Ambientes de Interacción Eólica-Fluvial en Valles Intermontanos: ejemplos actuales y antiguos

arid to semiarid regions usually show a close interaction between fluvial and aeolian processes resulting in a particular pattern of landforms and sedimentary facies (langford, 1989; langford and chan, 1989). here we present a characterization of the fluvial-aeolian interaction environment and its distinctive facies, both in modern settings (guandacol valley, la rioja province) and in a sedimentary section of the vinchina formation (northwestern pampean ranges). recognition of these interaction facies in ancient sequences becomes critical not only because of its paleoenvironmental and paleoclimatic significance but also on account of its potential importance as reservoir rocks (ellis, 1993; meadows and beach, 1993). methodology in guandacol valley included mapping of subenvironments by remote sensing and field survey, definition, characterization and sampling of landforms, textural analysis of sediments and description of stratification styles in natural exposures. in the ancient fluvial-aeolian deposits main lithofacies and facies association were identified and described, together with the characterization of sandstones by petrographic studies. fluvial-aeolian interaction environment in guandacol valley (figs. 1 and 2) is characterized by an ephemeral high-energy gravelly-sandy braidplain associated with abundant aeolian landforms (tripaldi y limarino, 1998; tripaldi, 2002, tripaldi et al., 2003). this region presents an arid/semiarid regime with average annual precipitations of 130 mm, focus on spring and summer. two subenvironments have been distinguished in the guandacol valley, channel and floodplains (table 3). the former comprises different kinds of fluvial bars, channel bed deposits and aeolian landforms (fig. 3). since most of the year channels remain dry and vegetation cover is scarce, wind action reworked fluvial sediments, determining aeolian rippled mantles and sand shadows (figs. 4 and 5). according to grain size and morphology two kinds of ripples we