Abstracts / Quaternary International 279-280 (2012) 121–232 185

New glaciers were formed and existing glaciers expanded during the LittleIce Age to their largest extent since the Late Glacial Maximum around year1900. The extension of warm-based ice again increased. The position offossil pingos, active pingos and springs in Svalbard has been coupled to themost likely (nearest) glacier. Fossil pingos are related to glaciers that mostlikely disappeared or lost their accumulation zone during the HoloceneOptimum, while flowing springs and pingos are related to larger glaciers,with a continuous groundwater recharge. When a groundwater flowsystem closed and new permafrost was formed under the glacier and inthe discharge zone, it could not be reactivated during the Little Ice Age.

THE PAST, CURRENT, AND FUTURE OF NORTH AMERICAN GREAT PLAINSDUNE FIELD RESEARCH: LINKING CHRONOLOGICAL DATA TO CLIMATE

Alan F. Halfen. University of Kansas, United StatesE-mail address: afhalfen@ku.edu

Over the past 30 years, numerous papers have been published on the linksbetween North American Great Plains aeolian dune activity and climate,the majority of which include either 14C- or optically-derived chronologies.Although individual dune field activation can be linked to climatic events,it has been difficult to reconcile patterns of these events across the entireregion. Correlating dune activity to climate is problematic for severalreasons: (1) the spatial distribution of studied dune fields, and theirchronologies, is not consistent across the region, (2) 14C and first-genera-tion optical ages may be unreliable considering recent advances in datingtechniques, and (3) it is still not fully understood how climate in centralNorth America is linked to mesoscale and global climate changes. To helpovercome these problems, current research has emphasized constrainingthe geographical and chronological patterns of well-documented mega-droughts with high spatial and temporal resolution, optical-age chronol-ogies. In Nebraska, for example, chronologies have identified at least twoperiods of widespread megadrought activity. Similarly, chronologies fromKansas have been used to show that megadroughts following the MCAextended further east than previously modeled. In the future, enhancedatmospheric models may be able to better link dune activity to climate,however, aeolian research will also play an important role, especially withthe release of the INQUAQuaternary Dune Atlas, an extensive geographicaland chronological database of global aeolian dune fields. The true potentialof this database lies in the quantitative nature of the data. Within GreatPlains dune fields, new statistical relationships between aeolian activityand climate may be shown based on longitude, latitude, dunemorphology,and other database attributes. This data mining should better helpresearchers identify past and future drivers of aeolian activity in theregion.

MEDIEVAL CLIMATIC ANOMALY AND LITTLE ICE AGE DUNE ACTIVITY INTHE ARKANSAS RIVER VALLEY, CENTRAL GREAT PLAINS, USA

Alan F. Halfen. University of Kansas, United StatesE-mail address: afhalfen@ku.edu

Aeolian dunes of the Hutchinson, Arkansas Valley and Great Bend SandPrairie Dune Fields are prominent features in the Arkansas River valley ofthe Central Great Plains. Collectively, these dune fields form a 10,000-km2

area that spans a 400-km east-west climatic transect of the region. Annualprecipitation on the eastern margin averages 750 mm, while precipitationon the western margin averages 390 mm. This dramatic precipitationgradient, together with the geographical position of these dune fields,makes them important locales for studying the influences of past climateon dune activity in the Great Plains. We present a new chronology of duneactivity from the Arkansas River valley, which is derived from previouslyreported ages, new AMS 14C ages, and 110 new optical ages derived overthe past two years. Holocene dune sediments directly overlie a system ofPleistocene terraces deposited between 66 ka and 12 ka. Early- andmiddle-Holocene dune activity, however, has been difficult to reconcilebecause younger episodes of activity have likely overprinted those older.Nevertheless, isolated areas of the Arkansas River valley show dune acti-vation in the middle Holocene 6-4 ka. The vast majority of activation agesfrom the Arkansas River valley are from the last 1000 years, and clusters of

these ages indicate that widespread activity began at the height ofwarming during the Medieval Climatic Anomaly (MCA). Activity continuedthroughout the MCA but intensified as climate shifted towards coolerconditions between 0.8 ka and 0.7 ka. At the onset of the Little Ice Age (LIA)dune activity decreased, but did not cease, and, by the end of the LIA,activity again intensified between 0.3 ka and 0.2 ka. Dune activity in theArkansas River valley, especially that of the past 1000 years, is coeval withother Great Plains dune fields and suggests that these dunes, like othersthroughout the region, were highly sensitive to changes in climate.

LATE-GLACIAL AND HOLOCENE ICE FLUCTUATIONS, SCORESBY SUND,EAST GREENLAND

Brenda Hall. Earth Science Department & Climate Change Institut, UnitedStatesE-mail address: BrendaH@maine.edu

The response of the cryosphere to past climate changes affords context formodern ice fluctuations in Greenland. Here, we present data through thelate Pleistocene-Holocene transition to present for independent ice capsand outlet glaciers of the adjacent Greenland Ice Sheet in the ScoresbySund region of East Greenland.During Late-Glacial time, both local ice caps and Greenland ice sheet outletglaciers produced two prominent moraine sets during the Milne LandStade. Retreat was accompanied by marine inundation. More than 150radiocarbon dates of shells in raised beaches and deltas are the basis fortwo relative sea-level curves, each of which shows very high rates ofrelative sea-level change typical of recently deglaciated regions. The curvesboth indicate total uplift (including areas now drowned by rising sea level)of slightly less than 200 m. The marine limit (134 m) dates to w12,400 calyr B.P. We suggest that this is a close minimum age for formation of theolder set of moraines. The second set of Milne Land Stade moraines formedat w11,300 cal yr B.P. Our Holocene data come from landforms and sedi-ments adjacent to mountain glaciers in the Stauning Alper and indepen-dent ice caps. Marine terraces extending to the historical (Little Ice Age)drift limit indicate that these glaciers retreated to a position similar to – orless extensive than – at present by w10,000 cal yr B.P. as a response toearly Holocene warming. Analysis of glacial landforms, as well as sedi-ments from glacially fed lakes, suggests that ice remained in this retractedstate for much of the Holocene, including during the Medieval WarmPeriod. Our results so far indicate that the only prominent Holocene glacialadvance occurred during the Little Ice Age.

DEGLACIATION OF CORDILLERA DARWIN, SOUTHERN CHILE, DURINGTHE LAST TERMINATION

Brenda Hall. Earth Science Department & Climate Change Institut, UnitedStatesE-mail address: BrendaH@maine.edu

The geographic expression and relative phasing of events during the lasttermination are important for isolating mechanisms behind changes in theclimate system and thus for understanding how Earth emerges from an iceage. The Mystery Interval (14.5–17.5 kyr B.P.) is key for understanding thetermination because of the apparently contradictory climate signalsrecorded by proxy records at that time. Here, we present new data fromCordillera Darwin, southernmost Chile (54-55o S, 69-70oW), that show thefirst evidence of rapid glacier collapse during the Mystery Interval insouthern South America. This collapse was coeval with ice recession atsome other Southern Hemisphere sites, with increased upwelling in theDrake Passage, with a warming of oceanic SSTs offshore of Chile, and witha rise in atmospheric CO2. Together, these data indicate a coherent responseto the start of the termination in the southern middle and high latitudes.

HOLOCENE ICE FLUCTUATIONS AT VENTISQUERO MARINELLI,CORDILLERA DARWIN, SOUTHERN SOUTH AMERICA

Brenda Hall. Earth Science Department & Climate Change Institut, UnitedStatesE-mail address: BrendaH@maine.edu