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Abstract. The Rio Sella in northern Spain drains a catchment area of around 1200 km2. It originates in the Picos de Europa and erodes a variety of outcropping lithologies, mainly of Palaeozoic and minor Mesozoic to Cenozoic age. These rocks include siliciclastics, their metamorphic equivalents, carbonates and mixed sedimentary lithologies but almost no (meta-)igneous rocks. Some of the mentioned rock types are only found in specific areas within the study area, and most of them are identified by specific heavy mineral associations. It is therefore possible to make preliminary estimates of the potential detrital heavy mineral contribution of each region in the Rio Sella catchment. Further sampling of modern, i.e. currently deposited, river and beach sediments allows for sediment routing during transport and recycling processes. This also includes the impact of grain size effects and signal dilution due to different heavy mineral fertilities of the eroded strata. The influence of anthropogenic activities is reflected by the abundance of heavy anthropogenic particles, and the potential of this for sediment research or environmental impact is yet to be determined. The initial results indicate the potential and necessity of detailed heavy mineral characterisation of both fluvial sediments and outcropping lithologies within a catchment. This is particularly important when aiming to reconstruct sedimentary and particle fluxes at a high spatial resolution.

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Abstract. High alpine peatlands are naturally impacted by extreme climatic conditions and heterogeneous topography. In the Alps, humans have been influencing their development for millennia, and accelerating climate change puts them under additional pressure. In the Swiss part of the Fimba Valley (or Val Fenga; > 2350 m a.s.l. (metres above sea level)), small-scale peatlands have been investigated to gain knowledge on climatic and anthropogenic impacts on alpine landscapes using quantitative and semi-quantitative geochemical parameters derived from inter-calibrated portable X-ray fluorescence spectrometry (pXRF) and XRF core scanning, sedimentology, and radiocarbon dating. The onset of peat formation, after the retreat of the Fimba Valley glacier, has been dated to a time window between 10 450 and 9000 cal BP at the lower (northern) end and to 6600 cal BP at the upper (southern) end of a 470 m long transect. Holocene cold episodes appear to have increased erosive glacial activity in the western side of the valley, resulting in high minerogenic sediment loads being deposited on the peatlands by a meltwater channel, interrupting peat accumulation repeatedly. In the early Holocene, distinct minerogenic layers suggest glacier growth and cold and potentially wet conditions around 9200, 8200, and 6300 cal BP. With the impact and extent of the 8.2 ka cold event still being under discussion for this region of the Alps, a coarse gravel layer is strong evidence for a marked glacial response in the Silvretta Mountains to a particularly cold and wet episode. Cooler climate conditions seem to have prevailed around 5400, 5000, 4500, and 3600 cal BP. Afterwards, the proportion of anthropogenic forcing in erosional processes and other disturbances increased. During and since the Middle Ages, soil or sediment erosion and decreasing peat accumulation were and have continued to be consequences of at least one of the following factors: deforestation; livestock grazing and traffic (trade, tourism); and, temporarily, the Little Ice Age. These impacts and their potential effects on carbon accumulation and flood risk mitigation in the valley should be considered in land management practice. Despite their strong minerotrophic character and a likely post-depositional release due to erosion and decomposition in recent layers, the peatlands have preserved clear signals of atmospheric lead (Pb) pollution: one correlated with the Roman period and another around 1450 cal BP. Rapidly changing sedimentation and hydrology in small mountain peatlands are a challenge for radiocarbon chronologies, high-resolution sampling, and the detection of atmospheric geochemical signals. Yet, our study demonstrates that dynamic glaciofluvial stream-bank mires are valuable for the reconstruction of the impact of climate and humans on alpine environments – from prehistory to the present.