Abstracts / Quaternary International 279-280 (2012) 233–345 279

the coastal line tends to landward migrate within the last hundred years.Coastline of Zhenzhu bay had migrated landward since 20th century.Qinzhou bay shows the trend of westward expansion and eastwardreduction. In the western coast area, there have a degradation of mangrovein the early 20th century. The area of tidal flat reduces due to the restrictedspace by human activities such as building dykes in 1960s and 1970s. Theeast coastline has obviously migrated seaward, corresponding to the rapiddeposition with more materials from Qinjiang River since 1980s.

LATE NEOGENE EAST ASIAN MONSOON: FROM WINTER TO SUMMERDOMINATED SUB-REGIME AND PERIODICITY TRANSITION FROM 100KYR TO 41 KYR

Fengjiang Li. Key Laboratory of Cenozoic Geology and Environment, ChinaE-mail address: fengjiangli@mail.iggcas.ac.cn

More and more evidence indicates that the onset of the East Asian (EA)monsoon can be traced back to the Oligocene-Miocene boundary.However, its evolutionary process is still less well known. Here weinvestigate its late Neogene evolution by analyzing a terrestrial mollusksequence, from the Chinese Loess Plateau, covering the period between 7.1and 3.5 Ma. Considering the modern ecological requirements of theseorganisms, we were able to define two groups of cold-aridiphilous andthermo-humidiphilous species, representing the EA winter and summermonsoon variations, respectively. Variations in these two groups indicatetwo different monsoon dominated periods during 7.1-3.5 Ma. First,between 7.1 and 5.5 Ma, the EA winter monsoon, with a 100 kyr period-icity, was dominant. Second, between 5.1 and 4 Ma, the EA summermonsoon dominated, with a 41 kyr periodicity. Furthermore, our molluskrecord yields valuable evidence for a late Miocene-Pliocene transition ofabout 400 kyr from winter monsoon dominated towards summermonsoon dominated, associated with a periodicity transition from weak100 kyr to 41 kyr. The strengthened winter monsoon interval, with a 100kyr periodicity, is coeval with orbital-scale global ice volume changes, inconjunction with the uplift of the Tibetan Plateau which probably rein-forced the winter monsoon sub-regime. Conversely, closures of thePanama and Indonesian seaways, associated with changes in obliquitybetween 5.1 and 4 Ma, are probably major forcing factors for the observeddominant summer monsoon with 41 kyr frequency, favoring heat andmoisture transports between low and high latitudes to allow TH mollusksto grow and develop in the CLP. The transition from a 100 kyr dominatedinterval towards a 41 kyr dominated one is contrary to the mid-Pleistocenetransition (MPT), which corresponds to ice volume expansion at highlatitude and show a shift in the periodicity from 41 kyr to 100 kyr.

RELATIVE POLLEN PRODUCTIVITY ESTIMATES FOR HERBACEOUS TAXAIN THE HULUNBEIER STEPPE, INNER MONGOLIA

Yiyin Li. Peking University, ChinaE-mail address: lyy@urban.pku.edu.cn

The quantitative reconstruction of past vegetation in steppe with an openlandscape has been hampered by the lack of detailed information of pollenproduction and dispersal processes. Steppe is an important vegetation typein northern China. The Hulunbeier steppe is widely known as one of thelargest grasslands in Inner Mongolia with a rich biodiversity. Thirty-fourpollen trap samples matched with 34 soil surface samples were collectedfrom16 plots in the Hulunbeier steppe, InnerMongolia. The vegetationwassurveyed in concentric rings around each trap out to a 20m radius. Eightplotswith 14 trapswere located in Leymus chinensis steppe, three plotswith8 traps in Stipa Baicalensis steppe, one plot with 2 traps in mixed grasssteppe, and four plots with 10 traps in pastures. Pollen productivity esti-mates (PPEs) for 5 common taxa, Gramineae, Artemisia, Chenopodiaceae,Compositae and Cyperaceae, which are often found in Quaternary sedi-ments, were calculated using ERV model. Our results show that the pollenproductivity estimates relative to Gramineae, which is set as one are: forArtemisia, Chenopodiaceae, Compositae and Cyperaceae 15, 14, 10, and 6,respectively. Compositae and Cyperaceae with large pollen grains and highfall speeds are poorly dispersed and often deposited near the plants thatproduce the pollen. Gramineae, Artemisia and Chenopodiaceae with smallpollen grains and slower fall speed arewell dispersed and often form a high

proportion of the background pollen. The pollen taxa in trap and surfacesamples mainly come from plants growing within 15.5m radius as mostherbaceous plant pollen can not disperse for great distance.

DISPERSAL CHARACTERISTICS OF CHARCOAL PARTICLES OF DIFFERENTSIZES IN THE DAXING'AN MOUNTAIN OF NORTHERN CHINA AND THEIRIMPLICATIONS FOR FIRE ACTIVITIES

Yiyin Li. Peking University, ChinaE-mail address: lyy@urban.pku.edu.cn

Charcoal is one of the important proxies for reconstructing fire history andecological processes. However, our knowledge of dispersal, deposition andpreservation of charcoal is still very limited. Located on forest-steppe witha wide distribution of Pinus pumila, a flammable species and with a longhistory of human activity, Daxing'an Mountain is known to have a highfrequency of fire activity. This is an ideal place to study dispersal, depo-sition and preservation of charcoal for a better understanding of fireactivities and their implications. We collected surface samples from firecentres to the margin of 10km distance with 100m spacing along differentdirections. Charcoal was extracted from surface samples and divided into 4size fractions: macrofossil charcoal of greater than 500mm, large charcoal500- 180mm, small charcoal 180-125mm and microfossil charcoal of lessthan 125mm. The charcoal particle concentration for different sizes hasbeen estimated to understand the fire intensity, frequency and spatialextent. We find that the pattern of change in charcoal concentration ofdifferent sizes is similar: relatively high in the burning area and lowoutside burning area. However, a detailed comparison among the charcoalconcentration of inside and outside burning areas reveals certain differ-ences in their fluctuations. The concentration of large charcoal seems tofluctuate with greater amplitude than that of the microfossil charcoal.

OXYGEN AND CARBON ISOTOPIC FRACTIONATION IN THE OSTRACODEUCYPRIS MAREOTICA: RESULTS FROM A CULTURE EXPERIMENT ANDIMPLICATIONS FOR PALEOCLIMATE RECONSTRUCTION

Xiangzhong Li. State Key Laboratory of Loess and Quaternary Geolo, ChinaE-mail address: lixiangzhong@ieecas.cn

Oxygen and carbon isotopic analysis of the adult ostracod Eucypris mar-eotica cultured at controlled temperatures (10, 15, and 19�C) was used tomeasure isotopic fractionationduring shell calcification. Theostracod shellsthat precipitated at experimental temperatures are almost in isotopicequilibrium with the culture water as compared to the oxygen isotopefractionation of inorganic carbonates. Moreover, they had almost constantoffsets from equilibrium based on the oxygen isotope fractionation ofinorganic carbonates. The d18O values of ostracod shells from the 10�Ccultureswere higher than those of the 15 and 19�C cultures by 1.6 and 2.7&,respectively. The oxygen fractionation factors of E. mareotica are very closeto those of synthetic calcite formed in isotopic equilibrium. However, theostracod shells that precipitated at experimental temperatures are inisotopic non-equilibriumwith the water DIC , but the mean offset betweend13Cshells and d13CDIC becomemuchmore close to the fractionation betweencalcite and HCO3

- with increasing pH of culture water.Therefore, the carbon isotopic fractionation of ostracods living in differentwater environment should be considered, if the d13C data for E. mareoticaare used in palaeoenvironmental reconstruction. However, the ‘vitaloffsets’ of shells-d18O for E. mareotica is so small that we can neglect itseffect when using the d18O of E. mareotica living in lake waters with highpH and salinity to reconstruct the paleoenvironment. The paleotemper-ature or paleoisotopic composition of lake water interpreted from a core oflacustrine sediment may be closer to the true values when the d18O datafor E. mareotica are used.Keywords: Eucypris mareotica, temperature, culture experiment, oxygenand carbon isotope fractionation

POLLEN-VEGETATION-CLIMATE RELATIONSHIP IN SOME DESERT ANDSTEPPE COMMUNITIES IN NORTHERN CHINA

Yuecong Li. Hebei Normal University, ChinaE-mail address: lyczh@sohu.com

Abstracts / Quaternary International 279-280 (2012) 233–345280

We consider the relationship between pollen assemblages, vegetation andclimate in some desert and desert-steppe areas in northern China usingboth surface soil samples and pollen trap samples. Discriminant analysisshows that samples originating from different climatic or geographicalregions can be separated reliably on the basis of pollen assemblageregardless of sample type. DCCA analysis indicates that surface soil pollenassemblages show significant correlations with climate parameters. DCCAAxis 1 is negatively correlated with the mean temperature in the warmestmonth (MTwa; r ¼ -0.58), whilst axis 2 is positively correlated with meanannual precipitation (Pann; r¼ -0.73). Artemisia-to-Chenopodiaceae ratiosare generally lower in desert areas than in desert-steppe areas. Pollenproductivity relative to Chenopodiaceae (RChenopodiaceae) was estimatedusing least-squares linear regressionof pollen influxdata against vegetationdata and ERV model analysis of percentage pollen data against vegetationdata. Rank order of RChenopodiaceae is consistent regardless of dataset oranalysis method. Artemisia has RChenopodiaceae values greater than 3,whilst RChenopodiaceae Nitraria is around 0.1 and RChenopodiaceae Poa-ceae is below 0.1. Our results provide useful information for quantitativereconstructions of paleovegation and paleoclimate in arid or semi-arid Asia

SURFACE POLLEN AND ITS RELATIONSHIPS WITH MODERNVEGETATION AND CLIMATE IN NORTH CHINA

furong li. Lanzhou University, ChinaE-mail address: lifr09@lzu.edu.cn

A dataset consisting of 37 modern pollen samples from shrublands, steppe,steppe desert and desert in north China provide an opportunity to studythe relationships between surface pollen and modern vegetation andclimate. The principle components analysis (PCA), correlation analysis andpollen ratios were used in studying the relationship between surfacepollen and environmental factors. Climatic data for each site, includingmean annual precipitation (MAP), July precipitation (PJuly), mean annualtemperature (MAT) and July temperature (TJuly) were estimated from thenearest climate stations according to calculated elevational local lapserates based on the difference between the altitudes of the climate stationand the sampling site.The results reveal that the surface pollen assemblages of different vege-tation types faithfully represent the modern vegetation in main compo-sition taxa and dominant types. The PCA results indicated that MAP andTJuly are the twomain climate factors controlling the modern pollen rain aswell as the vegetation in Loess Plateau. Pollen environment correlationanalysis shows that the A/C ratio is positively related with MAP andnegatively related with latitude, Pinus pollen abundance is positivelyrelated with MAP while some other types, such as Chenopodiaceae,Ephedra and Nitraria pollen are negatively related with MAP.

VEGETATION DYNAMICS IN DRYLAND SYSTEMS FROM 1982 TO 2006,WITH A SPECIAL REFERENCE TO THE DISTRICT OF XILIN GOL, CHINA

Hongwei Li. Institute of Geology and Geophysics, Chinese Acade, ChinaE-mail address: lihw08@mail.iggcas.ac.cn

Located in the east margin of Gobi Desert, Xilin Gol is a transition regionbetween steppe and desert. Steppe, desert-steppe and fixed dune field arethree main subsystems in this region. In this study, AVHRR NDVI data,covering from 1982 to 2006, are used to investigate dryland's response toclimate change from the perspective of vegetation dynamics. Generally, interms of annual mean growing period NDVI, areas with increasing trendare much larger than those with decreasing trend, which are 7% and 0.6%,respectively. Compared with other seasons, spring vegetation changedmore significantly. 12.7% of the study area had a positive trend in thesecond half of April, while 5.6% had a decreasing NDVI. However, a nega-tive trend occurred in the first half of the May, which covered as much as25% of the area, and nearly no increase happened in this half month. Thisphenomenon should be attributed to the rising spring temperature, whichcaused the snow thawing, since the spring is commonly a dry season andno notable change of precipitation is detected. Overall, steppe, wheresignificant trend of vegetation occurred, is the most dynamic in the threesubsystems. With a moderate NDVI value, vegetation activity in fixed dunefield is relatively stable, characterized by a low standard variation and

coefficient of variation of the annual mean growing period NDVI. Thus,more attention should be paid on the steppe to control desertification.

CAN POLYMICTS BE USED AS PROXIES FOR PALEO ICE STREAM FLOW?

Kathy Licht. Indiana University Purdue University Indianapolis, United StatesE-mail address: klicht@iupui.edu

Coarse-sand size aggregates composed of sediment <250 microns, hereincalled polymicts, are observed in grain mounts of till collected: a) beneaththe Siple Coast ice streams of West Antarctica, b) from subglacial tilldelivered to the ice surface at Lonewolf Nunataks at Byrd Glacier, and c)from LGM-age till from the Ross Sea continental shelf. Polymict grains arespheroidal- to rod-shaped and may contain a "core" grain. For till sampleswith >10% clay-size particles, no correlation is evident between claycontent and polymict abundance. Three types of polymicts were identifiedbased on plasmic fabric and internal structure. The classification includespolymicts with: (1) diffuse edges and no internal structure, (2) moderatelydefined edges, and aweak inner core grain and plasmic fabric and (3) well-defined edges, an inner core grain and plasmic fabric.Till samples collected from Lonewolf Nunataks average 50% polymictfragments. This site is dominated by Type 2 and 3 polymicts. In contrast,polymict grains from the Siple coast ice streams contain primarily Type 1polymicts. Ten depth intervals analyzed from cores collected beneath theactive Whillans and Bindschadler ice streams average 74% polymict grains,whereas the samples from beneath the inactive Kamb ice stream average<8%. Downcore petrography from Ross Sea cores show either consistentpolymict frequency downcore or a broad mix of sand grain compositioninterrupted by intervals with >90% polymict grains. We will assess claymineral composition from these sites to determine whether it is related topolymict abundance.We hypothesize that water and possibly freezing at the bed promotescohesion of sediment and the grain shape may be subsequently modifiedduring transport. The association between active ice streams and polymictabundance in till suggests that polymict-rich intervals inRoss Sea tillmaybeindicative of times when streaming ice flowed across the continental shelf.

PROVENANCE INDICATORS OF WEST ANTARCTIC SUBGLACIAL TILLCOMPOSITION AND PAST ICE STREAM FLOW DIRECTIONS IN THEROSS EMBAYMENT, ANTARCTICA

Kathy Licht. Indiana University Purdue University Indianapolis, United StatesE-mail address: klicht@iupui.edu

Sand petrography of till from Reedy Glacier and till from the base ofWhillans and Kamb ice streams in West Antarctica revealed similarmineral and rock types indicating that sediment fill in the West Antarcticbasin beneath these two ice streams was eroded from the southernTransantarctic Mountains. However the Reedy Glacier samples containhigher proportions of feldspar and less quartz than the WAIS samples.When compared to the Ross Sea samples, the central Ross Sea tillcomposition aligns more closely with Reedy Glacier samples than WestAntarctic samples. We have expanded our till provenance studies in theRoss Embayment to include U/Pb detrital zircon age distributions as anadditional fingerprinting tool. Till samples from Whillans, Kamb andBindschadler ice streams contain abundant Ross and Grenville age zirconsthat are similar to East Antarctic detrital zircon populations. However,Kamb and Bindschadler tills also contain a distinctive age peak at w105Ma; this peak is also seen in eastern Ross Sea LGM-age till. These Creta-ceous zircons are interpreted to derive from Marie Byrd Land's MountPrince Granite or the sediments shed from it, into the catchments of Kamband Bindschadler ice streams. In sum, the petrographic and detrital zirconcan be used to determine the origin of subglacial sediments filling theWest Antarctic basin and support the presence of a boundary between Eastand West Antarctic ice near 180� in the central Ross Sea during the LGM.

POTENTIAL RESOLUTION OF DISCREPANCIES BETWEEN SCALINGMODELS FOR IN SITU COSMOGENIC NUCLIDE PRODUCTION RATES

Nathaniel Lifton. Purdue University, United StatesE-mail address: nlifton@purdue.edu