共和盆地马四剖面12 cal ka BP以来色度特征及环境演变

CHROMATICITY CHARACTERISTICS AND ENVIRONMENTAL EVOLUTION SINCE 12 CAL KA BP IN THE MS PROFILE OF THE GONGHE BASIN

本文以共和盆地马四剖面古风成砂-古土壤沉积序列为研究对象,利用CM-5分光测色计获得土壤色度参数亮度(L^(*))、红度(a^(*))及黄度(b^(*))值,分析色度参数的变化特征,结合Fe2O3、有机质及利用磁化率重建的温度、降水量指标探讨色度参数的古气候意义,重建12 cal ka BP以来共和盆地的气候演变过程。结果表明:(1)色度参数L^(*)、a^(*)、b^(*)均值在剖面中整体表现出古风成砂层高于古土壤层的特征, a^(*)/b^(*)与之相反;(2)色度参数可作为有效的气候代用指标重建古气候,b^(*)及a^(*)/b^(*)对气候转变反应敏感,b^(*)高值指示气候冷干,b^(*)低值指示气候温湿,a^(*)/b^(*)高值代表气候温湿, a^(*)/b^(*)低值代表气候冷干。L^(*)、a^(*)在此区域对气候的响应具有一定的局限性;(3) 12 cal ka BP以来共和盆地马四剖面色度揭示的气候演变可划分为7个阶段,表现出冷干-温湿旋回的变化特征。

In this paper, the paleotropic sand-paleotropic sedimentation sequence of the MS profile of the Gonghe Basin was used as the research object, and the brightness(L^(*)), redness(a^(*)) and yellowness(b^(*)) values of soil chromaticity parameters were obtained by CM-5 spectral color meter, the variation characteristics of the chromaticity parameters were analyzed, and the paleoclimate significance of the chromaticity parameters was discussed by combining Fe2O3, organic matter and temperature and precipitation indexes reconstructed by using susceptibility, and the climate evolution process of the Gonghe Basin since the reconstruction of 12 cal ka BP was reconstructed. The results show that:(1) The means of the color parameters L^(*), a^(*), and b^(*)showed the characteristics of the paleoclavonic sand layer as a whole in the profile as a whole higher than that of the paleotropic layer, and a^(*)/b^(*)was the opposite;(2) The color parameter can be used as an effective climate substitution index to reconstruct the paleoclimate, b^(*)and a^(*)/b^(*)are sensitive to climate transition response, b^(*)high values indicate climate cool dryness, low values indicate climate temperture and humidity, a^(*)/b^(*)high values represent climate temperature and humidity, and low values represent climate cold and dry.L^(*), a^(*)have certain limitations in the climate response in this region;(3) The climate evolution revealed by the four-sectional complexion of the horse in the Gonghe Basin since 12 cal ka BP can be divided into seven stages,showing the variation characteristics of the cold-dry-warm-wet rotation, and the coincidence with the climatic stage inversion of the profile using other indicators is very high, indicating that the chromaticity parameter is a reliable climatic substitution index.