30 MALLET: GEOLOGY OF DARJILING AND WESTERN DUARS. 



doubt a bed intercalated in the slates, like the talc schist of the Pagli 

 naddi. 



Impure, thin-bedded limestone, covered by flaggy quartzite, is exposed 

 at the mouth of the Basra gorge ; and in the Alaikuri there are green 

 and dark-grey slates, passing into, and interbanded with, flaggy quartzite. 

 Near the head of the river a thick band of quartzite is crossed twice ; 

 whether the same repeated is uncertain. It is coarsely cleaved at a 

 high angle to the bedding. Blocks of a conglomerate, composed of flat 

 rolled pebbles lying parallel to the bedding, mostly of white quartzite in 

 a purple arenaceous matrix, are common in the Alaikuri, as in some other 

 streams to the west, but I did not see the rock in situ : it comes, however, 

 from near the head of the gorge. Blocks of gneiss and mica schist form 

 most of the debris above the 38th boundary mark, coming down from 

 the Gechijo ridge. 



There is a rock sometimes met with (as in the Raimatang naddi) 

 amongst the impure calcareous beds of the series, which consists of 

 interbanded layers of dolomite, varying in color from dirty white to dark 

 red,* red jasper, and thin seams of micaceous iron, and including besides, 

 irregular seam-like nests of quartz mixed with chlorite. The rock varies 

 from one in which the dolomite and jasper are interbanded in irregular 

 layers of \ or J inch thick or more, to an impure dolomite merely con- 

 taining seams and nests of jasper, &c. The alternations show well the 

 sharp foldings on a small scale, which are common in the Baxas. The 

 rock is a subordinate one, and has no connection with the great dolomite 

 band. Large blocks of hornblende rock are also brought down by the 

 Raimatang. 



None of the streams west of Baxa bring down boulders from the 

 dolomite band, which, however, re-appears in full force in the Jangti. The 

 stream flows in this part of its course, through a narrow rocky gorge 

 encumbered with huge blocks of stone fallen from the sides, down which 



* The color-giving iron is in the state of peroxide, and hence the rock is a ferruginous 

 dolomite, not a true ankerite. 



( 36 ) 



