Abstracts / Quaternary International 279-280 (2012) 9–12066

relate eco-geohydrological to paleoglaciological questions, integratingboth fields. GW monitoring data and subsurface mapping were combinedin a regional model (NEBG/FEFLOW interface; Imod 2.3.5./MIPWA) cali-brated to the field measurements. Surficial drainage and GW flow mapswere comparedwith deep subsurface data. Correlations exist with tectonicblocks and saltdome crests, indicating postglacial activity, but importantlyalso syn-glacial activity. This includes faults below the Zechstein salt,hinting that part of the salt may be anhydrite “hard-rock”, rather than“plastic” halite. This notion is of importance for the process of glacio-isostasy into peripheral crustal movements during glaciations too. Anotherstrong conclusion is that thermohaline processes drive deep groundwaterflows, today but also when the area was last under ice. The effect isstrongest in the subarea with Elsterian buried subglacial channels. Nestedsemi-isolated hydrological systems exist at fixed points with specificgroundwater characteristics (bicarbonate rich water; higher Pw and T).This approach and its insights are relevant for GW resource- and natureprotection in ice-marginal Europe (NL, N-GER, DK, Poland, Baltic).

CLAY MINERALS COMPOSITION: A USEFUL TOOL FOR GLACIAL TILLSTUDIES AND PALEO RECONSTRUCTION OF ICE-STREAMS

E.P.H. Bregman. UtrechtUniversity/ depart. Physical Geography/ pro,NetherlandsE-mail address: bregkema@home.nl

Knowledge on glacial features such as tills contributes to a better under-standing of glaciations. Our study tests a newmodel for phasing of the MIS6 glaciation of the Netherlands and NW Germany (Pierik, this conference)using clay mineralogical composition XRD analysis on tills. We sampledtills from a series of stages of glaciation of Drenthe, the Netherlands, withattention to (i) phasing, (ii) local substrate and (iii) position within icestreams. Four hundred XRDmeasurements confirm inferred ice-streamingin different phases of the Saalian glaciation, complementary to other till-analysis techniques. Our main finding is that clay minerals are a useful toolfor paleo environmental reconstruction of glacial landscapes of differentages, which give more information about material transport, positionaland local conditions of till formation. Clay mineralogical analysis of tillsdoes not demand quarry faces for sampling: cores are fine. This benefitssampling in areas such as Drenthe.We show that in Drenthe the lower tills are subregional formed undersaline subglacial groundwater conditions. Under glaciating circumstances,shallow and deep groundwater interaction temporarily changed, asrecorded in till composition. It formed a closed subglacial system, based onpresence of authigenic minerals and the ratio of illite-smectite con-tent(TSI). The observations agree with previous paleo-geohydrologicalreconstructive modelling. Till types of similar TSI, but differentiallyaffected by post-glacial weathering and seepage of groundwater areseparated. Our new approach not only differentiates tills based on thepresence of endogeneous tills and authigenic minerals, but also givesinsight in the till-forming processes and impact of weathering, of impor-tance for the glaciation story as well as for modern water quality andecology.

ENHANCING GLACIAL TEPHROCHRONOLOGY IN THE NORTH ATLANTICREGION, PROBLEMS AND PROSPECTS

Jo Brendryen. University of Bergen, NorwayE-mail address: jo.brendryen@geo.uib.no

This presentation focuses on our ongoing work to enhance teph-rochronology as a tool to accurately and precisely synchronize climatearchives from the glacial North Atlantic region on annual to decadal timescales. Our work (Brendryen et al., 2010, QSR 29, 847–864) points toa potential source of error in this respect; the intermittent storage oftephra in ice sheets and subsequent iceberg transport that may delaytephra deposition. We present an account of the tephrostratigraphy of SE-Norwegian Sea core MD99-2289 for the interval spanning Marine IsotopeStage (MIS) 5 and part of MIS-4 and for the interval around the NorthAtlantic Ash Zone II (NAAZ-II) in MIS-3. In order to address the complicatedregional dispersal of tephra associated with large volcanic eruptionsduring glacials in the North Atlantic region, we have compared the

stratigraphical occurrence of the NAAZ-II tephra complex in the Greenlandice cores with three high resolution archives from the North Atlantic andthe Norwegian Sea. This comparison shows that the peak shard concen-tration of the rhyolitic component (II-RHY-1) of the NAAZ-II is depositedw100-400 years after the eruption event in some North Atlantic andNorwegian Sea cores, while being near-synchronous in others. While stillallowing for a correlation of the archives on millennial timescales, this isa major obstacle when addressing for example lead-lag relationship onshorter timescales. From the MIS-4 andMIS-5 intervals we describe tephradeposits from in the order of 100 volcanic eruptions in Iceland and on JanMayen. The most important transport mechanism of tephra to the core siteis considered to have been iceberg rafting. This clearly limits the use ofsome of the tephras as isochronous markers. However, twelve discretetephra deposits show stratigraphical and geochemical characteristics thatsuggest them to have been deposited near–contemporaneously with theirsource volcanic events.

WAS THE EARLY GLACIAL TERMINATION II SEA-LEVEL HIGHSTANDCAUSED BY A COLLAPSE OF THE EURASIAN ICE SHEET?

Jo Brendryen. University of Bergen, NorwayE-mail address: jo.brendryen@geo.uib.no

Quaternary sea-level record contains several episodes of abrupt global sea-level rise with the Meltwater Event 1a (ME-1a) of the glacial termination Ias a prominent example. Another such episode is the sea-level rise into theearly sea-level highstand of glacial termination II (TII). Although themagnitude and rate of sea-level rise during this event is not yet wellconstrained due to lack of data and imprecise dating, the availableevidence suggest that it might have been evenmore dramatic than theME-1a, amounting to a rise in sea-level of 50-100 m over only 1000-2000years. Herewe present evidence for that the early TII sea-level highstand iscoeval (within the dating uncertainty) with a large meltwater event in theSE-Norwegian Sea, suggesting that meltwater from the Eurasian Ice Sheet(EIS) is a major source for the TII highstand. During Late MIS-6 the EISformed a huge and largely marine-based “Antarctic type” ice sheet, esti-mated to have storedw50 % of the glacial ice volume (Lambeck et al., 2006,Boreas 35, 539-575). The importance of the EIS in driving the early TII sea-level rise is supported by a comparison of the Norwegian Sea records withNorth Atlantic surface and deep water oxygen isotope records. Thiscomparison shows that while the start of the decrease in North Atlanticdeep water d18O (associated with global ice volume reduction) occurscoeval with the Norwegian Sea melt water event, the decrease in NorthAtlantic surface water d18O (associated with the destabilization of theLaurentide Ice Sheet during Heinrich event 11) occurs later in TII. If ourinterpretation is correct and it is possible for a huge continental ice sheet,like the penultimate EIS, to partially collapse within 1000-2000 years andbeing the main source of a global sea-level rise of in the order of 50-100meters, it might influence our understanding of what we can expect fromEarth's remaining continental ice sheets in a changing climate.

UNCERTAINTY IN LARGE-SCALE CLIMATE RECONSTRUCTIONS

Simon Brewer. University of Wyoming, United StatesE-mail address: sbrewer2@uwyo.edu

An increasing number of palaeoenvironmental studies aim to synthesisedata from a collection of sites, with the aim of analyzing spatial patterns orproducing composite curves in which any regional signal is emphasized atthe expense of local variations. The workflow involves any of the followingsteps: estimation of environmental value by transfer function, estimationof age from radiometric dates and compositing of individual series. All ofthese steps involve errors, which may be more or less well qualified.However, in synthetic studies, these errors are rarely integrated to providea more comprehensive probability distribution of reconstructed values,but instead, are generally used for site or sample selection by choosing anerror threshold. We present here a regional climate reconstruction basedon a set of pollen sequences covering the last 12000 years, in which weattempt to account for and integrate as much of the known errors aspossible. A Monte Carlo approach is used to propagate errors from thetransfer function and the age-depth models through to the final values.

Abstracts / Quaternary International 279-280 (2012) 9–120 67

The results are used to help highlight the difficulties with full erroraccounting and to provide a framework for future research.

BENCHMARK DATA SETS: VEGETATION AND TERRESTRIAL CLIMATES

Simon Brewer. University of Wyoming, United StatesE-mail address: sbrewer2@uwyo.edu

Pollen and plant macrofossil records for the late Quaternary provide a richsource of information for studying past ecosystem changes over the last21000 years. These records can also be used in conjunction with transferfunctions in order to infer the climatic changes that drove the ecosystemresponse. Development of regional and continental scale databases ofthese records has allowed reconstructions to be made over spatial scalesthat are compatible with the grid size of most General Circulation Models(GCMs). These spatial reconstructions have been used to examine regionalvariations in past environments and identify several robust features of pastclimates that can be used as benchmarks for comparisonwith the output ofpaleo-GCMs, either by a) comparing simulated and reconstructed climateor b) comparing reconstructed vegetation to that simulated by an offlinevegetation model. We present here examples of these datasets and themethodology involved in both vegetation and climate reconstructions. Wereview their uses and limitations, and some examples of their use intesting paleo-GCMs. Finally, we outline an agenda for the future devel-opment of terrestrial benchmark datasets.

MODELLING EROSION, SEDIMENT TRANSPORT AND SEDIMENTATION INRESPONSE TO CLIMATE CHANGE – A THREE-DIMENSIONAL RIVERCATCHMENT MODEL

Rebecca M. Briant. Department of Geography, Environment andDevelopment, United KingdomE-mail address: b.briant@bbk.ac.uk

River systems are critical components of the landscape. An understandingof their response to variations in the Earth's climate is vital in light of theexpected changes in global climate (e.g. 1.8 to 4.8�C temperature rise) thatare forecast to occur over the next c. 100 years. Most future river-basin-scale predictions focus on water, assuming channel stability and minimalsediment movement. Whilst this may be appropriate in the very shortterm, over the medium to longer-term, channel positions are likely to shift,even if artificially constrained, and sediment movement will be animportant feature of landscape change to which human populations mustadjust. It is therefore crucial to understand climate-driven flows of bothsediment and water within river basins, especially since ‘little work hasbeen done on the expected impacts of climate change on sediment loads inrivers and streams’ (IPCC 4AR WG3, 2007, p.190).This poster describes a pilot study that developed and applied a numericalmodel, integrating both sediment and water movements utilising cellularautomaton strategies, to a paleo-record from the last interglacial (c.125,000 years) onwards. The value of calibrating the model againsta record over this time period is that it emulates the scale of changes thatare increasingly likely to be seen over the longer term future (c. 5-6�C). Thedata against which the model is calibrated come from stacked fluvialsediments distributed across the catchment, for which the timing ofdeposition has been estimated using a combination of radiocarbon andoptically-stimulated luminescence dating. Future research will apply themodel to landscape change under future climate change scenarios.

LUMINESCENCE DATING INDICATES RADIOCARBON AGEUNDERESTIMATION IN LATE PLEISTOCENE FLUVIAL DEPOSITS FROMEASTERN ENGLAND

Rebecca M. Briant. Department of Geography, Environment and Developme,United KingdomE-mail address: b.briant@bbk.ac.uk

Robust geochronological control is crucial for interpreting and correlatingthe environmental record from fragmentary terrestrial sequences from thelast glacial period. Traditional terrestrial stratigraphies are typically relianton radiocarbon dating, although estimates of antiquity for samples older

than 40 ka may be unreliable. Optically stimulated luminescence (OSL)dating of sediments is an alternative for dating the whole of the last glacialperiod and also provides the opportunity to independently test radio-carbon based chronologies. This paper presents a set of nine directlycomparable paired OSL and accelerator mass spectrometry (AMS) radio-carbon ages from multiple sites within Devensian fluvial sediments inlowland Britain and shows that it is possible to obtain robust OSL ageestimates throughout this time period. The two techniques agree well forages younger than ca. 29 14C ka BP (ca. 35 cal. ka BP) but disagree beyondca. 35 14C ka BP (ca. 40 cal. ka BP). This is thought to be due to radiocarbonages on older organic material having been contaminated by low levels ofmodern carbon. It is therefore suggested that all conventionally pre-treated radiocarbon ages greater than 35 14C ka BP should be treated withextreme caution.

LATE CENOZOIC FLUVIAL ARCHIVES: EVIDENCE FOR COUPLINGBETWEEN CLIMATE AND LANDSCAPE EVOLUTION

David Bridgland. Durham University, United KingdomE-mail address: d.r.bridgland@dur.ac.uk

Global comparison of fluvial archives has led to important advances. Firstwas the realisation that aggradational terrace sequences are a worldwidephenomenon and record progressive regional (epeirogenic) uplift on LatePliocene–Quaternary timescales. There is evidence that the uplift thatdrove the formation of river terraces, and the dissected landscapes towhich they belong, accelerated in the Middle Pleistocene, in all likelihoodas a response to the enhanced climatic forcing after the ‘Mid PleistoceneRevolution’, when the 100 ka Milankovitch cycles began. This impliescoupling between climate and crustal processes, providing an explanationfor the long-recognized contrast between the subdued landscapes of thelate Tertiary and Early Pleistocene and the more dynamic landscapes, withdeeply incised valleys, of the later Quaternary. The second observation isthat terrace sequences, although found in all ice-free continents and in allclimatic zones, do not occur everywhere; other types of fluvial sedimen-tary archive exist. The first of these has long been recognized: stackedsediments in subsiding basins with modern surfaces that are flat, such asthe Great Hungarian Plain or the Rhine Delta. Another important excep-tion, not widely recognized hitherto, characterizes highly stable Archaeancratons. Here the stability has precluded significant uplift, so that ancientfluvial sediments are preserved in close vertical proximity to modernvalley floors, giving rise to sequences that, although describable asterraces, are poorly separated, recording little vertical movement duringthe Quaternary. Another key conclusion that is that much of the uplift inplate-boundary regions like the Mediterranean, which has in recent yearsbeen attributed to the effects of plate tectonic activity, is nothing of thesort; the active fault movements in such areas have merely been over-printed onto the background regional uplift that has been affecting post-cratonic crust worldwide.

QUATERNARY LANDSCAPE AND ENVIRONMENTAL CHANGE IN THELEVANT AS A CONTEXT FOR EARLY HUMAN EXPANSION FROM AFRICA

David Bridgland. Durham University, United KingdomE-mail address: d.r.bridgland@dur.ac.uk

Coinciding with the boundary zone between the African, Arabian,Turkish and Eurasian tectonic plates, the study area is traversed by majoractive fault systems (the northern Dead Sea Fault Zone and the EastAnatolian Fault Zone). The development of topography in this region, formany years attributed solely to the active faulting related to the motionsof these plates, can instead be attributed to regional uplift driven byerosional isostasy and thus coupled with surface processes. This isdemonstrated by the resolution of the uplift, which can be reconstructedfrom river terrace sequences, into phases following periods of well-established global climate change, such as the Mid-Pliocene climaticoptimum (w3.1Ma), the ‘conventional’ Pliocene–Pleistocene boundary(w2.0Ma), and the Mid-Pleistocene Revolution (w0.9Ma). Such corre-lations suggest that these vertical crustal motions have been forced bythe climate change, via the resultant changes in rates of surfaceprocesses (e.g., erosion/sedimentation). The post-2.0 Ma phase of uplift