白垩纪钙质古土壤的发生学特征及古环境意义  

CRETACEOUS CALCAREOUS PALEOSOLS:PEDOGENETIC CHARACTERISTICS AND PALEOENVIRONMENTAL IMPLICATIONS

作　　者：黄成敏[1] Gregory John Retallack 王成善[3] 

机构地区：[1]四川大学环境科学与工程系,成都610065 [2]Department of Geological Sciences, University of Oregon, Eugene OR 97403, USA [3]中国地质大学地球科学与资源学院,北京100083

出　　处：《土壤学报》2010年第6期1029-1038,共10页Acta Pedologica Sinica

基　　金：国家重点基础发展计划课题(2006CB01401);教育部新世纪优秀人才支持计划项目(NCET-08-0379)资助

摘　　要：古土壤形成于过去环境,是揭示环境变化历史的重要材料。新近纪(23.03 M a)以前形成的古土壤,年代久远、埋藏深、受成岩作用改造强烈,其发生学特征研究是古环境重建的基础。本文通过对白垩纪时期不同地点的钙质古土壤的发生学研究,拟恢复研究区域古环境。研究表明,古土壤剖面中的A层和B层形态分别产生变化,但层次差异依然明显,且表层土壤有机质含量一般高于表下层,钙积层(Bk)普遍发生并富含碳酸盐结核。可以观察到古土壤中方解石沿根孔淀积特征以及具滑擦面。钙质古土壤质地偏粗,为壤质砂土和砂质壤土。古土壤Bk层中的Ca、Mn、Sr相对富集,其余常量元素与Ba、Sc、Nb、Th、U、Cr、V、Co、N i等元素降低;δCe和δEu负异常以及相对富集重稀土元素。分别按照中国土壤分类系统和美国土壤系统分类两种分类体系进行了古土壤分类。由古土壤类型和特征可以推断白垩纪不同时期,在四川盆地梓潼—巴中地区、辽宁金岭寺—羊山盆地和松辽盆地出现过半湿润至半干旱的气候环境。Paleosols formed during the geological past are archives of paleoenvironment.Although pre-Neogene paleosols were formed a long long time ago,buried deep and subjected to strong diagenetic alteration,their pedogenetic characteristics are the basis for studying and reconstructing paleoenvironment.In an attempt to reconstruct paleoenvironment of the study regions,where calcareous paleosols of Cretaceous were discovered at several localities,a research project was launched to study pedogenesis of the paleosols.Results show that A-and B-horizons of the soils altered morphologically,but the difference between the two remained distinct;organic matter contents were generally higher in the surface soil layer than in the subsurface layer,and a calcic horizon（Bk） was commonly spotted abundant in carbonate nodules.Slickensided peds and precipitation of the calcites along the plant roots were observed in thin sections of the paleosols.The paleosols were sorted as loamy sand and sandy loam with texture being a bit too coarse.The Bk horizons of the soils were relatively enriched with Ca,Mn and Sr,but quite low in other macro-and micro-elements,like Ba,Sc,Nb,Th,U,Cr,V,Co and Ni.And negative anomaly of δCe and δEu as well as enrichment of heavy rare earth elements were detected in Bk horizons relative to A hozrions in paleosols.Classification of the paleosols in line with the Chinese Soil Taxonomy and US Soil Taxonomy were tried.Based on the findings,it is concluded that climates between semi-humid and semi-arid once appeared in Zitong-Bazhong area（Sichuan Basin） during the Berriasian-Valanginian age,in Jinlingsi-Yangshan Basin（Liaoning Province） during the Barremian age,and in Songliao Basin（Heiliongjang Province） at the Maastrichtian age.

关 键 词：白垩纪 钙质古土壤 土壤发生学特征 古土壤分类 古环境重建 

分 类 号：S151.2[农业科学—土壤学] P534.53[农业科学—农业基础科学]