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根据西藏拉萨桑达第四系剖面的研究,采用植硅体、分子化石等气候待用指标,并配以TL测年,探讨了拉萨地区5000a来气候及环境变迁。结果表明:1)在5.889Ka.BP-2.3 Ka.BP,植硅体形态类型为齿形-平滑棒型、石屑型、网脊块状,反映的植被景观为森林-草原景观,气候温凉;C27+C29/C31+C33值>1,木本植物含量逐渐增多。2)2.3 Ka.BP-2.1 Ka.BP,植硅体显示以为长方型-平滑棒型、多面体型组合,反映植被景观为草原或森林-草原景观;C27+C29/C31+C33比值由大逐渐减小,同时ACL比值增大、CPI值出现波动,反映在木本占优势的前提下,草本植物逐渐增加;3)2.1 Ka.BP-1.9 Ka.BP,植硅体为长方型、齿型-平滑棒型组合带,反映植被景观为草原景观,气候较寒冷;C27+C29/C31+C33值波动变化,且向1靠近,ACL值显示从小-大-小的变化,显示植被从木本向草本替演的特点;4)1.9 Ka.BP以来,植硅体为齿型、帽型-平滑棒、多面体型,C27+C29/C31+C33值趋向于1,CPI逐渐增大,ACL值增大,显示气候寒冷的特点。
According to the study of Quaternary facies in Lhasa Sodar, Tibet, climatic indices such as phytoliths and molecular fossils are used, together with TL dating, the climate and environmental changes in Lhasa since 5000 a are investigated. The results show that: 1) At 5.889Ka.BP-2.3 Ka.BP, the morphological types of phytoliths are toothed-smooth rods, stone chips and net-spine lumps. The vegetation landscapes reflect the forest-grassland landscape, Cool; C27 + C29 / C31 + C33 value> 1, woody plants gradually increased. 2) 2.3 Ka.BP-2.1 Ka.BP, phytoliths showed a rectangular - smooth bar, polyhedron combination, reflecting the vegetation landscape as grassland or forest - grassland landscape; C27 + C29 / C31 + C33 ratio from large And the CPI value fluctuated, reflecting the gradual increase of the herbaceous plants under the premise of woody predominance; 3) 2.1 Ka.BP-1.9 Ka.BP, the phytoliths were rectangular, Tooth-smoothing bar combination zone, reflecting the vegetation landscape as the grassland landscape, the climate is colder; the C27 + C29 / C31 + C33 values fluctuate and are close to 1; the ACL values show the change from small to big to small, Woody herbs to the performance of the replay; 4) Since 1.9 Ka.BP, the silicon plant for the tooth type, cap type - smooth bar, polyhedral, C27 + C29 / C31 + C33 value tends to 1, CPI gradually increased, ACL value increases, showing the characteristics of the cold climate.