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Previous studies point to a discrepancy in the timing of the maximum extent of the Alpine glaciation during the last glacial cycle (Würmian) in the Western Alps. Work carried out on the Lyon palaeoglacier lobe in France suggests that the glacial maximum occurred during Marine Isotope Stage (MIS) 4, while more recent studies on the Rhône palaeoglacier lobe in Switzerland provide evidence of a maximum during MIS 2. Here, we present new chronological data from the karst region of the Western Bauges (French Alps). Between 500 m and 1200 m a.s.l. several karst systems were in lateral position to the Isère palaeoglacier. This palaeoglacier invaded the Bauges limestone massif and the Chéran valley by a transfluence controlled by the Frêne pass at 980 m a.s.l. Allochthonous glacier-derived gravel and sand interbedded with speleothems are present in caves, providing terminus ante quem and post quem age constraints on the timing of several glacial advances. Other speleothems were submerged by rising water levels in the karst due to damming by the glacier. Finally, some speleothems show shatter marks caused by the impact of pebbles transported by highly turbulent meltwaters. 25 U/Th dates of speleothems cover MIS 9 to 1. For MIS 4 to 2, they allow, indirectly, to constrain the different glacial advances into the Bauges limestone massif and to re-evaluate the timing of the maximum Alpine glaciation during the Würmian in this part of the Western Alps. Although the new data and observations do not exclude the possibility of a maximum glacier advance during MIS 2, they argue for a maximum advance during MIS 4 and a local, smaller one during MIS 2. [Display omitted] • Clastic deposits in caves of the western Bauges record several phases of glaciation. • U-Th speleothems dates (MIS 9 to 1) constrain the age of these deposits. • The glacial retreat was followed by a phase of karst "cleaning". • These results hint towards a larger MIS 4 advance than during MIS 2. [ABSTRACT FROM AUTHOR]

Summary: Because of its impact on water quality, organic matter (OM) in karst groundwater has been widely studied. The present article describes a method for monitoring OM in karst aquifers characterized by quick responses to rainfall. This method combines weekly manual sampling and continuous monitoring to provide, qualitative and quantitative information about OM flow. Weekly samples were analyzed for Total Organic Carbon (TOC) content and spectrofluorescence, while continuous monitoring was carried out at the main spring, using a field fluorimeter (310/400–700nm and 280/300–600nm) to quantify chromophoric organic matter (COM). The type and quantity of COM were defined by decomposing Excitation Emission Matrices (EEMs) and by applying a 2D fluorescence decomposition method. Continuous monitoring data showed that the dominant COM was humic-like (HL). We found three types of relationship between HL and discharge and between HL and TOC, showing that caution must be exercised when using field fluorimeter measurements to quantify TOC. Each relationship was characterized by global differences in OM content and by the presence of different percentages of non-chromophoric organic matter. These three relationships are associated with changes in hydrology and microorganism activity during the year. We used these relationships to estimate the annual OM flow (about 15kg/ha/year) and thereby quantify OM flow during the year. Our results show the importance of the non-chromophoric organic matter in such estimation. That work illustrates the need to couple qualitative and quantitative monitoring of OM in karst spring to improve the global comprehension of karst system and of the sources implies in the OM flow. [ABSTRACT FROM AUTHOR]