Descripción: Landforms and soils in the Traful River Valley, Neuquén Province. The Andes Patagónicos Region is characterised by the presence of strong west-east bioclimatic, geomorphological and lithostratigraphical gradients, that controlled the genesis and geographical distribution of soils. In this contribution soil-landscape relationships in a sector of a transitional zone in the northern Andes Patagónicos are studied. The Traful River valley is located in Neuquén Province aproximately at 40°40′S and 71°15′W. Diverse geomorphological units were distinguished which were formed through glacial and fluvioglacial action, and partially modified in recent times by fluvial and eolian processes and by mass wasting. Holocen ashes and lapilli were deposited in different volcanic events and constitute the soils'main parent material. We recognize soils belong to three orders: entisols, mollisols and andisols. A strong gradient of variations in soils properties was observed. The Andisolization process decrease with distance from the Cordillera zone. © 1999 Asociación Geológica Argentina.

Descripción: In the south of Santiago del Estero Province and in the north of Cordoba Province, the regional outcrops of Late Precambrian igneous-metamorphic basement show a N to NE tectonic trend which varies from the mainly N-S trend of the hills of central and southern Cordoba ranges. This ancient basement is dominated by granites and acidic porphyritic rocks which are best exposed in the Ambargasta Hills. Minor outcrops of medium-high grade metamorphic rocks (gneisses, schists, amphibolites and marbles) are better exposed in the central and southern. Cordoba ranges. In the main, this paper deals with unconformable overlying Eopalaeozoic folded quartzose sandstones, conglomerates and pelitic hornfels that compose the El Escondido and La Clemira formations, almost exclusively confined to the Ambargasta hills. The folded rocks are partially affected by contact metamorphism associated with intrusive granites dated as being of Late Cambrian (K/Ar 517± 15 Ma, intruding La Clemira Formation) and Carboniferous age (K/Ar 325±10 Ma, intruding in El Escondido Formation). The lithologic characteristics and location of these units, at the western boundary of the Chacoparana Basin, allow correlation with the subsurface marine Early Paleozoic units of that basin. However, tectonic studies by means of statistical mapping of ductile deformation structures (So; fold axis measurements), show the preservation of D2 (328) and D3 (18) deformations of Late Cambrian to Ordovician-Silurian age in El Escondido Formation, and recognized in several locations in the regional Late Precambrian metamorphic rocks of the Cordoba Pampean ranges. The stratigraphical position of the La Clemira and El Escondido Formations is restricted to the Cambrian-Early Ordovician, and could probably correlate with Las Brenas Formation or the Cambrian-Ordovician deposits of the Las Brenas Basin. A modification of the boundary of the Early Paleozoic Chacoparana and the Las Brenas basins is therefore suggested, extending them towards the southwest over the southern Santiago del Estero Hills.