1 he Nubian sandstone is probably a lacustrine deposit laid down over the tioor of a vast inland lake, the boimdarics of which, owing to extensive ge<dogical changes, it is now impossible to define except at distant intervals. One portion of this boundary was undoubtedly formed of the rocks of the Sinaitic group of mountains ; other portions
• Except where c»rboniferou8 or votcanic beds are pn'wnt. i A view of thil gorge is given in the (rontLspieoo of llull'l Mount Seir.
154 GEOLOGY OF PALESTINE
GEOLOGY OF PALESTINE
may be discovered in Central Africa ; and tlie lake itself may have been connected with the Cretace- ous ocean in the direction of the Mediterranean.* The formation was accumulated from the waste of ^anitic and plutonic rocks forming the sur- rounding lands now partly submerged beneath tlie waters of the ocean.
(e) Crctaceotis Limestone. — This great series of calcareous strata immediately succeeds the Nubian sandstone ; and as it is altogether a marine deposit, it must have been formed over the bed of the ocean after a general subsidence and submergence of the region occupied by the lacustrine waters of the previous period. The lower beds are cliiuHy formed of white calcareous marls succeeded by harder limestone strata with bands of siliceous chert or Hint. The following section taken in the Wady (ilHessi, at the S.E. border of the Badict et- Tlh, will serve to give a general idea of the character of the lower portion of the forma- tion. (1) Lowest beds; — light-blue calcareous marl, passing downwards into dark-blue clay with selenite, 250 ft. thick ; (2) soft white limestone, with rare bands of chert, 200 ft.; (3) hard silice- ous limestone with numerous bands of cliert, forming the top of the cliff, about 200 ft. thick. Fine sections are also laid open on ascending the flanks of the escarpment overlooking the basin of the Dead Sea (the ' Ghor ') on the eastern side, of which Lartet gives the details.f The total thick- ness of the Cretaceous limestone series may reach 800 to 1000 ft., and amongst the fossil foims the following may be cited : Ammonites Lut/ncsi, A. rhotamargensis, Pholadomya Luynesi, Ostrea Mermeti, 0. flahellata, Hippurites, etc. Forami- nifera, visible only under the microscope, doubt- less are abundantly present.
Building Stone. — The uppermost beds of the Cretaceous limestone yield an excellent building stone wliich has been used in the construction of the buildings in and about Jerusalem, including the walU of the temple. The stone has been extracted from the large quarries and caverns near the Damascus gate. The rock is hard, compact, and delicately coloured, capable not only of fur- nishing large blocks such as may be seen at the ' WaUing Place of the Jews,' but of being worked into ornaments and smaller objects of use, and of recei%'ing a polish. Fraas gives the following section of the beds in descending order at this spot t : —
1. Craie blanche {Senonien).
2. fttage sup^rieure des Hippurites (' Misseh ').
3. Etage inierieure des Ilippjcrites (' Melekeh ').
4. Zone of Ani7nonites rkotomargen^is {Tnroniiin). No. 2 ('Misseh') of the above section afiords the principal building stone, and is 16 ft. in thickness ; and Sir C. W. Wilson has shown that the reser- voirs, sepulchres, and cellars under and around the city are excavated in the soft beds of No. 3 ('Melekeh') underlying the firmer beds of the ' Misseh,' which form the platforms for the build- ing9-§
(/) Lovtcr Eocene Beds ; Nummulite Limestone. — This formation, though belonging to the Tertiary division of the geological series, immediately succeeds the Cretaceous limestone just described, and bears so general a resemblance to it that to- gether they appear to constitute one great cal- careous formation, incapable of separation. This apparent continuity is, however, illusory, as has
• In North Africa the boundary lay along the northern base of the Ahafr^'ar Mountains in lat. 25° N. and the Morocco Atlaa on the north, as the present writer has shown elsewhere ; 'Geo- loeical Historj' of E^-jpt and the Nile Valley,' Tram. Vict. Imt. vol. xxjv. p. 307 (with ilap).
♦ Voyage d'exploratioji, p. 70, fig. 6. t Aus dem Orient, p. 54.
§ Ordnance Survey of Jerutalem.
been sho\vn by Zittel in the case of Egypt and the Nubian Desert ; and a detailed survey would doubtless have the result of showing that the two formations are disconnected by an unconformity, however slight. The latest explorer of the geo- logical features of Palestine, Dr. Blanckenkorn, ia clearly of opinion that the two formations are capable of separation ; * and Lartet had previously e.xpressed the same view.
Tlie Nummulite limestone is but sparingly repre- sented in Palestine. It forms the southern slopes of part of the Lebanon, t is found cai)ping Mount Carmel, and occurs in isolated masses at Sebastieh (Samaria), Nablfls (Shechem), and the vicinity of Jerusalem. It also overspread.s a large tract of the western Tih plateau, as it lias been identified l)y its characteristic fossils in the limestone dills which overlook the Isthmus of Suez, but its inland limits remain to be determined with any degree of accuracy.
The lower beds of the formation consist of wliite marls and clialky limestone with Nummulites, sur- mounting the harder beds of Cretaceous age : these are succeeded by white limestones with bands of Hint, resembling those of the latter period ; and, as Lartet has pointed out, this general resemblance causes much uncertainty in the discrimination of the two formations on the spot. The Nummulite limestone is an oceanic deposit laid down under similar conditions of deposition to those of tlie Cretaceous beds, but with an interval of slight disturbance and movement in the floor of the sea. The fossils are distinctly of Tertiary genera and species.