黄土高原西部会宁地区66万年以来冰期—黄土旋回的孢粉记录

The Spore-pollen Records of Glaciation-loess Cyclesin Huining Area in the West Part of the LoessPlateau Since 660 000 a B.P.

根据野外剖面观测及古地磁资料,将会宁黄土地层与兰州、洛川黄土地层进行对比。在孢粉分析的基础上,把该区约66万年以来的植被与气候演变历史划分为13个阶段,并将其与深海沉积氧同位素阶段及冰期旋回进行了对比。约66万年以来,该地植被变化于温性针阔叶混交林与荒漠草原之间,气候变化于温暖半湿润-寒冷干旱之间。

According to the spore-pollen assembleges in a loess profile in Huining, Gansu Province, and comparing with those in Lanzhou, Gansu Province and Luochuan, Shanxi Province based on the observation of the stratigraphic sections and the paleomagnetic data, the history of the paleo-vegetation and climate during the last about 660 000 years in this region may be divided into 13 stages. These stages may be compared with the oxygen-isotope stages in deep-sea cores. In the 1st stage (ca. 660 000 to 630 000 a B. P.), the vegetation was steppe consisting of Artemisia, Chenopodiaceae, Corylus, etc.; and the climate was cool and dry. This stage was corresponded to oxygen-isotope stage 17. In the 2nd, 4th, 6th, 8th and 10th stages (The time are respectively between 630 000 and 555 000, 446 000 and 410 000, 350 000 and 330 000. 290 000 and 250 000, 200 000 and 140 000 a B. P.), vegetation types were all desert steppe composed of Artemisia, Chenopodiaceae, Nitrarias Ephedra, Tamariceae, ect. During those periods, the clamite was cold and dry. They were successively corresponded to the isotope stage 16, 12, 10, 8 and 6. In the 5th, 7th, 9th, 11th and 13th stage (Their time is from 410 000 to 350 000, 330 000 to 290 000, 250 000 to 200 000, 140 000 to 70 000 and 10 000 to 0 a B. P. separately in proper order), the types of vegetation were all forest steppe consisting of Betula, Quercuse, Pinus or Picea and herbs; and the climate was temperate and semihumid or mild-cool and semiarid. The stages were successively correlated with isotopic stage 11, 9, 7, 5 and 1. In the 12th stage between 70 000 and 10 000 a B. P., the vegetation was coniferous forest consisting of Picea, Pinus and Abies. The climate was relatively cold and wet. It was corresponded to the isotopic stage 2, 3 and 4. In the 3rd stage (from 555 000 to 446 000 a B. P.), the climate was warmer and wetter than other stages. The vegetation was needle-broadleaved mixed forest (or forest steppe) composed of Quercuse, Betula, Pinus, Corylus, Ulmus, Tilia, etc. The stage was correlated with the isotopic stage 13, 14 and 15.