Resumo

ZARATE, Marcelo  e  FOLGUERA, Alicia. On the formations of the Pampas inthe footsteps of Darwin: south of the Salado. Rev. Asoc. Geol. Argent. [online]. 2009, vol.64, n.1, pp.124-136. ISSN 0004-4822.

In1833 during his journey across the Buenos Aires Pampas, Charles Darwin madeobservations that reflected his thoughts on two major landscape units, Pampa interserrana and Pampa deprimida, later identified byother authors. Darwin grouped the Pampean sediments into a single unit, the PampeanFormation, based upon the lithological homogeneity and the large extensionof the deposits; the unit was thought to be of estuarine-marine origin andattributed to the Recent Epoch considering the paleontological content(vertebrates and mollusks). At present, the Pampean sedimentary succession,which accumulated approximately during the last 11-12 Ma, is interpreted as a pedosedimentarysequence due to the ubiquity of pedogenetic features throughout the deposits.Four main subcycles of sedimentation are identified related to reactivations ofthe Pampean landscape. At a regional scale, the outcrop distribution of Pampeansediments of different ages suggests the dominance of more stable conditionssince the late Miocene-Pliocene in a vast area of Pampa interserrana, documented by theformation of calcretes. However, sedimentation during the latePliocene-Pleistocene was active within the domain of the Salado tectonic basin andSierras de Tandil. The regional disparity shown by the Pampean stratigraphicrecord reveals the major morphostructural differences of its basement.

Palavras-chave : Charles Darwin; Pampeansediments; Calcrete; Geomorphology; Buenos Aires.

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