Resumo

BEILINSON, Elisa. Evolución de la arquitectura fluvial en sucesiones del Plioceno-Pleistoceno del centro-este de Argentina (aloformación Punta San Andres). Rev. Asoc. Geol. Argent. [online]. 2012, vol.69, n.4, pp.578-595. ISSN 0004-4822.

The deposits of the Punta San Andrés Alloformation (Plio-Pleistocene) register the evolution of different styles of fluvial systems. During the first stage of this evolution, a mixed-load system was developed which included low-sinuosity channels and a high participation of floodplain deposits. During the second stage the system shifted towards a higher sinuosity, braided fluvial system where the floodplain deposits didn't have so much participation. Finally, the third stage was characterized by the development of a classic braided fluvial system, without any preservation of floodplain deposits. During the Punta San Andrés Alloformation accummulation, glaci-eustatic changes and climate exerted a fundamental control on the balance between generation of accommodation space rate and sedimentary supply. Nevertheless, comparative analysis of the diverse indicators (fluvial architecture, paleosols, etc.) has shown a strong variability for the studied depositional systems that can be assigned to different process hierarchies. In this way, fluvial aggradational cycles are represented by high-frequency alternation between calcic and vertic paleosols. In this case, base level fluctuations were responsible for the cyclic accommodation rate - sediment supply change. The evolution of the identified depositional systems can be assigned to higher-order cycles, which controlled drainage design by changes in accommodation space and represents changes in the rate of generation of accommodation space linked to glaci-eustatic changes at a global scale.

Palavras-chave : Fluvial architecture; Controls; Pliocene; Pleistocene; Argentina.

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