Soil geomorphology relationships and pedogenic processes in Península Valdés

Abstract

The soil landscape of the Penínusla Valdés region is review based in soilgenesis analysis and soil?geomorphic relationships. The main soil types of the studyarea are grouped into two Soil Orders: Aridisols and Entisols. The oldest geomorphicsurface corresponds to a relict terrace level from the Rodados Patagónicos lithostratigraphicunit, with Xeric Petrocalcids?Xeric Haplocalcids soil complex.Pleistocene landforms as youngest terrace levels, piedmont pediments (endorheicbasins and coastal zone), and paleo-beach ridge units, an intricate soil distributionpattern occurs. This soil distribution is registered by a soil complex constituted byNatrargids, Natrigypsids, Calciargids and Haplocalcids, all of them with xericregime soil moisture. In playa lakes of the endorheic basins, the soils were classifiedas Calcic Aquisalids. The Entisols are developed on Holocene geomorphic surfaces;Xeric Torripsamments in stabilized aeolian fields, and Typic Torriorthents inbajadas (coalescing alluvial fans associated to piedmont pediments).In salt marshes,geomorphic elements, anoxia degree, and vegetation communities are associated tosoil type; Haplic Sulfaquents, Sodic Endoaquents and Sodic Psammaquents, arerelated to the low salt marsh, while Typic Fluvaquents and Sodic Hydraquents aredeveloped in the high salt marshes. The main pedogenic processes registered in thePenínsula Valdés soils are clay illuviation, calcification, gypsification, and sulfideproduction?sulfidization. As the calcretization process progresses, a transformationand neoformation of clay minerals occurs in the following sequence: smectite?palygorskite?sepiolite. The isotopic composition of d13C y d18O in pedogeniccarbonate could be used as paleoecological and plaeoclimate proxy indicators,respectively.