400 Frof. R. Sjogren — Valleys of the Caucasus. 



fucoid impressions — the geological position of the whole complex 

 can only be determined indirectly. The petrographic features remind 

 one strongly of the Eocene formations in the Eastern Caucasus, and 

 the superposition upon limestone in the case of Nial-Dagh is 

 analogous to the superposition on Senonian white chalk in the other 

 instance. Moreover, the occurrence of stronglj' ferruginous clay- 

 slates both to the N. and S. of the eastern Caucasus is especially 

 characteristic of the Eocene period. At the northernmost end of 

 the two valleys, on the side of Baba-Dagh itself, there are thinly 

 laminated limestones raised at considerable angles. 



We will now turn to the structure of the ridge of mountains which 

 the channel of the Gerdiman-tschaj enters as it leaves the Lagitsch 

 valley. This ridge I have myself crossed on the way from Mudschi, 

 a village on the S.E. side, over to Lagitsch, as well as by the route 

 through the Gerdiman-tschaj gorge, in which the stratification is 

 very finely displayed. Eegarded as a whole, the Nial-Dagh ridge 

 consists of a colossal fold leaning over towards the S. and is mainly 

 composed of limestones and stratified eruptive tuifs. If we look 

 to the details we see that massive eruptive rocks, with the character 

 of basalt and andesite, also enter into the composition of the ridge. 



It must still be left an open question whether these eruptives 

 occur as dykes in the stratification or formed beds originally. 



As one ascends the slopes of Nial-Dagh from Mudschi, one passes 

 across a series of zones, which in petrographical respects differ 

 from each other distinctly. The series is as follows, beginning from 

 below : — 



1. Compact grey thin-bedded limestones, together with light grey crystalline 

 thick-bedded limestones, both of these alternating with soft stratified tuffs, 

 which are often much weathered. 



3. Eruptives varying from dark grey to a greyish-green together with the accom- 

 panying tuffs, the first forming compact rocks of andesitic and basaltic 

 character, which often split spheroidally, the latter being foliated or thinly 

 bedded. 



3. Dark grey shaly tuffs together with conglomerates and pudding-stones ; the 



pebbles of eruptive material or limestone ; the matrix calcareous or tuff-like. 



4. Light grey crystalline limestones in thick beds, with greyish green shaly and 



much weathered tuffs. 



5. Dark clay-slates, sometimes with green calcareous layers intervening ; in some 



of the conglomerate beds green grains are abundantly distributed and probably 

 come from disintegrated eruptive material. 



6. Light grey limestones and greyish green tuffs, as in 4. 



7. Thinly-laminated clay-slates, sometimes strongly ferruginous, in thin, reddish 



brown, sandstone-like beds, and with numerous veins of calc-spar. 



The whole of this complex of strata reaches a thickness of some 

 8250 feet. In 1 the dip was 65°-70° N.N.E,, and the strike 

 N. 60° W. ; in 4 the dip was 62°-65° N.E., while the strike lay 

 N. 45° E. At the pass (6600 feet) the strata of 7 stood vertically. 



I will now shortly state the observations I made during the 

 passage of the Gerdiman-tschaj gorge. The direction is N.E. to 

 S.W., the length about five miles, and to the S.W. the defile 

 increases in width, while the mountains decrease in height. 



At the entrance of the gorge, a little S. of Lagitsch, come first 

 the same clay-slates which occupy the greater part of the Lagitsch 



