Sedimentological maps of the typical loessic units in North Pampa, Argentina

Abstract

Application of grain size data allowed the construction of maps of two typical loessic formations of North Pampa . A Sand Sea covering the central Argentine plain and a Peripheral Loess Belt to the northeast, compose the Pampean Aeolian System. A region of 20,000 km 2 in the Loess Belt (Santa Fe and Córdoba provinces) was studied. Thick loess outcrops are located in this region. The Tezanos Pinto Loess, Upper Pleistocene-Lower Holocene in age, and the San Guillermo Fm, Late Holocene in age, are analysed in this article. The silt content has been taken as the main parameter for mapping. In general, the pattern of the isoplethic curves is similar in both maps. These maps show that the silt content in both loessic units progressively increases from SSW to NNE. In the Loess Belt, the silt content increases from 55 to 60% in the SSW (at the transition belt to the Sand Sea) up to 75–80% in the NNE (along a distance of 120–200 km). Other sedimentological data of the outcropping loess-paleosols sequences are presented as complementary information.