Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps)
Cold climate carbonates can be used as paleoclimatic proxies. The mineralogy and isotopic composition of subglacially precipitated carbonate crusts (SPCCs) provide insights into the subglacial conditions and processes occurring at the meltwater-basement rock interface of glaciers. This study documen...
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Frontiers Media S.A.
2017-09-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | http://journal.frontiersin.org/article/10.3389/feart.2017.00070/full |
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| author | Christophe Thomazo Jean-Francois Buoncristiani Emmanuelle Vennin Pierre Pellenard Theophile Cocquerez Jean L. Mugnier Emmanuelle Gérard |
| author_facet | Christophe Thomazo Jean-Francois Buoncristiani Emmanuelle Vennin Pierre Pellenard Theophile Cocquerez Jean L. Mugnier Emmanuelle Gérard |
| author_sort | Christophe Thomazo |
| collection | DOAJ |
| description | Cold climate carbonates can be used as paleoclimatic proxies. The mineralogy and isotopic composition of subglacially precipitated carbonate crusts (SPCCs) provide insights into the subglacial conditions and processes occurring at the meltwater-basement rock interface of glaciers. This study documents such crusts discovered on the lee side of a gneissic roche moutonnée at the terminus of the Bossons glacier in the Mont Blanc Massif area (France). The geological context and mineralogical investigations suggest that the Ca used for the precipitation of large crystals of radial fibrous sparite observed in these crusts originated from subglacial chemical weathering of Ca-bearing minerals of the local bedrock (plagioclase and amphibole). Measurements of the carbon and oxygen isotope compositions in the crusts indicate precipitation at, or near to, equilibrium with the basal meltwater under open system conditions during refreezing processes. The homogeneous and low carbonate δ13C values (ca. −11.3‰) imply a large contribution of soil organic carbon to the Bossons subglacial meltwater carbon reservoir at the time of deposition. In addition, organic remains trapped within the SPCCs give an age of deposition around 6,500 years cal BP suggesting that the Mid-Holocene climatic and pedological optima are archived in the Bossons glacier carbonate crusts. |
| first_indexed | 2024-12-14T00:34:39Z |
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| institution | Directory Open Access Journal |
| issn | 2296-6463 |
| language | English |
| last_indexed | 2024-12-14T00:34:39Z |
| publishDate | 2017-09-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Earth Science |
| spelling | doaj.art-b3dfbfcfd7f44b79bcb76c86cd8f3b8d2022-12-21T23:24:43ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632017-09-01510.3389/feart.2017.00070260440Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps)Christophe Thomazo0Jean-Francois Buoncristiani1Emmanuelle Vennin2Pierre Pellenard3Theophile Cocquerez4Jean L. Mugnier5Emmanuelle Gérard6Laboratoire Biogéosciences UMR 6282 UBFC, Centre National De La Recherche Scientifique, Université Bourgogne Franche-ComtéDijon, FranceLaboratoire Biogéosciences UMR 6282 UBFC, Centre National De La Recherche Scientifique, Université Bourgogne Franche-ComtéDijon, FranceLaboratoire Biogéosciences UMR 6282 UBFC, Centre National De La Recherche Scientifique, Université Bourgogne Franche-ComtéDijon, FranceLaboratoire Biogéosciences UMR 6282 UBFC, Centre National De La Recherche Scientifique, Université Bourgogne Franche-ComtéDijon, FranceLaboratoire Biogéosciences UMR 6282 UBFC, Centre National De La Recherche Scientifique, Université Bourgogne Franche-ComtéDijon, FranceCentre National De La Recherche Scientifique, Université de Savoie-Mont-BlancChambéry, FranceInstitut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Centre National De La Recherche Scientifique UMR 7154Paris, FranceCold climate carbonates can be used as paleoclimatic proxies. The mineralogy and isotopic composition of subglacially precipitated carbonate crusts (SPCCs) provide insights into the subglacial conditions and processes occurring at the meltwater-basement rock interface of glaciers. This study documents such crusts discovered on the lee side of a gneissic roche moutonnée at the terminus of the Bossons glacier in the Mont Blanc Massif area (France). The geological context and mineralogical investigations suggest that the Ca used for the precipitation of large crystals of radial fibrous sparite observed in these crusts originated from subglacial chemical weathering of Ca-bearing minerals of the local bedrock (plagioclase and amphibole). Measurements of the carbon and oxygen isotope compositions in the crusts indicate precipitation at, or near to, equilibrium with the basal meltwater under open system conditions during refreezing processes. The homogeneous and low carbonate δ13C values (ca. −11.3‰) imply a large contribution of soil organic carbon to the Bossons subglacial meltwater carbon reservoir at the time of deposition. In addition, organic remains trapped within the SPCCs give an age of deposition around 6,500 years cal BP suggesting that the Mid-Holocene climatic and pedological optima are archived in the Bossons glacier carbonate crusts.http://journal.frontiersin.org/article/10.3389/feart.2017.00070/fullglacierpaleoclimateMont Blancsubglacially precipitated carbonate crustsstable isotopeHolocene climatic optimum |
| spellingShingle | Christophe Thomazo Jean-Francois Buoncristiani Emmanuelle Vennin Pierre Pellenard Theophile Cocquerez Jean L. Mugnier Emmanuelle Gérard Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps) Frontiers in Earth Science glacier paleoclimate Mont Blanc subglacially precipitated carbonate crusts stable isotope Holocene climatic optimum |
| title | Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps) |
| title_full | Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps) |
| title_fullStr | Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps) |
| title_full_unstemmed | Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps) |
| title_short | Geochemical Processes Leading to the Precipitation of Subglacial Carbonate Crusts at Bossons Glacier, Mont Blanc Massif (French Alps) |
| title_sort | geochemical processes leading to the precipitation of subglacial carbonate crusts at bossons glacier mont blanc massif french alps |
| topic | glacier paleoclimate Mont Blanc subglacially precipitated carbonate crusts stable isotope Holocene climatic optimum |
| url | http://journal.frontiersin.org/article/10.3389/feart.2017.00070/full |
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