A phenomenon of “dune tectonics”: Curonian Spit, southeastern Baltic Sea coast

Abstracts / Quaternary International 279-280 (2012) 9–12052

regulation. Thus, the way the prehistoric societies have selected andhunted their preys brings significant data to the environmental meaning oftheir predation and to the environmental conditions. In order to test suchecological framework, the Upper Pleistocene Paris Basin looks to beinteresting for several reasons. Firstly, the regional approach offers to fixthe well-known physical environment parameter, and this way, allowsfocusing on the impact of another crucial factor, climate fluctuations.Secondly, since several cultural entities have been recorded during theUpper Pleistocene in the region, the continuity or discontinuity in preychoices appears crucial from an evolutionary point of view. Thirdly, recentadvances realized in the understanding of hunting practices of Magdale-nians and Azilians (around 13 000-12 000 BP) show how complex couldhave been the human-large mammals interactions.

ECOLOGICAL RESPONSES TO LATE-GLACIAL CLIMATE CHANGES INNORTHERN AND WESTERN NORWAY

Hilary H. Birks. University of Bergen, NorwayE-mail address: hilary.birks@bio.uib.no

Chironomids react swiftly to temperature changes, both as larvae in lakesand as adults. The relationship of chironomids to mean July air tempera-ture has been well established and can be used with confidence toreconstruct past late-glacial temperatures in lake-sediment sequences.Plants also react to temperature changes. Late-glacial plant macrofossilassemblages can be used to demonstrate local presence of species and toreconstruct vegetation changes through assemblage analogy. To investi-gate the speed of plant responses to climate changes, detailed late-glacialchironomid and plant macrofossil records are needed from the samesediment corewith good chronological control. Using chironomid-inferredtemperatures as a base-line for climate changes, the responses of plantsand vegetation, both terrestrial and aquatic, can be assessed. How closelydo plant responses follow the temperature changes? If they lag, by howmuch? Do different vegetation types show different responses? Doesmigration play a role? We shall present comparisons from three late-glacial sites from northern and western Norway.

STRENGTHS AND WEAKNESSES OF QUANTITATIVE CLIMATERECONSTRUCTIONS BASED ON LATE-QUATERNARY BIOLOGICALPROXIES

H. John B. Birks. Department of Biology and Bjerknes Centre for Climate,NorwayE-mail address: John.Birks@bio.uib.no

The importance of reconstructing past environments quantitatively inpalaeoecology is reviewed by showing that many ecological questionsasked of palaeoecological data commonly involve the reconstruction ofpast environment. Three basic approaches to reconstructing past climatefrom palaeoecological data are outlined and discussed in terms of theirassumptions, strengths, and weaknesses. These approaches are the indi-cator-species approach involving bioclimate-envelope modelling; theassemblage approach involving modern analogue techniques andresponse surfaces; and the multivariate calibration-function approach.Topics common to all approaches are reviewed - presentation and inter-pretation, evaluation and validation, comparison, uncertainties, andgeneral limitations of climate reconstructions. Challenges and possiblefuture developments are presented and the potential future role ofquantitative climate reconstructions in palaeoecology is summarised.

BEHAVIOURAL VARIABILITY IN OLDOWAN HOMININS: THE CASE FROMKANJERA SOUTH, KENYA

Laura C. Bishop. Liverpool John Moores University, United KingdomE-mail address: l.c.bishop@ljmu.ac.uk

Recent research at Kanjera South, Kenya shows that by about 2 Ma,hominins had a considerable armoury of behavioural capabilities. The sitewas formed in low energy settings and, over 169m2 of excavations, the KS-2 stratum has yielded 2190 fossils and 2471 artifacts. Both the weatheringstages of the fossil remains and the limited development of pedogenic

features over the 1.5m of KS-2 deposits suggest that the site was formedover decades or centuries. Studies of biostratigraphy and palaeomagnetismsuggest an age of around 2 Ma for the hominin activities in Bed KS-2.Multiproxy palaeoenvironmental reconstruction shows that the KanjeraSouth palaeohabitat was predominantly open grassland during this periodof hominin occupation. Taphonomic studies of the faunal remains indicatethat hominins were the primary cause of their deposition. The faunalremains predominantly derive from juvenile and/or small individualungulates. Breakage patterns and cut- and toothmark studies show thathominins had early access to these animals. Oldowan artifacts weremanufactured from both local and more distant raw material sources.Differential reduction and retouch strategies show that hominins selectedand transported certain types of stone over great distances, based on theirmechanical properties. Hominins employed a technological strategy thatconserved high quality raw materials that were transported the greatestdistances.

IMPLICATIONS OF THE PALEOSEISMICITY OF THE EASTERN BALTIC SEAREGION

Albertas Bitinas. Coastal Research and Planning Institute, Klaipeda ,LithuaniaE-mail address: albertas.bitinas@corpi.ku.lt

The historical seismic activity in the Eastern Baltic Sea region is signifi-cantly lower comparing with seismicity of Fennoscandian shield. Still,several tens (w 40) of small scale seismic events with magnitudes up to4.8; with the earthquakes in Kaliningrad District (Russia) in year 2004(with maximal magnitude up to 5) have been recorded in the area. Also,assumptions about tsunami event in 1779 at the Baltic Sea coast nearTrzebiatów (Poland) have been implied. All these facts evidence somerecent seismic activity of the Eastern Baltic Sea region. Rather highseismic activity of Fennoscandian shield and adjacent Baltic Sea territo-ries during the Late Glacial and Holocene (last 13 000 years) is welldocumented by numerous paleoseismic investigations and correspondingpublications, whereas the paleoseismological studies of the Baltic Sea andwider Eastern Baltic Sea Region has not been carried out up till now andno seismites evidencing paleoseismicity in the region have been recorded.However, the recent analysis of the Quaternary deposits of the EasternBaltic Sea region in the background of the state-of-the-art of the modernpaleoseismology, resulted in new assumptions of the paleoseismicityof the region: several geological structures, early interpreted as cry-oturbations, glaciotectonic features or so-called water-escape structures,shows characteristics of the liquefaction-inducted sediment deforma-tions. Such a structures have been distinguished in a several localities inEstonia, Latvia, Lithuania and Belarus. Majority of these seismites-likestructures were formed during the Late Glacial and Holocene times;several of them are related to Middle Pleistocene, Eemian Interglacial andEarly Weichselian strata.

A PHENOMENON OF “DUNE TECTONICS”: CURONIAN SPIT,SOUTHEASTERN BALTIC SEA COAST

Albertas Bitinas. Coastal Research and Planning Institute, Klaipeda ,LithuaniaE-mail address: albertas.bitinas@corpi.ku.lt

The exposures of so-called “lagoon marl” represented by composite set oforganic sediments such as clayey gyttja and organic-rich clay, are commonalong the lagoon coast of the Curonian Spit, Lithuania. An integratedinvestigation of lagoon marl and associated coastal sediments was con-ducted during 2005-2010 and included: ground-penetrating radar (GPR)imaging, deep boreholes, paleoecological analyses (pollen, diatoms, andmollusks), radiocarbon (bulk and AMS) dating, and examination of phys-ical-mechanical properties of the marl. The outcrops of lagoon marl reachup to 4-5 m in height and reflect a unique geological process, termed here“dune tectonics” – a phenomenon of extrusion of the marl from below thewater table through loading of by massive sand dunes. An integrated studyof the marl sequence supports its formation in a freshwater lagoon duringthe Holocene Litorina Sea stage. In boreholes, the top of the in situmarl lies6.8-8.9 m belowmean sea level, and the thickness varies from 5.4 to 9.0 m.

Abstracts / Quaternary International 279-280 (2012) 9–120 53

The largest exposure of the marl, which does not occur in situ, is locatedabout 3 km south of Nida settlement, at the state border between theRepublic of Lithuania and Russian Federation: its length is about 700 m,height – approximately 3.5 meters, and width – 60 meters. The lagoonmarl is also outcropping in two smaller exposures beneath the Parnidisdune dislocated about 1 km south of Nida. One of the exposures wasextruded onto the surface during the 2007-2008 autumn-winter periods.This segment of the marl unit (”undeveloped” exposure) was imaged byground-penetrating radar during the field investigations in 2005. Theextruded section contains abundant Holocene mollusk shells, wood frag-ments, partial fish skeletons, dropstones, and other materials often missedby drilling. A dynamic model that explains the processes leading to thepresent context of the lagoon marl exposures is presented.

THE LAST SCANDINAVIAN ICE SHEET IN THE BALTIC COUNTRIES: A NEWPATTERN OF DEGLACIATION

Albertas Bitinas. Coastal Research and Planning Institute, Klaipeda, LithuaniaE-mail address: albertas.bitinas@corpi.ku.lt

The results of recent geomorphological, sedimentological and geochro-nological investigations of glacial deposits formed by the last ScandinavianIce Sheet lead to change a standpoint about a number of processes andphenomena related with ice sheet, including deglaciation. The origin ofkey forms of glacial relief, such as kame terraces on distal slopes of therecessional marginal ridges and plateau-like glaciolacustrine kames on thehighest parts of glacial relief can not be explained by the theory of ice-marginal fluctuations or readvances induced by climate changes duringthe so-called ‘stadials-interstadials’ or ‘phasials-interphasials’. Thesefeatures can be point out by another pattern of glacial dynamics anddeglaciation, i.e. the interaction of active ice lobes (surges) fronted byzones of dead ice. In addition, there is not stratigraphic evidence to supportnon-glacial conditions between periods of glaciation during the LateWeichselian. The results of cosmogenic dating (10Be) of boulders indicatethat prior to the YD readvance, the ice sheet covered a large area betweenthemarginal ridge of the so-calledMiddle Lithuanian Phase and the Gulf ofFinland, before it completely melted about 13.5 – 13.0 ky BP. The process ofice decay occurred as surface melting and thinning, so that the arealdeglaciation was significantly more important than the ice margin retreat:the latter prevailed only during the initial stage of deglaciation about 19.0– 17.0 ky BP. The fact of prevalence of areal deglaciation is supported byarchaeological data –14C dating of reindeer bones suggests a rapid colo-nization of entire territory of the Baltic countries directly after the degla-ciation about 13.5 – 12.0 ky BP. The so-called ‘stadial’ or ‘phasial’ marginalmorainic ridges are the result of SIS surges during the final stage ofdeglaciation that were asynchronous in different parts of the ice sheet.This study was financed by the Research Council of Lithuania (no. LEK-10005).

THE PITFALLS OF TUNED PROXY ARCHIVES

Maarten Blaauw. Queen's University Belfast, United KingdomE-mail address: maarten.blaauw@qub.ac.uk

By aligning fossil proxy archives at wide spatial scales, regional, hemi-spheric or global pictures of past environmental changes can be recon-structed. The reasoning is that sediment boundaries or proxy events musthave been produced by major climate or environmental events of suchintensity and scale that they were registered in multiple regions and typesof deposits in a (nearly) simultaneous manner. These same climate orenvironmental events can then be used as isochrons to date individualarchives by aligning, or wiggle-matching, their proxy events to those inother, distant archives. This tuning approach will be reviewed by dis-cussing a number of literature examples, ranging from peat and tephralayers to orbital tuning and d18O series from marine and ice deposits.Problems and traps involved in tuning will be highlighted such as thedangers of circular reasoning and unrecognised chronological uncer-tainties, and some solutions will be suggested. Especially promisingappears to be statistical approaches to objectively compare the timings ofevents between independently dated chronologies from individualdeposits. Fossil proxy research could become enhanced if tuning were

approached in a more quantitative, reliable and objective way. Ideally,individual proxy archives should remain non-tuned and kept on inde-pendent time-scales.

DATING AND IMPACTS OF HOLOCENE ALASKAN VOLCANIC ERUPTIONS

Jeff Blackford. University of Manchester, United KingdomE-mail address: Jeff.Blackford@manchester.ac.uk

For time periods prior to historical and meteorological records, palae-oecological data can be used to assess the impacts of past volcanism. Thispaper will present data on the timing and impacts of Aniakchak II, theWhite River Ash and a further eruption c. 300 BP by examining themicrofossils above and below associated tephras found in distal peatdeposits. The mid-Holocene eruption of Aniakchak volcano was one of thelargest in Alaska in the post-glacial period. In this study we estimate theage of this eruption through a sequence of radiocarbon dates usingselected plant macrofossils to be approximately 1608-1458 cal. BC,younger than previous estimates, perhaps questioning the identification ofthis ash and its age in the GRIP core, or the effectiveness of AMS radio-carbon analysis of peat components. Pollen and oribatid mite data, anda probable century-scale hiatus in the sequence of radiocarbon dates, showa significant impact on the arctic ecosystem at the sampling point.Microtephras in peat from SE Alaska have been linked to the White RiverAsh and a possible more recent Mt. Churchill eruption around 300 BP(Payne and Blackford, 2008). Testate amoebae are used to reconstruct thewater table and acidity across the tephra layers, and their assemblagechanges are tested against a volcanic impacts model using RDA. The resultsare variable, with statistically significant changes associated with sometephras but not others. Overall, we conclude that volcanic impacts onpeatlands have been significant, and that future eruptions could causelong-term changes through a range of mechanisms. Proximity to theeruption, tephra loading, seasonality and antecedent mire conditions areall significant in determining the impacts.

RESPONSE OF VEGETATION AND EROSION DYNAMICS TO CHANGES INPRECIPITATION IN THE NILE RIVER DRAINAGE BASIN DURING THEHOLOCENE: IMPLICATIONS FOR THE TERMINATION OF THE AFRICANHUMID PERIOD

Cecile Blanchet. IFM-GEOMAR, University of Kiel, GermanyE-mail address: cblanchet@ifm-geomar.de

During the mid-Holocene, the gradual decrease in summer insolationinduced a decrease in monsoon strength and subsequent aridification ofnorthern Africa. The timing and rate of environmental and climaticresponses to this slow orbital forcing is still under debate, with studiesreporting either a gradual or an abrupt termination of the AfricanHumid Period (AHP). Here we use a 6 m-long sediment core from theNile deep-sea fan (P362/2-33, 700 m water-depth) that covers the last9,500 years, with laminated sediments being deposited at very highrates (up to 600 cm/ka) during the AHP. These sediments allow toinvestigate the linkages and feedbacks between climate, vegetation anderosion dynamics up to seasonal resolution. Continental run-off andvegetation changes are reconstructed using major and trace elements,radiogenic isotope compositions of sediments and abundance andisotope composition of specific biomarker lipids. Fresh-water dischargeis monitored using d18O and d13C of planktonic foraminifera andradiogenic isotopes of foraminifera and seawater-derived ferromanga-nese coatings. High sedimentation rates, high Ti/Ca ratios and sea-waterεNd values similar to the Nile River suggest that massive amounts offresh water and sediments were delivered by the Nile River to the deep-sea fan between 9.5 and 8 ka. This time interval was also characterisedby the dominance of C4 grasses and well-developed soils, as indicatedby heavier d13C values for higher plants n-alkanes and elevatedconcentrations in soil biomarkers. Fresh-water and sediment dischargedecreased rapidly around 8.5 ka, followed by a continuous and moregradual decrease between 8 and 4 ka. Vegetation gradually shifts fromC4- to C3-dominated environments between 8 and 6 ka, possiblyreflecting the aridification of the Sahara, with n-alkanes mainly origi-nating from southern sources after 6 ka.