Mount Seir, Sinai and Western Palestine/Chapter 21
CHAPTER XXI.
SUMMARY OF SCIENTIFIC RESULTS.
I propose to give here a summary of the scientific results of the Expedition; reserving for a future work, which will be devoted to this subject fuller details on the several heads here referred to, and which I hope will be completed in the course of the year 1885. I do not wish it to be supposed that the work done by the members of our Expedition was always new, and altogether original. Several men of science of great eminence—amongst whom the names of Russeger, Fraas, Lartet, Vignes, together with those of investigators connected with the Palestine and Sinaitic Surveys, will always hold a prominent place—had previously entered this field. The members of the Expedition have had the advantage of their labours, and it would have been culpable on their part either to neglect or ignore them. On the contrary, we have endeavoured, I trust with proper acknowledgment, to utilise the observations of our predecessors in this wide field of research, which is every day receiving fresh accessions of explorers.[1] The results, then, are as follows:—
1. A complete triangulation of the district lying between the mountains of Sinai and the Wâdy el Arabah, together with that of the Wâdy el Arabah itself, bounded on the west by the tableland of the Tîh, and on the east by the mountains of Edom and Moab. This was entirely the work of Major Kitchener, and his assistant, Mr. G. Armstrong (formerly Sergeant-Major R.E.). An outline survey along the line of route was also made, and has been laid down in MS. on a map prepared by Mr. Armstrong on the same scale as the reduced Map of Palestine, viz., ⅜ inch to one statute mile, or 1168960.
2. Some important rectifications of the borders of the Salt Sea, and of the Gulf of Akabah, were also made. 3. A geological reconnaissance along the line of route through the districts of Sinai, Akabah, and the Wâdy el Arabah, including the following particulars:—
(a) Collections of fossils from the Wâdy Nasb Limestone; additions to those already made by Mr. Bauerman and Colonel Sir C. W. Wilson. These fossils (which are being examined by Professor Sollas) go to show that this limestone is of Carboniferous age. The Wâdy Nasb limestone was found to continue over a considerable region north of Mount Sinai, and was again recognised amongst the mountains of Moab on the east side of the Salt Sea in the Wâdy el Hessi. As this limestone rests upon a red sandstone foundation, this latter may also be assumed to be of the same geological age, and therefore cannot be the representative of the "Nubian Sandstone" of Rosiere, which (as Professor Zittel has shown) is of Cretaceous age. I propose to call this formation, therefore, "the Desert Sandstone." It forms, with the limestone, a strip along the borders of the ancient rocks of Paleozoic, or Archaean, age, and is about 400 feet in average thickness; the base is generally a conglomerate.
(b) Above the Wâdy Nasb limestone is another sandstone formation, of which a large portion of the Debbet er Ramleh is formed. It is laid open in the Wadies Zelegah, Biyar, &c., and along the mountains of Edom and Moab. Out of this rock have been hewn the ancient temples, tombs, and dwellings of Petra and the Wâdy Mûsa. It stretches along the southern escarpment of the Tlh plateau, and forms the base of the limestone cliffs along the margin of the Wâdy el Arabah as far north as Nagb es Salni. This sandstone formation is soft, red, or beautifully variegated. It is (in all probability) of Cretaceous age, and, if so, the true representative of the "Nubian Sandstone" of Eusseger. It will thus be seen that there are two red sandstone formations, one below, the other above the Carboniferous limestone of the Wâdy Nasb.
(c) The geological structure of the Wâdy el Arabah was examined throughout a distance of 120 miles from south to north. That it has been hollowed out along the line of a main fault (or line of fracture and displacement) ranging from the eastern shore of the Salt Sea to that of the Gulf of Akabah, was clearly determined. The position of the fault itself was made out and laid down on the map[2] in six or seven places; one being about ten miles north of Akabah, another near the watershed, in which places the limestone of the Tih (Cretaceo-nummulitic) is faulted against the old porphyritic and metamorphic rocks, as illustrated by the section across the Arabah Valley, given in a previous page (p. 77).
There are numerous parallel and branching faults along the Arabah Valley, but there is one leading fracture running along the base of the Edomite Mountains, to which the others are of secondary importtance; this may be called "the Great Jordan Valley fault." The relations of the rocks in The Gh6r and Jordan Valley have already been shown by Lartet, Tristram, Wilson, and others, to indicate the presence of a large fault corresponding with the line of this remarkable depression, and the author considers the fracture he has observed in the Arabah Valley to be continuous with that of the Jordan.
(d) The ancient rocks which form the floor either of the Desert, or Nubian, Sandstone formations, consist of granite, gneiss, porphyries, and more rarely of metamorphic schists—together with volcanic rocks, consisting of agglomerates, tuffs, and beds of felspathic trap. The author is disposed to concur with Dr. Lartet in considering the gneissose and granitoid rocks to be of Archaean (or Laurentian) age, as they are probably representative of those of Assouan in Upper Egypt, which Prof. Sir J. W. Dawson has recently identified with those of this age.[3] The granites and porphyries are traversed by innumerable dykes of porphyry and diorite both throughout the Sinaitic mountains and those of Edom and Moab; and the author considers it probable that the volcanic rocks which are largely represented along the bases of Mount Hor, and of Jebel es Somrah near Es Safieh, are contemporaneous with these dykes. As far as the author was able to observe, none of these dykes penetrate the Desert or Nubian Sandstones, and, if so, they may be considered of pre-Carboniferous age. The upper surface of the ancient rocks was originally extremely uneven, having been worn and denuded into ridges and hollows, previous to the deposition of the Desert Sandstone; over this irregular floor the sandstone strata were deposited.
4. The occurrence of terraces of marl, gravel, and silt, through which the ravines of existing streams have been cut at an elevation (according to aneroid determination) of about 100 feet above the level of the Mediterranean, was taken to show that the level of the Salt Sea (Bahr Lut) at one time stood about 1,400 feet higher than at present. These beds of marl were first observed at the camp at 'Ain Abu Beweireh; they contain blanched shells of the genera Melanopsis and Melania. The beds of marl were observed to be enclosed by higher ground of more ancient strata in every direction except towards the north, where they gently slope downwards towards the borders of The Ghôr, and become incorporated with strata of the 600 feet terrace.
5. The author concurs with Dr. Lartet in thinking that the waters of the Jordan Valley did not flow down into the Gulf of Akabah after the land had emerged from the sea; the disconnection of the inner and outer waters was very ancient, dating back to Miocene times.
6. The occurrence of beds of ancient lakes—consisting of coarse gravel, sand, and marl, amongst the mountains of Sinai, and in the Wâdy el Arabah, where now only waterless valleys occur, taken in connection with other phenomena, have impressed the author with the conviction that the former climatic conditions of Arabia Petræa were very different from those of the present day. Such terraces have been observed by Dr. Post in the Wâdy Feirân, and Colonel Sir W. Wilson in the Wâdy Solaf, and by the author in the Wâdies Gharandel, Goweisah, Hamr, Solaf, and Es Sheikh or Watiyeh. It would appear that, at a period coming down probably to the prehistoric, a chain of lakes existed amongst the tortuous valleys and hollows of the Sinaitic peninsula. The gypseous deposits of Wâdy Amarah and of 'Ain Hawareh are considered to be old lake beds, and Mr. Bauerman has observed remains of fresh-water shells (Lymnæa truncatula) and a species of Pisidium in "lake or river alluvium" of the Wâdies Feirân and Es Sheikh ("Quart. Journ. Geol. Soc," Vol. XXV, p. 35).
7. The author considers it probable that these ancient Sinaitic lakes belong to an epoch when the waters of the Mediterranean and of the Red Sea rose to a level considerably higher than at present; and when, consequently, there was less fall for the inland waters in an outer direction. The evidence of a submergence, to a depth of at least 200 feet, is abundantly clear in the occurrence of raised beaches or sea beds with shells, corals, and crinoids, of species still living in the adjoining waters. The raised beaches of the Mediterranean and Red Sea coasts have been observed by the officers of the Ordnance Survey, and by Fraas, Lartet, Schweinfurth, Post, and others. They were observed by members of the Expedition at the southern extremity of the Wâdy el Arabah, and shells and corals were found round the camp of the 3rd December at an elevation of about 130 feet above the Gulf of Akabah.
These ancient sea beds are represented in the Egyptian area by the old coast-line of 220 feet, discovered by Fraas along the flanks of the Mokattam Hills above Cairo, and recently described by Schweinfurth. (Über die geol. schichtungliederung d. Mokottam bei Cairo; Zeit. d. Deuts. Geol. Gesel, 1883.) The period in which the sea rose to this level may be stated in general terms as the Pliocene, but it continued downwards till more recent times; and the author believes that at the time of the Exodus the Gulf of Suez reached as far as the Great Bitter Lake (Quarterly Statement, April, 1884). It is scarcely necessary to observe that throughout the longer portion of this period of submergence Africa was disconnected from Asia.
8. The Miocene period is not represented by any strata throughout the district traversed by the Expedition. The author considers that in this part of the world the Miocene period was one of elevation, disturbance, and denudation of strata; not of accumulation. To this epoch he refers the emergence of the whole of the Palestine, and of the greater part of the Sinaitic areas, from the sea, in which the Cretaceo-nummulitic limestone formations were deposited. To the same epoch also he considers the faulting and flexuring of the strata is chiefly referable; and notably the formation of the great Jordanic line of fault, with its branches and accompanying flexurings of the strata—which are very remarkable along the western sides of The Ghôr. These phenomena were accompanied and followed by extensive denudation, and the production of many of the principal physical features of the region referred to.
9. The evidences of a Pluvial period throughout this region are to be found (a) in the remains of ancient lake beds, (b) in the existence of terraces in the river valleys, (c) in the great size and depth of many valleys and gorges, now waterless except after severe thunderstorms, and (d) in the vastly greater size of the Salt Sea (or Dead Sea), which must have had a length of nearly 200 English miles from north to south, at the time when its surface was at a higher level than that of the Mediterranean at the present day. The author considers that this Pluvial period extended from the Pliocene through the post-Pliocene (or Glacial) down to recent times. As it is known, from the observations of Sir J. D. Hooker, Canon Tristram, and others, that perennial snow and glaciers existed in the Lebanon during the Glacial epoch, the author infers that the adjoining districts to the south of the Lebanon must have had a climate approaching that of the British Isles at the present day; and that, in a region of which many parts are over 2,000 feet in elevation, there must have been abundant rainfall. Even when the snows and glaciers of the Lebanon had disappeared, the effects of the colder climate which was passing away may be supposed to have remained for some time, and the vegetation to have been more luxuriant down to within the epoch of human habitation. The author's views generally coincide with those of Theobold Fisher, as extended by him to a much wider area (Studien über das Klima der Mediterranean Lander," Peterman's Mittheilungen, 1879).
10. The author considers that there are reasons for concluding that the outburst of volcanic phenomena in North-Eastern Palestine in the region of the Jaulan and Hauran, &c., has an indirect connection with the formation of the great Jordan Sea of the Pluvial period. The presence of water in considerable volume is now recognised as necessary to volcanic activity, and the author submits that this interdependence was brought about when the waters of the Lake stretched as far north as the little Lake of Hûleh. These waters, under a pressure of several hundred feet, would find their way into the interior of the earth's crust along the lines of the great Jordan Valley fault, and of its branches, and thus supply the necessary "steam power" for volcanic action. The period when the volcanoes of the Jaulan and Hauran were in action appears to have ranged from the Pliocene through the post-Pliocene to the beginning of the recent; when, concurrently with the falling away and partial drying up of the waters of the great inland sea, the volcanic fires became extinct and the outpourings of basaltic lava ceased to flow.
If these views are correct, it would seem that during the Glacial epoch, Palestine and Southern Syria presented an aspect very different from the present. The Lebanon throughout the year was snow-clad over its higher elevations, while glaciers descended into some of its valleys. The region of the Hauran, lying at its southern base, was the site of several extensive volcanoes, while the district around, and the Jordan Valley itself, was invaded by floods of lava. A great inland sea, occupying the Jordan Valley, together with the existing comparatively restricted sheets of water, extended from Lake Hûleh on the north, to a southern margin near the base of Samrat Fiddân in the Wâdy el Arabah of the present day, while numerous arms and bays stretched into the glens and valleys of Palestine and Moab on either hand. Under such climatic conditions, we may feel assured, a luxuriant vegetation decked with verdure the hills and vales of Palestine and Arabia Petræa to an extent far beyond that of the present; and amongst the trees, as Sir J. D. Hooker has shown, the cedar may have spread far and wide.
11. The author has not thought it necessary to go into the question of the origin of the salinity of the Salt Sea, as this question is now fully understood. He is obliged to differ with Dr. Lartet in his view of the origin of the salt mountain, Jebel Usdum,[4] which he (the author), as also Mr. Hart, regards as a portion of the bed of the Salt Sea, when it stood about 600 feet above its present level. This level exactly corresponds to that of the terraces, both along the south and east of The Ghôr, formed of lacustrine materials. The upper surface of Jebel Usdum was examined by Messrs. Hart and Laurence, of the Expedition, but previous explorers had considered the sides inaccessible.
12. The author concurs with previous writers in considering that the Cretaceous and Tertiary periods succeeded each other over this region (at least as far as the marine deposits are concerned) without any important physical disturbances; in consequence of which the limestone formations of these periods are in physical conformity and are generally incapable of separation without prolonged and detailed examination. It seems probable, however, that while the Nummulitic limestones predominate in the Egyptian and Nubian areas, those of the Cretaceous period were more fully developed over the area of Arabia Petræa and Palestine.
13. A complete series of meteorological observations, consisting of maxima and minima readings of the thermometer, and levels of the barometer, were made by Mr. Laurence, and will appear in the scientific work to follow.
14. A series of photographic views were taken by Dr. E. G. Hull, and a selection from them will be published.
15. A large collection of plants, and a smaller of animals, was made by Mr. H. C Hart.
- ↑ Amongst the most recent contributions to the natural history of this part of the globe may be mentioned Tristram's "Fauna and Flora of Palestine," and C. and W. Barbey's "Herborisations au Levant, Egypt, Syrie, et Mediterranée" (Lausanne).
- ↑ The map used was an enlarged plan from Smith and Groves' Ancient Atlas (J. Murray).
- ↑ Dawson has shown, however, that there are two metamorphic series in Upper Egypt. Geol. Magazine, Oct., 1884.
- ↑ Lartet regards the strata of this mountain as belonging to the Nummulitic period.