Renato R. Andreis
2015 Publicación Electrónica de la Asociación Paleontológica Argentina  
The evolution of the continental and marine Cretaceous basins of Patagonia and adjacent areas (Chilean marine strip, basins developed around the Malvinas Islands, and the austral extremity of South America) is here considered, taking into account their origin, lithofacies, sequences, fossiliferous content, and paleoclimatic changes. An attempt to separate three stages of evolution, with transitional limits, has been made: 1) Early rift-syn-rift (Mid Jurassic-Barremian): 2) Thermal sink (sag
more » ... e), and increased continental sedimentation (Aptian-early Maastrichtian), and 3) The late Cretaceous transgression (late Maastrichtian-Paleocene). The first stage, during the late Triassic-Late Jurassic tectonism, produced extensional faults of regional extent with EW orientation, related to the opening of the southern Atlantic Ocean. Also a marginal basin (Magallanes or Austral basin) was sketched between the active magmatic are and the stable platform with a NNW coast controlled by the Deseado Massif (Valanginian-Aptian). After the Initial Mirano events (Early Barremian) a westward regression occurs. In the San Jorge basin a progressive migration of the lacustrine depocenters to the East, and in the western and southern margins of the Magallanes basin the deposition of deeper slope and pelagic facies, related to ophiolithic magmatism occurred. Between the Initial and Middle Mirano movements (base of the Aptian) another magmatic cycle started on the western magmatic arc, throwing ashes into the San Jorge basin. Simultaneously, erosion of the faulted margins of this basin caused the progradation of fan deltas into the lacustrine sediments (Matasiete Fm.) and in NW Patagonia the sea invaded the Neuquén basin, with the deposition of deep marine anoxic shales, limestones, and submarine fans (Tithonian-Berriasian). This anoxic character is also common in the Malvinas, Magallanes and even the African basins. During the second stage, the Malvinas, North Malvinas and Magallanes basins include retrogradational and aggradational su [...]
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