Late Quaternary pedogenesis of lacustrine terraces in Gallocanta Lake, NE Spain

Abstract

Transitional areas of lake margins are complex environments whose evolution is strongly controlled by flooding frequency and persistence. The edaphic development of lacustrine marginal environments can be reconstructed by combining detailed geomorphological analysis with a systematic edaphic study of toposequences. This approach has been applied to a set of recent lacustrine terraces in the downwind palustrine area of the Gallocanta saline lake, located in a semiarid area in NE Spain. Up to five terraces, from 1.6 to 4.5m above the lake bottom, have been identified and mapped using stereo photointerpretation and airborne LiDAR data. Several cycles of water level fluctuations, as part of a general trend towards lake desiccation, have generated stepped terrace levels. The soils of these terraces have different morphological characteristics and provide evidences for the Gallocanta paleolake being larger than that of the present day. The soils have a sandy loam texture with variable clay content (1% to 46%) and a predominantly carbonate composition (mean=26%). The soils are developed in a sequence of lacustrine carbonate-rich (mean=37%) fine-grained gray layers overlaying detrital (mean=51% gravels) and frequently erosive, carbonate-poor reddish layers. The pedogenesis of the downwind palustrine area is mainly characterized by poorly-developed carbonate accumulations and common redox mottles associated with water level fluctuations in the lake, which continuously rejuvenate or truncate the soils. Integrating pedological and geomorphological features provides insight into recent complex lacustrine and soil forming processes and facilitates management strategies and plans for this protected saline environment.