Local formation of varved sediments in a karstic collapse depression of Lake Banyoles (NE Spain) Formación local de sedimentos varvados en una depresión de colapso kárstico del Lago Bañolas (NE España)

Banyolesisthelargestanddeepestlakeofkarstic-tectonicorigininthe Iberian Peninsula.The lake comprises several circular sub-basins characterizedbydifferentoxygenationconditionsattheirhypolimnions.Themultiproxy analysis of a > 5 m long sediment core combined with high resolution seis mic stratigraphy (3.5 kHz pinger and multi-frequency Chirp surveys), allow aprecisereconstructionoftheevolutionofakarsticdepression(namedB3) untilpresenttimes.Localmeromicticconditionsinthissub-basinhavebeen conducive to deposition and preservation of ca. 85 cm of varved sediments since the late 19th century.The onset of these conditions is likely related to lakewaterseutrophicationcausedbyincreasingfarmingactivitiesinthewa tershed. Increasing clastic input and organic productivity during the second