The geological sequence begins with the granite and schists of the central zone, which form a band extending from Fisht on the west to a point some distance beyond Kasbek on the east. Then follow the Palaeozoic schists and slates. Fossils are extremely rare in these beds; Buthotrephis has long been known, and doubtful traces of Calamites and ferns have been found, but it was not until 1897 that undoubted Palaeozoic fossils were obtained. They appear to indicate a Devonian age. Upon the Palaeozoic beds rest a series of Mesozoic deposits, beginning with the Lias and ending with the Upper Cretaceous. Whether the series is continuous or not is a matter of controversy. F. Loewinson-Lessing states that there is a more or less marked discordance between the Lias and the Upper Jurassic and between the latter and the Cretaceous; E. Fournier asserts that there exists a very strongly marked unconformity at the base of the Tithonian, and other writers have expressed other views. In general the Upper ajurassic beds are much more calcareous on the north flank of the chain than they are on the south. The Mesozoic beds are followed by the Tertiary deposits, which on the north are nearly horizontal but on the south are in part included in the folds—the Eocene and Miocene being folded, while the later beds, though sometimes elevated, are not affected by the folding. The final folding of the chain undoubtedly occurred at the close of the Miocene period. That there were earlier periods of folding is almost equally certain, but there is considerable difference of opinion as to their dates. The difference in character of the Jurassic beds on the two sides of the chain appears to indicate that a ridge existed in that period. The last phase in the history of the Caucasus was marked by the growth of the great volcanoes of Elbruz and Kasbek, which stand upon the old rocks of the central zone, and by the outflow of sheets of lava upon the sides of the chain. The cones themselves are composed largely of acid andesites, but many of the lavas are augite andesites and basalts. There seem to have been two periods of eruption, and as some of the lavas have flowed over Quaternary gravels, the latest outbursts must have been of very recent date.
Near the northern foot of the Caucasus, especially in the neighbourhood of the hot mineral springs of Pyatigorsk, a group of hills of igneous rocks rises above the plain. They are laccolites of trachytic rock, and raised the Tertiary beds above them in the form of blisters. Subsequent denudation has removed the sedimentary covering and exposed the igneous core.
(P. La.)
Bibliography.—Of the older works the following are still useful: A. von Haxthausen, Transkaukasia (2 vols., Leipzig, 1856); A. Petzholdt, Der Kaukasus (2 vols., Leipzig, 1866-1867); M.G. von Thielmann, Travels in the Caucasus (Eng. trans., 2 vols., London, 1875); F.C. Grove, The Frosty Caucasus (London, 1875); G. Radde, Reisen im mingrelischen Hochgebirge (Tiflis, 1866) and Vier Vorträge uber den Kaukasus (Gotha, 1874); E. Favre, Recherches géologiques dans la partie centrale de la chaîne du Caucase (Geneva, 1875); Batsevich, Simonovich and others, Mat. dlya geologiy Kavkaza (Tiflis, 1873 seq.); O. Schneider, Naturwissenschaftliche Beitrage zur Kenntnis der Kaukasuslander (Dresden, 1879), and J. Bryce, Transcaucasia (London, 1878). The more important amongst the more recent books are D.W. Freshfield, Exploration of the Caucasus (2nd ed., 1902, 2 vols., London); A.F. Mummery, My Climbs in the Alps and Caucasus (London, 1895); H. Abich, Geologische Forschungen in den kaukasischen Landern (3 vols., Vienna, 1878-1887), Aus kaukasischen Landern (2 vols., Vienna, 1896), and “Vergleichende Grundzuge des Kaukasus wie der armenischen und nordpersischen Gebirge,” in Mém. Acad. Sc. St-Pétersb. (sér. 6, Math. et Phys., vii. 359-534); R. von Erckert, Der Kaukasus und seine Volker (Leipzig, 1887); E. Chantre, Recherches anthropologiques dans le Caucase (4 vols., Lyons and Paris, 1885-1887); C. von Hahn, Aus dem Kaukasus (Leipzig, 1892), Kaukasische Reisen und Studien (Leipzig, 1896), and Bilder aus dem Kaukasus (Leipzig 1900); V. Sella and D. Vallino, Nel Caucaso Centrale (Turin, 1890); K. Koch, Der Kaukasus (Berlin, 1882); C. Phillipps Woolley, Savage Svanetia (2 vols., London, 1883); E. Levier, À travers le Caucase (Paris, ed. 1905), especially valuable for botany; G. Merzbacher, Aus den Hochregionen des Kaukasus (2 vols., Leipzig, 1901); A. Fischer, Zwei Kaukasische Expeditionen (Berne, 1891); E. Fournier, Description géologique du Caucase central (Marseilles, 1896); G. Radde, Reisen an der persisch-russischen Grenze. Talysch und seine Bewohner (Leipzig, 1886), Die Fauna und Flora des südwestlichen Kaspigebiets (Leipzig, 1886), Karabagh (Gotha, 1890), and Aus den daghestanischen Hochalpen (Gotha, 1887); and Count J. Zichy, Voyages au Caucase (2 vols., Budapest, 1897). F. Loewinson-Lessing has an account of the geology of the district along the military road from Vladikavkaz to Tiflis in the Guide des Excursions du VIIe Congrès géol. internat. (St Petersburg, 1897). N.Y. Dinnik writes on the fauna in Bull. Soc. Impériale des Naturalistes de Moscou (1901); J. Mourier on the folk-tales in Contes et légendes du Caucase (1888); and on modern history G. Baumgarten, Sechzig Jahre des kaukasischen Krieges (Leipzig, 1861). But a very great amount of most valuable information about the Caucasus is preserved in articles in encyclopaedias and scientific periodicals, especially the Izvestia and Zapiski of the Russian and Caucasian geographical societies, in P.P. Semenov’s Geographical Dictionary (in Russian, 5 vols., St Petersburg, 1863-1884), and in the Russkiy encyklopedicheskiy slovar (1894), and in the Kavkazskiy kalendar (annually at Tiflis). See also G. Radde and E. Koenig, “Der Nordfuss des Daghestan und das vorlagernde Tiefland bis zur Kuma” (Ergänzungsheft No. 117 to Petermanns Mitteilungen), and “Das Ostufer des Pontus und seine kulturelle Entwickelung im Verlaufe der letzten 30 Jahre” (Ergänzungsheft No. 112 of the same); by V. Dingelstedt in Scot. Geog. Mag.—”Geography of the Caucasus” (July 1889); “The Caucasian Highlands” (June 1895); “The Hydrography of the Caucasus” (June 1899); “The Riviera of Russia” (June 1904), “The Small Trades of the Caucasus” (March 1892); and “Caucasian Idioms” (June 1888). The best map is that of the Russian General Staff on the scale of 1 : 210,000 (ed. 1895-1901).
(J. T. Be.; P. A. K.)
[1] Exploration of the Caucasus (2nd ed., 1902), i. 30-31.
[2] Op. cit. i. 35-36.