Timing of deglaciation and postglacial environmental dynamics in NW Iberia: The Sanabria Lake record

The multiproxy study (sedimentology, geochemistry and diatoms) of sediment cores from Sanabria Lake (42°07'30″ N, 06°43'00″ W, 1000m a.s.l.) together with a robust ¹⁴C chronology provides the first high-resolution and continuous sedimentary record in the region, extending back the last 26ka. The development of a proglacial lake before 26calka BP demonstrates the onset of deglaciation before the global Last Glacial Maximum, similarly to other alpine glaciers in southern European mountains. Rapid deglaciation occurred at the beginning of the Greenland Interstadial GI-1e (Bølling, 14.6calka BP). Following a short-lived episode of glacier re-advance (14.4-14.2calka BP, GI-1d), a climatic improvement at 13.9calka BP suggests the glaciers retreated from the lake basin during the GI-1c. Another glacier reactivation phase occurred between ca13.0-12.4ka, starting earlier than the onset of GS-1 (Younger Dryas). Rapid deglaciation during the Early Holocene (11.7-10.1calka BP) was followed by a period of higher river discharge (10.1-8.2calka BP). After 8.2ka, the Holocene is characterized by a general decreasing trend in humidity, punctuated by the driest phase during the Mid Holocene (ca6.8-4.8), a wetter interval between 4.8 and 3.3calka BP, and a relatively decline of rainfall since then till present, with a minor increase in humidity during some phases (ca1670-1760) of the Little Ice Age.Discrete silt layers intercalated in the organic-rich Holocene deposits reflect large flooding events of the Tera River (ca10.1, 8.4, 7.5, 6.2, 5.7-5.6, 4.6, 4.2, 3.7, 3.3, 3.1, 2.7, 2.5 and 2.0calka BP). Their synchronicity with a number of cold and humid events described in the Atlantic demonstrates a strong control of NW Iberian climate by North Atlantic dynamics at centennial-millennial scale. Comparison with Western Mediterranean records points to similar regional dynamics during the Holocene, although modulated in the NW Iberian Peninsula by the stronger Atlantic influence.