Vegetation changes and hydrological fluctuations in the Central Ebro Basin (NE Spain) since the Late Glacial period: Saline lake records

Abstract

Although the Central Ebro Basin (northeastern Iberian Peninsula) is both the northernmost semi-arid area in Europe and one of the regions with the largest biodiversity, it has been insufficiently studied in terms of past climate variability due to the scarcity of suitable sites for palaeoenvironmental analyses. Previous studies from ephemeral saline lakes in the area, mainly based on palynological data, show abrupt and rapid arid/humid transitions throughout the last glacial cycle highlighting a complex palaeohydrological evolution. New cores from two saline lakes (La Playa and La Salineta) in the Los Monegros area provide multi-proxy records, including sedimentology, geochemistry, and pollen indicators. This study, together with a detailed review of the main saline records from the Central Ebro Basin, enables us to reconstruct the main features of the palaeoclimate evolution during the last glacial cycle. One of the main results of this study is the alternation of humid and dry phases as a characteristic of the climate evolution during the Late Glacial. Additionally, the study suggests an important role of the increased flow from the Pyrenean rivers during deglaciation in the hydrological balance of the Central Ebro Basin. The early Holocene is the wettest period of the studied sequences contrasting with the aridity of the middle Holocene interval, which is frequently absent as a result of intense aeolian erosive processes. The lack of archaeological remains associated with the middle Holocene (Neolithic) also supports increased aridity that would have impeded human settlements. Although anthropogenic activity partially masks the climate signal from the palynological data in the uppermost part of the studied sequences, there is some sedimentological evidence for a climate change during the last 2000 yr resulting in a recovery of average saline lake levels in the Central Ebro Basin.