植物硅酸体-气候因子转换函数及其在渭南晚冰期以来古环境研究中的应用

利用全国１６２块表层土壤样品的植物硅酸体组合及气候资料，建立植物硅酸体－气候因子(温度、降水量)转换函数，通过转换函数估算了渭南黄土剖面７１块样品(约３万年来)的年均温、年均降水量。在全新统部分样品中发现了少量的竹亚科植物硅酸体。古气候从末次冰消期向全新世的演变过程中，出现了两次比较明显的气候波动，分别与波令间冰阶、中仙女木冰阶、阿勒罗德间冰阶和新仙女木冰阶相对应。本文首次发现黄土高原末次冰消期气候转暖起始于１４０００ａＢ．Ｐ．。

CLIMATE TRANSFER FUNCTION FROM OPAL PHYTOLITH AND ITS APPLICATION IN PALEOCLIMATE RECONSTRUCTION OF CHINA LOESSPALEOSOL SEQUENCE

Abstract:There are mainly three kinds of approaches at present day using organism fossils to reconstruct paleoenvironmental and paleoclimatic changes: 1) indicative species, 2) climatic transfer function, 3) response surface. Among them, the climatictransfer function has been widely used in various fossil organisms such as foraminifera, radioraria, diatom, spore pollen and land snail etc. In this paper, opal phytolith-climatic factor transfer function has been established and introduced in considering the following factors: a variety of modern surface soil samples may not distribute in the same climatic zone or the same ecological conditions; species distributedin different climatic or ecological condition may be controlled by different factors;the relationship between organism assemblage and climatic parameter is not the simplelinear ones; how to ensure the reality of ecological factor of fossil assemblage tocorrespond to the modern ecological factor in the construction of climatic transferfunction; how to eliminate the effects of manmade and microecological environment.162 samples from modern surface soils of China and related meteorological datawere collected and analysed quantitatively. 250-350 identified phytolith grainswere obtained for each sample. 21 types of opal phytoliths, with significant climatic characteristics, were selected to establish the climatic factor transfer function. Ofthem, teeth and hat ones represented cool temperate climatic condition, dumbbell andshort saddle-shaped or barrel-shaped phytoliths represented hot arid climates, irregularand granular ones reflected a cool and dry environment. Mathematic statistics suchas factor analysis, system cluster analysis and regression analysis was used. The results could be expressed in the following regression functions:Y= 9.858 + 120.869X1 - 24.168X2 + 31.914X3 - 2.934X4 + 48.028X5- 31. 111X6 + 50. 845X7where Y = mean annual temperature, the regression error 13%, confidence 95%,and correspondence coefficient 0.88, and Y = 657.661 + 8 371.455X1 + 2 139.759X2 - 292.103X3 + 1 791.921X4+ 1 357.386X5 - 2 241.384X6 - 1 306.932X7where Y = mean annual precipitation, the regression error 14%, confidence 95%,correspondence coefficient 0.80.The studied loess-paleosol sequence is located at Weinan, in the east of Xian,Shaanxi Province. 626 samples from the uppermost 12 m deposits (about 0.15Ma)were taken to analyse the opal phytoliths. In this study, only 71 samples (0-4.7m)were analysed. For a high resolution study of the last deglaciation history of theLoess Plateau, the upper part 0-1.9m was sampled at 4cm intervals, 1.40-1.32mat 2cm intervals, below 1.9m at 10cm intervals. A great quantity of phytolithsoccurred in each sample, which analysed weight was only 5g. Based on the phytolithanalysis and the established climatic transfer function, climatic condition of the last30 000a B.P. was obtained and interpreted. Estimate for annual average' temperatureduring 30 000-23 000 aB.P. was varied in between 11-12.8℃ (in present-day Weinan, the average annual temperature is about 12℃), the annual precipitation was50-150mm higher than present mean (between 600-620mm). During 23000-14 000 aB.P., the mean annual temperature and precipitation were decreased gradually. At about 18000aB.P, the temperature reached the minimum value 5.3℃(thatmeads 7℃ lower than modern value), the precipitation was reduced to 350-400mm.A short warm stage appeared at about 14 000-13 000 a B.P. which approximatelycorresponded to the climatic turned warm period of the last deglaciation recordedin the east Atlantic Ocean and the South China Sea. At about 11 590a B.P, therewas an abrupt becoming cold event, a remarkable reduction of warm phytoliths andincrease of cool and dry ones indicated the impact of the Younger Dryas event.Entering Holocene, the temperature and precipitation were increased rapidly. .Puringthe optimum period, the mean annual temperature was 2-3℃ higher than presentvalue, the precipitation was up to 800 mm. It is noted that a small number ofbamboo phytoliths has been found in pa