CHAPTER XIII. 



THE LOWER ESSEQUIBO RIVER AND CUYUNI RIVER 



DISTRICT. 



The northern part of this district resembles generally the corresponding 

 part of the North-western District, and offers few features of geological 

 interest. 



The most northerly large tributary — the Supinaam Creek — of the 

 Essequibo River is on its left bank, and its general geology is thus 

 described by J. G. Sawkins : — 



" On the Supinaam Creek, about the Mission of Indiana, the land 

 rises nearly 50 feet, the creek divides into many streams near the rapids, 

 and numerous small islands are formed by deposits accumulated on the 

 rocks, and now sustain a forest vegetation. These I'ocks, as well as 

 those on the banks of the creek, are covered with a considerable 

 thickness of decomposed granite, or rocks of the granitic family. Quartz 

 occurs as aggregate pieces of conglomerate, cemented by red, white, or 

 pink clay. Where the clays are separated from the sands they are 

 mottled or streaked with red lines of oxide of iron, appearing to follow 

 the lines of siliceous matter by a process of segregation. Sands increase 

 ascending the creek, and occur, in many instances, without any 

 argillaceous admixture." 



A few prospecting expeditions have reported finding colours of gold 

 in the gravels of this creek. The higher ranges of land in the upper 

 parts of its course probably represent oflt-sets from the northern 

 extremity of the Blue Mountain range. 



About 20 miles south of the mouth of the Supinaam Creek the 

 Groete Creek falls into the Essequibo, on its left bank, in a part of the 

 river characterised by the occurrence of extensive sandbanks, no rocks 

 being exposed near its mouth. There are, however, some masses of 

 quartz on the west or left bank of the Essequibo near Rock Island, 

 about 9 miles north of the mouth of the Groete Creek. 



The most northerly exposures of rock on the Essequibo River are 

 near the left bank of the Ithaka Creek, which falls into the Essequibo 

 River on its right bank about 4 miles south-east of the mouth of the 

 Groete Creek. Great masses of a banded feldspathic gneiss of massive 

 texture are exposed in the bush, while exposures of the same rock are 

 seen on the right bank of the river near the Cable Station, and below 

 Mr. Wilkie's house at Ithaka. The rocks were, at some previous time, 

 quarried by blasting, and large quantities of them removed for use in 

 the sea-defences on parts of the coast of Demerara. The close-textured 

 massive rock, of various shades of pink and olive-green, is one of 



