THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE IV. VOL. III. 



No. II.— FEBRUARY, 1896. 



ORia-i:N\A_Ii ABTICLES. 



I. — On Dikes of Oligocene Sandstone in the Neocomian Clays 

 of the District of Alatyr, in Russia. 



By Dr. A. P. Pavlov, 



Professor of Geology in the University of Moscow. 



(PLATE V.) 



THE part of the province of Simbirsk lying to the north of Alatyr, 

 in the angle between the Soura and the Alatyr rivers, is formed 

 of Lower Cretaceous sh - ata, chiefly Neocomian clays, covered by 

 Boulder-clay (which is not rich in boulders), and part by Glacial 

 and iEolian sands. The same Neocomian clay expands widely to 

 the south and to the east from the town of Alatyr. Upon the 

 northern border of the Alatyr valley, and on the right side of the 

 Soura river, these clays are covered by ancient alluvial sands, 

 deposited probably at the time when the great ice-sheet dammed 

 the course of the Soura in the lower part of its valley, and caused 

 colossal overflowings of its waters, the traces of which are preserved 

 in the great masses of alluvial sands covered with fir wood, and 

 much resembling the " Haidesand " of Northern Germany. 



Only to the south-west of Alatyr, at a distance twenty kilom., 

 commences the region of the Upper Cretaceous beds, covered by 

 sands and quartz-sandstones without fossils, defined as Tertiary 

 from their resemblance to the Tertiary sands and sandstones of 

 the southern parts of the province of Simbirsk. A small outlier 

 of these sands is preserved also at a point to the north-west of 

 Alatyr at the same distance. 



I have been well acquainted with these general features of the 

 geological structure of the region since my geological researches in 

 this country in 1887. In 1892 I was once more in Alatyr, during 

 the construction of a bridge across the Soura river for the Moscow- 

 Kazan railroad. Mr. N. Th. Ditmar, a mining engineer then attached 

 to this railroad, had di-awn my attention to the sandstone brought 

 by the countrymen of a neighbouring village, Yavley, which they 

 found in a ravine ending in the Soura near this village. We went 

 with Mr. Ditmar to this ravine, which cuts, from west to east, the 

 high left border of the Soura valley, and I saw at a distance of 



DECADE IV. VOL. III. — NO. II. 4 



