中国黄土研究新进展 (二)古气候与全球变化

本文扼要介绍最近几年来在中国黄土高分辨率气候地层、第四纪古气候演化型式以及冷期和暖期中黄土高原古气候空间格局研究方面的一些新进展。根据土壤地层学与地球化学、地球物理学手段的结合,2.5 Ma来的中国黄土系列可划分出37个大的气候旋回,其中含74个气候阶段,这74个气候阶段又可细分为110个次级阶段。第四纪气候振荡的幅度受气候周期长短所控制。从冷期到暖期的气候转换具有突变性,从暖期到冷期的气候转换具有渐变性。冷期堆积的黄土与暖期形成的土壤在性状上都有地带性分布的特征。

PROGRESSES OF LOESS RESEARCH IN CHINA (PART 2): PALEOCLIMATOLOGY AND GLOBAL CHANGE

This paper represents the recent advance of research on the high-resolution chrono-climatostratigraphy, the evolutional pattern of the Quaternary climate and the spatial structure of climate at specific cold and warm periods of the Quaternary in the Loess Plateau.Basing on the concept of pedostratigraphy and the approaches of geochemistry and geophysics, the climate of the last 2.5 Ma in the Loess Plateau consists of thirty-seven cycles. The thirty-seven cycles can be divided into seventy-four climatic stages, and the climatic stages are composed of a hundred and ten substages.The amplitude of climatic fluctuations is dependent on their periodicities. The fluctuations with about 0.1 Ma period are characterised by big amplitude whereas that is much less in the oscillations with the periods around 40 000a and 20 000a. These phenomena may arise from a global climatic feedback mechanism.The transition from glacial to interglacial has abrupt features while it is gradual from interglacial to glacial.The loess accumulated in glacials and the paleosols formed in interglacials have zonal characteristics over the Loess Plateau. It has been inferred that in glacial periods, the western part of the Plateau was covered by desert-steppe vegetation, the central part by aridsteppe and the southern part by steppe, and that in interglacial periods, the West Loess Plateau was occupied by typical steppe vegetation, the centre of Plateau by forest-steppe, and the South Plateau by forest.The reconstruction of the spatial climatic pattern over the Loess Plateau at a specific temperature-increasing time in the Quaternary will give a reference to the prediction of the future climatic changes due to the influence of the green house effect.