| Popis: |
The southern Iberian Peninsula has been especially sensitive to Holocene climate changes [1]. Climatic and environmental variability has been reconstructed by the mineralogical and chemical analyses of lacustrine sediments. In this study we show the preliminary chronological, lithological, geochemical and magnetic susceptibility results of the sedimentary record of the Laguna Grande de Archidona (southern Spain). This record covers the last 3300 years and it reveals three paleoenvironmental stages. (1) A phase of relative aridity occurred between 3300-3000 cal yr BP, evidenced by fluctuating values of magnetic susceptibility and the presence of gypsum levels, which suggest high evaporation and fluctuating detritic inputs to the lake. (2) A humid phase is identified from 3000 to 1500 cal yr BP, deduced by significant detritic inputs to the lake (high magnetic susceptibility values) due to high catchment runoff during this period. This was the most humid period in the record, agreeing with other regional paleoclimatic records of the Iberian Roman Humid Period (2800-1500 cal yr BP [2]). Additionally, smaller-scale climatic oscillations are shown by the Sr/Al ratio fluctuations and the alternance of some carbonate and gypsum levels during this period. (3) Finally, all the proxies show abrupt changes and higher variability during the last 1500 years, depicting an aridification trend. This paleoenvironmental and paleoclimatic reconstruction agrees with previous studies from the southern Iberian Peninsula that show an arid phase between 3300-3000 cal yr BP, most-likely related with pervasive positive NAO conditions [3], and a decrease in arboreal pollen in Sierra Nevada sites (e.g., Borreguil de la Caldera [4]). A humid phase is identified during the Iberian Roman Humid Period, coeval with a dominant NAO negative mode [3] and also identified by enhanced erosion rates in other southern Iberia areas, such as in Zoñar lake [2] and by the increase of arboreal pollen in several records [1]. Finally, a trend towards more arid conditions is registered after 1500 cal yr BP in southern Iberia records, such as in Zoñar lake, which shows runoff decrease [2], or in other sites of southern Iberia that exhibit an increase in grasses [1, 5]. [1] Ramos-Román et al. (2018), Climate of the Past 14, 117-137; [2] Martín Puertas et al. (2010), Climate of the Past 6, 807-816; [3] Olsen et al. (2010) Nature Geoscience 5, 808-812; [4] Ramos-Román et al. (2016), Quaternary Science Review 143, 84-95; [5] Jiménez-Moreno and Anderson. (2012), Quaternary Research 77, 44-53. |
