Abstracts / Quaternary International 279-280 (2012) 462–565546

dunes, located in the semi-arid zone of eastern Inner Mongolia, northernChina) as example, we are studying the initiation and variations of thedune landscape in the eastern part of the desert belt in northern China. Ourfield work was carried out mainly along three N-S transects in this sandyland, ca. 21000 square kilometers in area. We are trying to decipher signalsof environmental changes from aeolian sequences which are sometimesintercalated by lacustrine deposits and often by paleosols. On the basis ofphysical and chemical features of the sediments and OSL ages of aeoliansands (quartz and feldspar grains) and radiocarbon dates from paleosolsand lacustrine deposits (organic carbon), we here argue that the dunesystem in the middle latitudes of eastern Asia is much younger thanpreviously reported and it reacts sensitively to the climate changes duringlate Quaternary and to human impacts in more recent centenaries. Theepochs of reworking or stabilization of the dunes are broadly consistentwith the weakening or enhancement of the east Asian monsoons,demonstrating that dune systems are important repositories of informa-tion for understanding climate changes also.

WARM-SEASON PRECIPITATION AS THE DOMINANT CONTROL ON C3/C4

PLANT VARIATIONS IN NORTHERN CHINA: EVIDENCE FROM CARBONAND OXYGEN ISOTOPE COMPOSITION OF PEDOGENIC CARBONATE

Shiling Yang. Key Laboratory of Cenozoic Geology and Environment, ChinaE-mail address: yangsl@mail.igcas.ac.cn

Plants use two principal biosynthetic pathways to fix carbon, the C3 andC4 cycles. C3 plants have d13C values ranging from -22& to -30&, and C4

plants from –10& to -14&. Generally, lower atmospheric pCO2, highertemperature and enhanced summer precipitation favor C4 over C3

plants. Evaluating how future climate changes may impact C3/C4

biomass in East Asia depends largely on the understanding of therelationship between past C3/C4 variations and monsoon circulation.Here we present isotopic results of soil carbonate from northern China,for the Holocene, the last and penultimate interglacial periods.Comparison of the observed and predicted d 18O values of modern soilcarbonate suggests that pedogenic carbonate forms mainly in warm,rainy season. Carbonate nodules from Chinese loess all demonstratea distinct negative d 18O- d 13C relationship, i.e. the lower d 18O valuesthe higher C4 component, both spatially and temporally. d 18O ofmeteoric precipitation from summer monsoon domain exhibits a trough(low d 18O values) in rainy season. This trough damps inland withweakened monsoonal influence, and thus a distinctive characteristic ofsummer monsoon precipitation. In this context, the negative d 18O- d 13Crelationship can be fully explained by the following mechanism:increased summer precipitation would have resulted in low d 18O valuesof soil water and simultaneously favored C4 over C3 plants. This mech-anism promises a rapid increase in C4 biomass under projected increasein summer precipitation due to global warming.

ORIGIN AND ENVIRONMENTAL IMPLICATIONS OF LOESS SEDIMENTS INTHE EASTERN TIBETAN PLATEAU

Shengli Yang. Nanjing Normal University, ChinaE-mail address: yangshengli09@gmail.com

The loess-like sediments, widely preserved in the eastern TibetanPlateau and its adjacent regions, have been regarded as a combinedresult of the uplift of the Tibetan Plateau and its related or coupledalterations of air circulation and climate environment. To reveal theformation and the timing of these deposits is of great importance tounderstand the impacts of the Tibetan uplift on climatic environmentalchanges. Geomorphic, sedimentologic/pedogenic, grain size distribu-tions and quartz oxygen isotopic evidence collectively demonstrates theaeolian origin of these sediments and its main source area on theTibetan Plateau. Detailed paleomagnetism dating demonstrates that theGanzi loess has an oldest age of ca. 1.13 Ma, while that at Huagai(Sichuan Basin) has an age of ca. 0.8 Ma. The onset and climatic proxyrecords of these loess in the eastern Tibetan Plateau exhibit a similardrying trend toward the present and three remarkable drying event atw1.13 Ma, w0.8 Ma and w0.5 Ma. This suggests the establishment ofa circulation system similar to the present one in conjunction with rapiduplift of the Tibetan Plateau at that time.

INVESTIGATION OF THE ULTRASTRUCTURAL CHARACTERISTICS OFFOXTAIL AND BROOMCORN MILLET DURING CARBONIZATION ANDITS APPLICATION IN ARCHAEOBOTANY

Qing Yang. Institute of Earth Environment, Chinese Academy of, ChinaE-mail address: yangqing@ieecas.cn

Fossilized caryopses (or grains) of foxtail millet (Setaria italica) andbroomcorn millet (Panicum miliaceum) are important archaeobotanicalmaterials for the study of early human agricultural activities. Themorphology and ultrastructural characteristics of carbonized modernmillet caryopses treated in a drying oven and burning in a field wereinvestigated at different temperatures to study how fossilized millets areformed. The caryopses shrank gradually at temperatures below 200�C, andstarch granules in the endosperm retained their crystalline structure. At250�C the foxtailmillet caryopses expanded,whereas the broomcornmilletcaryopses were greatly deformed. At this temperature, the structure of thestarch granules of bothmillets became amorphous. At 300�C the caryopsespartially turned to ash and became porous, and the ultrastructure of thestarch granules was transformed into alveolate cavities. Fossil caryopsesfrom the prehistoric storage cellar at the Beiniu Site retained their crys-talline structure and were formed by the dehydrating effect of carboniza-tion, indicating that water molecules were not involved in the starchcrystallization. The results of a field burning experiment demonstrated thatthe ultrastructure of carbonized caryopses placed on the ground under thefire was amorphous. The amorphous ultrastructure of the carbonizedcaryopses recovered from the archaeological layers is consistent with theexpected structure of caryopses that have been carbonized at 250�C.Therefore, we suggest that the recovered caryopses were formed at about250�C by baking rather than by burning in an open fire.

BIODIVERSITY OF THE CASPIAN SEA MOLLUSKS: NATURAL ANDANTHROPOGENIC IMPACT

Tamara Yanina. Moscow State University, Russian FederationE-mail address: didacna@mail.ru

The modern biodiversity of the Caspian Sea simply reflects a complicatedhistory of paleo-Caspian transgressions and regressions, desalinisation andsalinization and, recently, human activity. The Caspian history during thelast 10 ky includes the end of the Late Khvalynian transgression, Man-gyshlak regression and several stages of the New Caspian transgression.The Late Khvalynian basin emerged 11-9 thousand years ago under climateconditions, which were more humid and colder than the present one. Themaximum level of the Late Khvalynian transgression was close to the 0 m.The Mangyshlak basin formed about 9-8 thousand years ago. It emerged inthe period of postglacial warming and climate aridity. Its waters used tocover only depressions of the Middle and Southern Caspian. The level ofMangyshlak Lake was – 80 m. The New Caspian transgression maximumemerged approximately 5-6 thousand years ago. The sea level was -19 –

-20 m. In the 20th century it has been fluctuating within the range ofalmost four meters, approximately from -25 m in the beginning of thecentury to -29 m in 1977. In the end of the 20th century, the sea levelsoared, and in the beginning of the 21st century began to drop again. Theinfluence of the Caspian Sea level change on the mollusk biodiversity wetrace on two different areas: Turali (Dagestan, Middle Caspian) and VolgaDelta (Northern Caspian). The modern Caspian ecosystem is the result ofthe long-term biological evolution. For a long time, all levels of biodiversityformed and interacted naturally without human influence. The develop-ment of the human civilization resulted in strong anthropogenic impact,which interferes with the natural course of events. The humankind hasbecome a powerful external factor destabilizing the processes of the Cas-pian ecosystem.

BIOSTRATIGRAPHY OF THE CASPIAN PLEISTOCENE

Tamara Yanina. Moscow State University, Russian FederationE-mail address: didacna@mail.ru

Stratification of marine Pleistocene deposits is based on the verticalsuccession of fossil molluscan assemblages mainly belonging to DidacnaEichwald genus. N.I.Andrusov was the first to apply this approach at the