长白山地区全新世泥炭剖面地球化学特征及其古环境意义

Geochemistry of the Holocene peatland in Changbaishan Mountains and its implication for paleoenvironmental change

长白山地区是中国泥炭分布集中地区之一。本文选择长白山地区典型的泥炭剖面———大桥剖面 ,探讨其沉积物常量元素和微量元素的垂直分布规律及其对全新世气候变化的指示作用 ,并与该区另一代表剖面———金川泥炭剖面进行对比。结果表明 ,泥炭中常量元素含量最大值出现在 195cm ,向上、向下都减少 ,铁含量与灰分、容重在剖面上的变化规律基本一致 ,说明它主要来源于灰分 ;由于泥炭和砂土的基本性质 ,如容重、灰分、pH值有很大的区别 ,泥炭层微量元素大于下部砂土的含量 ,亚表层微量元素含量最高 ,这与灰分、纤维含量正好相反 ,与 pH值剖面变化一致 ;沉积物容重、灰分、pH值、Ca/Mg以及元素的富集因子、泥炭中总碳含量在剖面上的变化 ,显示很强的一致性 ,据此反映该区经历了早 ( 11880～ 76 0 0aBP)、中 ( 76 0 0～ 2 4 80aBP)、晚 ( 2 4 80～ 0aBP)全新世三个环境阶段 ,其结论与前人通过孢粉、同位素手段分析得到的金川泥炭剖面环境变迁规律相同 。

Changbaishan Mountains are one of regions where peatlands are distributed A typical profile of Daqiao peatland in the Changbaishan Mountains is chosen for this study The vertical distribution of major and selected trace elements in the sediments of the profile was determined Its implications for the climatic change in the Holocene are discussed The profile was compared with another standard profile named Jinchuan in this area The results show that most major elements are rich at the depth of 195cm, and decrease upwards and downwards from there The concentration profile of Fe correlates well with that of ash content and bulk density, and this indicates Fe is mainly associated with ash forming minerals The basic characters, such as bulk density, ash content and pH,are different between peat and sandstone;the content of trace elements in the peat is higher than that in the sandstone, and is the highest in the subsurface layer of peat The concentration profiles of bulk density, ash content, pH, Ca/Mg, total carbon content and enrichment factors relative to upper continental crust are distinctly consistent The area has gone through the Early Holocene(11 880～7 600 a B P),the Middle Holocene(7 600～2 480 a B P) and the Late Holocene(2 480～0 a B P) according to these indices These results gained from the Daqiao peatland are similar to those obtained by pollen and isotope analyses in the Jinchuan peatland It implies that these indices can be used as indicators of environmental change during the Holocene