Daniel Panario

The continental Uruguayan Cenozoic: an overview

Abstract Although Quaternary study in Uruguay was started in the 1970s, international diffusion of the results has been limited. This contribution is an updating of the continental aeolian and fluvial Cenozoic period, reinterpreted mostly from a geomorphological perspective. We discuss the limitations in the usage of chronostratigraphic generalizations in the Cenozoic based on a lithostratigraphic interpretation. The upper Pleistocene and the Holocene are reinterpreted through available 14 C dates, presenting a comparative preliminary table with the geological formations found in the neighbouring Argentine Provinces of Entre Rios and Corrientes.

The irruption of new agro-industrial technologies in Uruguay and their environmental impacts on soil, water supply and biodiversity: a review

In recent years, economic growth has produced a global change in the demand for food, fibre and energy supply. This has gone together with the globalisation of the agro-industrial production systems, leading to a qualitative change in land use because of intensive use of technological inputs. Uruguay, just as the other countries of the region, is part of this phenomenon. The massive introduction of forest crops has been made over native grassland ecosystems, replacing traditional productive activities of the post-colonial period. Research on eucalyptus afforestation shows depletion of the ecosystem services associated with grassland and loss of the resilience capacity of the system. Impacts on soil organic matter, soil physicochemical properties, the hydrological cycle and on biodiversity are analysed. This review (with emphasis on Uruguay and the River Plata Basin) tries to contribute to an integrated vision of the environmental consequences of current land-use change.

Land use change in a temperate grassland soil: afforestation effects on chemical properties and their ecological and mineralogical implications.

The current change in land use of grassland in the temperate region of South America is a process associated with the worldwide expansion of annual crops and afforestation with fast growing exotic species. This last cultivation has particularly been the subject of numerous studies showing its negative effects on soil (acidification, loss of organic matter and base cations, among others). However its effects on the mineral fraction are not yet known, as it is generally considered as one of the slowest responses to changes. This stimulated the present study in order to assess whether the composition of clay minerals could be altered together with some of the physicochemical parameters affected by afforestation. This study compares the mineralogical composition of clays by X-ray diffraction (XRD) in a grassland soil (Argiudolls) under natural coverage and under Eucalyptus grandis cultivation implanted 25 years ago in a sector of the same grassland. The tendency of some physicochemical parameters, common to other studies was also compared. XRD results showed, as a most noticeable difference in A(11) and A(12) subhorizons (~20 cm) under eucalyptus, the fall of the 10Å spectrum minerals (illite-like minerals), which are the main reservoir of K in the soil. Meanwhile, the physicochemical parameters showed significant changes (p<0.01) to highly significant ones under eucalyptus, particularly in these subhorizons, where on average soil organic matter decreased by 43%; K(+) by 34%; Ca(2+) by 44%, while the pH dropped to this level by half a point. Our results show that the exportation of some nutrients is not compensated due to the turnover of organic forestry debris; the process of soil acidification was not directly associated with the redistribution of cations, but with an incipient podzolization process; the loss of potassium together with soil acidification, leads to a drastic change in clay mineralogy, which would be irreversible.

Ancient Landscapes of Uruguay

In this chapter, based on the available geological information, a model for the genesis and evolution of the Uruguayan landscape is proposed. A structural framework of the landscape evolution is provided and the record of such evolution in the most representative geological units is considered. A brief summary of the Uruguayan geology and its location in the regional context is performed, from Precambrian to Cenozoic times.