Abstract

A preliminary correlation scheme of the upper Paleozoic sequences and their relationships with lower Mesozoic strata is proposed as a basis for interpreting the paleogeography and paleoclimates of the continent. Stratigraphic, biochronologic and radiometric data indicate that the upper Paleozoic and lower Mesozoic sequences are separated by an unconformity in the Andean region. Chronological uncertainties and/or conformable stratigraphic relationships make a separation of upper Paleozoic and Triassic sediments more difficult to trace in the southern subandean part of Bolivia, Precordillera of Argentina, in the Parnaiba Basin and parts of the Brazilian portion of Parana Basin.

Uppermost Permian and lowermost Triassic sediments are virtually absent from South American sedimentary basins and so the boundary can be discussed in only the broadest of terms. The paleogeographical and paleoclimatological development of South America are compared with the history of reassembled Gondwana continents during the upper Paleozoic and lower Mesozoic, and although a general similarity is indicated, a few points deserve further study.

The upper Paleozoic glaciation that affected South America started in the Early Carboniferous and ended rather abruptly in the Andean region, after Late Carboniferous time, but a glacial climate still prevailed locally during the Early Permian in parts of the Parana Basin. Starting in the Early Permian the climate became warmer and more arid conditions prevailed into the Late Permian and Triassic.