26 



SECOND YAEKAND MISSION. 



die of it are situated the forts Mirza-terek and Chakmak, some ten miles distant from each 

 other. The southern portion of this range consists at its base of undulating layers of 

 greenish or purplish shales, overlain by dark-coloured, mostly black, limestone in thick and 

 thin strata, the latter being generally earthy. The limestone occupies all the higher elevations, 

 and, as is generally the case, greatly adds to the ruggedness of the mountains. About 5 

 miles north of Chung-terek, I found in a thick bed of limestone an abundance of Megalodon 

 triqueter, a large Pinna, a Spiriferina of the type of S. stracheyi, blocks full of Lifho- 

 dendron corals, and numerous sections of various small Gastropoda, Thinner layers of the 

 same limestone were full of fragments of Crinoid stems, and of a branching Ceriopora, the 

 rock itself bearing a strong resemblance to the typical St. Cassian beds. In this place the 

 shales, underlying the limestone, were partly interstratified with it, in layers of from 5 to 

 10 feet; and from this fact it seems to me probable that they also are of triassic age, 

 representing a lower series of the same formation. 



Proceeding in a north-westerly direction, the Megalodon limestones are last seen near 

 Mirza-terek. From this place the greenish shales continue for a few miles further on, much 

 disturbed and contorted ; and at last disappear under a variety of dark-coloured shales, 

 slates, and sandstones, with occasional interstratified layers of black, earthy limestone. The 

 strike of the beds is from east by north to west by south, and the dip either very high to 

 north or vertical. At Chakmak the river has cut a very narrow passage through these almost 

 vertical strata, which rise precipitously to about 3,000 feet, and to the south of the fort 

 appear to be overlain by a lighter-coloured rock. It is very difficult to say what the age of 

 these slaty beds may be, as they seem entirely unfossiliferous, and we can at present only 

 regard them as representing, in all probability, one of the paleozoic formations. 



About 5 miles north-west of Chakmak a sensible decrease in the height of the range 

 takes place, and with it a change in the geological formation. The paleozoic beds, although 

 still crossing the valley in almost vertical strata, become very much contorted ; while, uncon- 

 formably on them, rest reddish and white sandstones and conglomerates, regularly bedded, 

 and dipping to north-west with a steady slope of about 40 degrees. The rocks, though 

 evidently belonging to a comparatively recent (casnozoic) epoch, appear to be much altered 

 by heat, some layers having been changed into a coarse grit, in which the cement has almost 

 entirely disappeared. I have not, however, observed any kind of organic remains in them. 

 A little distance further on, they several times alternate with successive, conformably bedded, 

 doleritic trap. The rock is either hard and compact, being an intimate, rather fine-grained 

 \ mixture of felspar and augite in small thin crystals, or it decomposes into masses of various 

 '< greenish and purplish hues, like some of the basic greenstones. 



After leaving the junction of the Suyok and Toyanda (or Chakmdk) rivers, and turning 

 northwards into the valley of the latter, the panorama is really magnificent. Shades of white, 

 red, purple, and black compete with each other in distinctness and brilliancy, until the whole 

 series of formations appears in the distance capped by a dark-bedded rock. 



Although, judging from the greater frequency of basaltic boulders, we already knew 

 that this rock must be found further north, we hardly realised the pleasant sight which 

 awaited us on the march of the 4th January, after having left our camp at Gulja, or Bokum- 

 bashi. The doleritic beds increased step by step in thickness, and after a few miles we 

 passed through what appeared to be the centre of an extensive volcanic eruption. Along the 

 banks of the river columnar and massive basalt was noticed several times, with occasional 

 small heaps of slags and scorise, among a few outcrops of very much altered and disturbed 



