Composition and Seasonal Structure of Glaciolacustrine Varves in Wind-Driven Lago Argentino

A mechanistic understanding of annual sediment composition and grain size change is key to support varve-sequence chronology. We use X-ray fluorescence (XRF) and laser-diffraction particle size analysis (LD-PSA) to analyze sub-mm scale sediment variability in Lago Argentino, a 1415 km² ultra-oligotrophic proglacial lake located in Southern Patagonia. We selected 24 intervals from 18 characteristic sites for high-resolution (200-500 mm) XRF and coupled lamina-scale LD-PSA from 47 lake cores distributed throughout the lake basin. High-resolution XRF intervals were selected from well-preserved cores representing the major lake depositional settings. Where core structures are interpreted as varves, high-resolution scans encompass 15-30 annual dark/light couplets. XRF data sets are nested within core-length scans at lower spatial resolution (5-10 mm), providing broader down-core compositional context. XRF and LD-PSA are further supported by petrographic smear slide observations.