Resumo

ODINO BARRETO, Andrea L et al. Sedimentology of the shallow marine deposits of the Calafate formation during the Maastrichtian transgression at Lago Argentino, Austral-Magallanes Basin, Argentina. Lat. Am. j. sedimentol. basin anal. [online]. 2018, vol.25, n.2, pp.169-191. ISSN 1851-4979.

The Maastrichtian shallow marine deposits exposed at the south margin of the Lago Argentino within the Austral-Magallanes Basin are known as the Calafate Formation. In order to interpret the depositional systems and reconstruct the se­quence stratigraphic architecture for this unit at its type locality (Cerro Calafate), we acquire new data from seven stratigraphic sections. We recognized six facies associations (FA-1 to FA-6) corresponding to shallow marine deposits, which are organized vertically displaying a transition from shallower to deeper conditions, representing a ~90 m thick transgressive succession. The Calafate Formation de­posits are differentiated into a lower wave-dominated coast (FA1, FA2 and FA3) and an upper tide-dominated coast (FA4, FA5 and FA6), each marked by the domi­nance of wave and tidal sedimentary processes, respectively. The Calafate Forma­tion overlies the fluvial deposits of the Chorrillo Formation by a transgressive sur­face (TS), which is overlaid by a transgressive marine succession characterized by a retrogradational stacking pattern. The latter is finally covered by offshore transition marine deposits marking a progressive deepening of the depositional system that culminates with the maximum flooding surface (MFS). From here, an aggradational stacking pattern dominates the upper sandstones of the unit repre­senting the highstand systems tract (HST), which is interpreted to be the cause of short-term periods when the accommodation space rate was nearly equaled to the sediment supply rate during the Maastrichtian.

Palavras-chave : Upper Cretaceous; Facies analysis; Transgressive infill; Wave and tidal systems; Austral-Magallanes basin.

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