山西临汾盆地洪积扇上全新世黄土-古土壤序列发育特征

The characteristic of holocene loess-paleosol sequence on the alluvial-fluvial fan in Linfen Basin,Shanxi

薜村黄土剖面位于山西临汾盆地西缘山前冲洪积扇上,剖面自上而下具浊黄色亚砂土+灰黑色垆土(含大量古文化陶片、灰坑)+红褐色古土壤+黄白色亚砂土的分层特征。通过区域地层、全新世气候特征及土壤发育过程对比,同时根据14C和光释光测年的限定,确定了剖面地层的年代序列。分析表明:剖面中S0由上、下两段界限明显的土层复合而成,上段为灰黑色垆土层,下段为红褐色古土壤,与前人所说的'填土'非常接近;全新世大的气候旋回控制了黄土-古土壤序列的发育,而且S0成壤过程受大暖期气候的控制,全新世黄土层中出现3条厚度不等的黑垆土带,说明干冷气候背景下小的暖湿波动;冲洪积扇上的黄土多形成于晚更新世以来,分布格局与我国黄土的整体分布形势相一致。

Xuecun section locates on the alluvial-fluvial fan in western edge of Linfen Basin,Shanxi,which consists of four main layers:dirty yellow loess,gray black loam,yellow white loess.Based on comparing regional geological stratum,Holocene climate characteristic,soil developing process and three dating results,we determined the age sequence of geological stratum in the section.The study shows that SO in the section is composed of two layers of soils with clear dividing line,upper layer of gray black loam and lower layer of brown red paleosoil which is close to"Lou soil"mentioned in previous studies.The great climate cycle in the Holocene controlled the development of the loess-paleosoil sequence,in which S0 had developed in the megathermal climate and the three layers of black loam of different thickness in the Holocene soil imply small warm-wet fluctuation in the dry-cold period.Loess on the alluvial-fluvial fan mainly developed since late of Late Pleistocene and its distribution is consistent with the entire loess distribution of our country.