东北平原东部天恒山钻孔色度变化特征与古气候意义及对松嫩古湖演化的指示

The indication of chroma characteristics and its palaeoclimatic significance in the Tianhengshan(THS)core from the eastern part of the Northeast China Plain to the evolution of Songnen paleo-lake

东北平原东部荒山(HS)剖面是我国东北地区的第四纪典型剖面,针对该剖面的色度研究未见报道。在该剖面北约50 m处进行钻探,通过该钻孔——天恒山(THS)钻孔对该区哈尔滨组黄土-古土壤地层开展了高分辨率的色度研究,与烧失量进行了相关性分析,并与磁化率、粒度曲线对比。结果显示,亮度(L^(*))主要受控于有机质含量。黄度(b^(*))在整个黄土-古土壤地层中变化特征明显,与磁化率曲线旋回的相似性较好,可能与土壤中铁氧化物的种类和含量关系密切,同时还受控于有机质含量。由于红度(a^(*))和b^(*)具有一定的相关性,认为它们具有较为一致的致色物质,可能受控于相近的气候因子。a^(*)可能并不能很好地作为该区气候代用指标。L^(*)、b^(*)、a^(*)/b^(*)可以作为较高纬度东北平原东部黄土地层良好的气候代用指标,并结合磁化率、粒度指标共同反映了该地区中—晚更新世以来的古气候变化过程,能较好重建该地区古气候环境的演化历史。经分析,以天恒山(THS)钻孔28.3 m为界,a^(*)和b^(*)发生明显变化,反映了沉积环境的显著改变,可能指示松嫩古湖于476 ka消亡。

The study of the chroma on the Huangshan(HS)Profile in the eastern part of the Northeast China Plain,a typical Quaternary Profile in Northeast China,has not yet been reported.Through study of the high resolution chroma parameters of the Harbin Formation loess-paleosol in the Tianhengshan core,correlation analysis was carried out with ignition loss,and was compared with the curve of magnetic susceptibility and grain size.The results show that lightness L^(*)was dominated by the content of organic matter mainly.Largely influenced by the categories and contents of iron oxide and correspond well with magnetic susceptibility,yellowness b^(*)could indirectly reflect the climate change and pedogenic environment in this region.At the same time,yellowness b^(*)was dominated by the content of organic matter.Redness a^(*)and yellowness b^(*)were controlled by the similar climatic factors and might process the consistent color material because of some correlation.Lightness L^(*),yellowness b^(*),a^(*)/b^(*)could be used as good indicators of climatic change.Only by using the combination between chromatic proxies,magnetic susceptibility and grain size,we could reconstruct a reasonable reliable process of climate change and the evolution history of paleoclimate environment in the eastern part of the Northeast China Plain since Middle-late Pleistocene.Considering the 28.3 m of Tianhengshan core as the boundary,redness a^(*)and yellowness b^(*)were obviously changed.It reflects the significant change of sedimentary environment,maybe indicate that Songnen paleo-lake disappeared at 476 ka.