Ancient and recent soils as indicators of the genesis and evolution of Salada de Chiprana from middle Pleistocene to present (Ebro Basin, NE Spain)

Abstract

The multidisciplinary study of soils, past and present, and the deposits around the Salada de Chiprana Lake (Central Ebro Basin, Spain) has provided valuable insights into the genesis of the lake, with important palaeoenvironmental and palaeoclimatic implications. The presence of a Middle Pleistocene (322.2 ± 21.6 ka) palaeosoil developed on perched aeolian deposits (CHI2) near the lake shore is evidence of ancient stages of lake bottom exposition under rather arid conditions, representing one of the oldest dated aridification episodes in the Quaternary of the Ebro Basin, coinciding with cold periods. Texture analysis of the soils and deposits, and the application of wind models to the reconstruction of the palaeowinds responsible for its genesis, helped to reconstruct the origin and conditions under which such deposits and soils developed. Regarding the genesis of the depression, the characteristics of the geological units in the lake basin, the relationship of the lake basin with fluvial terraces of the surrounding rivers, and the present morphology of the lake body, together with other indirect morphological indicators, point to the subsurface evacuation of soft sediments, very likely through piping-related processes. Additionally, a second soil (CHI1) was studied on a lacustrine terrace level at 152 m a.s.l., 8 m higher than the current level of the lake. It was dated at 9.0 ± 0.7 ka and corresponds to a period of more severe flooding of the lake during the early Holocene, an interpretation consistent with previous studies that established a Holocene age for the bottom sediments of the current lake. Altogether, our dataset indicates long-standing persistence of this lacustrine system and confirms its highly fluctuating character, typical of semiarid regimes such as the one that currently prevails in the centre of the Ebro Depression.