Palynostratigraphy and paleoclimatic inferences of the Balbuena and Santa Bárbara subgroups (Salta Group Basin, Cretaceous-Paleogene): correlation with Patagonian basins.

NARVÁEZ, P.; VOLKHEIMER, W,

Cenozoic Geology of the Central Andes of Argentina

SCS Publisher

Lugar: Salta; Año: 2011; p. 283 - 300

A review of the existing palynologic records corresponding to the K/T boundary and Paleogene of the Salta Group Basin (Balbuena and Santa Bárbara subgroups) is presented. Palynostratigraphic and paleoclimatic conclusions are drawn with all the data available. For the base of the Lecho Formation (Late Senonian), tropical environments are inferred from the assemblages. While the sedimentology of the Yacoraite Formation indicates marine environments at the time of accumulation, mixed conditions of fresh and saline water are inferred from the palynoflora in some areas of the basin. During the deposition of the Olmedo/Tunal formations (Danian), the climatic conditions were subtropical warm and humid, similar to the existing in the modern Yungas Transitional Forest. During the accumulation of the Mealla and Maíz Gordo Formation, a tendency towards less humid conditions is reflected by the presence of communities characteristic of subarid environments. Retraction of the ulmacean forests is inferred by the reduction in the Verrustephanoporites simplex percentages. In the Middle to Late Eocene, the palynologic assemblages of the Lumbrera Formation reflect a temperate and relative more humid climate. Palynostratigraphic data of the Salta Group Basin are compared with those from the Paleogene of the San Jorge, Colorado and Ñirhuau basins, and a discussion on the climatic evolution in Argentina is presented. During the Upper Cretaceous and the Paleocene, a subtropical vegetation was present in southern and northern Argentina; the ulmacean forest extended up to the San Jorge Basin. In the Early Eocene, the Patagonian flora was replaced by mixed floras while in northwestern Argentina the subtropical vegetation persisted. From the Middle Eocene onwards, the Nothofagidites records notably increase in the palynologic associations of southern Argentina, coincident with a process of aridization and cooling. The assemblages in the Middle Eocene of the Salta Group Basin are characterized by a mixed paleoflora, although living under climatic conditions not as cool as in Patagonia.