26 
SECOND YARKAND 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 Litho- 
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. Erom 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 he overlain by a lighter-coloured rock. It is very difficult to say what the age of 
these slaty beds may he, as they seem entirely unfossiliferous, and we can at present only 
regard them as representing, in all probability, one of the palaeozoic 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 palaeozoic 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 ocks, though 
evidently belonging to a comparatively recent (caenozoic) epoch, appear to be much altered 
by heat, some layers having been changed into a coarse grit, in which the cement has a lm ost 
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 Chakmak) 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, wc hardly realised the pleasant sight which 
awaited us on the march of the 4th January, after having left our camp at Gulja, or Bokum- 
hashi. The doleritic beds increased step by step in thickness, and after a few miles we 
passed through what appeared to he 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 scoriae, among a few outcrops of very much altered and disturbed 
