[Footnote 28: Public Works Ministry Report. Cairo, 1899.] [Footnote 29: BLANCKENHORN. _Geologie Aegyptens_, Berlin 1901, Pt. IV, pp. 339-344.] [Footnote 30: „ p. 341, Fig. 10. Skizze der Strukturlinien des Fayûm.] [Footnote 31: „ Taf. XIV. Querprofil durch den Fayûmgraben.] [Footnote 32: BLANCKENHORN, _Neue geologisch-stratigraphische Beobachtungen in Aegypten_, S.-Ber. d. math.-phys. Classe d. kgl. bayer. Ac. d. Wiss. Bd. XXXII 1902, Heft III, München 1902, pp. 428, 429.] PART III. =GEOLOGY.= * * * * * SECTION IX.—GENERAL AND CLASSIFICATION OF STRATA. The geology of the area[33] under consideration is almost entirely stratigraphical, the only igneous rocks being more or less local lava flows. The sedimentary rocks of the district have yielded an abundant fauna, both invertebrate and vertebrate; the latter is of unique interest, including as it does a number of highly interesting animal types quite new to science. An extended examination in the field, and comparisons with the stratigraphical succession in other parts of Egypt, checked by the determinations of the fossil molluscan fauna, make it possible to form a very fair estimate of the approximate age of the different rock-stages, although this may necessarily be subject to modification when the specific determinations of the entire collection of organic remains have been completed, and the development of vertebrate life has been correlated and compared with that in other parts of the world. The depression is cut out in a great series of sedimentary rocks of Middle Eocene, Upper Eocene, and Oligocene age, and one of the features of the stratigraphy of the region is the constancy of many beds over wide areas. The dip of the beds throughout the area is nearly due north and at a very low angle, averaging 2° or 3°, but varying from 1° to 5°; this low dip is very constantly maintained except when locally affected by small faults. The structural geology and tectonics have already been discussed at some length in the previous sections. The oldest beds found in the depression are the clays, marls, and limestones with _Nummulites gizehensis_, of Middle Eocene age. These are succeeded by a group of white marly limestones and gypseous clays, which largely underlie the cultivated alluvium of the Fayûm. They are followed by a series consisting of clays, sandstones, and calcareous grits, some beds of which are characterized by the abundance of small nummulites and _Operculina_. The latter series is followed by the uppermost truly marine Eocene beds, a group of alternating clays, sandstones and limestones, the “Qasr el Sagha Series” (or Carolia beds), characterized by an abundant invertebrate and vertebrate fauna, and equivalent to the Upper Mokattam beds of Cairo.