Notes on the Geology of Guyana in Venezuela

Abstract

I. I ntroduction .—The observations on which this notice is based were made during a trip of some two months' extent in the latter part of last year, and though having reference to a small section of the province of Guyana, in Venezuela, yet are applicable to an extensive area. The leading geological features are presented in a line of section from the Orinoco, proceeding in a southerly direction; my examination extended to the newly discovered auriferous district of Caratal, distant about 140 miles in a right line from Las Tablas, on the Orinoco. A few words in elucidation of the physical features of the country, will assist the reader in tracing out the leading geological characteristics of Guyana. Skirting the Orinoco are the Llanos ; these, as elsewhere, are characterized by a growth of coarse grass, Cyperacœ , and shrubby trees, the chief of which, and often the only species, is the chaparro ( Curtella Americana ); the soil is of the poorest description, being a loose sand, highly absorbent and of great heat-radiating power. At the distance of fifteen miles or so from the river, the land rises into scarped, low, more or less wooded heights, constituting the serranos , interspersed with grassy slopes and plains. These serranos by easy gradations lead us on to the range of the Itacama Mountains, which trend east and west and attain an elevation of about 3000 feet. The range occupies a breadth of about sixty miles; and its southern slope is bounded by an undulating grassy plain presenting