INVESTIGADORES
ZARATE marcelo Aristides
artículos
Título:
Composition and provenance of Late Pliestocene-Holocene alluvial sediments of the eastern Anden piedmont
Autor/es:
ADRIANA MEHL; ADRIANA BLASI; MARCELO ZÁRATE
Revista:
SEDIMENTARY GEOLOGY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2012 vol. 280 p. 234 - 243
ISSN:
0037-0738
Resumen:
The Andean cordillera, and its piedmont in the central western Argentina, has been long considered as one of
the main source areas of detritus for the Chaco?Pampean plain sand dune fields and loess/loess-like deposits
of central Argentina. The main goal of this study is to evaluate the composition of the late Pleistocene-
Holocene alluvial deposits of the Andes cordillera piedmont, from 33° to 34° S. The results are interpreted
in the context of the regional geology, tectonic setting of the study area and its implications in the
continent-wide perspective of modern alluvial sands proposed by Potter (1994). Sampling was conducted
at the alluvial stratigraphic sequences of four study sites along three Andean piedmont arroyos; modal
mineralogy in the very fine sand fraction (3 phi to 4 phi) was determined using standard petrographic microscope
methods.
Q:F:LF average compositions indicate that the Late Pleistocene-Holocene very fine-grained alluvial sands of
the Cordillera Frontal piedmont reflects the modern lithic arenites of the Argentine Association reported by
Potter (1994). The results show two geologically distinct sources in the catchment areas, volcaniclastic and
metamorphic rocks. High concentrations of mica and volcanic glass are likely related to particle morphologies
and to the deposition sedimentary environment recorded in the alluvial sequences?floodplains. The
overabundance of micas over the volcanic glass in the mid-late Holocene alluvial sequence indicates the
drainage of a metamorphic area at the expense of other lithological sources. Source areas are located mainly
in the Frontal cordillera, and to a lesser extent, in the piedmont Tertiary deposits, another likely source for the
analyzed Quaternary alluvial sediments. The mineralogical signature of the late Pleistocene and Holocene alluvial
sequences is in agreement with the composition of the southern Pampean sand mantles, loess and loesslike
deposits mainly formed by a volcanic mineral assemblage with source areas placed at the headwaters of
the main Andean rivers
