A comprehensive study is presented of the characteristics of calcareous concretions in the Connecticut Valley varved clay (CVVC), a glacial lake sediment, probed by an array of investigations, including compositional analyses via X-ray powder diffraction and energy-dispersive X-ray spectroscopy, mechanical property mapping by nanoindentation, selective dissolution, microstructure examination by optical and electron microscopy, and stable isotope analyses, with an objective to resolve some long-standing questions on their origin and growth mechanisms. Results show that these concretions are of a biogenic origin and consist of ~40 wt% primary host sediments and ~ 60 wt% secondary calcite post-depositionally precipitated as pore infills and inter-particle cement. The highly consistent layering and dry density between the carbonate-free host sediments in the concretions and in-situ varved sediments manifest that the precipitated calcite causes no disturbance to the original stratification and structure of the varved sediments. Moreover, both the mechanical properties (i.e., Young's modulus and hardness) and calcite concentration in concretions exhibit a radially decreasing pattern slightly disturbed by the sediments' layered textures. Further supported by the radial distribution patterns of stable carbon and oxygen isotopes, the CVVC concretions grow in a concentric pattern. A conceptual ion transport model is proposed to further interpret the growth mechanisms. These concretions grow radially in a nearly closed sediment system with diffusion-controlled transport of HCO₃⁻ from decaying organic matter and Ca²⁺ from porewater at direction-dependent rates dominated by the pore characteristics of the local host sediments. The diverse concretion morphologies are attributed to the different growth rates in different directions affected by the heterogeneous layering and pore sizes of the host sediments.

通过一系列研究，包括对X射线粉末衍射和能量色散X射线光谱的成分分析，对冰河湖沉积物康涅狄格河谷裂谷粘土（CVVC）中的钙质凝结物特征进行了全面研究。 ，通过纳米压痕进行机械性能制图，选择性溶解，通过光学和电子显微镜进行微观结构检查以及稳定的同位素分析，目的是解决有关其来源和生长机理的一些长期存在的问题。结果表明，这些凝结物是生物成因的，由约40 wt％的主要基质沉积物和约60 wt％的二次方解石组成，这些沉淀物后沉积为孔隙填充物和颗粒间胶结剂。固结物中无碳酸盐的宿主沉积物与原位脉状沉积物之间的高度一致的分层和干密度表明，沉淀的方解石不会干扰脉状沉积物的原始分层和结构。此外，固结物中的机械性能（即杨氏模量和硬度）和方解石浓度均显示出径向减小的模式，受到沉积物分层质地的影响。稳定碳和氧同位素的径向分布模式进一步支持了CVVC固结物以同心圆模式生长。提出了概念性的离子迁移模型以进一步解释生长机理。这些凝结物在具有HCO扩散控制传输的近乎封闭的沉积物系统中呈放射状生长 固结物中的机械性能（即杨氏模量和硬度）和方解石浓度均显示出径向减小的图案，该图案受到沉积物分层质地的影响。稳定碳和氧同位素的径向分布模式进一步支持了CVVC固结物以同心圆模式生长。提出了概念性的离子迁移模型以进一步解释生长机理。这些凝结物在具有HCO扩散控制传输的近乎封闭的沉积物系统中呈放射状生长 固结物中的机械性能（即杨氏模量和硬度）和方解石浓度均显示出径向减小的图案，该图案受到沉积物分层质地的影响。稳定碳和氧同位素的径向分布模式进一步支持了CVVC固结物以同心圆模式生长。提出了概念性的离子迁移模型以进一步解释生长机理。这些凝结物在具有HCO扩散控制传输的近乎封闭的沉积物系统中呈放射状生长 CVVC的凝结物呈同心圆状增长。提出了概念性的离子迁移模型以进一步解释生长机理。这些凝结物在具有HCO扩散控制传输的近乎封闭的沉积物系统中呈放射状生长 CVVC的凝结物呈同心圆状增长。提出了概念性的离子迁移模型以进一步解释生长机理。这些凝结物在具有HCO扩散控制传输的近乎封闭的沉积物系统中呈放射状生长₃ ^-从腐烂的有机物和Ca ²⁺在由本地主机沉积物的孔特性占主导地位的方向依赖率从孔隙水。固结形态的多样性归因于不同方向上受基质沉积物非均质分层和孔隙大小影响的不同生长速率。