Cretaceous paleogeography of southern South America

Abstract

During Berriasian-Hauterivian times the Andean regions north of 38°S and south of 42°S were occupied by two magmatic island arcs and two back-arc marine basins, the Andean and Austral Basins. At the same time the Chubut Basin of central Patagonia was being filled with continental sediments. In northern Argentina and Bolivia, the Aimara Basin began to develop with deposition of continental sediments intercalated with basaltic rocks. In northeastern Argentina, Paraguay, Uruguay and southern Brazil, a series of basins formed in Precambrian-Paleozoic basement were the site of continental sedimentation and eruption of basic flows. In Barremian-Cenomanian times the uplift of the Cordillera Principal of Argentina and Chile began and a general regression occurred in the Andean and Austral Basins. Continental sedimentation prevailed in the Chubut Basin of central Patagonia, as well as in all other basins of central-northern, and eastern Argentina and southern Brazil. In Bolivia a shallow marine transgression occurred during Cenomanian time. And in the Santos Basin of southern Brazil a proto-oceanic stage is represented by Aptian evaporites. In (Turonian-Coniacian) Santonian-Campanian times most of the Andean area was uplifted and thick volcanic and volcanoclastic sequences were accumulated in a series of restricted continental basins along the Andes of central and northern Chile. In the easternmost areas, south of 33°S, red continental sediments were deposited. In the Austral Basin marine sedimentation was restricted to the southern part. Most of the Parana Basin was emergent, although in the northern areas continental sedimentation continued. In northern Argentina and Bolivia continental sediments with interbedded basalts and shallow marine deposits were accumulated. The Atlantic basins of southern Brazil were characterized by marine sedimentation, and the Salado Basin was the site of continental deposition. In Maastrichtian time sedimentation was discontinued in the continental basins of west-central Argentina and central and northern Chile, although volcanism was still active. The marine area of the Austral Basin became more restricted. A large region of northern Patagonia, northeastern Argentina and Bolivia were covered by a shallow sea, and some restricted marine basins were developed on the coast of central Chile. Marine sedimentation was also continuous in the Atlantic basins of southern Brazil and central Argentina. Continental deposition was restricted to central Patagonia and the intracratonic Parana Basin of southern Brazil. There was a correlation between diastrophism, magmatic activity and global cycles of sea level changes. Contemporary regression existed in areas, such as the Andean Basin, where tectonic vertical movements were greater than eustatic changes of sea level. The Cretaceous flora is mostly known from Patagonia. Lower Cretaceous invertebrates are mostly known from west-central Argentina, whereas Upper Cretaceous invertebrates are almost exclusively known from southern Patagonia. Vertebrates are better known from continental Upper Cretaceous strata of central-northern Patagonia and southern Brazil. The Cretaceous climate north of 43°S was characterized by warm and extremely arid conditions. South of this arid belt was an area with temperate and humid climate.