6o8 



NA TURE 



[Oct. 23, 1884 



THE NEW GEOLOGICAL MAP OF RUSSIA ' 



GEOLOGISTS will be glad to hear of the appear- 

 ance of the first sheet of the " Geological Survey 

 of Russia," published by the Geological Committee 

 on the scale of 10 versts to an inch. It comprises 

 nearly the whole of the Government of Yaroslav and the 

 eastern parts of Tver, between 57 o' and 57° 42' N. lat., 

 and 43 10' to 47° 40' E. long., corresponding thus to 

 Sheet 56 of the General Staff Map of Russia. This 

 region, which is watered by the Upper Volga, the Mologa, 

 and the Sheksna, is an undulating plain, the highest points 

 of which, close to Bejetsk, reach 700 feet above the sea- 

 level, gently sloping east and west to a level of from 350 

 to 420 feet. It has been dealt with first on account of a 

 series of geological explorations which have already been 

 made within its limits. It was visited by Blasius, Mur- 

 chison, Keyserling, and Barbot-de-Marny, and careful 

 explorations have been undertaken during the last few 

 years within the limits of the province of Yaroslav, under 

 the direction of its Provincial Assembly and Statistical 

 Committee, by MM. Schurovsky, Piktorsky, Eremeyeff, 

 Dittmar, Kryloff, and Nikitin. 



The map, which has been prepared by M. Nikitin, is 

 very carefully printed, and will be the more welcome to 

 European geologists as all important names and expla- 

 nations are given in French, side by side with the Russian 

 text. The colours and the explanatory letterpress are in 

 conformity with the recommendations of the International 

 Geological Congress. A quarto volume, in Russian, by M. 

 Nikitin, with plates and drawings, accompanies the map, 

 the whole being summed up in German at the end of the 

 volume. 



The first thing which strikes one on looking at the 

 map is the very great space covered with the gray colour 

 of the Quaternary deposits. A greenish patch of Jurassic 

 rocks in the middle of the map, several patches of Trias 

 on its borders, and a very small Carboniferous patch, 

 altogether hardly cover one-third of the surface ; the re- 

 mainder representing the " Boulder Clay, which conceals 

 deposits of unknown age." The thick sheet of Boulder 

 Clay will be for a long time the stumbling-block of Russian 

 geologists. Natural sections are found only on the banks 

 of the greater rivers, while the valleys of the smaller ones, 

 to their very bottom, are cut through Quaternary deposits. 

 Even the two railways that cross the space covered by the 

 map have been laid without excavations of any importance 

 to the geologist ; and no artificial excavations worthy of 

 notice are to be found in the whole area. 



As to the geological description which accompanies the 

 map, it is full of interest. The Carboniferous deposits 

 which are denuded over a very limited space in the 

 north-west, belong to the Upper series, characterised by 

 Spirifer mosquensis. They probably extend throughout 

 the region in nearly horizontal strata gradually inclined 

 towards the east ; but they are concealed by the Varie- 

 gated Marls which are the subject of so lively a contro- 

 versy among Russian geologists, and which are considered 

 by the author as belonging to the Trias, contrary to the 

 opinion of the Kazan geologists, who consider them Per- 

 mian. Although appearing on the surface only in isolated 

 islands, these Marls probably also extend throughout the 

 Yaroslav region ; the salt-springs at least, which appear 

 at many places, and which usually take their origin, in 

 Russia, either in the Devonian or in the Variegated 

 Marls, seeming to indicate a great extension of these de- 

 posits. The Jurassic formations appear now (as through- 

 out Middle Russia) only as sporadic islands, which are 

 remains of a widely-extended strata destroyed by denu- 

 dation ; the Jurassic sea, according to the author, extend- 

 ing at least as far north as the latitude of Tver. The 

 Jurassic deposits, which have been, like the Variegated 



' " General Geological Map of Russia." Sheet 56, Yaroslav, &c. »By 

 S. Nikitin. (Memoirs of the Geological Committee, vol. i. No. 2. * St. 

 Petersburg, 1884.) 



Marls, the subject of special monographs by M. Nikitin, 

 are represented in the Yaroslav region ; the lower ones 

 by the Callovian and the Oxford Clay, the two chief sub- 

 divisions of the former being characterised respectively 

 by Cadoceras Milaschevici and Quenstedioceras Leachi, 

 and those of the latter by Cardioceras cordatum and C. 

 allcnians. The Upper Jurassic is represented by the "Volga 

 Series," Lower and Upper, respectively characterised by 

 Peris phinctes virgatus, Oxynoticeras fulgens, and Olco- 

 stephanus subditus. They are invariably covered with a 

 sheet of sands (like the Jurassic of Central Russia), which 

 seems to have been a littoral deposit accumulated during 

 the retreat of the Jurassic sea. 



A very interesting chapter is devoted to the Qua- 

 ternary deposits of Yaroslav and Central Russia. The 

 thick sheet of Boulder Clay which covers Central and 

 North-West Russia, and contains erratics from Fin- 

 land and Olonetz, as also from those regions which 

 the erratics had to cross on their way from the north, 

 has long been a puzzle to Russian geologists. Within 

 the limits of the map, it appears with its usual cha- 

 racters, that is, those of a layer 8 to iom. thick, spread 

 without interruption over the country — over the water- 

 sheds as well as the valleys — without any traces of stratifi- 

 cation or even of striation by water : the thickest boulders 

 and the finest particles appearing closely mixed together 

 without bearing any traces of sorting by water-currents. 

 As to the boulders, they are of all possible sizes, from a 

 grain of quartz to masses 2 and 3 m. in diameter. While 

 crystalline rocks and schists from Finland and Olonetz 

 are prevalent, local boulders — Carboniferous and some- 

 times Jurassic — are also not absent, especially in the 

 lower strata. The boulders have a tendency towards a 

 disposition in ridges which run from north-west to south- 

 east, crossing the rivers, or rising sometimes in the shape 

 of moraines, or eskers of great size. A sheet of boulder- 

 bearing sand, with traces of stratification, appears at many 

 places beneath the Boulder Clay, which passes also in 

 its upper parts into an unstratified sand with boulders. 



Such being the character of these deposits, it is obvious 

 that the theory fails which tries to explain them by floating 

 ice, as does also Prof. Trautschold's theory of " Eluvium." 

 The author accepts, therefore, the theory now generally 

 adopted by geologists, and specially advocated for Germany 

 by Berendt, Penck, and Bernhardi, and for Russia by 

 P. Krapotkin, and considers the Russian Boulder Clay as 

 an equivalent of the Krosstenslera of Sweden. Like the 

 British Till, it is no doubt the bottom-moraine of the great 

 ice-sheet which covered Northern Germany and Russia, 

 without reaching the Ural Mountains, during the ice- 

 period. This period succeeded to a relatively mild 

 climate, when the plains of Moscow were covered with 

 thick oak and maple forests, inhabited by the mammoth 

 and the rhinoceros, which were compelled by the ice- 

 sheet slowly advancing from the north-west to emigrate 

 east and south. The Loess of Southern Russia, and the 

 Loess-like deposits of the intermediate region, were 

 probably contemporary with the glaciation of the north. 



Another chapter is devoted to the formation of rivers 

 in European Russia, and to the great processes of denu- 

 dation in the later parts of the Quaternary period. This 

 subject has been keenly discussed of late by Russian geo- 

 logists. The author is to be congratulated on the scientific 

 manner in which he has laid the basis for a discussion 

 of the three important questions — as to the Variegated 

 Marls, the Boulder Clay, and the more recent alluvial 

 deposits — with which he has had to deal in this first fasci- 

 cule of the Geological Survey of Russia. 



EARTHQUAKES 



'T'HOSE observers who have undertaken the detailed 



■*■ study of a region severely injured by an earthquake 



are well acquainted with the difficulties that attend on 



