郭利成+吴佳斌+熊尚发+杨石岭

摘 要：沉积物颗粒分选流程在古环境、古气候研究中的应用非常广泛。虽然常用的颗粒分选方法均基于斯托克斯定律，但是在操作过程中试验装置和流程的细微差别会导致不同的分选效果，甚至影响后续理化分析和科学结论。因此，建立一套可靠的分选流程对于颗粒分选至关重要。目前，筛析法和沉降法的组合是被普遍接受的分选流程，前者针对粗颗粒组分，发展较为成熟，后者针对细颗粒组分，在试验器材、试验流程和结果检验等方面还存在较大的改善空间。对此，从静水沉降法原理入手，选择乙酸来去除碳酸盐组分，利用机械震荡法加速化学反应，采用U型头虹吸管减少底部粗颗粒上涌带来的分选误差，从而建立了一套可靠的基于静水沉降法的沉积物颗粒分选流程。结果检验显示，分选出的颗粒均服从对数正态分布，且至少70%的颗粒能够准确地被分选。建立的完整有效的分选流程较传统流程可以更高效地分选出土壤黏粒和粉砂级颗粒（粒径小于64 μm），为后续研究打下可靠的基础。

关键词：沉积物颗粒；静水沉降法；U型头虹吸管；黏粒；粉砂；对数正态分布；分选流程；古环境

中图分类号：X141 文献标志码：A

文章编号：1672-6561（2016）05-0694-06

Abstract： Sedimentary particle sorting process has been widely used to reconstruct the changes in paleoenvironment and paleoclimate. Common sorting methods of sedimentary particles are mainly based on Stokes Law； however， physicochemical analysis and scientific conclusions will be different if the sorting methods with varied experiment equipment and processes are applied. Therefore， setting up a trustworthy sorting process is vital for particle sorting. During last two decades， the combination of sieve and sedimentation methods has been increasingly used for sorting and measuring sedimentary particles. The former is applied for sieving for the coarse fractions sorting and well developed， while the latter is based on sedimentation rates for the fine fractions， and the experimental equipment， processes and result evaluating should be improved. For this purpose， based on the principle of hydrostatic sedimentation method， the acetic acid was chosen to remove the carbonate component， the mechanical oscillation was applied to accelerate the chemical reaction， and the siphon with U-shaped head was used to reduce the sorting errors which might derive from the upwelling of coarse particles， and a trustworthy sorting process of hydrostatic sedimentation method was set up. The results reveal that all sorted particles obey the lognormal distribution， and at least 70% sorted particles are posited in the expected particle-size ranges. It is concluded that the presented process is reasonable and can sort the clay and silt particles （the partical size is less than 64 μm） more successfully than the traditional process does. These particles sorted by this process can be further used in other research projects.

Key words： sedimentary particle； hydrostatic sedimentation method； siphon with U-shaped head； clay； silt； lognormal distribution； sorting process； paleoenvironment

0 引 言

粒度是指矿物或碎屑颗粒的大小，决定了岩石的类型和性质，可以有效指示沉积环境或沉积相。因此，粒度被广泛应用于不同时空尺度的古环境、古气候重建工作[1-3]。然而，粒度也在一定程度上影响岩石其他环境替代指标的解释，因此，如何剔除粒度的影响是通过岩石环境替代指标来揭示过去沉积环境变化的关键。……