Abstract

SUVIRES, Graciela M. Geocronología, paleoambientes y paleosuelos holocenos en las barrancas del arroyo Iglesia, provincia de San Juan (30° 20’ S Y 69° 11´ O). Rev. Asoc. Geol. Argent. [online]. 2015, vol.72, n.3, pp.345-354. ISSN 0004-4822.

In the terrace of Iglesia creek, Holocene paleosol sequences were found and analyzed in the neighborhoods of the Rodeo village. At the central and southern portion of the Iglesia valley, two analysis were made, firstly the identification and characterization of major geomorphological units and secondly the descriptions of two pedosedimentary sequences together with their paleosoils radiocarbon ages. The present study aims to contribute to paleoenvironmental and paleoclimatic knowledge of this area during the Holocene. Two alluvial piedmont units were differentiated, one of them from the western Andean chain and the other from the precordilleran ranges to the east. Both reliefs occupy opposite sides in the valley and expressed differences in the processes that occurred during the Late Pleistocene and Early Holocene. The palaeoenvironmental conditions in the terrace of Iglesia creek during the Holocene generated different surfaces of landscape stabilization making possible the formation of three soils in the distal piedmont alluvial plain (paleosoils Ps-1, Ps-2 and Ps-3). The sequences are profiles of approximately 680 cm of thickness, constituted for: A, Bw, 2Btb, 2Btkb 2BC, 3C, 4Btkb, 4BC and 5Btb respectively. The results from the pedosedimentary sequences along Iglesia creek, permitted to identify three main pedogenetic phases interrupted by two main morphogenetic depositional phase. The radiocarbon dates permitted to establish the age of the soils in order to the presence of wetter conditions and higher vegetation, at existing between Middle - Early Holocene to Late Holocene (ca 7,2 ka BP and ca 2,9 ka BP).

Keywords : Geomorphology; Radiocarbon dates; Paleosoils; Central Andes; Holocene.