摘要
以西安少陵塬S3古土壤剖面为研究对象,通过地球化学分析并结合野外剖面观察,探讨该剖面的元素迁移、化学风化特征及其所揭示的气候变化等问题。结果表明:(1)少陵塬剖面S3黏化层具有3层结构,根据铁质胶膜发育、Ca CO3迁移等可以将S3剖面构型划分为黏化层(Bts1-Bts2-Bts3)、风化淋滤黄土层(BC)和Ca CO3结核淀积层(Bck);(2)Bts层Ca O与Ca CO3迁移程度最大,淋失率分别达到了-99.3%、-83.1%,Sr、Na2O和Mg O也发生了显著迁移,而Fe2O3、Al2O3和Rb则在黏化层略有富集,尤其Fe2O3和Al2O3在Bts3层有明显富集;(3)少陵塬S3古土壤介于初等风化向中等强度风化的过渡阶段,风化作用由BC→Bts2→Bts1→Bts3逐渐增强,Bts3已基本完成初期脱Ca、Na风化过程;(4)依据Ca CO3与Fe2O3的迁移富集特点确定,少陵塬剖面S3古土壤Bts3发育时的土壤为弱碱性,而Bts1和Bts2为碱性;初步确定少陵塬S3为黄褐土,S3发育时期西安地区的年均降水量为800 mm左右。
The loess-paleosol sequence in the Loess Plateau of China contains a complete set of climate environment information since Quaternary,of which the extraction uses geochemical analysis as an important approach. In this paper,the key issue under discussion is whether the knowledge in the past coincides with the profile configuration and soil properties of the S3 paleosol developed during 336 to 307 ka BP in the Guangzhong region and the paleoclimate conditions under which it was developed. For that end,this study took the Shaolingyuan profile of S3 paleosol in Xi′an as subject,for exploration of,element migration in and chemical weathering characteristics of the profile and their implications in terms of paleoclimatic change through field investigations and geochemical analysis. The authors conducted three field investigations in March,2014. Based on the field observation and measurement,the author divided the S3 profile in configuation and collected 61 soil samples,one every 8 cm on average along the profile for analysis of,chemical composition and Ca CO3 content. Geochemical elements were determined with a PW2403 X-Ray fluorescence spectrometer analyzer of the Holland Panalytical Corp.,and Ca CO3 was with a BW14-08.53 calcium analyzer of the Holland Eijkelkamp Corp.Results show as follows：The profile could be divided into argillic horizon（Bts）,weathered and leached loess horizon（BC）and Ca CO3 nodule illuvial horizon（Bck）in the light of development offerruginous clay film and migration of Ca CO3,and the argillic horizon of the Shaolingyuan Profile S3 was formed of three layers（Bts1-Bts2-Bts3）. In Horizon Bts,migration of Ca O and Ca CO3 was the most significant,with leaching rate reaching up to-99.31% and-83.06%,respectively,and that of Sr,Na2 O and Mg O was significant,too,but Fe2O3,Al2O3 and Rb accumulated slightly,particularly,Al2O3 and Fe2O3 in Bts3 layer. The Shaolingyuan Profile of S3 paleosol lied in the transient phase between the primary weathering stage and the moderately strong weathering stage,with weathering displaying a rising order of BC Blt2 Blt1 Blt3 in intensity. The Bts3 layer had basically completed the primary chemical weathering process characterized by leaching of Ca and Na,but had not yet started the next process characterized by leaching of K. In the light of migration and accumulation of Ca CO3 and Fe2O3,it could primarily be determined that the soil of the Bts3 layer was slightly alkaline during its development,and the soils in the other two layers,Bts1 and Bts2 were alkaline,and,the Shaolingyuan profile S3 belonged to yellow cinnamon soil. During the period of S3 paleosol development,the annual mean precipitation in Xi＇an region was calculated to be around 800 mm.
出处
《土壤学报》
CAS
CSCD
北大核心
2016年第2期311-321,共11页
Acta Pedologica Sinica
基金
国家自然科学基金国际合作项目(41210002)
河南省高校"专业综合改革试点"项目(070502)资助~~
关键词
古土壤
元素迁移
化学风化
古气候
西安少陵塬
Peleosol
Element migration
Chemical weathering
Paleoclimate
Shaolingyuan in Xi＇an
