View of The Amazonas region of southeastern Colombia is underlain by the western part of the Guiana Shield. Isotopic age measurements are reported on granites and gneisses of the shield basement, mafic intrusives, and a sequence of rhyodacitic lavas overlying the

Return to Article Details The Amazonas region of southeastern Colombia is underlain by the western part of the Guiana Shield. Isotopic age measurements are reported on granites and gneisses of the shield basement, mafic intrusives, and a sequence of rhyodacitic lavas overlying the Download Download PDF