to the Fayûm, Egypt, with Description of some New Mammals_. Geol. Mag. N.S. Dec. IV, Vol. X. Aug. 1903, pp. 337-343. Also _Further Notes on the Mammals of the Eocene of Egypt_ (Parts I, II, III). Geol. Mag. N.S. Dec. V., Vol. I. March, April, May 1904.]

[Illustration: PLATE II.

BAHR YUSUF AT LAHUN BEFORE ENTERING THE FAYUM.]