The Caribbean mountain system, northern South America; A summary
The major tectonic features of northern South America (Fig. 1) are depicted in detail in the tectonic map compiled by Martin (1978), a regional synthesis presented by Bellizzia and others (1981), and a classification of tectonic provinces by Case and others (1984). One of the most prominent features is the Precambrian Guyana shield, a large cratonic block around part of which the Phanerozoic basins and mountain systems are developed. The shield consists mainly of metamorphic and igneous rocks but also includes substantial areas of unmetamorphosed sedimentary and volcanic rocks. Isotopic ages for rocks of the Guyana shield indicate that major geologic events took place between 3.4 and about 1.0 Ma.
The region that extends from the exposed shield to the western Andes, including the Llanos and the Amazonas, was part of the South American craton, at least since the beginning of Paleozoic time (Restrepo and Toussaint, 1988). Proterozoic rocks now form the cores of the major mountain ranges of the Andes, the Sierra de PerijÃ¡ and the Sierra Nevada de Santa Marta. In the GarzÃ³n massif, Colombia, these rocks date from 1,800 to 1,180 Ma (Restrepo and Toussaint, 1988).
Paleozoic sedimentary, metamorphic, and igneous rocks are exposed in the Andes, PerijÃ¡, and Santa Marta regions, and small parts of the Caribbean mountain ranges and are known at the subsurface in the basins that separate these mountains from the shield. The Paleozoic sedimentary sequence varies, even in places as close as the Venezuelan Andes, the Cordillera Oriental (Colombia), and Sierra de PerijÃ¡.