The End of the Last Interglacial in the Iberian Peninsula : The Villarquemado Sequence (Iberian Range, Spain)

The study of terrestrial and marine records of the last interglacial in the Western Mediterranean reveals discrepancies about the sea level fluctuations, the moisture evolution in the continents, and the duration of the different climate phases. A North - South variability in temperature, humidity and even timing of some of these stages has been proposed, but more multiproxy records from SW Europe are needed to test it. The scarce available terrestrial palaeoclimatic records for the Iberian Peninsula (IP) are mainly based on pollen data and show a large variability, although generally they indicate higher humidity during MIS 5 and a transition to colder conditions at the onset of MIS 4. Moisture patterns are even more variable and suggest more arid conditions in the south during the onset of MIS 4. Very few multi-proxy lake studies with adequate chronologies in the IP cover the last interglacial and the last glacial inception (ca. 120 ka). Here we present detailed sedimentological and geochemical analyses of the Villarquemado sequence (Iberian Range), the first continuous continental record spanning the Eemian and the inception of the last glacial cycle in northern Spain. The 74 m long Villarquemado palaeolake sequence was dated by combining 14C (for the uppermost 14 m) and OSL (for the remaining 58 m) techniques providing a basal age of ca. 120 ka. Lacustrine, alluvial fan and peat facies alternate and have been characterized using magnetic susceptibility, mineralogical (X-Ray diffraction), elemental (TOC/TIC) and high-resolution geochemical (XRF core-scanner) analyses. Pollen studies are in progress. Carbonate-rich and peat sediments were deposited during the interglacials (Holocene and MIS 5), clearly marking more humid conditions. Detailed facies analyses of the MIS 5 interval show eight major lacustrine carbonate - peat sequences. The lacustrine facies are Chara sand and silt, banded to laminated grey silt, and variegated, bioturbated, mottled carbonate mud and silt. The three oldest sequences reflect dominance of carbonate lake environments in the basin and suggest deeper depositional conditions during the Eemian (MIS 5e) and afterwards (MIS 5d and MIS 5c). Better development of peatbog environments characterized MIS 5b and MIS 5a and illustrates a trend towards relatively lower humidity during the second half of the last interglacial. The hydrological signature of the MIS 4 onset is rather abrupt and characterized by the retreat of the wetlands and the progradation of the distal alluvial fans both indicative of a tendency towards lower lake levels. Depositional and paleohydrological evolution of the Villarquemado Lake during the last interglacial is coherent with more humid conditions during MIS 5 but unravels higher moisture variability in the IP than expected and an abrupt inception of the last glacial cycle.