摘要
本文对青藏高原与黄土高原毗邻地区近20个剖面(点)的黄土沉积进行了孢粉分析表明,自晚更新世以来,研究区黄土剖面中古土壤层的孢粉种类、数量以及木本植物花粉成分均比黄土中多得多,反映了该时期研究区的气候条件比现今要温和湿润,植被较繁茂,以后逐渐旱化,但并不连续。此阶段研究区主要植物群的演替规律是:针叶林→森林草原→草原。
Among the comtinental deposits, the loess of the loess plateau, due to its continuous deposition and homogeneous structare in substantial composition, is an ideal geological body for studies on the evolutionary process of palaeoclimate, especially on the palaeosoil in loess.
Systematic studies on the evolutionary process of palaeoe-nvironments have been carried on by the authors through pollen analysis of pollen samples from 9 natural loess sections and surfece samples of 13 sites, in Qinghai and Gansu provinces .
In this region the development of vegetation in the Quaternary period may be divided based on spore pollen assemblages into three stages, which are in transitional relationship from coniferous stage to forest-steppe stage and then to steppe stage. The first stage is marked by the presence of more pinaceous pollen (over 60%), such as Pinus, Picea,Abiesindicating a rather cool climate. The second stage is characterized by the presence of more Pinus and herbaceous pollen with some deciduous broad-leaved tree pollen, indicating a warmer and moister climate than the present climate. In the last stage, however, such xerophilous her bs as Chenopodiaceae, Artemisia, Compositae, Cruciferae, etc., were prevailing in the are, indicating that the climate was rather cool and dry. It has been confirmed that the evolutionary process of the palaeoclimate enviroment revealed by the loess deposites shows a general tendency of rhythmic fluctuation since Pleistocene being in transition from humid forest proirie to arid desert steppe By comparing the spore-pollen assemblages of loess and the palaeosoil in loess, the authors suggest that the palaeoclimate during the deposition of palaeosoil was warmer and wetter than that during the deposition of loess.
出处
《冰川冻土》
CSCD
北大核心
1990年第2期125-140,共16页
Journal of Glaciology and Geocryology
基金
国家基金
