Descripción: The continental deposits found in southern and western Uruguay show important climatic changes along the Cenozoic. The sequence begins with Paleocene palustrine carbonates known as the Queguay Formation, associated with calcretes of phreatic origin which developed mainly on fluvial sediments of Mercedes Formation (Late Cretaceous), and indicates a semiarid climate, seasonally contrasted. The Asencio Formation (Early Eocene) is separated from Mercedes Formation by the Yapeyu paleosurface, limiting two sedimentary cycles. Fluvial deposits lies above this surface, on which Ultisols developed under a warm and humid climate; periods of intense dryness would provoked their induration and formation of ferricretes, which under subsequent increased precipitation were dismantled. Above, Fray Bentos Formation (Oligocene-Early Miocene) lies unconformably. It is composed by loessic sediments deposited in a semiarid climate, paleosols and diverse pedogenic calcretes developed on these sediments, among which a new type named tubular calcrete, are here described; in the latter the tubular units are related to a coarse prismatic structure derived from shrink-swell processes and the surface morphology of this calcrete refers to a gilgai microrelief, typical for Vertisols. The pedogenic calcretes point to a seasonal semiarid climate. The Raigón Formation (Late Pliocene- Middle Pleistocene) of fluvial origin was formed in a humid period, and shows a paleosol at the top developed in a seasonally contrasted climate. Lying unconformably, the Libertad Formation (Early to Middle Pleistocene) is composed by loesses deposited during glacial periods that were subsequently modified by pedogenesis during interglacial periods.

Descripción: In 1833 during his journey across the Buenos Aires Pampas, Charles Darwin made observations that reflected his thoughts on two major landscape units, Pampa interserrana and Pampa deprimida, later identified by other authors. Darwin grouped the Pampean sediments into a single unit, the Pampean Formation, based upon the lithological homogeneity and the large extension of the deposits; the unit was thought to be of estuarine-marine origin and attributed 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 pedosedimentary sequence due to the ubiquity of pedogenetic features throughout the deposits. Four main subcycles of sedimentation are identified related to reactivations of the Pampean landscape. At a regional scale, the outcrop distribution of Pampean sediments of different ages suggests the dominance of more stable conditions since the late Miocene-Pliocene in a vast area of Pampa interserrana, documented by the formation of calcretes. However, sedimentation during the late Pliocene-Pleistocene was active within the domain of the Salado tectonic basin and Sierras de Tandil. The regional disparity shown by the Pampean stratigraphic record reveals the major morphostructural differences of its basement.

Descripción: Pedosedimentary processes, recorded in a late Quaternary section near Zarate city, north Buenos Aires province are reconstructed in this study. Both field features and laboratory results were analyzed as a whole. Grain size, sand, silt and clay mineralogy, micromorphology, Rb and Sr concentrations, optical stimulated luminescence (OSL) ages as well as preliminary paleomagnetic analysis were performed in order to get a detailed information on processes involved. All studied paleosols were developed on loess horizons. Four definite breaks in sedimentation and a coupled development of paleosols were observed. On this basis four units showing different types of calcretes were defined. Welded paleosols at unit C, could be correlated to those studied at Baradero (Buenos Aires province) and Lozada (Córdoba province), which probably record the last interglacial stage before present, the Marine Isotopic Stage 5 (MIS5), studied on marine cores. The highest values of Rb/Sr ratio reflect changes due to chemical weathering processes and generally match paleosol levels occurrences. Development of ground water-related and pedogenic calcretes, as well as their association to smectite, illite and ferric oxide indicate drier weather conditions than present and strong seasonality. Finally, a tentative correlation between one of the paleosols and the marine isotope stage 11(MIS 11) is suggested.