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《Arid Land Geography》 2018-05
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Palynoflora of lacustrine sedimentation in the northern margin of the Kongqi River,Xinjiang from 72-51 ka BP

BAI You-liang;ZHAO Zhen-hua;SUN Qi;LI Bo;Northwest Institute of Nuclear Technology;  
In this paper,the author chose LX02 section of the lake sedimentary with a thickness of 5. 4 meters which located at the north margin of the Kongqi River in south Xinjiang,China,as the research object. From the top down to the bottom,six Optically Stimulated Luminescence( OSL) ages were achieved as follows 53. 1 ± 4. 4 ka BP at 0. 18 m,56. 1 ± 3. 2 ka BP at 1. 19 m,57. 9 ± 3. 3 ka BP at 2. 21 m,60. 5 ± 4. 0 ka BP at 3. 10 m,67. 0 ± 6. 0 ka BP at 3. 71 m,and 71. 0 ± 3. 6 ka BP at 4. 69 m. The chronology sequence of the LX02 section was established on6 OSL age results from 72 ka BP to 51 ka BP. In the meanwhile,80 pollen samples were analyzed and 13 541 grains of pollen and spores were identified( 169 grains/sample on average). A total of 47 spore and pollen types were identified. On the whole,arboreal pollen taxa were dominant in most of the samples,ranging from 18. 91% to 91.03% in abundance with an average of 58. 20%. Shrubs and herbs were less dominant,fluctuating between 8. 97%and 60. 12% in abundance and averaging at 35. 02%. Fern spores and algae ranged from 0. 00% to 13. 64% in content and had a mean of 6. 78%. These indicated that,during the deposition of this section,the study area was generally covered continuously by coniferous and broadleaved forests,under which various shrubs and herbs grew vigorously. Ferns and algae mainly distributed in some low-lying humid places within the study area. The main vegetational types included Pinus,Quercus,Castanea,Corylus,Cyperaceae,Artemisia,Chenopodiaceae,and Polypodiaceae. There were also some Carya and Pterocarya,and these subtropical types occurred commonly with low and erratic percentages. Specifically,the palynoflora of section was divided into three stages according to the variation of major pollen type and B. T. P./( S. P. + H. P.) : in zonesⅠ( 72. 4-66. 8 ka BP),Ⅲ( 56. 1-51. 0 ka BP),the broadleaved arboreal pollen was always low in abundance while the shrub and herb pollen was usually high. In zoneⅡ( 66. 8 ~ 56. 1 ka BP),the broadleaved tree pollen was generally high and the shrub and herb pollen was low on the whole. This indicated the characteristics of climate fluctuate in the study area between dry-cold and humid-warm patterns during the Late-Pleistocene period. This mode of climate change in the study area is not only well correlated with the changes of weathering intensity revealed by the character of clay mineral and geochemistry,but also well matched with the Ostracoda abundance in upper well Dacan1 located in the southeast Qaidam Basin,Luminescence Chronology of High Lake levels of Paleolakes in the Late Quaternary eastern Qaidam Basin,Organic Carbon Isotopic characteristics of Beijing Plain. Nevertheless,the internal forcing mechanism for this mode of climate changes in the study area remains unclear up to now and deserves further investigation.
【CateGory Index】: P467;P532
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