Elemental (C/N ratios) and isotopic (δ15Norg, δ13Corg) compositions of sedimentary organic matter from a high-altitude mountain lake (Meidsee, 2661 m a.s.l., Switzerland): Implications for Lateglacial and Holocene Alpine landscape evolution

The deposition of Late Pleistocene and Holocene sediments in the high-altitude lake Meidsee (located at an altitude of 2661 m a.s.l. in the Southwestern Alps) strikingly coincided with global ice-sheet and mountain-glacier decay in the Alpine forelands and the formation of perialpine lakes. Radiocarbon ages of bottom-core sediments point out (pre-) Holocene ice retreat below 2700 m a.s.l., at about 16, 13, 10, and 9 cal. kyr BP. The Meidsee sedimentary record therefore provides information about the high-altitude Alpine landscape evolution since the Late Pleistocene/Holocene deglaciation in the Swiss Southwestern Alps. Prior to 5 cal. kyr BP, the C/N ratio and the isotopic composition of sedimentary organic matter (δ15Norg, δ13Corg) indicate the deposition of algal-derived organic matter with limited input of terrestrial organic matter. The early Holocene and the Holocene climatic optimum (between 7.0 and 5.5 cal. kyr BP) were characterized by low erosion (decreasing magnetic susceptibility, χ) and high content of organic matter (Corg > 13 wt.%), enriched in 13Corg (> −18‰) with a low C/N (~10) ratio, typical of modern algal matter derived from in situ production. During the late Holocene, there was a long-term increasing contribution of terrestrial organic matter into the lake (C/N > 11), with maxima between 2.4 and 0.9 cal. kyr BP. A major environmental change took place 800 years ago, with an abrupt decrease in the relative contribution of terrestrial organic material into the lake compared with aquatic organic material which subsequently largely dominated (C/N drop from 16 to 10). Nonetheless, this event was marked by a rise in soil erosion (χ), in nutrients input (N and P contents) and in anthropogenic lead deposition, suggesting a human disturbance of Alpine ecosystems 800 years ago. Indeed, this time period coincided with the migration of the Walser Alemannic people in the region, who settled at relatively high altitude in the Southwestern Alps for farming and maintaining Alpine passes.

[1]  R. Psenner,et al.  Holocene temperature variations at a high-altitude site in the Eastern Alps: a chironomid record from Schwarzsee ob Sölden, Austria , 2011, Quaternary science reviews.

[2]  W. Vyverman,et al.  Bulk organic geochemistry of sediments from Puyehue Lake and its watershed (Chile, 40°S): implications for paleoenvironmental reconstructions. , 2010 .

[3]  B. Mourier,et al.  Soil evolution and subalpine ecosystem changes in the French Alps inferred from geochemical analysis of lacustrine sediments , 2010 .

[4]  J. Robbins,et al.  Carbon cycling in Lake Erie during cultural eutrophication over the last century inferred from the stable carbon isotope composition of sediments , 2010 .

[5]  F. Anslow,et al.  Surface‐melt driven Laurentide Ice Sheet retreat during the early Holocene , 2009 .

[6]  H. Birks,et al.  Last nine-thousand years of temperature variability in Northern Europe , 2009 .

[7]  T. Fichefet,et al.  The spatial and temporal complexity of the Holocene thermal maximum , 2009 .

[8]  F. Favilli,et al.  Effect of north and south exposure on organic matter in high Alpine soils , 2009 .

[9]  W. Haeberli,et al.  Comparison of different methods of obtaining a resilient organic matter fraction in Alpine soils , 2008 .

[10]  R. Schmidt,et al.  Siliceous algae-based seasonal temperature inference and indicator pollen tracking ca. 4,000 years of climate/land use dependency in the southern Austrian Alps , 2007 .

[11]  Z. An,et al.  Stable isotopes in bulk carbonates and organic matter in recent sediments of Lake Qinghai and their climatic implications , 2006 .

[12]  P. Kubik,et al.  Chronology of deglaciation based on 10Be dates of glacial erosional features in the Grimsel Pass region, central Swiss Alps , 2006 .

[13]  Martin Beniston,et al.  Mountain Weather and Climate: A General Overview and a Focus on Climatic Change in the Alps , 2006, Hydrobiologia.

[14]  P. Kubik,et al.  Glacier response in the European Alps to Heinrich Event 1 cooling: the Gschnitz stadial , 2006 .

[15]  A. Lotter,et al.  Holocene and Lateglacial summer temperature reconstruction in the Swiss Alps based on fossil assemblages of aquatic organisms: a review , 2005 .

[16]  P. Deline,et al.  Glacier fluctuations in the western Alps during the Neoglacial, as indicated by the Miage morainic amphitheatre (Mont Blanc massif, Italy) , 2005 .

[17]  S. Girardclos,et al.  Petit‐Lac (western Lake Geneva) environment and climate history from deglaciation to the present: a synthesis , 2005 .

[18]  M. Magny,et al.  Glacier and lake-level variations in west-central Europe over the last 3500 years , 2005 .

[19]  J. L. Teranes,et al.  Factors controlling δ13C values of sedimentary carbon in hypertrophic Baldeggersee, Switzerland, and implications for interpreting isotope excursions in lake sedimentary records , 2005 .

[20]  M. Danubio,et al.  The effects of geographical and prolonged cultural isolation on the marital behaviour of an Alpine community (Valsesia-Italy, 1618–1899) , 2005 .

[21]  H. Synal,et al.  Timing of deglaciation on the northern Alpine foreland (Switzerland) , 2004 .

[22]  J. Buoncristiani,et al.  A reconstruction of the last glacial maximum (LGM) ice-surface geometry in the western Swiss Alps and contiguous Alpine regions in Italy and France , 2004 .

[23]  M. Leng,et al.  Palaeoclimate interpretation of stable isotope data from lake sediment archives , 2004 .

[24]  R. Schmidt,et al.  A multi proxy core study of the last 7000 years of climate and alpine land-use impacts on an Austrian mountain lake (Unterer Landschitzsee, Niedere Tauern) , 2002 .

[25]  F. McDermott,et al.  Centennial-Scale Holocene Climate Variability Revealed by a High-Resolution Speleothem δ18O Record from SW Ireland , 2001, Science.

[26]  Eric Pawson,et al.  History and (Re)discovery of the European and New Zealand Alps until 1900 , 2001 .

[27]  C. Schlüchter,et al.  The Alps with little ice: evidence for eight Holocene phases of reduced glacier extent in the Central Swiss Alps , 2001 .

[28]  B. Hagedorn,et al.  Lithological and biochemical properties in sediments of Lama Lake as indicators for the late Pleistocene and Holocene ecosystem development of the southern Taymyr Peninsula, Central Siberia , 1999 .

[29]  W. Tinner,et al.  Synchronous Holocene climatic oscillations recorded on the Swiss Plateau and at timberline in the Alps , 1998 .

[30]  P. Meyers,et al.  Organic geochemical proxies of paleoceanographic, paleolimnologic, and paleoclimatic processes , 1997 .

[31]  T. Johannessen,et al.  A high resolution palaeoclimatic record for the last 27,500 years in tropical West Africa from the carbon and nitrogen isotopic composition of lacustrine organic matter , 1992 .

[32]  G. Lister.  A 15,000-year Isotopic Record from Lake Zürich of Deglaciation and Climatic Change in Switzerland , 1988, Quaternary Research.

[33]  J. Poté,et al.  (Pre-) historic changes in natural and anthropogenic heavy metals deposition inferred from two contrasting Swiss Alpine lakes , 2011 .

[34]  K. Koinig.  Soil development as trigger for lake productivity in a high alpine ecosystem , 2010 .

[35]  J. L. Teranes,et al.  Sediment Organic Matter , 2002 .

[36]  C. Schlüchter,et al.  The deglaciation of the Swiss-Alps : a paleoclimatic event with chronological problems , 1988 .