福建晋江科任剖面老红砂主元素反映的晚更新世以来气候变化

摘要

以福建晋江科任剖面老红砂为研究对象,对剖面主元素地球化学特征及其指示的古环境意义进行初步研究.结果表明:(1)科任剖面以湿润型元素SiO2、Al2O3、Fe2O3为主,含量范围依次为68.88％～93.77％、9.03％～19.1％和2.14％～5.32％；干旱型元素CaO、Na2O、MgO和K2O的含量均小于0.5％,K2O的含量略高于2％,表现为较强烈淋溶；主元素分布特征、风化特征值、CIA值等均表明,科任剖面老红砂总体上属于轻度富铝化.(2)对特征元素组合、元素比值和磁化率等古气候古环境代用指标进行分析,认为晚更新世中期以来,科任剖面记录了较干冷-暖湿-干冷-暖湿4个阶段的气候变化:55.9～43.9 ka BP和27.0～10.8ka BP两个时期,气候干冷,冬季风强烈,为风沙堆积的两个主要阶段；43.9 ～27.0 ka和10.8 ka以来,气候温暖湿润,为风沙经历强烈风化和红化作用阶段.%This paper focuses on the research of "old red sand" section of Keren in southeast coast of Fujian Province. We analyzed the content of major elements and ratios of oxide in Keren section, and found that; (1) The old red sand was mainly composed of wet-type elments such as SiO2 , Al2O3 and Fe2O3, and their content range change as 68. 88% -93. 77%, 9. 03% -19. 1%, and 2. 14% -5. 32% , respectively. Dry-type elements such as CaO、 Na2O and MgO, whose content are all below 0. 5%, only the content of K2O is a bit higher than 2%, showing intensely eluviated. (2) Since the Late Pleistocene, the history of climate change recorded by Keren section can be divided into 4 stages, they are cold-dry, warm-wet, colder-dryer and warm-wet climates. And the major deposition phases of coast eolian sand took place under cold-dry climate during 55. 9-43. 9 ka BP and 27. 0 ~ 10. 8 ka BP, which had a lower sea level and strong winter monsoon environment. However, during 43. 9 - 27. 0 ka BP and since 10. 8 ka BP, the climate significantly became warm and humid, also, which had a higher sea level. So, in these phases, the earlier deposition of coast a eolian sand experienced a strong weathering and reddening process.