isotopic ratios for both elements. In zone ISO 1 (40-34 cm), the isotopic composition of the sediment shows steady values around -1.5 for and -1.2‰ for Zone ‰ δ18O δ13C. ISO 2 (34-29 cm) is characterized by lower isotopic compositions, less than -1.5 δ18O and mean values ~ 1.2‰, respectively. In zone ISO 3 (29-23 cm) values are ‰ δ13C higher than in ISO 1, reaching mean values of -1.3‰ for and -1.3‰ for . δ18O δ13C Zone ISO 4 (23-15 cm) is marked by a decrease of and with mean values of δ18O δ13C, -1.8‰ and -1.9‰, respectively. Zone ISO 5 (15-8 cm) has the most enriched isotopic compositions, reaching values around -0.4 for and 0.0‰ for The upper ‰ δ18O δ13C. part of the sediment core, zone ISO 6 (8-0 cm), is characterized by decreasing values from ISO 5 with minima at the surface. DISCUSSION The isotopic composition of lake waters are controlled by the hydrological balance between inputs (groundwater, direct precipitation, surface and stream inflows) and outputs (groundwater loss, evaporation, surface and stream outflows) (Leng et al., 2005). As a consequence different types of lake physiography mean that water isotopic composition can respond differently to the same forcing (Jonsson et al., 2009). As a closed lake in a karstic catchment, topographically isolated from fluvial inflows and outflows, regional influence of surface water can be excluded from Lagunillo’s mass balance. The surface waters of Lagunillo del Tejo plot below the Global Meteoric Water Line (GMWL; Fig. 2) indicating that evaporative processes control the lake's isotopic mass balance. The fundamental controls on the isotope signature in sediment are quite well understood and documented (e.g. Leng et al., 2005; Ito, 2001). In the specific case of sediment that shows a covariant trend between and the isotopic signal can be used as a δ18O δ13C,
isotopic ratios for both elements. In zone ISO 1 (40-34 cm), the isotopic composition of the sediment shows steady values around -1.5 ‰ for δ18O and -1.2‰ for δ13C. Zone ISO 2 (34-29 cm) is characterized by lower isotopic compositions, δ18O less than -1.5 ‰ and δ13C mean values ~ 1.2‰, respectively. In zone ISO 3 (29-23 cm) values are higher than in ISO 1, reaching mean values of -1.3‰ for δ18O and -1.3‰ for δ13C . Zone ISO 4 (23-15 cm) is marked by a decrease of δ18O and δ13C, with mean values of -1.8‰ and -1.9‰, respectively. Zone ISO 5 (15-8 cm) has the most enriched isotopic compositions, reaching values around -0.4 ‰ for δ18O and 0.0‰ for δ13C. The upper part of the sediment core, zone ISO 6 (8-0 cm), is characterized by decreasing values from ISO 5 with minima at the surface. DISCUSSION The isotopic composition of lake waters are controlled by the hydrological balance between inputs (groundwater, direct precipitation, surface and stream inflows) and outputs (groundwater loss, evaporation, surface and stream outflows) (Leng et al., 2005). As a consequence different types of lake physiography mean that water isotopic composition can respond differently to the same forcing (Jonsson et al., 2009). As a closed lake in a karstic catchment, topographically isolated from fluvial inflows and outflows, regional influence of surface water can be excluded from Lagunillo’s mass balance. The surface waters of Lagunillo del Tejo plot below the Global Meteoric Water Line (GMWL; Fig. 2) indicating that evaporative processes control the lake's isotopic mass balance. The fundamental controls on the isotope signature in sediment are quite well understood and documented (e.g. Leng et al., 2005; Ito, 2001). In the specific case of sediment that shows a covariant trend between δ18O and δ13C, the isotopic signal can be used as a
revision_clean2.docx