Deglaciation timing in the Atlantic Iberian mountains: an example from lake sediments in Serra da Estrela (Portugal)

The Serra da Estrela range in Central Portugal is a key  region to explore the Last Glacial termination in the Atlantic region of Iberia. We present the Late Glacial and Holocene record of Lake Peixão to reconstruct past environmental and climatic conditions at decadal timescales. We retrieved an 8.5m long core in the central and deepest zone of the lake. From the base to the top, the sediment core is composed of i) a thick layer (aprox. 0.5 m) of gravel-to-sand quartz clasts; ii) an alternation of one meter thick grey to pale-brown sandy deposits; and iii) homogeneous dark brown and pale-brown organic-rich muddy facies (ca. 7 meters). Using a Bayesian statistical model based on 16 radiocarbon dates using pollen concentrated samples and ²¹⁰Pb measurements, we have developed an age-depth model covering the last ca. 14.6 ka, recording the onset of the lake at that time. Lake and mire records previously published in the area generally support this chronology for the formation of proglacial lakes. In addition, the proposed timing for the disappearance of the Serra da Estrela glaciers has been based on Cosmic-Ray Exposure dating (in situ cosmogenic ³⁶Cl) of exposed moraine boulders and glacially polished bedrock surfaces. These results indicate that the end of the glacier’s presence in Serra da Estrela occurred at ca. 14.2 ka BP (during the Bølling-Allerød Interstadial). Therefore our results broadly suport the timing of the end of the deglaciation at the Serra da Estrela and highlight the value of lake sedimentary records. Moreover, the availability of last termination and Holocene highly-resolved sediments from Lake Peixão is likely to record very valuable evidence of climatic and environmental changes at decadal timescales extending from the last deglaciation, through the Holocene. This new multi-proxy data of the Lake Peixão sedimentary sequence will enable comparisons to other decadal-resolved records and support further investigations from the Mediterranean Iberian region.
The financial support for this work was possible through the following FCT project: HOLMODRIVE—North Atlantic Atmospheric Patterns Influence on Western Iberia Climate: From the Late Glacial to the Present (PTDC/CTA-GEO/29029/2017).