Hydromorphic paleosols in the upper Puesto La Paloma Member, Cerro Barcino Formation, mid Cretaceous, Patagonia Argentina: environmental and stratigraphic significance

KRAUSE, J.M.; UMAZANO, A.M.; BELLOSI, E.S.; WHITE, T.S.

Puerto Madryn

Otro; XIV Reunión Argentina de Sedimentología; 2014

Asociación Argentina de Sedimentología

A series of stacked hydromorphic paleosols have been recognized in the upper part of the Puesto La Paloma (PLPM) and the lower part of the Cerro Castaño (CCM) Members (Cretaceous Cerro Barino Formation)within the Somuncurá-Cañadón Asfalto basin, north-central Chubut Province. For this contribution, two localities are considered: La Juanita and Tres Cerros. The PLPM, up to 42 m thick, is mostly composed of tabular, greenish, tuffaceous beds. It mainly constitutes the record of unconfined flow deposits, subordinated fluvial channels, along with shallow lacustrine and eolian deposits. The CCM, up to 215 m thick, is composed of brownish to reddish tuffaceous sandstones and mudstones, deposited in fluvial channels and extended sandy floodplains. Paleosols are present along both units, but are more frequent and show a stronger degree of development close to the member contact, which is transitional. This interval is also relevant because frequent dinosaur remains are found here. The studied paleosols are located in the uppermost section (10-16 m) of the PLPM, of Albian age. Seven types of paleosols were recognized, all of them developed in fine to very fine, tuffaceous sandstones (Table 1, Fig. 1). Geochemical analyses of these paleosols displays the following values:Al2O3/bases