The Lower Exfieqidho River and Cuyiml River District. 131 



The Arimu — The Arimu Creek falls into the Cuyuni River on its 

 right bank about a mile west of Wariri. The rocks first seen in this 

 creek near its mouth are contorted mica-schist. About a mile from the 

 mouth masses of epidiorite occur, and other exposures are seen about a 

 quarter of a uiile further on. At a small rapid about fift}^ yards above 

 these exposures, the inassive epidiorite gradually changes to a foliated 

 rock, and is succeeded by somewhat basic gneiss. About two miles 

 from the mouth of the creek its course is interrupted by a low cataract. 

 This is caused by a belt of compact hornblende-schist, containing 

 abundant small grains of pyrites. It is intersected in places by veins 

 of quartz, varying from mere films to tongues three or four inches in 

 breadth. 



The belt of hornblende-schist giving rise to the cataract, and the 

 exposures of basic rock lower in the Arimu, are jn'obably off-sets from, 

 or are connected with, the Wariri amphibolite. 



Exposures of granitite-gneiss are seen about a ([uarter to half a mile 

 above the cataracts. 



About two miles above the cataracts other exposures of granitite- 

 gneiss occur, and continue at intervals until near Benjamin's Creek. 

 During the fifteen miles above this there are no exposures of rocks, the 

 banks of the creek being usually low, and consisting of white feldspathic 

 clays. About two miles above Benjamin's Creek the Arimu cuts througli 

 some low hills of deep-red clay, having a well-marked foliated structure. 

 These appear to be spurs of low hills, running more or less parallel 

 with the banks of the Cuyuni River. The red clays are residues from 

 the decomposition of epidiorites or hornblende-schists. About half a 

 mile to a mile below the junction of the Little Arimu there are 

 exposures of banded granitite-gneiss. Near the junction the creek 

 cuts through a hill of red clay, similar to those seen in the lower part 

 of its course. 



A few exposures of gneiss occur in the Little Arimu Creek. The 

 countr}?- traversed by the Arimu appears to be mainly a gneissose one, 

 with, here and there, belts of basic intrusives, probably the sources of 

 the gold in the placer-gravels near its banks. 



