Abstract
Much of the Phanerozoic Andean mountain chain is floored by Precambrian basement1–3, in places as old as 2,000 Myr4,5, but relations between these rocks and those of the Brazilian Shield have long been obscure, mainly because of the intervening Cenozoic sedimentary cover. We describe here recent work over the Bolivian sector of the Brazilian Shield (Fig. 1) which shows a pattern of Proterozoic mobile belts approximately parallel with the Andean chain to the west. When the trends of these Bolivian belts are projected towards the Andes under the Cenozoic cover, their ages broadly accord with those of the Andean basement. Our interpretation is that the two domains are linked in the form of a chain of five Andean-trending mobile belts with a combined width of ∼1,000 km, becoming progressively younger to the west with ages ranging from 1,300 Myr to the present.
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