Soil–Geomorphology Relationships and Pedogenic Processes in Península Valdés

The soil landscape of the Penínusla Valdés region is review based in soil genesis analysis and soil–geomorphic relationships. The main soil types of the study area are grouped into two Soil Orders: Aridisols and Entisols. The oldest geomorphic surface corresponds to a relict terrace level from the Rodados Patagónicos lithostratigraphic unit, with Xeric Petrocalcids—Xeric Haplocalcids soil complex. Pleistocene landforms as youngest terrace levels, piedmont pediments (endorheic basins and coastal zone), and paleo-beach ridge units, an intricate soil distribution pattern occurs. This soil distribution is registered by a soil complex constituted by Natrargids, Natrigypsids, Calciargids and Haplocalcids, all of them with xeric regime soil moisture. In playa lakes of the endorheic basins, the soils were classified as Calcic Aquisalids. The Entisols are developed on Holocene geomorphic surfaces; Xeric Torripsamments in stabilized aeolian fields, and Typic Torriorthents in bajadas (coalescing alluvial fans associated to piedmont pediments). In salt marshes, geomorphic elements, anoxia degree, and vegetation communities are associated to soil type; Haplic Sulfaquents, Sodic Endoaquents and Sodic Psammaquents, are related to the low salt marsh, while Typic Fluvaquents and Sodic Hydraquents are developed in the high salt marshes. The main pedogenic processes registered in the Península Valdés soils are clay illuviation, calcification, gypsification, and sulfide production—sulfidization. As the calcretization process progresses, a transformation and neoformation of clay minerals occurs in the following sequence: smectite—palygorskite—sepiolite. The isotopic composition of δ¹³C y δ¹⁸O in pedogenic carbonate could be used as paleoecological and plaeoclimate proxy indicators, respectively.