引用本文:鄂崇毅,张 晶,吴成永,孙永娟,孙满平,闫文亭,李 萍,吕顺昌.青海湖流域草甸土光释光年代学研究[J].土壤学报,2018,55(6):1325-1335.
E Chongyi,ZHANG Jing,WU Chengyong,SUN Yongjuan,SUN Manping,YAN Wenting,LI Ping,LÜ Shunchang.Study of Chronology of the Meadow Soil in the Qinghai Lake Basin by Means of Optically Stimulated Luminescence[J].Acta Pedologica Sinica,2018,55(6):1325-1335
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青海湖流域草甸土光释光年代学研究
鄂崇毅,张晶,吴成永,孙永娟,孙满平,闫文亭,李萍,吕顺昌
青海师范大学,青海师范大学,青海师范大学,青海师范大学,青海师范大学,青海师范大学,青海师范大学,青海师范大学
摘要:
高山草甸土是青藏高原的主要土壤类型,其特征为土层薄、土壤发育微弱,但由于土壤具体的发育时代尚不明晰,限制了对草甸土成土过程和气候背景的理解。选取青海湖流域西南部的橡皮山顶草甸土两个剖面(XPSD1、XPSD2)和东南部的日月山垭口两个剖面(RYS1、RYS2)进行了光释光(Optically Stimulated Luminescence, OSL)年代学研究,系统分析草甸土中颗粒(38~63 μm)石英单片再生法测年的可靠性,探讨了草甸土发育的气候背景。结果表明:(1)OSL测年方法可有效运用于高山草甸土的测年中,释光自检验表明该测年结果可靠。(2)四个剖面的年代结果显示,现存的草甸土主要是晚全新世(4~0 ka)形成的,可能是相对干冷气候下的产物,其成土发育过程以风尘加积为主。(3)橡皮山顶2号剖面底部的黄土母质年代为16.2±1.8 ka,与上部土壤呈假整合接触,存在约14 ka的沉积间断。
关键词:  青海湖  高山草甸土  光释光测年  土壤年代学
DOI:10.11766/trxb201801090021
分类号:
基金项目:国家自然科学基金项目(41761042,41361047)和青海省自然科学基金项目(2017-ZJ-901)
Study of Chronology of the Meadow Soil in the Qinghai Lake Basin by Means of Optically Stimulated Luminescence
EChongyi,Zhangjing,WuChengyong,Sun Yongjuan,Sun Manping,Yan Wenting,Li Ping and Lv Shunchang
Qinghai Normal University,Qinghai Normal University,Qinghai Normal University,Qinghai Normal University,Qinghai Normal University,Qinghai Normal University,Qinghai Normal University,Qinghai Normal University
Abstract:
【Objective】Soil chronology is of great pedogenetic significance, for it is closely related to the forming and developing processes of a soil. In this paper, the Optically Stimulated Luminescence (OSL) dating method was employed to determine age of the alpine meadow soil in the Qinghai Lake Basin on the northeast fringe of the Qingzang Plateau. Four alpine meadow soil profiles (XPSD1, XPSD2, RYS1 and RYS2) were prepared for dating. Adaptability and reliability of the OSL dating method for alpine meadow soils in the Qinghai Lake Basin was evaluated. Pedogenic process and its climatic background were also discussed. 【Method】The silt-sized (38~63 µm) quartz OSL single-aliquot regenerative (SAR) dose protocol was used to acquire equivalent dose (De). OSL signals of all the samples decayed very quickly, displaying characteristics of the signals of the typical fast quartz fraction. The preheating test set 240 ℃ as preheating temperature. All De distributed quite concentratively, showing a Gaussian distribution curve, which demonstrates that the quartz particles in the profile of Xiangpishan were well bleached before deposition. Environmental dose rates were determined using the inductively coupled plasma mass spectrometry (ICP-MS). Eventually age of the meadow soil of the profile was determined. In addition, development of the soil was characterized through analysis of particle size and organic matter content of the soil.【Result】According to the theory of pedogenesis, the genetic horizon of the meadow soil could be divided into grass felty layer (Afe), humus layer (Ah), parent material layer overlapped with a humus layer (CAhb) and parent rock layer (C). The bottom of XPSD1, XPSD2, RYS1 and RYS2 dated back 0.9±0.1 ka, 16.2±1.8 ka, 3.2±0.2 ka and 3.7±0.2 ka, respectively. The parent materials of the alpine meadow soil in the Qinghai Lake Basin was mainly of aeolian loess deposit, with 50%~75% of silt, 10%~40% of sand and 10%~20% of clay, so the soil is sorted as sandy silt. The aeolian dust plays an important role in the pedogenetic process of the alpine meadow soil in the Qinghai Lake Basin. Considering the alpine meadow soil features strong grass and humus accumulation, the OSL of the bottom of the Ah layer or the interface between the Ah and CAhb layers is used as indicator for dating of the alpine meadow soil. The OSL dating results demonstrate that the meadow soil in the Qinghai Lake Basin developed mainly during late Holocene (4~0 ka). The phenomenon of an inverted chronosequence of old upper layer (2.6±0.1 ka) and new bottom layer (70 cm depth, 0.6±0.1 ka) was discovered at Profile XPSD2, which could probably be attributed to the effect of freezing and thawing erosion.【Conclusion】The OSL dating method is validated to be adaptable and reliable for dating alpine meadow soils. The alpine meadow soil in the Qinghai Lake Basin is derived from aeolian deposits, and follows the mode of aeolian dust aggradation in soil development. The alpine meadow soil in the Qinghai Lake Basin formed mainly during the late Holocene (4~0 ka) and is deemed to be a product of dry and cold climate, taking into account the environmental records of the region. In profile XPSD2, the bottom loess parent material layer goes in parallel unconformable contact with the upper soil layer, showing a deposition hiatus of ~14 ka.
Key words:  Qinghai Lake  Alpine meadow soils  OSL dating  Soil Chronology