Resumo

BOUZA, Pablo J. Paleosuelos en Cordones litorales de la formación Caleta Valdés, pleistoceno superior, noreste de Chubut. Rev. Asoc. Geol. Argent. [online]. 2014, vol.71, n.1, pp.1-10. ISSN 0004-4822.

The aim of this study was to evaluate the climatic and ecological changes recorded in the paleosols of Caleta Valdés Formation (Upper Pleistocene), and to determine the soil properties that can be used as paleopedological indicators. The study area is located in northeastern Chubut province (Península Valdés). The surficial stratigraphy presents three depositional units that were alternatively modified by pedogenetic processes. The most ancient paleosols (3Btkb-3Bkmb), formed in littoral gravelly deposits of the Pleistocene, present a higher pedogenetic Fe content, probably hematite, a dominance of smectite clays and lower δ13C y de δ18O contents, indicating a higher proportion of C3 plants and a seasonally contrasting, Mediterraneantype climate (xeric soil moisture regime). Considering that these littoral deposits could have been formed during MIS 5e, the paleosol might have been developed at the end of this interglacial isotopic stage. This paleosol was probably eroded and covered by sedimentary episodes, probably associated to periglacial processes of isotope stages 4-2. These deposits, along with the eolian deposits, were the parent materials of a new soil that evolved to a 2Btb-2Btkb-2Bkb-2Ck horizon sequence during a period of environmental stability. This pedogenetic event is probably associated to a more humid period, with a marked seasonality in the precipitations that occurred during the late Glacial- early Holocene, followed by a drier period and a temperature increase that was recorded in the region during the mid Holocene. The third pedogenetic event is represented by the A-C horizon sequences.

Palavras-chave : Horizontes argílicos; Carbonatos pedogenéticos; Hierro pedogenético; Isótopos estables; Costa Patagónica.

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