Abstract Volume Swiss Geoscience Meeting · 2014-11-26 · 174 Symposium 8: Quaternary Research Swiss Geoscience Meeting 2010 Platform Geosciences, Swiss Academy of Science, SCNAT

Abstract Volume8th Swiss Geoscience MeetingFribourg, 19th – 20th November 2010

Department ofGeosciences

8. Quaternary Research

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Platform Geosciences, Swiss Academy of Science, SCNATSwiss Geoscience Meeting 2010

8. Quaternary Research

Naki Akçar

Swiss Society for Quaternary Research (CH-Quat)

8.1 AkçarN.,DelineP., Ivy-OchsS.,ChristlM.,KubikP.W.,SchlüchterC.: Surfaceexposuredatingof1717ADrockavalanchedepositsintheupperFerretValley(Italy)withcosmogenic10Be

8.2 AlpouS.,GodefroidF.&KindlerP.:OriginofBahamianlaminarcrusts:newgeochronologicalandpetrographicdata

8.3 ChairiR.: Organic andmineral sedimentarydeposits in the evaporators’ environmentsof the Sahel ofTunisia(Mahdia):theBaghdadiswampandtheconjugatedsebkhaofGotaiaandEliane

8.4 ColombaroliD.,HenneP.,KaltenriederP.,GobetE.,TinnerW.:Howdidfire,humanimpactandclimatechangeaffectHolocenetreelinedynamicsintheAlps?AcaseofstudyfromGouilleRion(Valais,Switzerland)

8.5 DehnertA.,KemnaH.A.,AnselmettiF.S.,Drescher-SchneiderR.,GrafH.R.,LowickS.,PreusserF.,ZügerA.,FurrerH.:ErosionandfillingofaglaciallyoverdeepenedtroughinthenorthernAlpineForelandasrecordedindeepdrillcoreNW09fromNiederweningen,Switzerland

8.6 DeplazesG.,HaugG.H.,LückgeA.,PetersonL.C.:High-resolutionsedimentcolourandgeochemicalanalysisofDansgaard-Oeschgerevents(CariacoBasin,NorthernArabianSea)

8.7 GirardclosS.,Rachoud-SchneiderA.-M.,BrutschN.:RhoneglacierdeglaciationinwesternLakeGeneva:newsismo-andbiochronostratigraphyresults

8.8 GöktürkO.M.,FleitmannD.,BadertscherS.,ChengH.,EdwardsL.,FankhauserA.,TüysüzO.,KramersJ.:ClimateinthesouthernBlackSeacoastduringtheHolocene:ImplicationsfromtheSofularCaverecord

8.9 HaghipourN.,KoberF.,BurgJ-P.,ZeilingerG.,Ivy-OchsS.,KubikP.,FaridiM.:IncisionanddeformationrecordedbyQuaternaryf luvialterracesinMakranaccretionarywedge,SE-Iran

8.10 HaudenschildE.,AkçarN.,YavuzV., Ivy-OchsS.,AlfimovV.,KubikP.W., SchlüchterC.: TheKestanbolGranite(Western Turkey) and its importance as a building stone: Application of cosmogenic 10Be to an archaeologicalproblem

8.11 HeiriO.,BirksJ.,BrooksS.,KirilovaE.,MagyariE.,MilletL.,MortensenM.F.,SamartinS.,TinnerW.,TothM.,VeskiS. & Lotter A.F.: European climate change at the end of the last glaciation: chironomid–based temperaturereconstructiononacontinentalscale

8.12 HippeK.,Ivy-OchsS.,KoberF.,WielerR.,SchlüchterC.:ReconstructingthedeglaciationhistoryoftheGotthardPassarea,CentralSwissAlps,usingcosmogenic10Beandin-situ14C

8.13 KindJ.,HirtA.,vanRadenU.:DomagneticpropertiesreflectclimatehistoryinSwisslakes?

8.14 KremerK.,GirardclosS.:Giantsub-lacustrinemassmovementinLakeGenevasedimentrecord

8.15 LaigreL.,ReynardE.,Arnaud-FassettaG.,BaronL.,LambielC.: ContributionofgeoelectricalmeasurementsandshallowdrillingsfordetectionofHolocenepalaeochannelsintheSaillonregion(Valais)

8.16 Larocque-ToblerI.,QuinlanR.,MüllerStewartM.,GrosjeanM.:Chironomidsasindicatorsofthepast1000yearsofmeanJulyairtemperatures:theSivaplanaandSeebergseerecords

8.17 LombardoU.,Canal-BeebyE.,FehrS.,VeitH.: Pre-Columbianhumanadaptationtoseasonal inundationsintheLlanosdeMoxos,BolivianAmazonia.

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8.18 MalatestaL.,CastelltortS.,PicottiV.,MantelliniS.,HajdasI.,SimpsonG.,WillettS.:HoloceneClimaticVariabilityInCentralAsia;AGeo-ArchaeologicalCaseStudyInSamarkand,Uzbekistan

8.19 OttA.,Ivy-OchsS.,BauderA.,AkçarN.,SchlüchterC.:HoloceneglacieroscillationsatDamma

8.20 PlotzkiA.,VeitH.:HolocenelandscapeevolutionoftheLlanosdeMoxos,NEBolovia

8.21 PreusserF.,GrafH.R.,KellerO.,KrayssE.,SchlüchterC.:QuaternaryglaciationhistoryofnorthernSwitzerland

8.22 ReberR.,TikhomirovD.A.,AkçarN.,YavuzV.,SchlüchterC.:QuaternaryglacialchronologyinAnatolia

8.23 SamartinS.,HeiriO.,TinnerW.: LateGlacialandearlyHoloceneclimaticchanges in theSouthernSwissAlps,reconstructedusingsubfossilchironomidassemblages.

8.24 SchlüchterC.,BurkhalterR.:SwitzerlandattheLastGlacialMaximum(LGM) Anewmap(2009)byswisstopo1:500000

8.25 Schmitt J., Seth B., Fischer H.: How to derive weathering rates from ice core measurements of atmospherictetrafluoromethane?

8.26 SteinemannS.,HamannY.,GilliA.:Detectionofvolcanicashlayersbyhigh-resolutionXRFcorescanning

8.27 StummD.,FischerU.H.,SchnellmannM.,HaeberliW.:AreviewontunnelvalleysinnorthernEurope

8.28 Tikhomirov D., Alfimov V., Akçar N., Ivy-Ochs S., Schlüchter C.: Calibration of 36Cl Production Rate on 39K inSaturatedAntarcticaSamples

8.29 vanRadenU.,GilliA.,KindJ.:HowdoestheelementalcompositionofSwisslakesedimentsreflectpastclimateconditions?

8.30 ZechJ.,ZechR.,KubikP.W.,VeitH.:PastglaciationintheCentralAndesrecordalterationinthetropicalcirculationandtheSouthernWesterlies

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8.1

Surface exposure dating of 1717 AD rock avalanche deposits in the upper Ferret Valley (Italy) with cosmogenic 10Be

AkçarNaki1,DelinePhilip2,Ivy-OchsSusan3,ChristlMarcus3,KubikPeterW.3&SchlüchterChristian1

1 Institut für Geologie, Baltzerstrasse 1+3, CH-3012 Bern ([email protected])2 EDYTEM Lab, Université de Savoie, CNRS, 73376 Le Bourget-du-Lac, France3 Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zürich

OneofthelargestrockavalanchesoftheAlpsoccurredonSeptember12th1717ADinMontBlancMassif.IntheupperFerretValley(Italy),arockvolumelargerthan10millionm3andahugevolumeoficefromtheTrioletglacierweremo-bilizedandmovedmorethan7.5kmdownvalleyandreachedthelowerpartofthevalley(DelineandKirkbride,2009).Thismasscomposedoficeandsedimentdestroyedtwosmallsettlementswith7casualtiesandlossoftheircattle.

Accumulationsofgraniticbouldersandirregularridgesoveradistanceof2kmintheupperFerretterminatedownvalleywitha5m-higharcuatefront(DelineandKirkbride,2009).Thisextensivedepositwasfirstattributedtoglacialdeposits(Deline,2009).Intheirdetailedstudy,PorterandOrombelli(1980)interpretedthisdepositastherockavalancheof1717AD.Aeschlimann(1983)debatedthisinterpretationandclaimedthatthemainpartofthisdepositisaLateglacialmoraine(Deline,2009).Recently,DelineandKirkbride(2009)concludedthatthisdepositisacomplexofglacial,anearlierrockavalancheand1717ADrockavalanchedeposits.Cancosmogenic10Betellusmoreonthisdilemma?

Withtheaimofansweringthisquestion,9graniticboulderswithintheuppervalleydepositand3fromthebouldersoutsideweresampledforsurfaceexposuredatingwith10BeandpreparedforAMSanalysis.10Beexposureagesvarybet-ween300and500yearswithinthelimitsoferror.Theseexposureagesindicatethattheextensivegraniticboulderdepo-sitionwithirregularridgesbelongstothe1717ADrockavalanche.ThisrelationconfirmsthemainpartofthePorterandOrombelli(1980)interpretations.

Figure1.DepositsofupperFerretValley.Yellowline:extentofgraniticboulderaccumulations.Purpleribbon:limitoftherecentmo-

rainiccomplexofGlacierdeTriolet(Deline,2009).

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REFERENCESAeschlimann,H., 1983: ZurGletschergeschichtedes italienischenMontBlancGebietes:ValVeni -Val Ferret - Ruitor.

Ph.D.thesis,UniversitätZürich,Switzerland.Deline,P.2009:Interactionsbetweenrockavalanchesandglaciers intheMontBlancmassifduringthelateHolocene.

QuaternaryScienceReviews,28,1070-1083.Deline,P.&Kirkbride,M.P.,2009:Rockavalanchesonaglacierandmorainiccomplex inHautValFerret (MontBlanc

Massif,Italy).Geomorphology,103,80–92.Porter,S.C.&Orombelli,G.,1980:CatastrophicrockfallofSeptember12,1717ontheItalianf lankoftheMontBlanc

massif.ZeitschriftfürGeomorphologie,24,200–218.

8.2

Origin of Bahamian laminar crusts: new geochronological and petrogra-phic data

AlpouSylvia1,GodefroidFabienne1&KindlerPascal1

1 Section of Earth and Environmental Sciences, rue des Maraîchers 13, CH-1205 Genève ([email protected])

Petrographic examinationand radiometricdatingof surficial laminar crusts collected fromvariousBahamian islandsshowthat,contrarytopreviousthinking,thesecrustsmostlyresultfrombiologicallycontrolledprecipitationattherock/atmosphereinterfaceduringthepast10ka.

LaminarcrustsarewidelyexposedontheBahamasislandsandhavebeeninterpretedasresultingmainlyfromphysico-chemicalprecipitationduringpedogenesis.Further, theyhavebeen identifiedas the lowerhorizonofaWisconsinianpaleosol,whenoccurringinassociationwithclay-richconglomeratesbetweenPleistoceneandHolocenecarbonateunits.Toverifythesehypotheses,wehaveexaminedmicroscopicallyandcarbondatedseveralcrustscollectedfromMayaguanaandSanSalvador.

Allstudiedprofilesconsistofonesingle,orangetobrown,cm-thickcrust,showingasmoothuppersurfacethatrisesandfallswiththepresenttopography.InallcasesitrestsoninduratedPleistocenelimestone.AtGreenCay(nearSanSalvador)andBetsyBay(Mayaguana),thecrustdirectlyoccursattherock/atmosphereinterface,whereasatNWPoint(Mayaguana)andSingerBarPoint(SanSalvador)itiscappedbyaHolocenecalcarenite,withinterveningpocketsofclay-richbrecciaatthelatterlocality.Thecrustlaminationscorrespondtomm-thinalternatingzonesof:

(a)dense,orange,homogeneousorclottedmicritecontainingsparsecalciticspherulites(b)darkerporousmicritecontainingroundedfeatureswithacellulartexture,andalsopeloidsthathavepreservedtheir

primaryaragoniticmineralogy.

TheboundarywiththeslightlyalteredunderlyingPleistocenelimestoneissharp,evenatthin-sectionscale.Rawradio-carbonagesobtainedfromthesecrustsrangefrom9,210to3,270yearsBP.

Ourpetrographicdatashowthatbiological factors, suchascyanobacterial, fungal,andpioneer-plantactivityplayedagreaterrolethanphysico-chemicalprocessesintheformationofthesecrusts.TheiryoungagesuggestthatthisbiologicalactivitycouldberelatedtotheHolocenetransgression,andthattheoverlyingpocketsofclay-richbrecciamustbeinter-pretedasareworkedsoilsedimentofHoloceneage,ratherthanaWisconsinianpaleosol.

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8.3

Organic and mineral sedimentary deposits in the evaporators’ environ-ments of the Sahel of Tunisia (Mahdia): the Baghdadi swamp and the conjugated sebkha of Gotaia and Eliane.

RajaCHAIRI

Laboratoire de Géoressources. Centre de technologie des eaux (CERTE), Technopole Borj cedria BP 273. 8020 SOLIMAN. TUNISIE ([email protected])

Themineralandorganicsedimentarystudiesarerealizedonsedimentarycolumnsof1mofdepthinevaporatorssystemsinthesahelofTunisia(Mahdia).ThesesystemsaretheresultofTyrrheniantectonicaccidents.

TheanalysisoftheorganicmatterbypyrolysisRock-Eval6reveledthepresenceofaheterogeneousorganicmatterstockdominatedbytheligneousfraction.Theoriginatedorganicfractionislimitedinbacteriaactivity.Thehypersalineenvi-ronmentsorevaporatoressystemsareknownforthelowbiologicalvariety.Itisidentifiedwellbythepresenceofsomebiomarkers:alkylbenzenes(C18,C19andC20),hopanes(norlupaneansoleane,)andsteranes(stigmastane,cholestane).

siltyfractionistheessentialmineralfractioninthesystemoftheSahelfromTunisia.Thequartzrepresentsthemainpartofthemineralprocession(90%).Threeclaymineralsarepresents:kaolinite,illiteandsmectite.Onlythesmectiteispartiallysynthesizedintheseenvironments.Theabundanceofthekaoliniteinperipheralsedimentssupportsthesignifi-cantterrigenecontributions.Theidentifiedevaporatesarehalite,gypsumandcalicite.Inthecenter,thehailteconstitutesthesurfacesediments.

Sizedistributionsareinfluencedbytheprevioushistoryofthesedimentandclimatecondition.Clayparticlesaretrans-portedanddepositinthecenterofthesysteminlowenergyconditions.Sandlocatedattheperipheryisdepositbyhighenergy.Thepresenceofbimodalshapeindicatestheperiodofmuddinginthisevaporatorsystemwhichischaracterizedbysquatdynamicenvironment.Howeverthelevelsofsandinthecenterspecifytheinterruptionbythecycleofimportantactivity.

REFERENCESChairiR.,DerenneS.,AbdeljaouedS.&LargeauC.2010):Sedimentcoresrepresentativeofcontrastingenvironments in

saltf latsoftheMokninecontinentalsabkha(EasternTunisia):Sedimentology,bulkfeaturesoforganicmatter,alkanesourcesandalteration.

Chairi, R., 2005 : Etude du remplissage sédimentaire d’un systèmehypersalin de la Tunisie orientale au cours duquaternairerécent:lasabkhadeMoknine.Quaternaire16,107–117.

DisnardJ.R.,JacobJ.&LavrieuxM2008:Marqueursorganiquesetimpactdesactivitéshumainessurlasédimentationlacustre récente du Lac d’Aydat (Puy-de-Dôme). Comptes-rendus du 7èmeCongrès International de Limnologie-Océanographie,Rouan,France.

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8.4

How did fire, human impact and climate change affect Holocene treeline dynamics in the Alps?A case of study from Gouille Rion (Valais, Switzerland)

ColombaroliDaniele1,HennePaul1,KaltenriederPetra1,GobetErika1&TinnerWilly1

1 Institute of Plant Sciences and Oeschger Centre for Climate Change Research, University of Bern, CH-3013 Bern, Switzerland. Corresponding author: [email protected].

IntheAlpineregion,thetreelineecotoneishighlysensitivetoclimaticandland-usechanges.Risingtemperaturesinduceupslope migration of individual species, allowing treeline expansion into unforested landscapes (Harsch et al. 2009).Additionally,ongoingagriculturalabandonmentfavoursafforestationinformerhigh-elevationpastures(Rutherfordet al.2008).Incontrast,forestfiresaffectthetreelineecotone,byreducingfuelloadsandpromotingdominanceoffire-pronespecies.Sofar,fewlong-termpaleoecologicalstudieswithhightemporal-resolutioninvestigatedhowfirevariabilityaffec-tedtreelinedynamicsespeciallyintheAlpineregion,wherepeoplehavealteredfireregimesatleastsincetheNeolithic(Gobetet al.2003).

Inthispaper,weuseahigh-resolutionrecordofmacroscopiccharcoalandplantmacrofossilrecordsfromalakeintheSwissAlps(GouilléRion,2343ma.s.l.)to:1)investigatechangesofbiomassburningoverthelast12,000years;2)toderiveresponsesoftree-linevegetationtofireoccurrence;3)todisentangletheroleofhumanvs.climaticfactorsfortheobservedvariabilityinfirefrequency.Forourpurposes,weusedsedimentcharcoaltoreconstructthefrequencyoffireepisodesaroundthelake(e.g.Gavinet al.2007).Secondly,weusedregressionanalysesbetweencontiguousseriesofplantmacro-fossils,macroscopiccharcoalandanavailable reconstructionofpast summer temperature (Heiri et al. 2003), toderivespeciesresponsetofirevariabilityandtosummertemperature.Finally,weusedadynamiclandscapevegetationmodel(LandClim),toexplorepotentialforcingmechanismsoffire-regimechange,specificallytodisentangletheroleofclimatevs.humansonfireoccurrence.

OurresultsshowthatfirewasanaturaldisturbanceagentatthetreelineecotonebutsincetheBronzeAge(c.4000cal.yearsBP)humandisturbanceoverrodetheeffectofclimateincontrollingfirevariability.Also,anthropogenicfireandclimateaffecteddifferentlythecompositionofplantspeciesatthetreeline.Forinstance,whenmeanJulytemperatureswerelowerthanmodernmeanJulyvalues,Juniperus nanaandLarix deciduawereatanadvantageoverP. cembra.Within-creasinganthropogenicfire,openlandswith J. nanareplacedL. deciduaandP. cembraforeststands.Pinus cembrainsteadcouldexpandduringperiodswithtemperatureabovethemodernmeanJulytemperatureiffiredisturbancewasnottoosevere.

Figure1.A)LocationoftheinvestigatedsiteintheValais.B)OccurrenceofPinuscembranearthesiteatthetreeline(photofrom

Tinner1996).C)Reconstructedlocalfirehistoryoverthelast12,000years(modifiedfromColombaroliet al.inpress).

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OurstudymightberelevantforfuturedevelopmentofAlpineecosystemsunderglobalchangescenarios,suchasthere-sponseofthetreelineecotonetowarmingtemperatureandincreasinganthropogenicfire(Tinner&Kaltenrieder2005).Althoughclimatechangewillaltervegetationcomposition,futuredynamicsofmountainforestswillbeco-determinedbyanthropogenicfire.Forinstance,highfirevariabilitymaydelayorimpedeupslopeestablishmentofforestsinresponsetoclimaticwarmingasexpectedforthiscentury,withseriousimplicationsforforestdiversity.

REFERENCES:Colombaroli,D.,Henne, P.D.,Gobet, E., Kaltenreider, P.&Tinner,W.: Species responses to fire, climate, andhuman

impact at tree-line in theAlps as evidencedbypaleo-environmental records anddynamic simulation approaches.JournalofEcology(inpress).

Gavin,D.G.,Hallett,D.J.,Hu,F.S.,Lertzman,K.P.,Prichard,S.J.,Brown,K.J.,Lynch,J.A.,Bartlein,P.&Peterson,D.L.2007:Forest fire and climate change inwesternNorthAmerica: insights from sediment charcoal records. Frontiers inEcologyandtheEnvironment,5:499-506.

Gobet,E.,Tinner,W.,Hochuli,P.A.,vanLeeuwen,J.F.N.&Ammann,B.2003:MiddletoLateHolocenevegetationhistoryoftheUpperEngadine(SwissAlps):theroleofmanandfire.VegetationHistoryandArchaeobotany,12,143-163.

Harsch,M.A.,Hulme,P.E.,McGlone,M.S.2009:Aretreelinesadvancing?Aglobalmeta-analysisof treelineresponsetoclimatewarming.EcologyLetters,12,10,1040-1049.

Heiri, O., Lotter, A.F., Hausmann, S. & Kienast, F. 2003: A chironomid-basedHolocene summer air temperaturereconstructionfromtheSwissAlps.TheHolocene,13,477-484.

Rutherford,G.N., Bebi, P., Edwards, P.J.&Zimmermann,N.E. 2008:Assessing land-use statistics tomodel land coverchangeinamountainouslandscapeintheEuropeanAlps.EcologicalModelling,212,460-471.

Tinner2006:TreelinestudiesIn:EliasS.A.(ed.)EncyclopediaofQuaternaryScienceElsevier,Amsterdam2374-2383.Tinner,W.&Kaltenrieder, P. 2005: Rapid responses of high-mountain vegetation to earlyHolocene environmental

changesintheSwissAlps.JournalofEcology,93,936-947.

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8.5

Erosion and filling of a glacially overdeepened trough in the northern Alpine Foreland as recorded in deep drill core NW09 from Niederweningen, Switzerland

AndreasDehnert1,HansAxelKemna1,FlavioS.Anselmetti2,RuthDrescher-Schneider3,HansRudolfGraf4,SallyLowick5,FrankPreusser5,AndreasZüger6&HeinzFurrer1

1 Palaeontological Institute and Museum, Karl Schmid-Strasse 4, CH-8006 Zurich ([email protected])2 Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf3 Schillingsdorferstrasse 27, A-8010 Kainbach bei Graz4 Matousek, Baumann & Niggli AG, Mäderstrasse 8, CH-5401 Baden5 Institute of Geological Sciences, Baltzerstrasse 1+3, CH-3012 Bern6 Oeschger Centre for Climate Change Research, Zähringerstrasse 25 CH-3012 Bern

AsthemajorweatherdivideinEurope,theAlpsrepresentoneofthemostinterestingareasforunderstandingpastclima-techangeanditsimpactoncontinentalenvironments.However,ourknowledgeoftheQuaternaryenvironmentalhistoryoftheregionisstillratherlimited,especiallyforthetimeprecedingthelastglaciationoftheAlps.

GeologicalandgeophysicalstudiesintheWehntal,20kmnorthwestofZurich,in2007and2008haverevealedtheexis-tenceofaglaciallyoverdeepenedtroughcutintoMiocenemolassebedrock,whichistodayfilledwith~90to180mofQuaternarysediments.

InMarch2009,a93.6mlongsedimentcoreNW09/1hasbeendrilleddowntobedrockeastofafamousmammoth-siteinNiederweningen.Thisdrill core representsoneof thevery fewrecords in thenorthernAlpineForeland thatprovidescrucialinsightsintotimingoferosionandinfillinghistoryofpre-Eemianglaciallyoverdeepenedstructuresandalsohelpstounderstandtheclimateandenvironmentalhistoryofmultipleglacial-interglacialcycles.

Onthebasisofmulti-proxydataandextendedluminescencechronology,therecoveredsedimentsuccessionisinterpretedfrombottomtotopas:4.1mofin-situmolassebedrock,overlainby3.4mofdiamictictill.Theglacialsedimentwasde-positedbyalobeofthecombinedWalenseebranchofRhineGlacierandtheLinthGlacierduringMarineIsotopeStage(MIS)8. It issuggestedthatthisextensive iceadvance,whichoncecoveredtheentireWehntalvalley,causedthefinalerosionofthebedrock.Thetillmergesseamlesslyintoa29.5mthicksequenceoflaminated,carbonate-rich,fine-grainedsiliciclasticsedimentsthatareinterpretedasproglaciallakesediments,whichaccumulatedalsoduringMIS 8.Thisunitwaslikelydepositedinaproximalsettingtoacalvingglacier-frontconfirmedbythepresenceofnumerousdropstones.

ThedammingofthisWehntalpalaeolakewasmostlikelycausedbyaterminalmorainelocated~3 kmtothenorthwestofthedrillsite.Theoverlying37.9moffine-grainedlakesedimentsarecomparabletotheformerunit,butabsenceofdropstonesindicatesamoredistalproglaciallakefaciesandthus,aretreatofthefeedingglacierlobe.

Loworganiccarboncontentspointtoalmostnobiologicalactivitywithinthelakeandsuggestcoldenvironmentalcondi-tions.FeldsparluminescencedatingshowedthattheformationofthisunitoccurredoverthewholeMIS7.Thisunitisunconformablyoverlainby9.5moffine-grainedmaterial.ThehiatuscoversalmostthecompleteMIS 6,whichisbelievedtorepresentamajorglaciationofthenorthernAlpineForeland.

Although,astrikingdropincarbonatecontent(from~45to20wt%)andshearstrength,aswellasanincreaseingrain-size(fromclayeysilttofinesand)canbenoticed,noobviouserosionalfeaturescanbeseeninthesedimentfabric.ThechangeincarbonatecontentisinterpretedasadecouplingoftheWehntalcatchmentfromtheRhein/LinthGlaciersys-temsthatoriginateinacarbonate-richhinterland.

ThetopoftheunitdocumentsagradualinfillingofthepalaeolakeandonsetofbiologicalproductivityduetoclimatewarmingduringearlyMIS 5.Thisisalsodocumentedbyoccurrenceofpost-sedimentarypyriteandsideriteconcretions.

The prominent environmental change culminates in the abrupt accumulation of peat (1.8m) during late interglacialMIS 5e(Eemian).Afterwards,theWehntalwasreoccupiedbyayoungerpalaeolakef loodingthepeat.Theresulting4.9 mofbluish-graysiltysedimentshavecarbonatecontentsof~25 wt%andrelativehighorganiccarboncontents(~1 wt%).LuminescencedatesputthissedimentunitintoearlyMIS 3.

ThesourceofsedimentisinterpretedasderivedfromthemolassicZurichHighlandsandtheJurassiclimestoneoftheLägernmountainchain,whichborderstheWehntalvalleytothesouth.TheactualcauseofriseinwaterlevelsubsequenttodepositionoftheEemianpeat,however,hasnotyetbeenidentified.

Thereafter,theyoungerpalaeolakewasfilled,resultingintheaccumulationof0.7moffossil-richMiddleWürmianpeat,thesocalled‘Mammothpeat’,whichwasfinallycoveredwith2.0mofpost-Würmian-to-recentalluvialsiltsandsands.

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8.6

High-resolution sediment colour and geochemical analysis of Dansgaard-Oeschger events (Cariaco Basin, Northern Arabian Sea)

G.Deplazes1,G.H.Haug1,A.Lückge2,LarryC.Peterson3

1 Geological Institute, ETH Zürich, Sonneggstr. 5, CH-8092 Zürich, Switzerland ([email protected])2 Federal Institute for Geosciences and Natural Resources, Stilleweg 2, D-30655 Hannover, Germany3 Rosenstiel School of Marine & Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, FL 33149, USA

TheanoxicCariacoBasinonthenorthernshelfofVenezuelapreservesdetailedrecordsofpasttropicalclimatevariability.ThesedimentformationinthisbasiniscontrolledbythemigrationoftheAtlanticIntertropicalConvergenceZone(ITCZ)andthecorrespondingrainbeltandtradewinds.IntheoxygenminimumzoneoffPakistaninthenorthernArabianSeasedimentarchivesoflow-latitudemonsoonalclimatearepreserved.

Inthisstudysedimentsfromthetwosettingsthatcoverthelast80’000to110’000yearsarecomparedwithGreenlandicecorerecords.Sedimentcolouranalysisresultedinreflectancerecordswithdowntoannualresolution.ThereflectancerecordsoftheCariacoBasinandthenorthernArabianSeafaithfullymimictheGreenlandicecoreδ18Orecord.Anagemodelwassetupbycorrelationoftheserecordstotheδ18OrecordofNGRIP.Themajorelementchemistryofthesedi-mentswasanalysedwithX-rayf luorescencescanning.

Colourvariationsinthesemarinesedimentsreflectchangesinredoxstateandrelativecontributionsofterrigenousandbiogeniccomponents.Changesinanoxiaandproductivitycanbefurtherexploredusingelementproxiesasmolybdenum,manganeseandbromine.Variabilityintheterrigenousinputcanbetracedbyelementalproxiesastitanium.

ThenewhighresolutionproxyrecordsindicateanunbrokenassociationbetweenwarmclimateconditionsoverGreenland,anortherlypositionoftheAtlanticIntertropicalConvergenceZone,andastrongIndiansummermonsoonsincethelastglacial.ThetightcouplingisexplainedbyadominantroleoftheNorthAtlanticthatiscommunicatedlargelythroughtheatmosphere.NewinsightsofdynamicalmechanismsarisefromcomparisonofindividualDansgaard-OeschgereventsthatsuggestsathresholdresponseofthetropicstoNorthAtlanticcooling.

8.7

Rhone glacier deglaciation in western Lake Geneva : new sismo- and bio-chronostratigraphy results

GirardclosStéphanie1Rachoud-SchneiderAnne-Marie2&BrutschNicolas1

1 Dept Geology and Palaeontology, University of Geneva, Rue des Maraîchers 13, CH-1205 Geneva ([email protected])2 Route de St-Cergue 116b, CH-1260 Nyon

Seismicreflectionandgeotechnicaldrillingwereperformedinspring2009inthewesternpartofLakeGenevawithinapublicprojecttobuildalargebridgeoverthelake.Scientificanalyseofthisseismicandsedimentrecordrevealsnewin-sightsinthehistoryoftheRhoneglacierdeglaciationandLakeGenevaformation.

Seismicdata,acquiredwitha1in3airgunandapingersource,imagesthebedrocklakebasinaswellaseightsismostrati-graphicunitsofglacial,glacio-lacustrineandlacustrinefacies.Intheeasternpartofstudiedarea,gasreducesseismicdataqualitybutnevertheless,thelateralasymmetryofthebasingeometryandofthesedimentinfillappears.Inthewesternpart,thebedrock(i.e.Molasse)formsa3°rampbendingtowardeastwhichistoppedbyonlymaximum30mofsediment.Inthecentreandeasternpartofthelakebasin,thebedrockliesdeeperandiscoveredby70to110mofglacialtolacus-trineunits.

Thedeepestunit(U1),whichwasdetectedonseismiclinesbutnotdrilled,isinterpretedasglacialsedimentsleftduringanolderglacialcycle(Fiore2007).ItistoppedbythethickU6bandU7units,interpretedasmelt-outtilloftheRhoneglacier.Four35to75m-deepdrillingsconfirmthisinterpretationandshowthatunitU6bwascertainlycompactedbya

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re-advanceoftheRhoneglacier.Thisdatarevealsanewglacialstage,olderthanstagesofCoppetandNyon,withaglacialfrontnear‘LeReposoir’.TheasymmetryofunitU7alsoshowsthattheglaciermeltedfirstinthecentralandeasternpartofthelakebasinwhileitwasstilllyingontheMolasse‘ramp’intheWest.

Thenextsequence,representedbyunitsU8-U12,isinterpretedasglacio-lacustrinedeposits.Theyhavevariablesedimen-taryfaciesrangingfrommassivesilttolaminatedclayedsiltwithraresandlayers.Gravelsofalpineoriginand‘galetsmous’inthesiltymatrix,interpretedasdropstones’,pointtotherecurrentpresenceoficebergsinthelake.

TheseismicinfillendswithlacustrineunitsU13-U14.Theseunitsconsistoflacustrinemarlswithshellsandorganicde-bris.InunitU14,athicknessasymmetrybetweeneastandwestsideofthelake,aswellasonlapinggeometrytowardwest,pointtosedimenterosionandtransportbycurrentsdownto35-m-depth.

ThisresultagreeswithpreviousworkondeepcurrentsactioninwesternLakeGeneva(Girardclosetal.2003).OngoingpalynologicalanalysesandC14datingwillgiveanagetoglaciolacustrineandlacustrineunits.Preliminarypalynologicalresultsrevealthatnon-reworkedpollenissurprisinglypresentinglaciermelt-outtill(U7).

This project is partly financed by the Fondation Ernest Boninchi, the Fondation Ernest et Lucie Schmidheiny and the Swiss Civilian Service. Thanks to De Cerenville Geotechnique and the State of Geneva for access to drillings and geotechnical data.

REFERENCESFioreJ.2007:QuaternarysubglacialprocessesinSwitzerland:GeomorphologyofthePlateauandseismicstratigraphyof

WesternLakeGeneva.TerreetEnvironnement69.UniversityofGeneva,169pp.Girardclos,S.,Baster,I.,Wildi,W.&PuginA.2003:Bottom-currentandwind-patternchangesasindicatedbyLate-Glacial

andHolocenesedimentsfromwesternLakeGeneva(Switzerland).EclogaegeologicaeHelvetiae96Suppl.1,39-48.

8.8

Climate in the southern Black Sea coast during the Holocene: Implications from the Sofular Cave record

GöktürkOzanMert11,2,FleitmannDominik1,2,BadertscherSeraina1,2,ChengHai3,EdwardsLawrence3,FankhauserAdelheid1,TüysüzOkan4,KramersJan1

1: University of Bern, Institute of Geological Sciences, CH-3012 Bern, Switzerland (1 [email protected])2: Oeschger Center for Climate Change Research, CH-3012 Bern, Switzerland3: University of Minnesota, Department of Geology and Geophysics, MN-55455 Minneapolis, USA4: Istanbul Technical University, Eurasia Institute of Earth Sciences, TR-34469 Istanbul, Turkey

WepresenttheupdatedHolocenesectionoftheSofularcavestalagmitestableisotoperecordfromthesouthernBlackSeacoast(northernTurkey).δ13Ctimeseriesofthisrecordandthegrowthratesprovetobemoreusefulthanδ13Cindeciphe-ringHoloceneclimatevariations,astheyapparentlyreflectthehydrologicalconditionsabovethecave.

Althoughthegrowthratesimplythatprecipitationamountwasapparentlyhigherinthisregionintheearlytomid-Ho-loceneandtherainfallpatternscouldwellhavebeendifferentthanthepresent,thereisnodistinctdifferenceintheef-fectivemoisturelevel;afindingwhichcontrastswiththeevidencefromvariousEasternMediterraneansites.Moreover,somewell-definedclimaticanomaliessuchasthe4.2and8.2kyreventsarenotclearlyexpressedintheSofularcavere-cord;atleasttheylookunexceptionalconsideringsimilar‘anomalous’periods.

WeconcludethatthepeculiaritiesinourresultsreflecttheinfluenceoftheBlackSeaandtheAnatoliantopographyinmodifying the climate of this region, which should be important for the more subtle climatic changes during theHolocene.Nevertheless,theSofularcaverecorddoesprovidehintsandposenewquestionsabouttheconnectionbetweenregionalandlargescaleclimates,highlightingtheneedforamoreextensivenetworkofhighqualitypaleoclimaterecordstobetterunderstandtheHoloceneclimate.

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8.9

Incision and deformation recorded by Quaternary fluvial terraces in Makran accretionary wedge, SE-Iran

HaghipourNegar1,2,KoberFlorian1,BurgJean-Pierre1,ZeilingerGerold3,Ivy-OchsSusan4,KubikPeter5,FaridiMohammad2

1 Geological Institute, ETH Zurich, Sonneggstrasse 5, CH-8092 Zurich ([email protected]) 2 Geological Survey of Iran, Meraj Avenue, Azadi Square, P.O. Box 13185-1494, Tehran, Iran 3 Institute für Geowissenschaften, Universität Potsdam, D-14476 Golm, Deutschland4 Institute of Ion Beam Physics, Particle Physics, ETH Zürich, CH-8093 Zürich, Switzerland and Department of Geography, University of Zürich, CH-8057 Zürich, Switzerland5 PSI/ c/o Ion Beam Physics, Particle Physics, ETH Zürich, CH-8093 Zürich, Switzerland

Thewell-preservedsequencesofmarineandf luvialterracesfoundalongcoastalandinnerMakranarethegeomorphicexpressionofsurfaceuplift.TheMakranaccretionarywedgeisanexcellentexamplewherethepoorlydescribedquater-nary sequencesanddriving forces for theirgenesis canbe studied forabetterunderstandingof thecontributionandfeedbackofsurfaceprocessestothegrowthofthewedge.Wefocusedonf luvialterracestoextractpossibletectonicandclimaticdrivingforces.Forthispurpose,weaimtocorrelateriverterracesbetweencatchmentsandbetweendifferentsegmentsofthesamerivertodocumentthedistributionofdeformation-upliftonthewedgeinrecenttimes.Weinvesti-gatedfourmaincatchmentsintheIranianMakranwheretheriverspreserveseveralterraces.Fourterracelevelscanbetracedfromfieldsurveyanddetailedmappinginallthecatchments.Outofthesefourlevels,twoareregionallypreemi-nent.Deformedterracesarelocalizedandassociatedwithactivefaultsandfolds.DuetothelackoforganicmaterialandsandydepositsininnerMakran,ourdatingmethodwasrestrictedtoTerrestrialCosmogenicNuclides.Thepreliminaryagesfortheabandonmentoftwopreeminentterracesarearound90ka(T1)and21ka(T2).Thef luvialincisionratesbasedonthe10Beexposuresagesofthesetwolevelsare0.5mm/yrinthelatePleistoceneand1mm/yrinlatestPleistocene,whichsuggestsenhancementofsurfaceupliftrateinthelatestPleistoceneandQuaternary.Thesepreliminaryresultsdifferfrompreviousworkonmarineterraces,whichdocumented0to0.2mm/yrupliftrateinPleistocenetimes.Toavoidanyfalseinterpretation,especiallyonregionalscale,moreterracedatingisinprogress.

8.10

The Kestanbol Granite (Western Turkey) and its importance as a building stone: Application of cosmogenic 10Be to an archaeological problem

HaudenschildEsther1,AkçarNaki1,YavuzVural2,Ivy-OchsSusan3,4,AlfimovVasily3,KubikPeterW.3,&SchlüchterChristian1

1 Institut für Geologie, Baltzerstrasse 1+3, CH-3012 Bern ([email protected])2 Istanbul Technical University, Faculty of Mines, TR-80626 Maslak, Istanbul3 Institute of Particle Physics, ETH Hönggerberg, CH-8093 Zurich4 Department of Geography, University of Zurich, CH-8057 Zurich

KestanbolGranite,outcroppingintheEzinevillageofÇanakkale(Fig.1),havebeenoperatedfortheproductionandexportofbuildingstonessinceancienttimes.ItisknownthattheRomansweretradingtheKestanbolGranite(MarmorTroadense)allovertheMediterraneanregion(Lazzarini,1987).Today,leftoversofbuildingstonescanstillbefoundinrelictquarries.Thetypesofbuildingstonesvaryfrompavementstonesto11meterslongcolumns(Fig.2).Thereisalackofinscriptionsandofabsolutedatingof thesequarries (Ponti,1995), so that thearchaeologists canroughlyestimate the timeof thequarryingoftheKestanbolGranitefrom500BCto500AD(Feuser,2009).Suchvaguelimitationgivesneitheranypossibi-lityforunderstandingthedevelopmentintimeoftheexploitationareaofthequarriesnoraboutthehistoricalandpoli-ticalcontextofthequarrying(Ponti,1995).

Keepingtheseinmind,theaimofourstudyistodeterminethedistributionandoperationperiodsofantiquequarriesneartheEzinevillageofÇanakkale.Inordertoachievethis,thedetailedarchaeo-geologicalmapoftheextentofancient

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humanimpacthasbeenproducedandsurfaceexposuredatingwithin-situproducedcosmogenic10Beapplied.Forexpo-suredating,27samplesfromthequarries,buildingstonesandnatural(withoutanyhumanimpact)bedrockwerecollec-ted.Accordingtoourfirstresultsfromthebedrocksamples,thelandscapeinthestudyareaisolderthan120ka.Thesamplesfrombuildingstonesandquarriesarestillinprogress.Duringourmapping,fundamentsofseveralbuildingofunknownpurposes(notyetdescribedintheliterature)weredetermined.Furthermore,oreandslagpiecesinthestudyareawerefound.

OurresultsgivebothinsightstotheimportanceofthequarriesinthesocialstructureinancientcitiesintheregionsuchasNeandreiaandAlexandriaTroasandthechronologicaldevelopmentofthearealquarryexploitation.Inbrief,there-sultsofourstudycancontributeinshort-termtothedeclarationofthesequarriesasageoarchaeologicalheritagesite,andinlong-termtotheirrehabilitationasanopen-airmuseum.

Figure1.MapoftheapproximatearealdistributionofthequarriesintheKestanbolGranite(Ponti,1995).

Figure2.Ancientromanquarry“YediTaşlar”nearKoçali.

REFERENCESFeuser,S.,2009:DerHafenvonAlexandriaTroas.AsiaMinorStudien63,16-17.Lazzarini,L.,1987:IgranitideiMonumentiItalianieIloroproblemidideterioramentoin:Bureca,A.,Tabasso,M.L.&

PalandriG.:MaterialiLapideiII,Bollettinod’ArteSuppl.41,157-172.Ponti,G.,1995:MarmorTroadense–GraniteQuarriesintheTroad.Apreliminarysurvey.StudiaTroica5,1995,291-320.

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8.11

European climate change at the end of the last glaciation: chironomid–based temperature reconstruction on a continental scale

HeiriOliver1,2,BirksJohn3,BrooksSteve4,KirilovaEmilyia2,MagyariEnikö5,MilletLaurent6,MortensenMortenFischer7,SamartinStéphanie1,TinnerWilly1,TothMonika8,VeskiSiim9&LotterAndréF.1

1 Institute of Plant Sciences and Oeschger Centre of Climate Change Research, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland ([email protected]) 2 Palaeoecology, Utrecht University, Budapestlaan 4, CD 3584 Utrecht, Netherlands3 Department of Biology, University of Bergen, Allegaten 41, N-5007 Bergen, Norway4 Natural History Museum, Cromwell Road, London SW7 5BD, UK5 Hungarian Natural History Museum, P.O. Box 222, H-1476 Budapest, Hungary6 Laboratoire de Chrono-Ecologie, 16 route de Gray, 25 030 Besançon, France7 The National Museum of Denmark, Aarhus, Denmark7 Balaton Limnological Research Institute, Klebelsberg Kuno 3, HU-8237 Tihany, Hungary8 Institute of Geology at Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia

InEuropethewarmingtrendattheendofthelasticeagewascharacterizedbyanumberofabrupttemperaturesshifts,includingtherapidtransitionstowarmerclimateatthebeginningoftheLateglacialInterstadialandtheHolocene,andthecoolingat thestartof theYoungerDryascoldperiod.TheamplitudeandspatialpatternofLateglacial changes intemperaturecanprovideinformationabouttheforcingfactorscausingtheseclimateshiftsandaboutprocessesaffectingtheEuropeanclimatesystemduringatransitiontoawarmerclimatestate.However,spatiallyresolveddatasetsdescribingtemperaturechangeacrosstheEuropeancontinentduringtheLateglacialperiodatcentennialorhighertimeresolutionandbasedonthesamestandardizedapproacharepresentlynotavailable.Weaimtodevelopsuchastandardizeddatasetbasedonrecordsofpastsummertemperaturereconstructedfromfossilchironomidassemblagespreservedinlakesedi-ments.Acombinationofregionalcalibrationdatasetsprovidedthebasisforachironomid-basedinferencemodelforJulyairtemperaturewhichcoverstherangeofexpectedtemperaturesandchironomidassemblagestatesexpectedforEuropeduringtheLateglacialperiod.Thismodel,whichisbasedonmodernchironomidassemblagesfrom274lakesinNorwayandSwitzerlandandassociatedobservedvaluesofmeanJulyairtemperature,wasthenusedtoproducefirstchironomid-based temperature records from Estonia, Denmark, the Netherlands, southeastern France, southern Switzerland, andsouthernRomania.Thepreliminary results indicatedistinctvariations in theamplitudeof reconstructed temperaturechangesacrossEuropewithstrongershiftsininferredJulyairtemperaturesrecordedinnorthernpartsthanatlocalitiesmoretothesouthofthecontinent.FutureworkwillexpandthisdatasettoincludeadditionalsitesontheBritishIsles,theIberianPeninsula,Italy,BulgariaandScandinaviainordertoconfirmtheobservedspatialpatternofLateglacialtem-peraturechanges.

8.12

Reconstructing the deglaciation history of the Gotthard Pass area, Central Swiss Alps, using cosmogenic 10Be and in-situ 14C

HippeKristina1,Ivy-OchsSusan2,KoberFlorian3,WielerRainer1&SchlüchterChristian4

1 Institute of Geochemistry and Petrology, ETH Zürich, CH-8092 Zürich ([email protected])2 Institute for Particle Physics, ETH Zürich, CH-8093 Zürich3 Institute of Geology, ETH Zürich, CH-8092 Zürich4 Institute of Geological Sciences, University of Bern, CH-3012 Bern

DuringtheLastGlacialMaximum(LGM)upto500moficecoveredtheGotthardPassarea(2106ma.s.l.)atpeakconditions(Florineth&Schlüchter1998).ThisiceoriginatedfromtheRhoneicedome,oneofthetwobigicedomesthatexistedintheCentralSwissAlpsduringtheLGM.IcefromtheRhoneglacierf lowedovertheFurkaPassdowntowardstheUrserenarea,wheremassive iceaccumulatedandf lowedfurthersouthusingtheGotthardPassasacentralpathwayformasstransport.Icef lowovertheGotthardPassceasedwiththecollapseoftheLGMicedomesandthedecreaseoficeelevationintheUrserenarea.

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TodeterminethetimingoficeretreatwehavesampledglaciallypolishedbedrockalonganaltitudetransectatthewesternGotthardPassarea.Surfaceexposuredatingbycosmogenic10Beyieldpreliminaryagesof~9.5-12.8ky(correctedforsnowanderosion).Theoldestagewasobtainedfromthelowestelevationrightinthepassarea,whilehighersamplingpointsgiveyoungerexposureages.ThissupportstheconceptthatthepassarearecordstheiceextentoftheLGMwhereasslight-lyhigherelevationswereaffectedbylocalice,probablyduringtheLateglacial.

Ourdataareinagreementwith10BeexposureagesfromthenearbyGrimselPass,givingaminimumageof~14.0kyforthefinalbreakdownoficedomesintheCentralAlps(Kellyetal.2006).Withintheerrors,ouragesalsoagreewithradio-carbondatafromtheGotthardregionindicatingafinalretreatofsmalllocalglaciersatthebeginningoftheHolocene(Renner1982).

ComparedtoradiocarbonagesfromtheRhonevalley(Welten1982)andSimplonPass(Müller1984),whichshowcomple-telyice-freemainvalleys,theGotthardagesareslightlyyounger.Thus,todetectpossibleperiodsofpost-LGMlocalicecoverage,especiallyinareasapparentlyonlyaffectedbyLGMice,cosmogenicin-situ14Ciscurrentlyanalyzed.Theshort-lived14C(t1/25730y)decaysduringperiodsofburialandcanprovideinformationoncomplexexposurehistoriesandthedurationofburialepisodes.Resultswillbepresentedatthemeeting.

REFERENCESFlorineth,D.&Schlüchter,C.1998:ReconstructingtheLastGlacialMaximum(LGM)icesurfacegeometryandf lowlines

intheCentralSwissAlps.Eclogaegeol.Helv.91,391-407.Kelly,M.A.,Ivy-Ochs,S.,Kubik,P.W.,vonBlanckenburg,F.&Schlüchter,C.2006:Chronologyofdeglaciationbasedon

10BedatesofglacialerosionalfeaturesintheGrimselPassregion,centralSwissAlps.Boreas35,634-643.Müller,H.-N. 1984: SpätglazialeGletscherschwankungen indenWestlichenSchweizerAlpenund imNordisländischen

Tröllaskagi-Gebirge.205pp.BuchdruckereiKüng,Näfels.Renner,F.,1982:BeiträgezurGletschergeschichtedesGotthardgebietesunddendroklimatologischeAnalysenanfossilen

Hölzern.PhysischeGeographie8,1–180.Welten,M., 1982: Vegetationsgeschichtliche Untersuchungen in denwestlichen Schweizer Alpen: Bern-Wallis.

DenkschriftenderSchweizerischenNaturforschendenGesellschaft95,1–105.

8.13

Do magnetic properties reflect climate history in Swiss lakes?

JessicaKind1,AnnHirt1,UlrikevanRaden2

1 Institute of Geophysics ETH, CH 8096 Zurich, Switzerland ([email protected])2 Institute of Climate Geology ETH, CH 8096 Zurich, Switzerland

ThequestionofthisstudyiswhethermagneticparametersoflacustrinesedimentsfromSwisslakescanbeusedashigh-resolutionproxyforenvironmentalchange.Weexaminevariationsinthemagneticmineralogyfromtwolakes,SoppenseeandBaldeggersee,coveringthelatePleistoceneandHolocenetoinvestigatehowthesedimentsareaffectedbychangesinvegetation,erosional input, sedimentation, redoxchanges,andgeochemistry.Magneticmineralogy isdeterminedbyacombinationoflow-temperaturemeasurements,coercivitydistributionsandextraction.Themultiproxyclimaterecordsare currentlybeingestablished.Magneticproperties areused to indicate the typeand concentrationof ferromagneticmineralsinthelake.Weutilizeacombinationof:1)concentrationdependentparameters(magneticsusceptibilityχ,an-hystereticremanentmagnetizationIRM),2)compositionindicativeparameters(saturationisothermalremanentmagneti-zationIRM/SIRM),and3)grainsizedependentparameters(ARM/IRM,hysteresisparameters).

Significantchangesareseeninthesedimentology,geochemistryandmagneticmineralogyintheSoppenseethatarere-latedtotheWuermdeglaciation,Bøling/Allerød(B/A),YoungerDryas(YD),andtotheHolocenewiththeclimaticoptimum(Lotter,2001,Lotteretal.,1997a,Lotteretal.,1997).TheWuermdeglaciationischaracterizedbyhigherdetritalinputwithamixtureofpseudo-singledomain/multidomain(PSD/MD)magnetiteandlowconcentrationofsuperparamagnetic/singledomain(SP/SD)hematite.ClimatictransitionfromthecolderWuermperiodtothewarmerB/Aischaracterizedbyanin-creaseof lowcoercivemagnetite/maghemite,asaconsequenceofdecreasingdetrital input.ThebeginningYDreflectsmoreoxidizingconditionsatthesediment-waterinterface,andisinterpretedtobetriggerfortheappearanceofmagne-totacticbacteria(MTB),resultinginSDmagnetiteofuniformgrainsize,asshowninFigure1.

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TheformationofsideritevarvesisinitiatedinthecolderandanoxicYDwithasubsequenttransitiontocalciticvarvesbetween10to6calkyrPB(Lotteretal.,1997,Hajdasetal.,1993).RisingtemperatureduringtheclimateoptimuminLakeSoppenaround6calkyrBPincreasedprimaryproduction,leadingtoincreasedorganiccontent.Varvesdisappeararound5.5calkyrBPasaconsequenceofgeochemicalchangesatthesediment-waterinterface.Thehigherprimaryproductionatthesurfaceleadstoanuptakeofoxygenatthebottomofthelakeduetodecompositionoforganicmatter.HencethisstageismarkedbyrapidincreaseofferromagneticmineralsasdisplayedinFigure1a)andb).Inconclusion,wecanap-provetheinitialquestion.Thegoodagreementbetweenthechangesinmagneticpropertiesandtheclimaticevolutiondemonstratethatthemagneticpropertiesareausefulandfasttooltoprovideadditionalinformationforhighresolutionclimatestudies.

Figure1:MagneticpropertiesfromLakeSoppena)low-fieldmagneticsusceptibility,ARMintensity(120mTAFwithabiasfieldof100

μT),b)S-ratio(IRMwithabackfieldof300mTnormalizedbyIRMat1200mT),c)ARM/IRM,e)Cacontent,andsumparameterreflec-

tingdetritalinput(Al,K,Ti;Rb;Zr)measuredwithXRFcorescanning.

REFERENCES:HajdasI.,BonaniG.,ZolitschkaB.(2000).Radiocarbondatingofvarvechronologies:SoppenseeandHolzmaarlakesafter

tenyears.Radiocarbon42,349-353.LotterA. (2001). The paleolimnology of Soppensee (Central Switzerland), as evidence by diatoms, pollen, and fossil-

pigmentanalyses.JournalofPaleolimnology25,65-79.LotterA.,MerktJ.,andSturmM.(1997a).Differentialsedimentationversuscoringartefacts:acomparisonoftwowidely

usedpistoncoreingmethods.JournalofPaleolimnology18,75-85.LotterA.,SturmM.,TeranesJ.,andWehrliB.(1997).Varveformationsince1885andhighresolutionvarveanalysesin

hypertrophicBaldeggersee(Switzerland).AquaticScience59,304-325.

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8.14

Giant sub-lacustrine mass movement in Lake Geneva sediment record

KremerKatrina&GirardclosStéphanie

Department of Geology and Palaeontology, University of Geneva, Switzerland ([email protected])

LakeGenevawithanareaof582km2andamaximaldepthof310m,wasformedduringthePleistocenebyglacialerosionandisthefirstlargesinkforsedimenttransportedbytheRhoneriver.

AspartofaSwissNationalFundprojectonclasticsedimentinlacustrinerecords(nr.200021-121666/1),morethan100kmofhigh-resolutionseismicreflexionprofileswereacquiredwitha3.5kHzpingersourceinthedeepestpartoflakeGeneva.

Preliminaryresultsshowthattheupper5mofthissequenceconsistofalternatingseismicfacies,interpretedasturbiditicandhemipelagiclayers.Thesefaciesoccuragainfroma10-mdepthdownwards.Betweenthesetwosequencesa5-m-thickunitwithchaotic/transparentfacies,interpretedasamassmovementdeposit,coversanareaof50km2.Thisunit,withanestimatedminimumvolumeof0.3km3,representsthelargestsub-lacustrinemass-movementdepositinSwitzerland.Thethicknessmapofthisunitshowsanincreasetowardseast,thusattributingitsorigintotheRhonedeltaarea.Possibletriggerofthismassmovementisearthquake,rockfall,slopeslideoracombinationofthesecauses.

Ongoing10-m-deepsedimentcoringwillcharacterizethedepositaswellastheageofthemassmovementinordertolinkittoknownhistoricalandprehistoricalevents.

8.15

Contribution of geoelectrical measurements and shallow drillings for detection of Holocene palaeochannels in the Saillon region (Valais)

LaigreLaetitia1,ReynardEmmanuel1,Arnaud-FassettaGilles2,BaronLudovic3&LambielChristophe1

1 Institut de Géographie, Université de Lausanne, Dorigny – Anthropole, CH-1015 Lausanne ([email protected])2 Université de Paris Est-Créteil-Val-de-Marne – UMR 8591 CNRS – Laboratoire de Géographie Physique, Meudon.3 Institut de Géophysique, Université de Lausanne, Dorigny – Amphipôle, CH-1015 Lausanne

UpstreamofLakeGeneva,theRhôneRiverunderwentseveralmorphologicalchangesduringtheHolocene.Severalgeo-electricalmeasurementshavebeencarriedoutbetweenSionandMartigny(Valais),particularlyintheSaillonregion,inordertoidentifyformerburiedchannels.ComparisonsofseveralhistoricalmapsshowthattheRhôneRiverunderwentf luvialmetamorphosesduringthe19thcentury(Reynardetal.,2009;Laigreetal.,inpress).TheassociationofhistoricalmapsandDEM-LIDARanalyseshelpedustoidentifysomepalaeochannelsanteriortothoseindicatedbymaps.

Becauseofthedifferentelectricalresponsesgivenbygravels,sand,clayandsilts,geoelectricalmeasurementscangivepreciousinformationaboutthegeometryofsediments.Furthermore,ithelpedustolocaliseformerchannelsandtoret-racef luvialdynamics(channelmigration,changeoff luvialpattern).Twosetsofmeasurementswereappliedona500-mwidesite:(i)a5m-depthprofile,withafineresolution,inordertoobserverecentarchitectureofsediments;(ii)a40 m-depthprofile,withalowerresolutionthatprovidedadeeperviewofthesedimentstratigraphy.Inparallel,somehandhaugerdrillings(upto3m-depth)weredoneregularlyalongthegeoelectricalprofilesinordertocomparethenatureoftheextractedsedimentswithreturnedelectricalsignals.Thesetworesolutionrecordsshowtheexistenceofbraidedchan-nelsnowburiedatadepthofalmost20mthatdisappearatadepthof6m.Somechannelmigrationsarealsovisibleinthefirst5meters,andbringfundamental informationthathelpsustoreconstructthef luvialdynamicsoftheRhôneRiver,thatislittledocumentedupstreamofLakeGeneva.

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REFERENCESLaigre, L.,Arnaud-Fassetta,G., Reynard, E. Cartographie sectorielle dupaléoenvironnement de la plaine alluviale du

RhônesuissedepuislafinduPetitAgeGlaciaire: lamétamorphosef luvialedeViègeàRarogneetdeSierreàSion.BulletindelaMurithienne(inpress).

Reynard,E.,Arnaud-Fassetta,G.,Laigre,L.&SchoeneichP.2009:LeRhônealpinsousl’angledelagéomorphologie:étatdes lieux. In: LeRhône: dynamique,histoire et société (Ed.ByReynard,M., Evéquoz-Dayen,M.&Dubuis, P.) Sion:CahierdeVallesia21,75-102.

8.16

Chironomids as indicators of the past 1000 years of mean July air tempe-ratures: the Sivaplana and Seebergsee records

Larocque-ToblerIsabelle1,QuinlanRoberto2,MüllerStewartMonique1,&GrosjeanMartin1

1 Oeschger Center and Institute of Geography, University of Bern, Erlachstrasse 9A, 3012 Bern ([email protected])2 Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada, M3J 1P3

Chironomid(non-bitingmidges)larvaepreservedinlakesedimentscanbeusedtoquantitativelyandsuccessfullyrecon-structmeanJulyairtemperature,asshownbyacomparisonbetweenchironomid-inferredtemperaturesandinstrumentaldata(Larocqueetal.,2009).Althoughtheyareoneofthemostpromisingbiologicalproxytoreconstructclimate,theywere,up-to-date,rarelyusedtoreconstructhigh-resolutionclimaticchangesofthepast1000years.Thefirstnear-annualtemperaturereconstructionwasrecentlypublished (Fig.1;Larocque-Tobleretal.,2010)andshowed±1°Ctemperaturevariations(comparedtotheclimatenormal(1961-1990)duringtheendofthe“MedievalClimateAnomaly”,the“LittleIceAge”andduringthe“Anthropocene”inLakeSilvaplana,Engadine.LakeSilvaplana(46°26’56’’N,9°47’33’’E)isatanaltitu-deof1791ma.s.l.,ithasamaximumdepthof77mandavolumeof127X106m3.Attemptingatemperaturereconstruc-tionissuchadeep,varvedlakewas,forchironomids,unprecedentedatnear-annualresolution.

Basedonthissuccess,asecondattemptatreconstructingmeanJulytemperatureforthepast1000yearsathightemporalresolutionusingchironomidspreserved inthesedimentof themeromicticSeebergseewasmade.Seebergsee (46°37’N,7°28’E)islocatedat1830ma.s.l.inthenorthernSwissAlps.Thesurfaceareaofthelakeis0.06km2,itsvolumeis0.38km2andithastwobasinswithmaximumdepthsof15.5and9m.Anoxiaisoneoftheinfluentialfactors,otherthanclimate,affectingchironomidassemblagesandanoxiclakesareusuallydismissedforclimatereconstruction.However,biogenicvarvesareoftencreatedwhenanoxiaispresent.Ifanoxiclakesaredisregardedfortemperaturereconstructionusingchironomids,ithampersthepossibilityofhigh-resolutionrecords.Here,wereconstructedclimateusingchirono-midsinthesedimentofSeebergseetodetermineifa)chironomidsinanoxiclakecanbeusedtoquantitativelyandsuc-cessfullyreconstructmeanJulyairtemperatureandb)ifthepatternoftemperaturechangesforthepast1000yearsinbothcantons(EngadineandBern)issimilar.

Today,theanalysisinSeebergseehasbeenmadefortheAnthropoceneperiod(Fig.1).Thepatternoftemperaturechangesforthepast100yearsissimilartotheinstrumentaldata(Larocque-Tobleretal.submitted)andsimilartotheSilvaplanarecord.68moresamplesarebeingcurrentlyanalyzedandwillbepresentedduringthemeeting,tocompletethepast1000-yearreconstructionofmeanJulytemperatureatSeebergseeandcomparewiththeSilvaplanarecord.

REFERENCESLarocque, I., Grosjean,M., Heiri, O., Bigler, C. & Blass, A. 2009: Comparison between chironomid-inferred July

temperatures andmeteorological dataAD1850–2001 fromvarved Lake Silvaplana, Switzerland. J Paleolimnol 41:329–342

Larocque-Tobler, I., Grosjean,M., Heiri, O., Trachsel,M. &Kamenik, C. 2010: Thousand years of climate changereconstructed fromchironomidsubfossilspreserved invarved-lakeSilvaplana,Engadine,Switzerland.QuatSciRev29:1940-1949

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Figure1.TemperaturereconstructionsusingchironomidspreservedinthesedimentofSilvaplana(leftgraph;fromLarocque-Tobleret

al.2010)andSeebergsee(rightgraph).

8.17

Pre-Columbian human adaptation to seasonal inundations in the Llanos de Moxos, Bolivian Amazonia.

LombardoUmberto1,Canal-BeebyElisa2,FehrSeraina1,VeitHeinz1

1 Institute of Geography, University of Bern, Hallerstrasse CH-3012, Bern ([email protected])2 School of International Development, University of East Anglia, UK

TheLlanosdeMoxos(LM),inBolivia,isoneofthelargestseasonallyf loodedsavannahintheworldandcoversmostofthesoutheasternAmazonbasin.Inthelastdecade,theLM,hascapturedtheinterestofgeographersandarchaeologistsbe-causeoftheimpressiveamountofpre-Columbianearthworksitholds.

DifferentkindsofearthworksarefoundindifferentareasoftheLM,butitisstillunclearwhetherthisisduetothedif-ferentculturesthatinhabitedtheLMortodifferencesinthegeographicalsettingsbetweentheeasternandwesternsidesof the region. The western Llanos holds an impressive amount of pre-Columbian agricultural fields (raised fields),(Lombardo et al. submitted) while the eastern Llanos is characterized by a dense distribution of monumental earthmounds,canalsandcauseways(figure1)(Lombardo&Prümers,2010).Earthmoundsarehugebuildingsthatcancoverupto20hectaresandcanbeupto20metershigh.Archaeologicalexcavationshaveshownthattheyaremanmadeanddatebacktopre-Columbiantimes.

Currentmodelssuggestthatraisedfieldagricultureprovidedhighyieldswithouttheneedoffallowperiods,representingakindofpre-Columbiangreenrevolution.However,evidencesuggeststhatthehighestlevelofsocialcomplexitywasre-achedintheeasternLlanos,whereraisedfieldsarenotpresent.Ourresearchhasfocusedontryingtoexplainthisappa-rentcontradiction.

An importantdifferencebetween theeasternLlanosand thewesternLlanoswhichhasoftenbeenoverlooked is theirhydrology.FloodinginthewesternLlanosismoreseverethanintheeasternLlanosbecauseitistheresultoflocalpreci-pitationsandriveroverflows,whilefurthereastitonlyrespondstolocalprecipitations.Therefore,inthewesternLlanos,inordertoproducefood,morefar-reachingdrainageinfrastructureswereneededthanintheeast,whereconditionsweremorefavorableforcultivationandcanalsweresufficienttodrainthesoil.

Webelievethatraisedfieldagriculturewasnotaprehistoricgreenrevolution,assuggestedbysome,butratheraf loodriskmitigationstrategy.Raisedfieldsallowedpre-ColumbianpeoplesinthewesternLMlessentheriskofmoreintenseandfrequentf loodingthanwasexperiencedintheeasternLM.Itwouldappearthatpre-Columbianpeoplesadaptedto

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theharshenvironmentalconditionsoftheLMfollowingdifferentstrategiesindifferentareas:IntheeasternLMabetternaturaldrainageseemstohavefavoredthef lourishingofpre-Columbiansocietieswithhighlevelsofsocialcomplexity,whilefurtherwestseveref loodingobligedpre-Columbianpeoplestobuildraisedfieldsandconstrainedtheirgrowthanddevelopment.

Thisstudyhighlightstheimportanceofenvironmentalconstraintsinconditioningpopulationgrowthandculturaldeve-lopmentintheTropics.

REFERENCESLombardo,U.&Prümers,H., 2010. Pre-Columbianhumanoccupationpatterns in the easternplains of the Llanosde

Moxos,BolivianAmazonia.JournalofArchaeologicalSciences,37,1875-1885Lombardo,U., Canal-Beeby, E., Fehr, S., Veit,H., 2010. Raised fields in the BolivianAmazonia: a prehistoric green

revolutionoraf loodriskmitigationstrategy?.SubmittedtoJournalofArchaeologicalSciences

Figure1.MapoftheearthworksintheeasternLlanos.Thesmalltrianglesrepresentmoundsoflessthan8hectares,themediumtri-

anglesrepresentmoundsbetween8and16hectaresandthelargetrianglesrepresentmoundslargerthan16hectares.Thedotsre-

presentforestislandsandtheblacklinescausewaysandcanals.Theforestareaisshadedinlightgreyandthelakesareadarkener

grey(Lombardo&Prümers,2010).

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8.18

Holocene Climatic Variability In Central Asia; A Geo-Archaeological Case Study In Samarkand, Uzbekistan

MalatestaL.1,CastelltortS.1,PicottiV.2,MantelliniS.3,HajdasI.4,SimpsonG.5,WillettS.1

1 Institute of Geology, ETH Zurich, 8092 Zurich, Switzerland 2 Dipartimento di Scienze della Terra e Geologico-Ambiantali, Università di Bologna, 40127 Bologna, Italy 3 Facolta di Conservazione dei Beni Culturali, Università di Bologna, 48100 Ravenna, Italy 4 Insitute of Particle Physics, ETH Zurich, 8092 Zurich, Switzerland 5 Department of Geology and Palaeontology, University of Geneva, 1211, Geneva, Switzerland

ThelateHolocene(around0-500a.AD)climaticregimeofCentralAsiaischaracterisedbycoldwinters,relativelycoolsummersandaridconditions(Oberhänslietal.,2007).TotheWest,theAralSeaexperiencedanimportantregressionofover20mduringthe4thc.AD(Boomeretal.,2000).TheprecipitationpatternintheAralbasinislinkedbytheWesterliestotheatmosphericchangesintheEasternMediterranean,whichisthemainmoisturesourcefortheregion(Sorreletal.,2007).PaleoclimaticdataforthisregionhavebeenmostlygainedbythestudyofsedimentcoresfromtheAralSea(Boomeretal.,2000).FurthermoreHistoricalpaleoclimaticdataforthelasttwomillenniumsinEasternAsiaindicateacoolingtrendintheorderofca.1.2°Cbetween250and350aAD(Zhengetal.,2001).

ThedensehumanHistoryofthecentralAsianMesopotamia–thelandbetweenthetwotributariesoftheAralSea,theSyrDaryaandtheAmuDarya–providesapotentialsupplementaryrecordofpaleoclimateevolution.Settlements,whichwereinfluencedbylocalclimatevariability,stronglymodifiedinreturnthehydrologicregimeofthecatchmentdrainingtotheAralSeathroughextensiveirrigationworks(Kes,1995;Oberhänslietal.,2007).

ThisisparticularlytrueintheZeravshanValley,animportanttributaryoftheAmuDarya.Fromthe4thc.BConwards,itwasoneoftheSilkRoadmainpaths.Largeirrigationworkswereengineeredtosustaintheagriculturearoundthehis-toricalcityofAfrosiab,nowSamarkand(Mantellini,2001;Strideetal.,2009).

TheirrigationsystemupstreamfromthehistoricalcityofAfrosiabconsistsoftwomaincanals,theDargomandtheJangiAryk(Strideetal.,2009).AparticularlywellstudieddwellingnexttotheDargomdocumentsdestructivef loods.Byapply-ingsedimentologicalandsurfaceprocessesmethodstothisarchaeologicalsitewebringoriginalconstraintstotheframe-workandnatureofprecipitationsatthistime.

Wedatedthemainf loodingeventat160±80a.AD.X-RayDiffractionanalysisofthef lood-relatedsedimentssuggestsasourceforthesandsfurtherupstreaminthevalley,i.e.transportedinthecanalandnotcomingfromthenaturalsurroun-dinghillslopes.Weestimatethatanintenseprecipitationeventofatleast65mm/hforatleast2hoursallowsfora0.5mdeepf loodingofthearchaeologicalsitebasedonanumericalmodelsurfaceoverlandf low(SimpsonandCastelltort,2006).Theusualconstructiontype inthevalleyatthistime,elevateddwellings,andtherecurrenceoff loodhorizons inthestratigraphyattestarepetitionoff loodsofsimilarmagnitudeduringthefirstcenturiesADinwesternCentralAsia.

REFERENCES:Boomer,I.,Aladin,H.,Plotnikov,I.,andWhatley,R.,2000,QuaternarySciRev,v.19,p.1259-1278.Kes,A.,1995,GeoJournal.Mantellini,S.,2001,CooperationinArchaeologyandIslamicStudiesOberhänsli,H.,Boroffka,N.,andSorrel,P.,2007,IrrigationandDrainageSystemsSimpson,G.,andCastelltort,S.,2006,ComputGeosci-Uk,v.32,p.1600-1614.Sorrel,P.,Oberhaensli,H.,Boroffka,N.,Nourgaliev,D.,Dulski,P.,andRoehl,U.,2007,QuaternaryRes,v.67,p.371-382.Stride,S.,Rondelli,B.,andMantellini,S.,2009,WorldArchaeology.Zheng,J.,Zhang,P.,Ge,Q.,andMan,Z.,2001,ProgNatSci,v.11,p.280-287.

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8.19

Holocene glacier oscillations at Damma

OttAndrea1,Ivy-OchsSusan2,BauderAndreas3,AkçarNaki1&SchlüchterChristian1

1 Institut für Geologie, Baltzerstrasse 1+3, CH-3012 Bern ([email protected])2 Laboratory of Ion Beam Physics, HPK, Schafmattstrasse 20, CH-8093 Zürich3 Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW), Gloriastrasse 37-39, CH-8092 Zürich

IntherecentlyfreeforefieldoftheDammaglacierintheGöscheneralp,cantonUri,scientistsoftheBIGLINKprojectoftheETHZuricharestudyingmineralweathering,soilformationandinitialecosystemdevelopment.InordertoconstrainindetailwhentheBIGLINKsamplingsitesbecameice-free,ageomorphologicmapwasdrawn,togetherwithashorthis-toryoftheglacierretreatsandadvancessince1956.Formoreinformationabouttheageofthemorainesandassociatedlandforms,somerocksampleswillbetakenandmeasured.

ForthemappingoftheDammaglacierforefield,thefocuswassetongeomorphologicfeatures.CharacteristicfortheareaarethetwobigHolocenelateralmorainesreachingabout100moverthevalleybottom.Inbetween,afewmuchsmallerdistinctmorainesareclearlyvisible.

ThefrontpositionoftheDammafirnhasbeenmeasuredeveryyearsince1921.Detaileddocumentationincludingrefe-rencepointsandsketchmapsexistsbackto1956.Themeasurementsshowaretreatphasebefore1972whentheglacierre-advanceduntil1991,followedbyretreatstilllastinguntiltoday.Observedfrontvariationsdonotexactlymatchwithexistingmorainesintheforefield.Thedatabaseallowsustogeo-locateformerobservationsandcombinewithmapsandresolveinconsistency.

8.20

Holocene landscape evolution of the Llanos de Moxos, NE Bolivia

PlotzkiAnna1,VeitHeinz1

1 Geographisches Institut, Universität Bern, Hallerstrasse 12, CH-3012 Bern ([email protected])

TheLlanosdeMoxos,whicharelocatedinthelowlandsofnortheasternBolivia(Beni),areoneofthelargestseasonallyinundatedsavannahs intheworld.Theregionischaracterizedbyacomplexf luvialdrainagepatternbelongingtotheAmazonsystem.In2009,theUniversityofBernstartedtoinvestigatetheHolocenehydrogeomorphologyandpre-Colum-bianwatermanagementintheLlanosdeMoxos(fundedbytheSwissNationalScienceFoundation).Assofarlittledataexistabouthuman-environmentalinteractionsintheBeniregion,palaeoenvironmentalandgeoarchaeologicalstudiesarebeingconducted.Firstresultswithrespecttolandscapeevolutionarebeingpresentedhere.

Weexaminedsedimentarysequencesalongriverbanksacrossa300-km-longN-Stransectandfoundlargelyasystematicpedostratigraphicpattern.Sandysiltsatthebottomaresuperimposedbyyellow-ochretoredclayeysilts.Abovethesese-dimentsapalaeosolwasfoundinallsections.Itsmaximumthicknessisabout1.5manditissuperimposedbysilty-clayeydepositsagain.Insomeprofilesweidentifiedasecondburiedsoilinthesesilty-clayeylayers.AMS14Cdatesindicatethatsoilformationoccurredbetween9.3to3.4calkaBPandaround2.9to2.0calkaBP.

Basedontheevaluationofthesedimentarysequenceswedevelopedapreliminarychronologyoflandscapeevolution.Thedepositionofsiltyclayspriorto9.3calkaBPisinterpretedasalowenergeticsedimentaryenvironment.Itisassumedthatrelativelyhumidconditionsprevailed,withseasonalinundationofthesavannah.Betweenapproximately9.3and2.0calkaBPsoilformationwasthedominantprocess,suggestingadryerearlytomid-Holocene.Inundationsduringthatperiodwereabsentorlesssevere.Thislongsoilformationperiodwasprobablyinterruptedbyseveralshortmorehumidphases.Thesubsequentdepositionofsiltyclaysindicateashifttomodernwetconditionsaround2calkaBP.

ThisinterpretationisinaccordancewithpollenrecordsfromNoelKempffMercadoNationalPark(Burbridgeetal.,2004),lakelevelf luctuationsofLakeTiticaca(Bakeretal.,2001)andgeomorphologocalandsedimentaryanalysisintheBolivianChaco(Mayetal.,2008a,b).AdryearlytomidHolocenecouldbetheconsequenceofminimumsummerinsolationat15-20°SduringthattimeandacorrespondingweakeningoftheSouthAmericanSummerMonsoon(SASM).

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REFERENCESBaker,P.A.,Seltzer,G.O.,Fritz,S.C.,Dunbar,R.B.,Grove,M.J.,Tapia,P.M.,Cross,S.L.,Rowe,H.D.&Broda,J.P.2001:

ThehistoryofSouthAmericantropicalprecipitationforthepast25,000years.Science,291,640-643.Burbridge,R. E.,Mayle, F. E.&Killeen, T. J. 2004: Fifty-thousand-year vegetation and climatehistory ofNoelKempff

MercadoNationalPark,BolivianAmazon.QuaternaryResearch,61,215-230.May, J.-H., Argollo, J. &Veit,H. 2008a:Holocene landscape evolution along theAndean piedmont, BolivianChaco.

Palaeogeography,Palaeoclimatology,Palaeoecology,260,505-520.May, J.-H., Zech,R.&Veit,H. 2008b: LateQuaternarypaleosol-sediment-sequences and landscape evolution along the

Andeanpiedmont,BolivianChaco.Geomorphology,98,34-54.

8.21

Quaternary glaciation history of northern Switzerland

PreusserFrank1,GrafHansRudolf2,KellerO.3,KrayssEdgar4,SchlüchterChristian1

1 Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, CH-3012 Bern([email protected])2 Dorfstrasse 40, 8014 Gächlingen3 Brühlstrasse 90, 9320 Arbon4 Myrtenstrasse 9, 9010 St. Gallen

ArevisedglaciationhistoryofthenorthernforelandoftheSwissAlpsispresentedbysummarisingfieldevidenceandchronologicaldata fordifferentkeysitesandregions.TheoldestQuaternarysedimentsofSwitzerlandaremultiphasegravelsintercalatedbytillandoverbankdeposits(‘Deckenschotter’).MammalremainsplacetheoldestofthesedepositsintoMammaliaNeogeneZone17(2.5-1.8Ma).ThepresenceoftillwithinthesedimentarysequencesimpliesglaciationsoftheSwissalpineforelandduringtheEarlyPleistocene.Importantdifferencesinthebaselevelofthegraveldepositsallowdistinguishingtwosub-units(‘HöhereDeckenschotter’,‘TiefereDeckenschotter’),separatedbyaperiodofsubstantialin-cision.Eachofthesub-unitscontainsevidenceforatleasttwobutprobablyevenfourindividualglaciations.TheEarlyPleistoceneisseparatedfromMiddlePleistocenedepositionbyatimeofimportanterosion,probablyrelatedtotectonicmovementsand/orre-directionoftheAlpineRhine.TheMiddle-LatePleistocenecomprisesfourorfiveglaciations,namedMöhlin, Habsburg, Hagenholz (uncertain, inadequately documented), Beringen, and Birrfeld after their key regions.MöhlinrepresentsthemostextensiveglaciationoftheSwissalpineforelandandBeringenwasonlyofjustsmallerextent.The lastglacial cycle (Birrfeldglaciation)probablycomprises twooreven three independentglacial advancesdated toabout105ka,65ka,and25ka.Forthelastglacialadvance,adetailedradiocarbonchronologyforicebuild-upandmel-tdownispresented.

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8.22

Quaternary glacial chronology in Anatolia

ReginaReber1,DmitryAndreevichTikhomirov1,NakiAkçar1,VuralYavuz2,ChristianSchlüchter1

1 Institute of Geological Sciences, Baltzerstrasse 1+3, CH-3012 Bern,([email protected])2 Istanbul Technical University, Faculty of Mines, TR-80626 Maslak, Istanbul,

Surfaceexposuredatingisamethodusedtoplaceglacierf luctuationsandmorainesequencesintoachronologicalframe.Anatoliaisoneofthemostsensitiveplacestothechangesinatmosphericcirculationpatternsthatinfluencetheclimateof theEasternMediterraneanRegion.Consequently it is important to construct theQuaternary glacial chronology tounderstandtheclimatechangesinthepast.

Fromcosmogenic10Be,26Aland36Clsurfaceexposureagesitisknownthatthelastlocalmaximumglaciationoccurrednolaterthanaround20kainUludağ(Zahnoetal.,2010),21kainMountErciyes(Sarıkayaetal.,2009),20kaMountSandıras(Sarıkayaetal.,2008);andbetweenaround24and18kaintheDedegölMts.(Zahnoetal.,2009),22–18kaintheEasternBlackSeaMountains(Akçaretal.,2008andreferencestherein).ThisappeartobesynchronouswiththelastmaximumglaciationoccurredintheEuropeanAlps,CentralApennines(Italy)andtheGreekMountainsduringtheglobalLastGlacialMaximum(21±2ka)withinMarineIsotopeStage-2.

AttheLateglacialsubsequentglacieroscillationsweredated:ataround16kainMountSandıras(Sarıkayaetal.,2008),15kainMountErciyes(Sarıkayaetal.,2009);betweenaround16and15kainUludağ(Zahnoetal.,2010).ProbablytheLateGlacialadvanceintheEasternBlackSeaMts.wasrestrictedtothetributaryvalleys,butthetimingofthisadvanceisstillunknown,howeverthisadvancecontinueduntilaround16ka(Akçaretal.,2008andreferencestherein).SoanoscillatingglacierrecessioninAnatoliaduringTermination-1issuggestedbythisevidence.IngoodagreementwiththisAnatoliadataarepublishedsurfaceexposureagesrelatedtotheLateglacialGschnitzandEgesenmorainesintheEuropeanAlps.Thisimpliestheparalleloccurrenceofmajorclimaticshiftsonmillennialtime-scaleintheEuropeanAlpsandAnatoliaduringMIS-2.

Alreadyice-freeweretheglacialvalleysinSWAnatolia (Mt.Sandıras,DedegölMountains)andincentralAnatolia (Mt.Erciyes)duringYoungerDryas(Sarıkayaetal.,2008,2009;Zahnoetal.,2009),whereasinthesouthernBlackSeacoast,YoungerDryasoccurredbetweenaround13kaand11ka(Akçaretal.,2008andreferencestherein;Zahnoetal.,2010).During theHoloceneafter thedeglaciationof thevalleys in theEasternBlackSeaMountains, rockglaciersandsnow-avalancheridgeshavebeenactiveprocesses.Then10BeexposureagesfromtheseridgesshowthattheseeventsoccurredduringtheHoloceneandarethereforenotlinkedtoglacierf luctuations (Akçaretal.,2008andreferencestherein). InAnatoliaLittleIceAge(LIA)morainesappeartobeabsent.TerrestrialgeologicalrecordsinAnatoliawithregardtotheYoungerDryasandtheLIAcoolingstillremaintobestudiedindetail.HugeandactiverockglaciersinthecirqueareasmayberelatedtotheLIAcooling;absolutedates,however,arestillabsent.DryandcoldclimaticconditionsduringtheLIAcouldexplaintheabsenceofglacieradvance,astheconditionswerenotconduciveforthebuild-upofice.

REFERENCESAkçarN.,YavuzV.,Ivy-Ochs,S.,KubikP.W.,VardarM.,SchlüchterC.,2008:ACaseforadownwastingMountainGlacier

duringtheTermination-I,VerçenikValley,NETurkey.JournalofQuaternaryScience,23(3),273–285.Sarıkaya,M.A.,Zreda,M.,Çiner,A.andZweck,C.2008:ColdandwetLastGlacialMaximumonMountSandıras,SW

Turkey,inferredfromcosmogenicdatingandglaciermodeling.QuaternaryScienceReviews,27,769-780.Sarıkaya,M.A.,Zreda,M.andÇiner,A.2009:GlaciationsandpaleoclimateofMountErciyes,centralTurkey,sincethe

LastGlacialMaximum,inferredfromCl-36cosmogenicdatingandglaciermodeling.QuaternaryScienceReviews,28,2326-2341.

ZahnoC.,AkçarN.,YavuzV.,KubikP.W.,SchlüchterC.,2009:SurfaceexposuredatingofLatePleistoceneglaciationsattheDedegöl

Mountains(LakeBeyşehir,SWTurkey).JournalofQuaternaryScience,24(8),1016–1028.ZahnoC.,AkçarN.,YavuzV.,KubikP.W.,SchlüchterC.,2010:ChronologyofLatePleistoceneglaciervariationsat the

UludağMountain,NWTurkey.QuaternaryScienceReviews,29,1173–1187.

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8.23

Late Glacial and early Holocene climatic changes in the Southern Swiss Alps, reconstructed using subfossil chironomid assemblages.

StéphanieSamartin1,OliverHeiri1andWillyTinner1

1 Institute of Plant Sciences and Oeschger Centre for Climate Change Research, University of Bern, CH-3013 Bern, Switzerland.

Lakesarearchivesofpastenvironmentalconditions.Biological,chemical,andphysicalcomponentsaccumulate inthesediments,fromwithinandwithoutthelake(Douglas2006).LarvaeoftheChironomidaearefoundinmostfreshwatersituationsfromthetropicstothearctic;somespeciesareterrestrialorsemi-terrestrial;someareevenmarine(Brooksetal.2007).Duetotheirshortgenerationtimesandthedispersalcapacityofthewingedadults,theChironomidaerapidlyrespondtoenvironmentalchanges.ThestronglysclerotizedheadcapsulesoftheChironomidaelarvaepreservewellinlakesedimentsforthousandsofyears.Differenttaxahavespecificecologicalpreferencesandtoleranceswithrespecttoenvironmentalvariables,includingtemperature,pH,waterdepth,substratemorphologyetc.(Brooksetal.2007),makingthemusefulasproxyindicators.Knowledgeofchironomidecology,togetherwiththedevelopmentoftransferfunctions,hasallowedforthereconstructionofpalaeotemperatures(Walkeretal.1991;Lotteretal.1997).Withthesetransferfunc-tionssummerairtemperatureswithapredictionerrorof1-1.5°Ccanbereconstructed.Today,midgesarewidelyused,especiallyas indicatorsofclimaticchange,andhavebeenconsideredtobe“themostpromisingbiologicalmethodforreconstructingpasttemperature”(Battarbee2000).

AvailableclimaticreconstructionsofLateGlacialandHoloceneclimatefromtheNorthern,Western,andCentralAlpsandtheJuramountainsaremainlybasedonpollenandchironomidassemblages(Lotteretal.2000;Hofmann2001;Heirietal.2003a,b,2005; Ilyashuketal.2009). IntheSouthernAlpsonlyfewquantitativepalaeoclimaticreconstructionsareavailablesofar(Frisiaetal.2005;Heirietal.2007,LarocqueandFinsinger2008).Theabsenceofquantitativetemperatu-rereconstructionslimitsourcomprehensionofclimaticpatternsandofthebioticresponseofvegetationtotemperaturechangesonbothsidesoftheAlps.InthisstudywepresentaLateGlacialandearlyHolocenechironomid-basedsummertemperaturereconstructionfromFoppe(1470ma.sl.)intheSouthernSwissAlps.Chironomidassemblageswerestudiedin58samplesalonga6.4mlongsedimentcorecoveringthepast17200years.Twotrainingset(Swiss,Norwegian/Swiss)wereusedtoinfersummertemperatures(Heiri2003a,Heiriunpublished).

On thebasisof apreliminary chronology,ouranalyses suggest thatmidgeassemblageshave responded tomajorandminor climatic f luctuationsduring the last17200years, suchas theYoungerDryas event in theLateGlacial and thePreborealOscillationatthebeginningoftheHolocene.ThemodelsreconstructedsimilarJulyairtemperaturesofaround9.2°CduringtheOldestDryas,anabruptriseintemperatureofabout3.6°Cbetween17000and15500cal.BP(Pre-Bøllingwarming)upto12.8°C.AtthistimeafforestationintheSouthernAlpsstartedca.2000yearsearlierthanNorthoftheAlps(i.e.beforetheBøllingonsetatca.14700cal.BP(Vescovietal.2007).Thiswarmingisingoodagreementwithhigh-reso-lutionfaunal,isotopic,andsedimentologicdatafromtheEuropeanNorthAtlantic.Theserecordsindicateastrongtem-peratureincreasefrom17500-17300cal.BP(Lagerklint&Wright1999).Aclimaticwarmingpriortothelarge-scaleclima-techangeat15900cal.BPwasalsorecordedintheGRIPice-coreatca.17500-17000cal.BP(Björcketal.1998).Adistinctcoolingofabout1°Cataround14300cal.BP(11.8°C,maybesynchronouswiththeOlderDryas)isapparent.Temperaturesincreasegraduallyfrom14500cal.BPuntil12800cal.BP.Temperaturesofabout12.8°CarereachedattheendoftheAllerødbeforetemperaturesdeclineagainattheAllerød/YoungerDryastransition.Lowtemperaturesofaround10.4°CareinferredduringtheYoungerDryaswithseveralminorf luctuations.TheHolocenestartswithanabruptwarmingofaround4.4°Candreachesvaluesofabout14.8°C.At11600cal.BPtheFoppecoreshowsacoolingofabout1.4°CwhichcanprobablybereferredtoasthePreborealOscillation.AtFoppethefollowingamplitudesofchangeatclimatetransitionswererecorded:OldestDryas/Bølling:3.6°C,Allerød/YoungerDryas:2.4°C,andYoungerDryas/Preboreal:4.4°C.Inasecondstep temperature reconstructions fromtheSouthern,NorthernandCentralAlpswillbecomparedwithother recordsfromtheNorthAtlanticrealmtoinferspatialvariabilityofsummertemperaturechanges.

REFERENCES:BattarbeeR.W., 2000. Palaeolimnological approaches to climate change,with special regard to the biological record.

Quat.Sci.Rev.19:107-124.BjörckS.,WalkerM.J.C.,CwynarL.C.,JohnsonS.,KnudsenK.L.,LoweJ.J.andWohlfarthB.,INTIMATEmembers,1998.

AneventstratigraphyfortheLastTerminationintheNorthAtlanticregionbasedontheGreelandice-corerecord:aproposalbytheINTIMATEgroup.J.Quat.Sci.13:283-292

Brooks S.J., Langdon P.G.&HeiriO., 2007. The identification anduse of Palaearctic chironomids in palaeoecology.QuaternaryResearchAssociationTechnicalGuideQuat.Res.Assoc.TechnicalGuide,10:1-276.

DouglasM.S.V.,2006.Paleolimnology.InEncyclopediaofQuaternarySciences(S.A.EliasEd.),p.2021.Elsevier,Amsterdam.

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FrisiaS.,BorsatoA.,SpötlC.,VillaI.M.&CucchiF.,2005.ClimatevariabilityintheSEAlpsofItalyoverthepast17000yearsreconstructedfromastalagmiterecord.Boreas34:445-455.

Heiri O., Lotter A.F., Hausmann S. & Kienast F., 2003a. A chironomid-basedHolocene summer air temperaturereconstructionfromtheSwissAlps.Holocene13:477-484.

Heiri O.,Wick L., van Leeuwen J.F.N., van der KnaapW.& LotterA.F., 2003b.Holocene tree immigration and thechironomidfaunaofasmallSwisssubalpinelake(Hinterburgsee,1515masl).Palaeogeogr.Palaeoclimatol.Palaeoecol.189:35-53.

HeiriO.&Millet L., 2005.Reconstructionof LateGlacial summer temperatures fromchironomid assemblages in LacLautrey(Jura,France).J.Quat.Sci.20:33-44.

HeiriO., FilippiM.L.& LotterA.F., 2007. Lateglacial summer temperatures in the Trentino area (Northern Italy) asreconstructedbyfossilchironomidassemblagesinLagodiLavarone(1100ma.s.l.).StudiTrentinidiScienzeNaturali,ActaGeologica82(2005):299-308.

HofmannW.,2001.Late-Glacial/HolocenesuccessionofthechironomidandcladoceranfaunaoftheSoppensee(CentralSwitzerland).J.Paleolim.25:411-420.

IlyashukB.,GobetE.,HeiriO.,LotterA.F.,vanLeeuwenJ.F.N.,vanderKnaapW., IlyashukE.,OberliF.&AmmannB.,2009. Lateglacial environmental and climatic changes at theMaloja Pass, Central Swiss Alps, as recorded bychironomidsandpollen.Quat.Sci.Rev.28:1340-1353.

Lagerklint,M.I.andWright J.D.,1999.Lateglacialwarmingprior toHeinrichevent1:The influenceof iceraftingandlargeicesheetsonthetimingofinitialwarming.Geology27:1099-1102.

LarocqueI.&FinsingerW.,2008.Late-glacialchironomid-basedtemperaturereconstructionsforLagoPiccolodiAviglianainthesouthwesternAlps(Italy).Palaeogeogr.Palaeoclimatol.Palaeoecol.257:207-223.

LotterA.F.,BirksH.J.B.,HofmannW.&MarchettoA.,1997.Moderndiatom,cladocera,chironomid,andchrysophytecystassemblagesasquantitativeindicatorsforthereconstructionofpastenvironmentalconditionsintheAlps.I.Climate.J.Paleolim.18:395-420.

Lotter A.F., BirksH.J.B., EicherU.,HofmannW., Schwander J.&Wick L., 2000.YoungerDryas andAllerød summertemperatures at Gerzensee (Switzerland) inferred from fossil pollen and cladoceran assemblages. Palaeogeogr.Palaeoclimatol.Palaeoecol.159:349-361.

VescoviE.,RavazziC.,ArpentiE.,FinsingerW.,PiniR.,ValsecchiV.,WickL.,AmmannB.&TinnerW.,2007.Interactionsbetween climate and vegetationduring the Lateglacial period as recordedby lake andmire sediment archives inNorthernItalyandSouthernSwitzerland.Quat.Sci.Rev.26:1650-1669.

WalkerI.R.,SmolJ.P.,EngstromD.R.&BirksH.J.B.,1991.AnassessmentofChironomidaeasquantitativeindicatorsofpastclimaticchange.Can.J.Fish.Aquat.Sci.48:975-987.

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8.24

Switzerland at the Last Glacial Maximum (LGM): A new map (2009) by swisstopo 1 : 500 000

SchlüchterChristian1&RetoBurkhalter2

1 Institut für Geologie, Baltzerstrasse 1+3, CH-3012 Bern ([email protected])2 Geologische Landesaufnahme, Swisstopo, CH – 3074 Wabern

Map-sheetNo.9oftheAtlasofSwitzerland(1970)showingtheareaofthecountryattheLastGlacialMaximumbyEduardImhofundHeinrichJäcklihasbeensoldoutformanyyears.Thissimplefactandnewdataonthegeometryoftheinner-alpineLGMglaciers,mainlybyFlorineth(2000)andKelly(2004),initiatedtheideatoproduceanewmapoftheLGMinSwitzerland.Thisideawasthebeginningofahardjobwhichhaskeptusbusyforalmost10years.Thenewmap1:500000isavailablenowthroughbook-andmap-storesandcanbedownloadedatwww.swisstopo.ch.

Whatinformationisnewonthismap?Thisarethefollowingreconstructions:

(1)TheicecoveronthehighestandcentralpartsoftheJuraMountainsismoreextensiveandmoreimportantthanpre-viouslythought.ThemaindatainsupportofthisreconstructionisexcellentmappingevidencetothenorthwestoftheHighJurainFrance;

(2)TheHighlandsoftheNapfinthecentralSwissMidlandswithamax.elevationof1408mhasbeencoveredwithsmall,howeverwelldefinedvalleyglaciers.Thishasnotbeenrecognisedonthepreviousmap.ThelocalLGMvalleyglaciationoftheNapfissupportedbytheexistenceofnivationareasandsmallglaciersintheadjoininghills;

(3)DetailedmappingoftrimlinesintheHighAlpsbetweentheEngadineValleytotheeastandtheMontBlancareatothewestshowstheexistenceduringLGMtimeofwelldefinedicedomeareasintheUpperEngadine,intheSurselvaandintheUpperRhoneValley(includingtheiceplateauintheZermattarea).AllfoursuchiceaccumulationsaresituatedtothesouthofthemainorographicdivideoftheAlpswithinterestingimplicationsonatmosphericpaleocirculationpatterns.Asaresultofthisconfigurationicef lowwasfromsouthtonorthalongcertaintransfluencesaccrossthetheHighAlps.–ThehugeoutletglacierfromtheMattertal(drainingtheiceplateauintheuppervalleyofZermatt)tothemainvalleyoftheWalliswassoimportantthattheicefromtheupperRhonevalleywasblocked-offatBrig-VispanddiverteddirectlytothesouthaccrossSimplonpass(causingacomplexdivergenttransfluenticef lowregimeintheBrig-Visparea).WithsuchareconstructionofthepaleoiceflowintheRhonevalleyitispossiblenowforthefirsttimetoexplainthedistribu-tionoferraticindicatorlithologiesinthewesternSwissMidlands;

(4)TheglaciersinsouthernSwitzerlanddisplayanarrowvalleyglaciermorphology,quitedifferentfromearlierreconst-ructions.Thismorphologymayreflectglacierswithveryhighmassturnover(comparedtotheglaciersinSouthWestlandofNewZealand’sSouthIsland)asaresultofthemaintrackofprecipitationtotheAlpsfromthesouth.ThepositionsoftheLGMicedomescoincidewiththecentersoffoehncontrolledprecipitationtoday.

REFERENCESFlorineth,D.& Schlüchter, C., 2000:Alpine evidence for atmospheric circulationpatterns in Europeduring the last

glacialmaximum.QuaternaryResearch,54,295-308.Jäckli, H., 1970: Die Schweiz zur letzten Eiszeit, Karte 1:550 000. Atlas der Schweiz, Blatt 6, Bundesamt für

Landestopographie,Wabern–Bern,Switzerland.Kelly,M., Buonchristiani, J.F.,& Schlüchter,C., 2004:A reconstructionof the last glacialmaximum (LGM) ice-surface

geometryinthewesternSwissAlpsandcontiguousAlpineregionsinItalyandFrance.EclogaeGeologicaeHelvetiae,97,57–75.

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8.25

How to derive weathering rates from ice core measurements of atmospheric tetrafluoromethane?

JochenSchmitt*,BarbaraSeth*&HubertusFischer*

* Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Switzerland ([email protected])

Fluorite,whichisanaccessorymineralfoundinrockslikegraniteandgneiss,containstraceamountsoftetrafluorome-thane(Harnischetal.,1996).Recentsourcesaredominatedbyanthropogenicemissionsfromaluminumsmeltersandtheproductionforthesemiconductorindustry,whereasweatheringoff luoritebearingrocksistheonlynaturalsourceofthisatmospherictracegas.

Astetrafluoromethane(CF4)isinerttodestructionprocessesinthetroposphereandstratospheretheonlysinkliesinthehighmesosphereduetodestructionbyshortwaveUVradiation.Asaconsequence,CF4hasaverylonglifetimeintheorderof50-100kaorevenlonger.

AsCF4ismainlyreleasedfromweatheringofgraniticrocksweassumethatitsatmosphericconcentrationmightshowfluctuationsonlongertimescalesasweatheringintensityshouldchangeonglacial-interglacialtimescalesorlonger.AlsoglacialerosionofthelargecontinentalicesheetsinCanadaandScandinaviacouldbeimportantastheseareashavewi-despreadgraniticorgneissbasementrocksandglacialerosionismoreintensethanordinaryf luvialerosion.

Fromfirnairmeasurementsweknowthatitspreindustrialconcentrationwasabout35pptv(Wortonetal.,2007).TheonlyinformationfromoldertimescomesfromafewmeasurementsaroundtheLGMandthelastdeglaciationonoutcrop-pingicefromGreenland,withalmostconstantvaluesaround35pptv(Muhleetal.,2010).So,thereexistsnoindicationofvariationsontimescalesof10000years.

Ourfirstlowresolutionmeasurementscoveringthelast750kashowrelativelyconstantCF4concentrations,rangingbet-ween 31 and 37pptv.Additionally,wedon’t seemarked concentration changes during glacial-interglacial transitions.However,alotofquestionshavetobeansweredbeforepastatmosphericCF4concentrationscanbeusedtoestimatewea-theringrates,e.g.onlyfewrocksamplespercontinenthavebeenanalysedontheirCF4content (Harnischetal.,1998,Harnischetal.,2000).AstheCF4concentrationofthesegranitesamplesshowedalargevariability(oneorderofmagnitu-de),itisclearthatweatheringinoneregionemitsmoreCF4thanotherregionsthusbiasinganyglobalestimate.WithabetterdatabasisonCF4rockconcentrationonecouldpossiblyidentifykeyregions,whichdominatetheglobalCF4budged.

REFERENCESHarnischJ,BorchersR,FabianP,GaggelerHW,SchottererU.Effectofnaturaltetrafluoromethane.Nature1996;384:32.WortonDR, SturgesWT,Gohar LK, ShineKP,Martinerie P,OramDE,Humphrey SP, Begley P,Gunn L, Barnola J-M,

Schwander J,Mulvaney R. Atmospheric trends and radiative forcings of CF4 and C2F6 inferred from firn air.EnvironmentalScience&Technology2007;41:2184.

Muhle JM,GanesanAL,Miller BR, SalamehPK,HarthCM,GreallyBR,RigbyM, Porter LW, Steele LP, TrudingerCM,KrummelPB,O›DohertyS,FraserPJ,SimmondsPG,PrinnRG,WeissRF.Perfluorocarbonsintheglobalatmosphere:tetrafluoromethane,hexafluoroethane,andoctafluoropropane.AtmosphericChemistryandPhysics2010;10:5145.

HarnischJ,EisenhauerA.NaturalCF4andSF6onEarth.GeophysicalResearchLetters1998;25:2401.Harnisch J, FrischeM, Borchers R, Eisenhauer A, Jordan A. Natural f luorinated organics in f luorite and rocks.

GeophysicalResearchLetters2000;27:1883.

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8.26

Detection of volcanic ash layers by high-resolution XRF core scanning

SteinemannStefanie1,HamannYvonne1,GilliAdrian1

1 Geological Institute, ETH Zurich, Sonneggstrasse 5, 8092 Zürich, Switzerland ([email protected])

Volcanicashlayers(tephras)inlakesedimentsareveryimportantmarkerbedsforestablishingrobustagemodelsandtosynchronizerecordsfromdifferentarchive.Sofar,detectingtephrasinthesedimentaryrecordsoflacustrinelakeshasbeenlaboriousastheyareoftenverythin.X-rayf luorescence(XRF)corescanning,arapid,non-destructivemethodtoscansplitsedimentcoresfortheirrelativechemicalcomposition,wasnowsuccessfullyusedforthedetectionoftephrasinthesedimentaryrecordsoffourSwisslakes(Soppensee,Gerzensee,BaldeggerseeandBurgäschisee).

HavingtestedfourdifferentanalyticalsettingsforXRFcorescanningontheLaacherSeeTephra(12’880varveyearsBP;Braueretal.,1999) inthesedimentcoreofSoppensee (So08-02C2), itcanbeconcludedthat it ismost likelytodetectvolcanicasheswithamaximumtubevoltageof2000µA,ahighcounttimeof50sandadowncoreresolutionof0.2mm.TheelementpeaksintheLSTarehigherinusingsetting4thanintheothertestedsettings.

TheLaacherSeeTephra (LST),veryprominent in theobserved lakesand thereforeeasilydetectablewith thismethod,couldbecharacterizedbyhighelementpeaksofmainlyK,Ca,Rb,ZrandNb.Thechemicalcompositionofthesurround-ingsedimentand the thicknessof theash influence theXRFexpressionsof theLST.Two invisiblevolcanicash layers(cryptotephras)couldbelocatedbyXRFcorescanning.TheVassetKilianTephra(VKT)fromtheMassifCentral(9407±44calyearsBP;Hajdasetal.,1993)wasfoundinSoppenseeandtheIcelandicVeddeAsh,erupted12’225–11’832calyearsBP(Blockleyetal.,2007)couldsuccessfullybelocatedinBaldeggerseeandBurgäschisee,whereithasnotbeenfoundbe-fore.BothoftheseasheshavepositiveelementpeaksofK,RbandZrinXRFcorescanningdata.TheXRFdataoftheVKTintheSoppenseecoreisshownindetailinFigure1.

TheevidenceforhavingindeeddetectedavolcanicashlayerbyXRFcorescanningwasgivenforallthenamedtephrasbysmearslidesanalysis,wherethepresenceofvolcanicglassshardscouldbeconfirmed(Fig.2).

DetectingtheVeddeAshandtheVassetKilianTephrabyXRFcorescanningisapromisingresult,whichshowsthehighpotentialofthisapplicationfornicelylaminatedandwell-preservedsedimentcoreswithhomogeneousgrainsizes.Thepossibilitytoapplythisnon-destructive,fastandeasytechniquetodetectcryptotephrasinsedimentcoresisasteptoamoreefficientuseoftephrochronologyinlakesedimentstudies.

Fig.1:XRFcorescanningdata(intotalcountsofpeaksurface)aroundtheVKT(shadedarea)intheSoppenseecore(So08-01B3)

K Ca

RbZr

Core depth (mm) max.: 280 mm

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Fig.2:Microscopepictureofvolcanicglassshards(smearslide)fromtheLaacherSeeTephralayerintheGerzenseecore(left)andthe

Burgäschiseecore(right)

REFERENCESBlockleyS.P.E.,LaneC.S.,LotterA.F.,PollardA.M.,2007.EvidenceforthepresenceoftheVeddeAshinCentralEurope.

QuaternaryScienceReviews,26,3030-3036.BrauerA., EndresC.,GünterC., Litt T., StebichM.,Negendank J.F.W., 1999.High resolution sediment and vegetation

responses toYoungerDryas climate change in varved lake sediments fromMeerfelderMaar,Germany.QuaternaryScienceReviews,18,321-329.

Hajdas I., Ivy S.D.,Beer J.,BonaniG., ImbodenD., LotterA.F., SturmM., SuterM., 1993.AMS radiocarbondatingandvarvechronologyofLakeSoppensee:6000to1200014CyearsBP.ClimateDynamics,9,107-116.

8.27

A review on tunnel valleys in northern Europe

DorotheaStumm1,UrsH.Fischer1,MichaelSchnellmann1&WilfriedHaeberli2

1 Nagra, Hardstrasse 73, CH-5430 Wettingen ([email protected])2 Department of Geography, University of Zurich-Irchel, Winterthurerstrasse 190, CH-8057 Zürich

TheexistenceofburiedQuaternaryvalleysindicatesthatglacialerosionisanimportantprocessinshapingthelandscapeof theSwissalpine foreland.Considering the timeof concernof1Ma forhigh-levelnuclearwaste repositoriesglacialerosionneedstobeaddressedforassessingtheirlong-termsafety.AsoneapproachtobetterunderstandtheformationprocessesofQuaternaryvalleys,aliteraturereviewwithfocus‘tunnelvalleys’outsidethealpinerealmwascarriedout.

DeepglacialvalleyshavebeendocumentedinEurope,NorthAmerica,Africa,AustraliaandAntarctica.However,thefocusoftheliteraturereviewisontunnelvalleysinnorthernEurope(NorthSea,Denmark,northernGermany,theNetherlandsandnorthernPoland)whichhavebeeninvestigatedindetail.Herewegiveanoverviewofobservedvalleymorphologies,theirgeographicaldistributions,bedrockmorphologiesandformationprocesstheories.

Tunnelvalleysaredefinedaslarge,elongated,overdeepeneddepressionscutintosedimentsorbedrock(ÓCofaigh1996).Theyoccuras individualsegmentsorasananastomosingnetwork,areoftenseveralkilometres long,maximumafewhundredmetresdeepandhundredsofmetresuptoacoupleofkilometreswide(Jørgensen&Sandersen2006).Usuallytheyaresteep-sidedwithf latundulatingbottoms,beginandterminateabruptlyandareopenorfilledwithsediments(Kristensenetal.2007;Fig.1).Occasionally,eskersandlakesoccupythevalleys.Tunnelvalleysareformedbelowpasticesheetmargins,andaregenerallyorientedparalleltothesubglacialhydraulicpotentialgradient.Insomecases,thetunnelvalleysterminateatmajormoraineswheretheymaygradeintolargeoutwashfans.

Themostimportantformationprocessesoftunnelvalleysdiscussedintheliteratureincludemeltwaterdrainage,catast-rophicoutbursts(jökulhlaups)andsedimentdeformation,andareoccasionallycombinedwithdirectglacialerosion(e.g.Boulton&Hindmarsh1987;Jørgensen&Sandersen2006).However,thereisstillcontroversyabouttheoriginoftunnelvalleys(ÓCofaigh1996).

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Figure1.Exampleofburiedtunnelvalleysintheea-

sternNorthSeain(A)planand(B)perspectiveview

(TWT:two-way-traveltime).Theseafloorisabout60

mb.s.l.(80msTWT)andtheupperlimitofthetun-

nelvalleys,andthecolouredplaneistheNearBase

Quaternary(NBQ)horizon.Thetunnelvalleysseem

todeflectaroundtwosaltdiapirs(SD)thatpossibly

controlledthelocalsubglacialdrainagesystem

(Kristensenetal.2007).

REFERENCESBoulton,G.S.&Hindmarsh,R.C.A. 1987:Deformationof subglacial sediments: rheology andgeological consequences.

JournalofGeophysicalResearch,92,9059–9082.Kristensen, T.B.,Huuse,M., Piotrowski, J.A.&Clausen,O.R. 2007:Amorphometric analysis of tunnel valleys in the

easternNorthSeabasedon3Dseismicdata.JournalofQuaternaryScience,22,801–815.ISSN0267-8179.Jørgensen,F.&Sandersen,P.B.E.2006:BuriedandopentunnelvalleysinDenmark–erosionbeneathmultipleicesheets.

QuarternaryScienceReviews,25,1339−1363.Nagra2008:Vorschlag geologischer Standortgebiete fürdas SMA-unddasHAA-Lager.GeologischeGrundlagen.Nagra

TechnischerBerichtNTB08-04.Wettingen,Switzerland.ÓCofaigh,C.1996:Tunnelvalleygenesis.ProgressinPhysicalGeography,20,1-19.

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8.28

Calibration of 36Cl Production Rate on 39K in Saturated Antarctica Samples

TikhomirovDmitry1,AlfimovVasily2,AkçarNaki1,Ivy-OchsSusa2,3,SchlüchterChristan1

1 Institut fuer Geologie, Uni Bern, Baltzerstrasse 1+3, CH-3012 Bern ([email protected])2 Labor f. Ionenstrahlphysik, ETH Zürich3 Geographisches Institut, Uni Zürich

ThesurfaceexposuredatingofK-richmineralslikeK-feldsparandbiotitewiththecosmogenic36Clispresentlylimitedbypoorlyknownrateof36Clproductionfrom39K.36Clproducedinsituon39Kbysecondaryparticlesofcosmicraysinfollo-wingnuclearreactions:highenergyspallation,negativemuoncaptureandthermalneutroncapture.Atthesurfacemajorcontributionto36Clproductionismadebyspallationreactions,whilethenegativemuoncapturedominatesbelow2me-tersofrock.Previouslypublished36Clproductionrateson39Kbyspallationreactionsliesinwidebandofnumbersbetween106±8and228±18at·g(K)-1·yr-1 (Evans1997,Phillips1996,Swanson2001,Zreda1991).Moreaccurateevaluationof 36Clproductionratefrom39Kfromisessentialbecausetheinaccuracyoftheproductionratetranslatesintosignificanterrorsinderivedages.

Properproductionratecalibrationrequiresmanyconditionsonsamples tobemet.K-richminerals inthesamples forcalibrationshouldcontainlowlevelof40Caand35Cltoreducetheother36Clproductionpathways.Exposurehistory(shiel-ding,erosion)ofthesamplessincetheirexposureshouldbeclear.Exposuretimemustbewell-determinedbyotherinde-pendentmethodsorthesteadystateassumptionmustbejustified.

Inanidealcase,theobtainedproductionratecanbeuniquelyscaledtoanyotherlatitudeandaltitude,andappliedinanypossibletimespan.However,duetopresentdayknowledgeofscalingproceduresandpastmagneticfieldvariations,thescalingandapplicationofproductionratescanhaveacertainbiasduetoscalingschemeandestimationsofthemagneticfieldduringtimespanofthecalibratedsite.Theseuncertaintiescaninfluencetheapplicationoftheproductionrateatthelevelofupto10%,thereforeourestimatedlocalproductionrateswillbegiventogetherwithallrelevantlocalpara-meters.

LongtermexposedsamplesofgranitesfromTableMountain,Antarcticawerechosen(Ivy-Ochs1995).Steadystateof36Clbuildupandindependentdatingby10Bemakethesesamplesperfectforcalibration.Howeverpreviouscalibrationbasedonsimilarsamplesgaveavalue,whichishigherthanallotheravailableestimates.Verificationandexplanationofthisoutlierwillbeimportantfor36CldatingoflongtermexposedK-feldspars.

REFERENCESEvans,J.M.,Stone,J.O.H.,Fifield,L.K.,Cresswell,R.G.1997.Cosmogenicchlorine-36productioninK-feldspar.Nucl.Instr.

Meth.Phys.Res.,B123,334-340.Phillips, F.M., Zreda,M.G., Flinsch,M.R. 1996.A reevaluationof cosmogenic 36Cl production rates in terrestrial rocks.

Geoph.Res.Lett.,23,949-952.Swanson, T.W.&Caffee,M.L. 2001.Determination of 36Cl production rates derived from thewell-dated deglaciation

surfacesofWhidbeyandFidalgoIslands,Washington.Quart.Res.,56,366-382.Zreda,M.G.,Phillips,F.M.,Elmore,D.,Kubik,P.W.,Sharma,P.,Dorn,R.I.1991.Cosmogenicchlorine-36productionrates

interrestrialrocks.EarthPlanet.Sci.Lett.,105,94-109.Ivy-Ochs,S.,Schlüchter,C.,Kubik,P.W.,Dittrich-Hannen,B.,Beer,J.1995.Minimum10BeexposureagesofearlyPliocenefor

theTableMountainplateauandtheSiriusGroupatMountFleming,DryValleys,Antarctica.Geology,23,1007-1010.

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How does the elemental composition of Swiss lake sediments reflect past climate conditions?

UlrikevanRaden1,AdrianGilli1,JessicaKind2

1 Geological Institute, ETH Zurich, CH-8096 Zurich, Switzerland ([email protected])2 Institute of Geophysics, ETH Zurich, CH-8096 Zurich, Switzerland

Aspartofan interdisciplinarymulti-proxystudy,weconductedahigh-resolutionXRF-corescananalysison lacustrinesedimentsfromSoppensee(CentralSwitzerland)coveringthelatePleistoceneandHolocenetoanswerthequestionofhowtheelementalcompositionoflakesedimentsreflectspastclimateconditions.

Climatehasastronginfluenceonsedimentationrates,redoxconditions,primaryproduction,andtheamountoferosiveinputofalake,andthisinturnaffectsthecompositionofthelakesediment.Sincespecificelementsandelementratiosoftencharacterizespecificlithologicalproperties,XRFanalysishelpstodefinethesediment’ssourceandgiveshintstoreconstructthepaleo-environmentand-climate.

AtSoppensee,thesedimentdepositedattheendoftheWürmglaciationmainlyconsistofdetritalmaterial,detectedinhighratesofK,Al,Rb,Ti,andZr.WeobserveastrongdecreaseintheseelementsjustattheonsetoftheBölling/Alleröd(B/A)warmperiod.WiththebeginningoftheB/AtheCavaluesstarttoincreaseindicatingfirstauthigeniccalcitepreci-pitationdue tohigher temperaturesanddevelopingprimaryproduction.Siderite isdetectedbyXRDanalyses (Fischer1996)insedimentsdepositedduringtheB/AandYoungerDryas(YD).ThepresenceofSideritecanalsobeseeninhighFeandatthesametimelowK,Al,Rb,TiandZrvaluesintheXRFcorescanresults.Thisdepositionscoincidewithaperiodofsummeranoxiamostprobablycausedbyadditionalorganicmatterinputfromthecatchment,aswellaslongerphasesofstratificationduetoreducedwindexposurecausedbytheincreasedvegetationcover(Lotter2001).Atthesametimefirstmagnetotacticbacteriaappear,resultinginsingledomainmagnetiteofuniformgrainsize.

AttheendoftheYD,firstformationofcalciticvarvesstarts.Theseannuallylaminatedsediments,mainlyreflectedinhighCavalues,indicaterisingprimaryproductionatthelakesurfaceduetowarmertemperaturesintheupperwatercolumn,andanoxicconditionsatthesedimentsurfaceduetodecompositionoforganicmaterialandpoormixingofthehypolimnion.Varvesbecomedarker,discontinuousandeventuallyfaintataround5500calyBP.Forthesametimeperiod,previousstudiesreportincreasingairtemperaturesandachangeintreecoverintheenvironmentfrommainlymixedoakforesttoshadow-tolerantfir-beechforest(Lotter2001).Thesechangesintheenvironmentleadtomoreorganicmatterproducedwithintheepilimnionandalsotransportedintothelake,whichthendecaysatthelakebottom.ThisrottingprocessusesupoxygenandproducescarbonicacidandhenceleadstopHchangesinthehypolimnion,whichsupposedlycircumventsthebuild-upofcalcitevarves.Inaddition,thesemoreacidicandreducingconditionsresultinanrapidinc-reaseofferromagneticmineralsaswellasincreasedmobilityofmetalions,resultinginhighervaluesofmainlyFe,butalsoMn,ZnandPb.

FirsthumanactivityinthecatchmentandfirstlocalsettlementsmaybeseeninthesedimentrecordedbydecreasingCaandincreasingFeandMnvaluesatabout5500and3500ycalBPduetoanthropogenicchangesoftheenvironment.AnabruptincreaseinFeandMnduringtheMiddleAges(about1500-500ycalBP)coincideswithmassivedeforestationinthecatchmentandaroundthelake.Thelackofforestpresumablyenabledmixingofthelakewaterduetowindsandincre-asedsoilerosionsuppliedadditionalnutrientstothelake.Thetopmostpartofthelakesedimentisstronglyinfluencedbyanthropogeniceutrophicationofthelakeduetointenseagricultureinthecatchment.

OurresultsnotonlyconfirmpreviouslypublishedclimatereconstructionsofSwitzerlandandEurope,buttogetherwiththeinterpretationofpaleomagneticpropertiesoftheexactsamesedimentcorematerial,weareabletoaddnewinsightsaboutthedevelopmentandeffectsofpastenvironmentalandclimatechange.

REFERENCESLotter,A. 2001: Thepalaeolimnology of Soppensee (Central Switzerland), as evidencedby diatom, pollen, and fossil-

pigmentanalyses,JournalofPaleolimnology,25,65-79.Fischer A. 1996: Isotopengeochemische Untersuchungen (δ18O und δ13C) imWasser und in den Sedimenten des

Soppensees(Kt.Luzern,Schweiz),Diss.ETHNr.11’924

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Past glaciation in the Central Andes record alteration in the tropical cir-culation and the Southern Westerlies

ZechJana1,ZechRoland2,KubikPeterW.3andVeitHeinz1

1 Institute of Geography, University of Bern, Hallerstr. 12, 3012 Bern, Switzerland ([email protected])2 Department of Geological Sciences, Brown University, Box 1846, Providence RI 02912, USA3 Laboratory of Ion Beam Physics, ETH Zurich, Schafmattstrasse 20, 8093 Zurich, Switzerland

Themassbalanceofglaciersismostsensitivetochangesinprecipitationandtemperature.Thusthereconstructionofpastglacialadvancescanprovideimportantinformationaboutpastclimatechanges.InthearidCentralAndes,whereglaciersareparticularlysensitivetoprecipitationchanges(Kulletal.2008),thetimingofglaciationdocumentshowandwhenthethree main atmospheric circulation systems - the South American Summer Monsoon (SASM), the El Niño SouthernOscillationandtheSouthernWesterlies-changedtheirintensityandpositionovertime.

WedatedseveralwellpreservedglacialstagesintheSierradeQuilmes(~26°S)applying10Besurfaceexposuredating.Ourresultsshowthatglaciersadvancedinphasewiththegloballastglacialmaximum(LGM)at25.8±0.8kaandduringtheLateglacialat13.5±0.5kaand12.8±0.5ka.TheLateglacialadvancesarecoincidewiththeTauca(16-14ka)andCoipasa(13-11ka)laketransgressionphasesontheAltiplanoandreflecttheprecipitationsensitivityofglaciersinthearidCentralAndes.AglacierclimatemodelingstudycorroboratesthattheLateglacialadvancesoccurredasaresultofmoderatetomassiveprecipitationincreases;reconstructedtemperaturedepressionsare-1.4to-5.4°C(Schmidhauser2007).SufficientmoisturefortheLateglacialglacialadvancecanbeexplainedbyenhanceduppertroposphericeasterliesasresponsetoanintensifiedtropicalcirculationandsustainedlaNiña-likeconditionsintheeasternPacific.TheseresultsagreecloselywithpreviouslyreportedLateglacialadvancesfarthernorthinNWArgentina(~22°S)(Zechetal.2009)andBolivia(~17°S)(Zechetal.2010).OurnewglacialchronologyfromtheSierradeQuilmes,however, isunique, insofarastheoldestdatedmorainedocu-mentsanearlierglacialadvanceat~34.6±1.1ka.ThisisroughlycontemporaneouswiththelocalLGMfurthersouth,datedto~38kainnorthernChile(~30°S)andCentralArgentina(~39°S)(Zechetal.2008).Thesepre-LGMadvancesdocu-mentincreasedprecipitationrelatedtoanorthwardshiftandintensificationoftheSouthernWesterlies,whichaffectedthehydrologicalconditionsinregionsfurthernorth(northof30°S)thanpreviouslyassumed.ThenewresultsfromtheSierradeQuilmesthusraisequestionsregardingthesouthernmostmigrationofthetropicalcirculationsystemandtheroleoftheSouthernWesterliesforglacialadvancesevennorthof30°S.

REFERENCESKull,C.,Imhof,S.,Grosjean,M.,Zech,R.&Veit,H.,2008:LatePleistoceneglaciationintheCentralAndes:Temperature

versushumidity control -A case study from the easternBolivianAndes (17°S) and regional synthesis.Global andPlanetaryChange60,148-164.

Schmidhauser,A.2007:Modellingglacier-climateinteractionintheCentralAndeanSierradelQuilmes,NW-Argentina,DiplomaThesis,UniversityofBern,127.

Zech,J.,Zech,R.,Kubik,P.W.&Veit,H.,2009:GlacierandclimatereconstructionatTresLagunas,NWArgentina,basedon10Besurfaceexposuredatingandlakesedimentanalyses.Palaeogeography,Palaeoclimatology,Palaeoecology284,180-190.

Zech,J.,Zech,R.,May,J.-H.,Kubik,P.W.&Veit,H.,2010:LateglacialandearlyHoloceneglaciationinthetropicalAndescausedbyLaNiña-likeconditions.Palaeogeography,Palaeoclimatology,Palaeoecology293,248-254.

Zech,R.,May,J.-H.,Kull,C.,Ilgner,J.,Kubik,P.W.&Veit,H.,2008:TimingofthelateQuaternaryglaciationintheAndesfrom~15to40°S.JournalofQuaternaryScience236-7,635-647.

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Abstract Volume Swiss Geoscience Meeting · 2014-11-26 · 174 Symposium 8: Quaternary Research Swiss Geoscience Meeting 2010 Platform Geosciences, Swiss Academy of Science, SCNAT