Whiteschists from the Monte Rosa Nappe were examined in the field as well as with petrographic, geochemical, and isotopic methods to constrain the controversial origin of these rocks in their Alpine ...metamorphic context. Whiteschists occur as ellipsoidal-shaped, decametric-sized bodies, within a Permian metagranite, and consist mainly of chloritoid, talc, phengite, and quartz. The transition from whiteschist to metagranite is marked by multiple sharp mineralogical boundaries defining concentric zones unrelated to Alpine deformation. The development of reaction zones, as well as the geometry of the whiteschist suggest a pervasive fluid infiltration, facilitated and canalized by reaction fingering. Whole-rock compositions of whiteschists and metagranites indicate an enrichment in MgO and H
2
O and depletion of Na
2
O, CaO, Ba, Sr, Pb, and Zn in the whiteschist relative to the metagranite. Trace- and rare-earth elements, together with all other major elements, notably K
2
O and SiO
2
, were within uncertainty not mobile. Such a K and Si saturated, Na undersaturated fluid is not compatible with previous interpretations of fluids derived from ultramafic rocks, evaporites, or Mg-enriched seawater due to mantle interactions. Together with the large variations in δD and δ
18
O values, this indicates large fluid fluxes during metasomatism. Calculated δD and δ
18
O values of fluids in equilibrium with the whiteschist support a magmatic–hydrothermal fluid source, as does the chemical alteration pattern. Bulk rock
87
Sr/
86
Sr ratios in whiteschists confirm a pre-Alpine age of fluid infiltration. The
87
Sr/
86
Sr ratios in whiteschists were subsequently partially homogenized in a closed system during Alpine metamorphism. In conclusion, the granite was locally affected by late magmatic–hydrothermal alteration, which resulted in sericite–chlorite alteration zones in the granite. The entire nappe underwent high-pressure metamorphism during the Alpine orogeny and the mineralogy of the whiteschist was produced during dehydration of the metasomatic assemblage under otherwise closed-system metamorphism. While each whiteschist locality needs to be studied in detail, this in-depth study suggests that many whiteschists found in granitic bodies in the Alps might be of similar origin.
Information about past ecosystem dynamics and human activities is stored in the ice of Colle Gnifetti glacier in the Swiss Alps. Adverse climatic intervals incurred crop failures and famines and ...triggered reestablishment of forest vegetation but also societal resilience through innovation. Historical documents and lake sediments record these changes at local—regional scales but often struggle to comprehensively document continental‐scale impacts on ecosystems. Here, we provide unique multiproxy evidence of broad‐scale ecosystem, land use, and climate dynamics over the past millennium from a Colle Gnifetti microfossil and oxygen isotope record. Microfossil data indicate that before 1750 CE forests and fallow land rapidly replaced crop cultivation during historically documented societal crises caused by climate shifts and epidemics. Subsequently, with technology and the introduction of more resilient crops, European societies adapted to the Little Ice Age cold period, but resource overexploitation and industrialization led to new regional to global‐scale environmental challenges.
Plain Language Summary
Sophisticated microscopy and geochemistry analyses of glacier ice from the Monte Rosa Massif in the Swiss Alps reveal close linkages among European climate, vegetation, agriculture, pollution, pests, and fire during the past millennium. Our novel time series shows that societal and environmental dynamics were mainly controlled by climate, pandemics, and technological innovations. By placing the glacial information into historical context, we reveal some of the mechanisms that created prosperity and peril in Europe's past. Industrialization and import of maize and other new crops enabled European societies to transcend the crop failures and famines of the Little Ice Age climate period during the 19th century, but unintended environmental consequences resulted, which are now culminating in global warming and species loss.
Key Points
Novel ice core microfossil data reveal large‐scale dynamics among ecosystems, land use, and climate in Europe
Proxies preserved in ice cores link land‐use change to societal challenges caused by climate events and epidemics
Agricultural reforms and industrialization disrupted links between climate and land use and led to current environmental challenges
We analysed the spatial and temporal distribution of a selection of pesticides in Alpine glaciers used on the Po Plain in Northern Italy, near the Alps. By analysing a 102-m ice core taken from the ...Lys Glacier (Monte Rosa massif, Italy), we highlight historical contamination from the insecticide chlorpyrifos and the herbicide terbuthylazine, confirming the role of alpine glaciers as temporal sinks.
In addition, we collected meltwater samples from six glaciers distributed along the Alpine Arc during the summer of 2016, which showed widespread contamination by pesticides. Overall, chlorpyrifos and terbuthylazine dominated the contaminant fingerprint of all of the studied glaciers, with contamination peaks occurring at the beginning of the melting season. This highlights the importance of the medium-range atmospheric transport of these pesticides in connection with agricultural practices in the areas beneath the Italian Alps, where they are widely applied.
The release of pesticides in meltwater can lead to potential risks to the aquatic ecosystems of headwater streams, as we demonstrate for chlorpyrifos. This suggests that the medium-range atmospheric transport of pesticides should be considered as part of regulations to protect the water quality of these pristine environments.
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•Chlorpyrifos was detected in all glacial meltwater from Alpine Glaciers.•Terbuthylazine and its metabolite detected in glaciers closer to Po plain.•Chlorpyrifos and terbuthylazine concentrations in ice core vary with sale volumes.•Risk characterisation of chlorpyrifos indicates concern for alpine aquatic species.
Glaciers in the European Alps began to retreat abruptly from their mid-19th century maximum, marking what appeared to be the end of the Little Ice Age. Alpine temperature and precipitation records ...suggest that glaciers should instead have continued to grow until circa 1910. Radiative forcing by increasing deposition of industrial black carbon to snow may represent the driver of the abrupt glacier retreats in the Alps that began in the mid-19th century. Ice cores indicate that black carbon concentrations increased abruptly in the mid-19th century and largely continued to increase into the 20th century, consistent with known increases in black carbon emissions from the industrialization of Western Europe. Inferred annual surface radiative forcings increased stepwise to 13-17 W·m⁻² between 1850 and 1880, and to 9-22 W·m⁻² in the early 1900s, with snowmelt season (April/May/June) forcings reaching greater than 35 W·m⁻² by the early 1900s. These snowmelt season radiative forcings would have resulted in additional annual snow melting of as much as 0.9 m water equivalent across the melt season. Simulations of glacier mass balances with radiative forcingequivalent changes in atmospheric temperatures result in conservative estimates of accumulating negative mass balances of magnitude -15 m water equivalent by 1900 and -30 m water equivalent by 1930, magnitudes and timing consistent with the observed retreat. These results suggest a possible physical explanation for the abrupt retreat of glaciers in the Alps in the mid-19th century that is consistent with existing temperature and precipitation records and reconstructions.
The tectono‐metamorphic evolution of the European Alps is still contentious. The Monte Rosa tectonic unit is a prominent nappe in the Central European Alps and estimates of its peak Alpine pressure ...(P) and temperature (T) conditions are essential for reconstructing its tectono‐metamorphic evolution. However, the reported peak Alpine pressure and temperature estimates vary considerably between 1.2 and 2.7 GPa and 490 and 640°C for a variety of lithologies. Here, we show petrology and pseudosection modelling of metapelitic assemblages from the western portions of the Monte Rosa nappe (upper Ayas valley, Italy). We present newly discovered staurolite–chloritoid‐bearing metapelitic assemblages. These assemblages exhibit an Alpine high‐P metamorphic overprint of a former contact‐metamorphic mineral assemblage generated by post‐Variscan granitic intrusions. Staurolite contains major amounts of Zn (up to 1.0 atoms per formula units), which is currently, in contrast to Fe‐ and Mg‐staurolite end‐members, not considered in any thermodynamic database. We employ two end‐member mixing models for Zn in staurolite, site mixing, and molecular mixing. Both models enlarge the pressure and temperature stability range for the observed assemblage, where site mixing has the largest influence of ±0.2 GPa and ±20°C. Our results for three metapelite assemblages, with and without staurolite, indicate peak Alpine pressure of 1.6 ± 0.2 GPa and peak temperature of 585 ± 20°C. These peak pressure estimates agree with previously published estimates for metagranites in the nappe, and are in stark contrast with peak pressure obtained from talc‐, chloritoid‐, phengite‐, and quartz‐bearing lithologies termed ‘whiteschists’ (>2.2 GPa). Our results confirm a variation of peak Alpine pressure of 0.6 ± 0.2 GPa between metagranite/metapelite lithologies and a nearby whiteschist lens (>2.2 GPa) within the metagranite. Field observations indicate that the studied region is structurally coherent and that the whiteschist is not a tectonic slice formed by tectonic mélange. We suggest that the consistent peak pressure for metapelite and metagranite assemblages represents the regional peak pressure and that the higher pressure recorded in the whiteschist lens is likely due to dynamic pressure, possibly resulting from tectonic and/or reaction‐induced stresses. If the calculated pressure of 1.6 ± 0.2 GPa represents regional peak Alpine conditions, then the Monte Rosa nappe was exhumed from a significantly shallower depth than previously assumed, based on peak pressure estimates > 2.2 GPa for whiteschist lithologies.
Nitrogen contents and isotope compositions together with major and trace element concentrations were determined in a sequence of metagabbros from the western Alps (Europe) in order to constrain the ...evolution and behavior of N during hydrothermal alteration on the seafloor and progressive dehydration during subduction in a cold slab environment (8
°C/km). The rocks investigated include: (i) low-strain metagabbros that equilibrated under greenschist to amphibolite facies (Chenaillet Massif), blueschist facies (Queyras region) and eclogite facies (Monviso massif) conditions and (ii) highly-strained mylonites and associated eclogitic veins from the Monviso Massif. In all samples, nitrogen (2.6–55
ppm) occurs as bound ammonium (
NH
4
+
) substituting for K or Na–Ca in minerals. Cu concentrations show a large variation, from 73.2 to 6.4
ppm, and are used as an index of hydrothermal alteration on the seafloor because of Cu fluid-mobility at relatively high temperature (>300
°C). In low-strain metagabbros,
δ
15N values of +0.8‰ to +8.1‰ are negatively correlated with Cu concentrations. Eclogitic mylonites and veins display Cu concentrations lower than 11
ppm and show a
δ
15N–Cu relationship that does not match the
δ
15N–Cu correlation found in low-strain rocks. This
δ
15N–Cu correlation preserved in low-strain rocks is best interpreted by leaching of Cu–N compounds, possibly of the form Cu(NH
3)
2
2+, during hydrothermal alteration. Recognition that the different types of low-strain metagabbros show the same
δ
15N–Cu correlation indicates that fluid release during subduction zone metamorphism did not modify the original N and Cu contents of the parent hydrothermally-altered metagabbros. In contrast, the low Cu content present in eclogitic veins and mylonites implies that ductile deformation and veining were accompanied either by a loss of copper or that externally-derived nitrogen was added to the system.
We estimate the global annual flux of N subducted by metagabbros as 4.2 (±2.0)
×
10
11
g/yr. This value is about half that of sedimentary rocks, which suggests that gabbros carry a significant portion of the subducted nitrogen. The net budget between subducted N and that outgassed at volcanic arcs indicates that ∼80% of the subducted N is not recycled to the surface. On a global scale, the total amount of N buried to the mantle via subduction zones is estimated to be three times higher than that released from the mantle via mid-ocean ridges, arc and intraplate volcanoes and back-arc basins. This implies that N contained in Earth surface reservoirs, mainly in the atmosphere, is progressively transferred and sequestered into the mantle, with a net flux of ∼9.6
×
10
11
g/yr. Assuming a constant flux of subducted N over the Earth’s history indicates that an amount equivalent to the present atmospheric N may have been sequestered into the silicate Earth over a period of 4
billion years.
New strategies for preservation of geodiversity and geosystem services need to be developed for mountain areas that are vulnerable to climate change and human activities. Detailed geomorphological ...surveys and geosystem services analyses have been carried out in the Indren-Cimalegna area, southern slope of Monte Rosa (Western Italian Alps). From remote sensing analysis and field inventories, a geomorphological map (1:5000) was created, with a new GIS-compliant legend, targeted to the studies of glacial and periglacial environments. A geosystem services map (1:15,000) was also produced, presenting a two-fold analysis of interactions between geomorphology and human activity, showing (1) the role of distinct landforms as specific services offered to society and (2) the threats posed by morphodynamic processes to human activities. These maps are presented as tools for enhancing proper planning and management of high mountains modified by climate change and human activities within a sustainable development perspective.
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