Abstracts / Quaternary International 279-280 (2012) 462–565536

of Holocene climate provides the opportunity to examine spatial differ-ences in hydrologic response to climate events of the Holocene interglacialand a critical context to evaluate the magnitude of anthropogenically-induced hydrologic change.

DEVELOPMENT OF A METHOD TO QUANTIFY UV-B FLUX DURING THEQUATERNARY USING UV-B ABSORBING COMPOUNDS CONTAINED INFOSSIL PINUS SPP. SPOROPOLLENIN

Kathy J. Willis. Long-Term Ecology Laboratory, Institute of Biodive, UnitedKingdomE-mail address: kathy.willis@zoo.ox.ac.uk

UV-B radiation currently represents approximately 1.5% of incoming solarradiation. However, significant changes are known to have occurred in theamount of incoming radiation both on recent and geological timescalesdue to stratospheric ozone loss, solar activity1, Milankovitch oscillations,volcanic events and variations in cloud cover. Estimates from modellingsuggest that in some intervals of time (e.g. End Permian), incoming UV-Bcould have been up to 80% higher than present2. If these estimates arecorrect then the impact on terrestrial ecosystems could have beenprofound3. Up until now it has not been possible to reconstruct a detailedmeasure of UV-B radiation through time. Instrumental records of UV-Bradiation only extend back to the 1920s and modelling of past UV-Bradiation is extremely difficult due to the unknown spatial variation incloud and ash cover over time. Some success has recently been obtained indetermining short-term variations (<200 yrs) through the measurementof UV-B absorbing compounds contained in the sporopollenin of fossilpollen4. However, it has not been possible to obtain a systematic contin-uous record through time from one fossil species.In a recent study we aimed to determine the suitability of fossil Pinusspp.pollen to record variations in UV-B flux through the Cenozoic. Due tothe large size of the grain (and therefore extraction from sedimentarysequences without the use of chemicals), and its long fossil history, wehypothesised that this grain could provide a good proxy for recording pastvariations in UV-B flux. Preliminary results indicate the excellent potentialof this species for providing a quantitative record of UV-B variation duringthe Quaternary.

THE RURRAND FAULT AND THE 1756 DÜREN EARTHQUAKES -PALEOSEISMOLOGICAL STUDIES IN THE LOWER RHINE EMBAYMENT

Jonas Winandy. RWTH Aachen University, GermanyE-mail address: j_winandy@web.de

The Rurrand Fault (Rurrandverwerfung) in the Lower Rhine Embaymentlocated between Aachen and Cologne possibly indicates the Dürenearthquake sequence. In 1756 several strong events took place in westernGermany. At least two people died and hundreds of houses weredestroyed. The earthquakes were felt as far as Strasbourg and London,therefore, a magnitude of at least 6 is reasonable. However, to date theseismic source is not clear. Recurrence intervals for active faults in thestudy area are estimated to be in the order of tens of ka. Due to relativelyhigh erosion rates active faults are often not visible in the field. Therefore,seismic hazard might be underestimated.During road constructionworks in 2010 archaeological remains (Neolithic,Iron Age, Roman and Medieval) were found in the immediate vicinity ofthe Rurrand Fault, which was also disclosed by the archaeological trenches.Beside the Rhine Graben this fault is one of the most prominent NW-SEtrending normal faults with a morphological expression in the area. Wefound Holocene surface-near sediments with significant offsets covered bythin colluvial sediments. A complex fault geometry was observed duringthe archaeological excavations. Growing displacement of the major faultdownsection suggest at least two major, surface-rupturing earthquakesalong the Rurrand Fault in the Holocene/Late Pleistocene.Additional data were collected with shallow geophysical methods. Weapplied DC geoelectrics and georadar in order to image the deeper parts ofthe fault zone. Airborne laserscanning data allow creating a high-resolu-tion DEM. The morphological expression of the fault, the shallow depths ofthe offset sediments, and geophysical data led us to conclude on veryrecent seismicity along this active fault, despite radiocarbon and lumi-nescence dating of sediment samples are still in progress.

DYNAMICS OF STICK-SLIP MOTION, WHILLANS ICE STREAM,ANTARCTICA

J. Paul Winberry. Central Washington University, United StatesE-mail address: winberry@geology.cwu.edu

The stick-slip motion and associated seismic emissions of Whillans IceStream (WIS), West Antarctica are two of the many recent observations ofunexpected ice sheet behavior that are challenging traditional models ofrapid glacier motion. Here we find that the WIS slip events repeatedlynucleate from a sticky-spot located in the middle of the ice stream, actingsimilar to an asperity in traditional models of earthquake physics. Thisregion shows less motion than surrounding areas during the inter-slipperiods, thus, concentrating stress and producing a pulse of seismic energyat the onset of slip. The propagating rupture breaks through an additionalasperity in the northern part of the ice stream, producing another pulse ofseismic energy 6-12 minutes after initiation. Both asperities are regions ofhigher hydraulic potential than surrounding regions, suggesting they mayhave greater bed friction due to reduced water lubrication. Tidal pacing ofthe stress accumulation combined with fault healing controls the appliedstress at failure, with higher stress giving faster propagation of the rupturefront and higher slip velocities; these differences are reflected in the timingof the teleseismic arrivals. Our results highlight both the great sensitivity oflarge ice streams to small changes in external forcing and the importance oflimited regions of the subglacial bed in controlling their motion, as well asproviding insights to the mechanics of repeating earthquakes.

ECOLOGICALMODELS IN PALEONTOLOGY: ASSESSING INFORMATIONONTHE EXTINCTION OF SOUTH AMERICAN MEGAMAMMALS THROUGH ITSPOTENTIAL DISTRIBUTION PATTERNS

Gisele Winck. Universidade do Estado do Rio de Janeiro, BrazilE-mail address: gwinck@yahoo.com.br

We estimate the potential distribution of 27 South American taxa. Theoccurrence records were tested with 20 environmental data matrices ofthe Last Glacial Maximum (LGM). The resulting maps were compared withreconstructions of vegetation coverage of South America during the LGM.Accuracy measures were satisfactory (p<0.05). The group namedTempered comprises Glossotherium robustum, Glyptodon clavipes, Hemi-auchenia paradoxa, Mylodon darwini, Pampatherium humboldtii, Toxodonplatensis, Macrauchenia patachonica, Panochthus tuberculatus, Megatheriumamericanum andHaplomastodon platensis. It presents a potential to occurmainly in temperate semi-desert environments, by influence of theminimum temperature of the coldest month. Associated to this group isHippidion principale and Hippidion devillei, which include distribution onboth southern and northeastern SA. The second group named as Inter-tropical includes Panochthus greslebini, Xenorhinotherium bahiense, Para-panochthus jaguaribensis and Paleolama major. The main variable istemperature annual range and presents higher potential occurrence intropical semi-desert areas. A third group holdsHoplophorus euphractus andScelidotherium leptocephalum, and also Andean species: Cuvieronius hyo-don, Equus (Amerhippus) andium, Megatherium spp. (several species). Themain variable is the annual mean temperature. The fourth groupcomprises Equus (Amerhippus) neogeus and Glyptotherium sp., influencedmainly by annual precipitation. Haplomastodon waringi and Eremotheriumlaurillardi present largest distribution in tropical areas of semidesert andsavannah, and have greater influence of temperature seasonality andtemperature annual range. Megatherium medinae and Lestodon armatuswere isolated. All groups have highest potential of distribution mainly indriest areas with open vegetation. Current vegetation maps indicate thatthese areas have been eliminated or greatly reduced. Stochastic effectsmay have caused the extinctions.

DUST SOURCES TO THE SOUTHERN LATITUDES: SOUTH AMERICA ANDAUSTRALIA

Gisela Winckler. LDEO of Columbia University, United StatesE-mail address: winckler@ldeo.columbia.edu

Reconstructing climate-related changes in the rate of dust deposition, andin the provenance of the dust, provides critical constraints on hydrology